Synthesis and characterization of a novel carbocyclic allene complex of iron

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Title:
Synthesis and characterization of a novel carbocyclic allene complex of iron
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xiii, 146 leaves : ill. ; 28 cm.
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English
Creator:
Manganiello, Frank John, 1954-
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Subjects / Keywords:
Iron compounds   ( lcsh )
Allene   ( lcsh )
Organometallic compounds   ( lcsh )
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bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )

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Thesis:
Thesis (Ph. D.)--University of Florida, 1982.
Bibliography:
Includes bibliographical references (leaves 142-145).
Statement of Responsibility:
by Frank John Manganiello.
General Note:
Typescript.
General Note:
Vita.

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University of Florida
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Full Text










SYNTHESIS AND CHARACTERIZATION
OF A NOVEL CARBOCYCLIC
ALLENE COMPLEX OF IRON










BY
FRANK JOHN MANGANIELLO


A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL
OF THE UNIVERSITY OF FLORIDA IN
PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREE OF DOCTOR OF PHILOSOPHY




UNIVERSITY OF FLORIDA


1982

























to my wife and children,

Colleen, Wendy, and Micah,

for their love and understanding














ACKNOWLEDGEMENTS


I would like to thank Professor William M. Jones for his support

and help throughout the years. I would also like to express my grati-

tude for the support and encouragement that I received from my parents,

my wife's parents, and my grandparents.

Thanks must go to Dr. M. Radcliffe, Mr. R. Winchester and Mr. S.

Oon for all the 13C and low temperature NMR work. Finally, I would like

to thank Dr. M. Balci, Dr. L. Christinson, Dr. K. Biesiada and especially

Mr. J. Lisko for their help and friendship throughout the years.

Mrs. M. Waby deserves particular thanks for her invaluable assist-

ance in the preparation and typing of this manuscript.















TABLE OF CONTENTS



ACKNOWLEDGEMENTS . . .

LIST OF TABLES . . .

LIST OF FIGURES . . .

ABSTRACT . . .

CHAPTER

I INTRODUCTION . .

II ATTEMPTS TO GENERATE CYCLOPROPYLIDENE
COMPLEXES OF IRON . .

III GENERATION OF THE CARBOCYCLIC ALLENE
Fp COMPLEX . .

IV EXPERIMENTAL . .

Chemicals . .

Instrumentation . .

Bis[dicarbonyl-n5-cyclopentadienyl)iron]
[FP2] (45) . .

Potassium Dicarbonyl-n -cyclopentadienyl-
ferrate [Fp anion] . .

7-Chlorobicyclo[4.1.0]heptyl-7-carboxylic
Acid Chloride (66) . .

7-Bromobicyclo[4.1.0]heptyl-7-carboxylic
Acid Chloride (65) . .

Trans-2,3-diphenylcyclopropanecarboxylic
Acid Chloride (55) . .

iv


PAGE
iii

ix

x

xii


. .









Trans-2,3-diethylcyclopropanecarboxylic
Acid Chloride (56). . ... 92

Dicarbonyl-n5-cyclopentadienyl(cyclopropyl-
carbonyl)iron (51c) . .... .92

Dicarbonyl-n5-cyclopentadienyl(bicyclo[4.1.0]-
hepta-7-ylcarbonyl)iron. . 93

Reaction of Potassium n -Cyclopentadienyl-
dicarbonylferrate with 7-Chlorobicyclo-
[4.1.0]heptyl-7-carboxylic Acid Chloride. .... 94

Reaction of Potassium 5-Cyclopentadienyl-
dicarbonylferrate with 7-Bromobicyclo[4.1.0]-
heptyl-7-carboxylic Acid Chloride ... 95

Dicarbonyl-n5-cyclopentadienyl(trans-2,3-
diethylcyclopropylcarbonyl)iron (53). .. 95

Dicarbonyl-n5-cyclopentadienyl(trans-2,3-
diphenylcyclopropylcarbonyl)iron (52) ...... 96

Reaction of Potassium n5-Cyclopentadienyl-
dicarbonylferrate with Trans-2,3-diphenyl-
1-chlorocyclopropanecarboxylic Acid Chloride. 97

Bicyclo[4.1.0]hepta-7-yldicarbonyl-n5
cyclopentadienyliron (62) . 98

Dicarbonyl-n5-cyclopentadienyl(cyclopropyl)-
iron (28) . . ... .. 98

Dicarbonyl-n5-cyclopentadienyl(trans-2,3-
diethylcyclopropyl)iron (61). . ... 99

Dicarbonyl-n5-cyclopentadienyl(trans-2,3-
diphenylcyclopropyl)iron (60) ... 100









Attempted Synthesis of Dicarbonyl-n5-
cyclopentadienyl-7-chlorobicyclo[4.1.0]-
heptyl-7-iron (64). . ... 101

Reaction of 7,7-Dibromobicyclo[4.1.0]-
heptane with Potassium n -Cyclopenta-
dienyldicarbonylferrate . ... 102

Reaction of 7,7-Dichlorobicyclo[4.1.0]-
heptane with Potassium n5-Cyclopenta-
dienyldicarbonylferrate . ... 103

Dicarbonyl-n -cyclopentadienyl(methoxy-
methyl)iron (71). . .. 104

Dicarbonyl-n5-cyclopentadienyl(cyclo-
hexenecarbonyl)iron (140) . .... 104

Dicarbonyl-n5-cyclopentadienyl(cyclo-
hexene)iron (95). . ... 105

Dicarbonyl-n5-cyclopentadienyl(cyclo-
hexene)iron Hexafluorophosphate (96). ..... .106

Reaction of Dicarbonyl-n5-cyclopenta-
dienyl(cyclohexene)iron with Tetrafluoroboric
Acid in the Presence of Trimethyl Phosphite 106

1-Bromo-7-methoxycycloheptene (75). ... 107

Method A . . .... .. 107

Method B . . ... .. 108

Method C . . ... .. 108

7-Methoxycycloheptene-l-carboxylic Acid (78). ... 108

7-Methoxycycloheptene-l-carboxylic Acid
Chloride (79) . .... 109









Dicarbonyl-n5-cyclopentadienyl(7-methoxy-
cycloheptene-l-carbonyl)iron (74) ... 110

Dicarbonyl-n5-cyclopentadienyl-n -(7-methoxy-
1-cycloheptenyl)iron (72) . .. 111

Attempted Synthesis of Dicarbonyl-n5-cyclo-
pentadienyl-nl-(7-methoxy-l-cycloheptenyl)iron. 112

1-Bromo-7-ethoxycycloheptene (109). ... 113

7-Ethoxycycloheptene-l-carboxylic Acid (110). ... 113

7-Ethoxycycloheptene-l-carboxylic Acid
Chloride (111). . . ... 114

Dicarbonyl-n5-cyclopentadienyl(7-ethoxy-
cycloheptene-l-carbonyl)iron (112). ... 114

Dicarbonyl-n -cyclopentadienyl-n -(7-ethoxy-
1-cycloheptenyl)iron (108). . ... 115

1-Bromo-6-methoxycyclohexene (127). ... 116

6-Methoxycyclohexene-l-carboxylic Acid (129). ... 116

6-Methoxycyclohexene-l-carboxylic Acid Chloride
(130) . .... .. .. .117

Dicarbonyl-n5-cyclopentadienyl(6-methoxy-
cyclohexene-l-carbonyl)iron (131) ... 118

Dicarbonyl-n -cyclopentadienyl-n -(6-methoxy-
1-cyclohexene)iron (126). . ... 119

Reaction of Dicarbonyl-n5-cyclopentadienyl-
n1-(7-methoxy-l-cycloheptenyl)iron (72)
with Trimethylsilyl Trifluoromethanesulfonate
Followed by the Addition of Ethanol ... 119









Reaction of Dicarbonyl-n5-cyclopentadienyl-
n -(6-methoxy-l-cyclohexenyl)iron (126) with
Trimethylsilyl Trifluoromethanesulfonate
Followed by the Addition of Ethanol ... 120

Treatment of Dicarbonyl-n5-cyclopentadienyl-
n1-(7-methoxy-l-cycloheptenyl)iron (72)
with Me3SiOSO2CF3 .. . ... 121

Treatment of Dicarbonyl-n5-cyclopentadienyl-
n1-(7-methoxy-l-cycloheptenyl)iron (72)
with HBF4Et20. . . ... 124

Treatment of (72) with Me3SiOSO2CF3 Followed
by the Addition of Fp Anion . .... 127

Treatment of (72) with Me3SiOS02CF3 Followed
by the Addition of Tetrabutylammonium Iodide. 128


Reaction of (72) with Me3SiOS02CF3:
Isolation of Allene Complex (35). .

Treatment of (35) with Nal in d6-Acetone. .. .

Decomposition of (35) in the Air. .

Decomposition of (35) in CH2C12 ........
5 2
Dicarbonyl-n -cyclopentadienyl-n -(1,2-
cyclononadiene)iron Hexafluorophosphate (23).


Treatment of (126) with Me3SiOSO2CF3 .........

Decomposition of (35) in CH2C12 in the
Presence of Ph3CH . . .

APPENDIX LIST OF REAGENTS PURCHASED FROM
SPECIFIC CHEMICAL SUPPLY HOUSES . .

REFERENCES . . .

BIOGRAPHICAL SKETCH . . ... ..


viii


. .














LIST OF TABLES



TABLE PAGE

1 Yields from the reactions of Fp~ with the
corresponding acid chlorides . .... .14

2 Yields from the photolysis of the
corresponding acyl complexes . ... 18

3 1H NMR resonances of the Cp of i-complexes .. 35

4 1H NMR resonances for (106a-c) . .... .47














LIST OF FIGURES


FIGURE PAGE

1 1H NMR spectrum of (74) in CDC13 ........... 31
2 1H NMR spectrum of (72) in CDC13 .......... 32
3 1H NMR spectrum of the crude products from the
addition of HBF4 to (72) . ... 34
4 1H NMR spectrum of (90) in d6-acetone ... .. 40
5 1H NMR spectrum of the crude products from the
addition of Me3SiOSO2CF3 to (72) . ... 43

6 'H NMR spectrum of the addition of Nal to the
crude products of Figure 5. . 44
7 100 MHz 1H NMR spectrum of the crude products
from the addition of Me3SiOSO2CF3 to (72) in
CDC13 at -300C . . 49

8 'H NMR spectrum of (23) in CD3NO2 at room
temperature . . ..... 51
9 100 MHz H NMR spectra displaying the fluxional
behavior of (35) . . 52
10 The addition of Nu- to (107) .. ... 54

11 H NMR spectrum of (108) in CDC13 ... 57

12 100 MHz H NMR spectrum of (35) in d6-acetone
at -200C ... .. 60
13 13C NMR spectrum of (35) in CD3NO2 at -200C ... 61

14 1C NMR spectrum of (23) in CD3NO2 at
room temperature . ..... 62
15 100 MHz 'H NMR spectra of (35) in d6-acetone ..... 65

16 (a) 100 MHz 1H NMR spectra of 35) in d -acetone;
(b) irradiation of Ha at -20C; (c) irradiation
at -600C . . 68











(a) 100 MHz 1H NMR spectrum of (35) in d -acetone;
(b) irradiation at Ha at -400C; Tc) irradiation at
-600C. . . .. .


18 H NMR spectrum of (35) and NaI in d6-acetone
at room temperature . .

19 H NMR spectrum of the crude products from the
addition of Ph CH to (35) in d6-acetone .. ..

20 1H NMR spectrum of the addition of Nal to the
products in Figure 19 . .

21 H NMR spectrum of the crude products from the
exposure of (35) to the air . .

22 H NMR spectrum of (131) in CDC. .

23 1H NMR spectrum of (126) in d6-benzene .

24 1H NMR spectrum of the crude products from the
addition of Me3SiOSO2CF3 to (126). .

25 H NMR spectrum of (96) in d6-acetone. .

26 Calibration curve of a) 1,3-cycloheptadiene
and b) cycloheptene . .

27 Calibration curve of cycloheptanone. .

28 1H NMR spectrum of (35) in d -acetone at -200C
after 1 hour at room temperature .

29 An expansion of the 1H NMR spectrum of (35)
in d6-acetone at -200C after 1 hour at
room temperature . .

30 1H NMR spectrum of (35) in CD3NO2 at -20C .

31 Calibration curve of a) 1,3-cyclohexadiene
and b) cyclohexene . .


* 71


* 72


* 73


* 75

. 81

. 82


. 83

. 86


. 123

. 126


131

132


138


FIGURE

17


PAGE



69


. .














Abstract of Dissertation Presented to the
Graduate Council of the University of Florida
in Partial Fulfullment of the Requirements for
the Degree of Doctor of Philosophy


SYNTHESIS AND CHARACTERIZATION
OF A NOVEL CARBOCYCLIC
ALLENE COMPLEX OF IRON

By

Frank John Manganiello

December, 1982

Chairman: William M. Jones
Major Department: Chemistry

The smallest stable carbocyclic allene is 1,2-cyclononadiene. As

one would anticipate as the carbocycli-c allene ring is decreased in

size, the stability is also decreased. In contrast, transition metal

complexes of Pt have been employed to stabilize these strained carbo-

cyclic allenes. Here, it was found that treatment of dicarbonyl-n -

cyclopentadienyl-n -(7-methoxy-l-cycloheptenyl)iron [(7-methoxy-1-

cycloheptenyl)Fp] with trimethylsilyl trifluoromethanesulfonate gave a

71% yield of dicarbonyl-n5-cyclopentadienyl-n2-(1,2-cycloheptadienyl)-

iron trifluoromethanesulfonate as a crystalline solid.

Examination of the 1H NMR, at low temperatures, revealed the

fluxional behavior of the metal, Fp, associated with known Fp allene

complexes. Furthermore, the activation energy, AGt, for the inter-

conversion, [1,2]Fp shift, of the isomeric allene complexes was observed

at 280C with a AGt of 13.9 0.2 kcal/mole. Further proof of the








structure of the carbocyclic allene Fp complex was obtained by the use

of spin saturation transfer which allowed additional examination of the

[1,2]Fp shift at low temperatures.

The 13C NMR, at low temperatures, revealed that the carbocyclic

allene Fp complex shows some metallocyclopropyl character, as seen in

the Pt carbocyclic allene complexes, as characterized by the extreme

upfield shifts of the C1 + C2 carbons of the carbocyclic allene.

Contrary to earlier reports on the addition of MeO~ to acyclic

allene Fp complexes, it was found that addition of EtOH occurred on the

C1 carbon of the n2-allene fragment. This generated the sigma complex,

dicarbonyl-n5-cyclopentadienyl-n1-(7-ethoxy-l-cycloheptenyl)iron, in a

54% yield.

A second attempted approach to the carbocyclic allene complex was

through the generation of the cyclopropanonyl-iron sigma complex.

Previously, it was reported that the parent cyclopropanol complex of Fp

would not decarbonylate to the corresponding sigma complex. Contrary

to these earlier reports, photodecarbonylation of the corresponding acyl

complexes gave excellent yields of the desired sigma complexes.

However, attempts to generate the desired alpha-halo sigma complexes

were unsuccessful, thus not allowing entrance into the allene manifold.

Unfortunately, methoxy abstraction from dicarbonyl-n5-cyclopenta-

dienyl-nl-(6-methoxy-l-cyclohexenyl)iron with Me3SiOSO2CF3 did not

afford the carbocyclic allene complex but rearranged products derived

from carbocation intermediates.


xiii












CHAPTER I
INTRODUCTION


The synthesis, bonding, and structure of transition metal complexes
of carbenes have been investigated and reviewed many times over the last
few years.1-4 The bonding within complexes containing hetero atoms or
n-systems which are alpha to the carbene carbon can be considered in
terms of three principal canonical forms (1, 2, 3).1-3 Resonance form 1


ME

+
x Y
2


M
II
C
X Y
3


shows no interaction of the vacant pz orbital of the methylene carbon
while resonance form 2 represents the vacant pz carbene orbital interact-
ing with the r-system (4, 5)5,6 or the lone pair on the hetero atom




Fp= I (CO)5Cr-

4 5

Fp = C5H5Fe(CO)2


Me


X Y
1








(X or Y) of the ligand (6, 7, 8).7-9 Resonance form 3 represents



/OMe /NR2 + /NR2
(CO)5Cr =C (CO)5Cr =C Fp =C NR2
Me Ph NR2
6 7 8


interaction of the vacant pz orbital with the d orbitals of the metal.
The energy difference between the metal d orbital and that of the pz
orbital influences the contribution of resonance form 3. This so called
"back bonding" can be assessed with the use of x-ray crystallographic
and spectroscopic data.
The first transition metal complex of a carbene (5) with a (4n+2)-
i-system (n=O) was reported by Ofele6 in 1969. More recently the



Ph

(CO)5Cr=<
Ph


-55
synthesis of a series of aromatic transition metal complexes (4 and 9)
with (4n+2)r-electrons (n=l) was achieved by Allison and co-workers.5













Fp Fp=


4 9
In principle cyclic conjugated ligands such as C7H6 could exist in
either a carbene (10) or allene form (11). In the case of such complexes


M +M +M




1O 11
10 11
as(4)and(9)it is clear from the NMR spectra that the ligand is completed
in the form of the carbene rather than an allene;5 even in the case
where a P(C4Hg)3 derivative was prepared the carbene form was favored.11
This is notable because recent evidence (theoretical and experimental)
has pointed to the probability that in nonmetallic compounds the twisted
allene structure (12) is lower energy than the carbene structure (13).10



H H




12 13
To date, evidence for an example of a metal-cycloheptatetraene (11) has
not been found. This indicates that in the cases reported to date,








either the carbene complex (10) is of lower energy than the allene (11)

or the method of synthesis leads to a higher energy but kinetically

stable form.

The question arises, then, can transition metal complexes of carbo-

cyclic allenes (either conjugated or nonconjugated) be prepared? A

review of the literature reveals that carbocyclic allenes are generally

very reactive and rather unstable molecules.12-17 The smallest stable

carbocyclic allene is 1,2-cyclononadiene (14). If the carbocyclic ring


is decreased in size, the strain within the ring is increased; thus 1,2-

cyclooctadiene (15) can only be observed spectroscopically (at low

temperature) and trapped, whereas 1,2-cycloheptadiene (16)18'19 can be

generated and trapped but has never been observed (spectroscopically).


* An idealized (C=C=C) angle of 1800 and torsional angle of 900 dictates
the requirement for relatively large rings.













15 16
On the other hand, in 1972, Visser and Ramakers20 synthesized
platinum complexes (17, 18, 19) of a number of carbocyclic allenes and
succeeded in isolated stable crystalline products for cyclic allenes as


L2Pt


few as seven carbons. Preparation of these carbocyclic allene complexes
(20) was achieved by the generation of the carbocyclic allene (21)


0

21


+ 4 PtL2


L2Pt


(dehydrohalogenation of the bromocycloalkenes at low temperatures)20 in








the presence of (22). These complexes were presumably formed by addi-
tion to the vacant coordination site of the metal followed by the loss
of ethylene.21 One iron complex of a carbocyclic allene has also been
reported. In this case, Foxman and co-workers22 were able to prepare
a stable carbocyclic allene complex (23) (93%) by the exchange reaction
of (24) with the stable carbocyclic allene (14); the smaller carbocyclic





Fp + A Fp+

CH2C12

24 14 23



allenes would not work here due to the high temperature needed to gen-
erate the metal allene complexes.
Other carbocyclic allenes (i.e., cyclonona-1,2,6-triene and cyclo-
deca-1,2,6,7-tetraene)2324 are known to form 1:1 complexes with silver
nitrate or with cuprous chloride; however these are not applicable here.
Reflecting back on the interconversion of (10) and (11) one sees
that this is a specific example of a much broader question of the

M +M +M
+ M




10 11


energetic and valence isomerization of the types of metal complexes

(25), (26), and (27). Here the isomeric form (25) shows a sigma bond










+ +
M M M



25 26 27

with virtually no back bonding possible, a sigma bond in (26) with ex-
tensive back bonding and a i-bond in (27).
A review of the literature reveals only a few examples of these
kinds of interconversions. Recently Cohen and co-workers25 found that
hydride abstraction from (28) gave the allene complex (29), presumably


+ + II



28 30 29


via (30). Lennon and co-workers26 found that methoxy abstraction from
(31) also gave the allene (29). However, here the iron may assist in



S -Oe +F



OMe

31 32 29

the direct loss of the methoxy so that the sigma complex (31) may go
directly to the allene complex (29), bypassing the cation (32), via
an anti Fp assistance.








To study the interconversion of (25), (26), and (27) ideally one
would like to enter a given manifold at one of the higher energy forms
and then observe its collapse to one of the more stable complexes (i.e.,
(30) to (29), the more stable product).
It was the aim of this research to study the interconversion of Fp
complexes of small carbocyclic valence isomers (33, 34, 35) entering a
given manifold at one of the higher forms and observing its collapse to





_


33 34 35

a more stable complex. Since the platinum complex of 1,2-cyclohepta-
diene (19) has been trapped, we elected to begin with attempts to
generate the cyclopropylidene and the cycloheptenyl Fp complexes (34)
and (35), respectively, to see if they would collapse to the allene
form (35).











CHAPTER II
ATTEMPTS TO GENERATE CYCLOPROPYLIDENE COMPLEXES OF IRON


In principle, the simplest method to generate cyclopropylidene
complexes of Fp, (30), would be simple hydride abstraction from appro-
priately substituted sigma Fp complexes. And, indeed, one example of
such a reaction has been reported using an exotic reagent (36) with
the sigma complex (28).25 However, hydride abstraction does not




F + H ;p -


36 28 30 29
appear to be a generally useful method for preparing this kind of
complex. For instance, Cutler and co-workers27 have found that
attempts to abstract hydride from (28) with trityl did not give the
desired complex (30), but rather the addition product (37).




ICFP Fp C33


28 37




10


We therefore turned our attention to the synthesis of sigma cyclo-
propyl Fp complexes in which the alpha-hydrogen has been replaced by a
better leaving group such as a halogen or a methoxy group.
The first synthetic approach chosen for the synthesis of sigma
bonded alpha-halocyclopropyl Fp complexes was patterned after that of
Culter and co-workers,27 who found that the parent complex could be
prepared by either treatment of cyclopropyl bromide (38) with Fp anion
or by the alkylation of FpBr with cyclopropyllithium (39). By analogy,


>:Br


c;x
C> x


Fp Fp


FpI


Li

39
39


either the reaction of (40a) or (40b) with Fp anion or the reaction


Fp


40a
40b


sFp
Of

Fpl
-----


Cl
Li4


42a
42b


(41) with Fpl, could result in the formation of (42a) or (42b).
Unfortunately, when (40a) was added to a suspension of Fp anion (at
00C) (42a) was not observed; only (43), (44), (45) and unreacted













Q Br


THF
Fp


+ H + Fp2


40a


starting material were recovered. Likewise, when (40b) was treated
with Fp anion, under the conditions as above, only (45), (46)


C40

40b


THF
Fp


+ Fp2


*Cl


unreacted starting material were found. Formation of (44)
(46) finds analogy in the report of Marten and co-workers,28
found that the reaction of (47) with Fp anion gave the reduced


> ciCl
>

Fp


D> C
H


+ Fp2


45


product (48). Since the addition of the Fp anion to the dihalo com-
pound gave only the reduction products, an attempt was made to


and
and
who








generate (42b) by the reaction of the anion (41) with Fpl. Unfortunately,
again all attempts failed. Isolation of the products gave only (46),


Li

c>Cl


+ FpI---


42b


(49), and (50), the latter presumably arising from the reaction of


Li
c Cl


Fpl
- --_


I
Fe


49


L Cl + FpC4Hg


unreacted BuLi with FpI.
Since alpha-substituted Fp complexes could not be prepared by
either of the above methods, a third approach was attempted as illus-
trated below:


0
II Fp
R2-C- C--C1
XTHF
x


0
R2C- --Fp hv >
X
Acyl
Complex


R2C-Fp
X
Sigma
Complex


It is well known that metal anions readily react with acid
chlorides to generate the corresponding acyl metal complexes which,


OFp
C> Cl







in turn, can normally be decarbonylated (either thermally or photo-
chemically) to the corresponding sigma metal complex.29 Unfortunately,
Bruce and co-workers30 had reported that attempts to decarbonylate the
acyl cyclopropyl metal complexes (51a-d) were unsuccessful. These


0
II
C-MLx MLx

>
51 (a-d)
a) MLx= Mn(CO)5 b) MLx=Re(CO)5
c) MLx= Fe(CO)2Cp d) MLx= Ir(CO)CVPPh3)2

attempts included thermolysis, photolysis and reaction with
31-33
(Ph3P)3RhC3133 (known to be an efficient abstractor of carbon
monoxide). Despite their failure, we noted that their attempts were
limited to the parent complexes and suspected that the substituents
on the cyclopropyl rings of the Fp complexes might cause these com-
plexes to behave differently. We therefore undertook the synthesis
of a series of model alpha-hydrogen substituted cyclopropyl Fp com-
plexes to see if effective decarbonylation conditions could be found.34
The synthesis of the desired substituted acyl complexes (52), (53)35
and (54) was found to be straightforward. Treatment of the substi-
tuted cyclopropyl acid chlorides (55), (56) and (57) with Fp anion
(at 00C) gave poor to excellent yields (Table 1) of the desired metal
complexes (52), (53) and (54).





14







Table 1. Yields from the reactions of Fp with the corresponding
acid chlorides.


Reaction of yield % Acyl Complex
Fp and Acyl Holide

H EAc EylF
Et H Et




Ph 0 X Ph 0
H -CIH 77% H --Fp
H X Br 15%



C-CI 20 % C--Fp
H H


(C-CI?


18 %
17%
3%


0
C-Fp
(>H











Fp
0O THF


R


E+


Fp
00 THF


57


0
C-Fp
Of
54


Since the unsuccessful attempts to photodecarbonylate the parent
acyl Fp complex (51c) had been carried out in petroleum ether (or neat)
an alternate solvent was sought. Recently, Graham and Heinekey36
reported that the photolysis of (58) in acetone (at -780C) gave the
corresponding sigma complex (59) in a good yield (60%). We therefore
carried out our photodecarbonylation in acetone and were gratified to

0


-Re(CO)5


H Re(CO)5


hv- 780
acetone


58


R


E+


59







find that (52) underwent smooth decarbonylation (at 00C; in 2 hours) to
give an excellent yield (97%) of the desired sigma complex (60).35



H 11 H
I/C-Fp hv 0OC H Fp
IH H d. -acetone I H H


52 60
Likewise photolysis of (53)35 and (54), under the same conditions, also
gave the alkyl complexes (61) and (62), albeit the latter in only 15%
yield.


Et 0
H -Fp
H H

53


hv OC
d, -acetone


Et
H Fp
iH H
Et


0
II
C--Fp
QXH


hv O0C
de -acetone


54 62
As a result of these encouraging results, photodecarbonylation of
the parent acyl Fp complex (51c) was also attempted in d6-acetone.








Indeed, photolysis of (51c), at 00C for 10 minutes, led to the forma-

tion of a new metal complex (a new Cp resonance appeared at 6 4.90).


0

2C-Fp hv O*C FP
H d -acetone H


51c .28

After photolysis for one hour and 10 minutes the 1H NMR showed nearly
complete loss of starting material. The solution was worked up at

this time to give the desired Fp complex (28) in a 75% yield.

Since our photolyses were conducted in d6-acetone, while those of
Bruce and co-workers30 had been carried out in petroleum ether (or neat),

we desired to photolyze (51c) and (52) in petroleum ether to see if
this led to reduced yields. Indeed, in both cases even though the
photolysis gave the desired sigma complexes (28) and (60) the yields

in each case were significantly lower than in d6-acetone. The photol-

yses were also carried out in d6-benzene. Again each acyl complex
gave the desired sigma complex but in this case yields were between

those observed in d6-acetone and petroleum ether (Table 2).








* The product (28) may have not been detected by Bruce and co-worker30
due to low yield (16%).


















Table 2. Yields from photolysis of the corresponding acyl complexes.

Acyl Photolysis Sigma yield %
Complex Solvent Complex

Ph 0 d ocetone Ph 97%
H -Fp d benzene H eP 64%
H H 5 1 0
H Petroleum ether Ph H 51 %


Et 0 Et
H -- Fp d -acetone H EFo 75 %
H H
Et Et



H d, -acetone H75 %
SC--Fp d,-benzene HF 52 %
H Petroleum ether H H 16 %
H H


CxF


ds-ocetone


52 %


(--Fp










0
C-Fp
'H


52

51c


hv


60

28


Having demonstrated the viability of the decarbonylation step for
the model system we then turned our attention to the preparation of
alpha-halo acyl Fp complexes.
We first attempted to prepare (63) and (64). Unfortunately, in
each case reaction of the alpha-halo acyl halide (65 and 66) with Fp


(N C-Fp
II
0


65
.66
anion resulted
(63) and (64),


X X
Br 63 Br
CI 64 CI
not in the formation of the desired metal complexes
but rather the reduced complex, (54).


F 0




20







THF OOC


,H
'C-Fp
I
O


X
Br 54
CI
was also found to be the case for the reaction of (67) with
again only the reduced product (52) could be isolated.


0
.C-Fp


FPO
THF 00C


52


The mechanism of the reduction is not known. However, one
reasonable possibility is shown below.



C-CI _Fp_ C=


68


Fp


65
66
This
Fp anion;


67





21



In this mechanism the Fp anion induces elimination to give the ketene

(68) which further reacts to give the reduced products.

Since it appeared that alpha-halo acyl chlorides could not be used

to prepare the desired carbene precursors, we turned our attention to

complexes with a methoxy group in the alpha position. We were optimis-

tic about this as a viable approach because Cutler and co-workers37

were able to generate the acyl Fp complex (69) by reacting (70) with Fp

anion; no reduction occurred. In turn, we were able to photodecarbony-

late (69) in d6-acetone (at 00C) to give the known sigma complex (71).




0 0
II THF II
Fp + CICCH2OMe Fp- C-CH2OMe

70 69



0
II hv
Fp- C-CH2OMe --- Fp-CH2OMe

69 71


We expect that methoxy abstraction may have real potential for

the preparation of cyclopropylidene Fp complexes. However, a search

of the literature revealed very few alpha-methoxycyclopropyl carboxylic

acids and we expect their synthesis to be quite a challenge. Further-

more, concurrent with this work, we were also exploring ways to enter

the seven membered ring manifold at the allyl cation (33). Since this





22









Fp

F Fp



33 34 35

was progressing better than the cyclopropylidene investigation, we

turned our attention to this new area.














CHAPTER III
GENERATION OF THE CARBOCYCLIC ALLENE Fp COMPLEX


In view of our unsuccessful attempts to generate the cyclopropyli-

dene complex (34) alternate approaches into the valence isomer manifold





Fp Fp +

=Fp .. _



33 34 35


(33, 34, 35) were explored. Ideally one would like to enter this mani-

fold at a higher energy form and observe its collapse to a more stable

complex. We therefore undertook an approach aimed at the preparation

of the allyl cation complex (33) to see if it would rearrange to the

carbocyclic allene (35) or even cyclize to the cyclopropylidene complex

(34).
As mentioned before, it was reported some years ago that treatment

of the ether complex (31) with HBF4 Et20 gave the stable acyclic allene

complex (29),26 possibly via the allyl cation (32). Applying the same












Fp


HBF4
Ooc


-] Fp+

-----


methodology to the carbocyclic system, preparation of (72) was under-
taken.


OMe
J Fp


In principle (72) could be prepared from (73) by employing the
two approaches discussed in Chapter 2 [i.e., either by the alkylation
of Fpl or chlorocarbonylation of (73) followed by conversion to the
sigma complex (72)]. Thus, the synthesis rested on the preparation
of (75) (using the logic shown in the following scheme).











OMe


OMe


72





OMe


COFp


Recently, Balci and Jones38 prepared the alcohol (76) by treatment




OH
Br
r acetone/H90 ,
r AgClO4 A 4


40a 76


of (40a) with AgCO14 in the presence of H20/acetone in an 80% yield.
With (76) in hand we found that treatment with NaH followed by Mel gave














1) NaH/THF %
2) Mel

76 75



the desired ether (75) in a 41% yield. Later a more direct and higher
*
yield preparation of (75) was achieved by treatment of (40a) with AgNO3
in MeOH.




OMe


O Br
Br


MeOH
AgNO3 A


40a


* AgClO4 in MeOH gives a higher yield (97%) but the reaction mixture
proved explosive.








The first approach to the synthesis of the carbocyclic sigma

complex (72) is shown below:


OMe


OMe


Unfortunately, although treatment of (75) with n-Buli, at -780C, gave






OMe OMe
r Li
n-BuLi THF
-780C


a yellowish solution that was apparently (73), treatment of this

solution with FpI at -78C did not give the desired sigma complex

(72), but rather (77) in a 55% yield.












OMe


-780C
Fpl


Since the above approach to the desired sigma complex (72) failed,

a second approach was attempted as seen in Scheme 1.

Treatment of (75) with n-BuLi at -110C followed by addition of


OMe


1)CO2

2)H+


CO2 and acid work-up gave the acid (78) in a 66% yield. The acid (78)


CO2H
Benzene
SOC12


n-BuLi
-110C


CO2H


OMe


COC1


OMe












OMe OMe
Li

-c)


73 78



OMe
)2H 1OCi




79


OMe
Cl COFp



74



OMe
SFp Fp



72

Scheme 1









was then treated with SOC12 (in benzene) to give the acid chloride (79)

in a 70% yield. Addition of the acid chloride (79) to a suspension of


COC1


COFp


THF -780C
Fp-


Fp anion in THF at -780C gave a 27% yield of the desired acyl complex

(74) as an air-sensitive, brownish oil. The 1H NMR spectrum of (74)

is given in Figure 1. Photodecarbonylation of (74) in d6-acetone at

00C gave an air-sensitive, brownish oil (72) in a 53% yield. The 1H

NMR spectrum of (72) is given in Figure 2.


hv
00C acetone


At this point the question arises, will (72), when treated with

HBF4.Et20, behave similarly to the model system (31) as reported by

Lennon and co-workers?26 It was found that treatment of (72) with







































r-

.0



O J --
Q- 4
o




... ..... ... ... r-PfOliii'- l Cz L
n


T































E


-c







-r1








I-





C-3








E



U,
U)



-It, z

r


r4





5-

Li.







HBF4*Et20 at -78C gave an immediate precipitate which, from the low
field Cp resonances (6 -5.65) in the 1H NMR spectrum (Figure 3)
suggested the formation of r-complexes of Fp. This downfield shift
is consistent with known r-complexes of Fp as indicated in Table 3.
It is well known that n-complexes of Fp undergo facile displacement
of olefinic ligand by halide ions, usually I whereas sigma complexes
of Fp are unreactive.3941 The precipitate from above was therefore


a Fp






QaFp


Nal
acetone





Nal
acetone


treated with Nal in d6-acetone to immediately give a color change
which upon work-up revealed that Fpl had been produced. Further exami-
nation, glpc, revealed that the ligands that had been displaced were
cycloheptanone (80) or its precursor, cycloheptene (81),and trace
amounts of 1,3-cycloheptadiene (82) by GC/MS.


0


+ Fpl


N.R.


























E










--I"
L.-


-ed u


CO
4r
*r
c0









0






S.-
4a







.-a














E


4-3
a)
"-







5-
4)










Table 3. H NMR resonances of the Cp of r-complexes.


Cp (in ppm's)


7Fp


SFp +


Fp



Fp +


Fp +


Fp +
^-r,'


5.78



5.62



5.60



5.61



5.65


5.62


5.67









One possible mechanism to rationalize these products is seen in

Scheme 2.

Addition of HBF4*Et20 to (72) could initially generate two dif-

ferent intermediates (33) and (83). Simple protonation of the double

bond of (72) would generate the carbocyclic carbene (83) which could

rearrange to give the i-complex (84). A closer examination of the 1H

NMR spectrum of the crude protonation product (Figure 3) reveals a

singlet at 3.80 ppm, a triplet at 4.30 and a singlet at 5.70 which is

a good indication of structure (84) since (85) shows similar resonances

at 4.03 ppm, 3.06 and 5.52. It should be noted that the resonances at


C34.30 6 5.08
iC4.03 I4.3O
MeO OMe H CH
++ +3+
-Fp 5.52 Fp 5.70 Fp Fp

H e- 6 3.06 e6 4.3 6 3.75 H


85 84 86 87


3.06 ppm in (85) and 4.30 ppm in (84) are somewhat different, but this

difference is not unexpected since alkyl substitution in (86) vs. the

parent complex (87)42 causes a comparable difference in the chemical

shifts of the protons.

The second proposed reaction is protonation of the methoxy group
*
to give the allyl cation (33) which abstracts a hydride to generate






* Possible hydride donors include Et20, CH30H (unlikely) or starting
material.




37



Scheme 2


OMe


B" F4


HBF,


33
H


83b 83a


Fp

84
Nal acetone

0


Fp


89a


Q- Fp
88


QFp


89b

I


NaI/ 90
acetone


OMe







the sigma complex (88). This, in turn, could react with any acid
present to give the carbocyclic carbene (89) which should rearrange
to the 7-complex (90). This is reasonable since Casey and co-workers43
recently found that treatment of (91) with HBF4*Et20 gave the i-complex


Fp


- ~- O 92

Fp =


L(Fp-- P(OMe)3


94

(92), via the carbene (93). The latter was trapped with P(OMe)3to give
(94). Further evidence for the proposed conversion of (88) to (90) was
obtained by treating the carbocyclic sigma complex (95) with HBF4.Et20,


*Fp


Et20 -78

HBF4.Et20


0C


Fp-


H


So-Fp







at -780C, to afford (96) in a 96% yield. Evidence for a carbene
intermediate (97) was obtained by protonation of (95) in the presence
of P(OMe)3 which led to the isolation of (98). Finally, further proof




SFp Fp
+ .]

H+ ) K Fp P(OMe)3


95 97 98


for the formation of (90) comes from the fact that the H NMR spectrum
(Figure 3) reveals a singlet at 6 5.80 (Cp) which can be overlapped
with the known carbocyclic r-complex (90) as seen in Figure 4.
As mentioned above, treatment of (84) and (90) with excess
Nal in d6-acetone should release the corresponding carbocyclic
compounds (99) and (81), respectively. Although it seems unlikely


OMe OMe
Fp+ Fp+ Nal


84 90 99 81

that (99) could result from reaction with I- to generate
(80), it is feasible that in the presence of Fpl this
could be possible. Further proof of this can been seen in





















































0)
*
mu



0

I
'.0
O







01
01l|





E
O'










C.)
a2


*!-
0.
U)




-- '



a)






*
L
3:
r-
-<0
*
*a-






S-(



01
f '















Ia
acetone


the treatment of the known r-complex (86)44awith excess Nal in

d6-acetone to give Fpl and acetaldehyde.44b


+ OMe

Fp--


Nal
acetone


Fpl + CH3CHO


Regardless of the mechanism of formation of these products the

desired allene complex (35) was not observed although some reaction

appeared to be taking place on the double bond. Therefore, a search

for a methoxy abstractor which would not react with the double bond

was conducted.

Recently Brookhart and Tucker45 reported that treatment of (100)

with trimethylsilyl trifluoromethanesulfone, Me3SiOS02CF3, (101)

afforded the carbene complex (102) by simple methoxy abstraction.











OMe -

Fp '-(H Me3SiOSO2CF3 F
Me Me

100 102





Accordingly, (72) was treated with Me3SiOSO2CF3 at -780C to give an

immediate precipitation which when warmed to room temperature followed

by removal of the solvent afforded a brownish oil (Figure 5). When ex-

cess Nal was added to a d6-acetone solution of this oil an immediate

color change, brown to purple, occurred (Figure 6). Work-up afforded

FpI, cycloheptene (81), 1,3-cycloheptadiene (82) and trace amounts of

cycloheptanone (80) by GC/MS. A possible mechanism for formation of

these products is seen in Scheme 3.

In this scheme addition of Me3SiOSO2CF3 gives the allyl cation

(33) which could rearrange to (90) as the solution is warmed as seen

in Scheme 2. In a competing reaction (33) could lose H+ to give (103).

This in turn could then react with H+ to give the more stable carbene







* The Fp may not be able to assist in the loss of the methoxy group
because this would force the leaving group into the center of the
ring system.


























*


Cl
0
E 4-




C/)
C"
a)

0
0












S-
r-








(-
a-
0





K-








- S -











E

U
.|
"0
-^










.E
4-

<(-
03







44

















E
L
-0




L







4-
0




-o

0
























4-3
c)



L-
3
S-
U




o





e-




o
-o






S r"
(0 o










S.--






O

r-

L.-
^^^. \ -N
^^^ S U
-^^^^ /* -

\ \









{ ^~
} C.
1 0
\ ~ ^
\ "0
--* -0








Scheme 3


OMe


Fp

Me3SiOSO2CF3

-H


104b


89b 89a


105

NaIacetone


90

Nal acetone


104a








complex (104) followed by rearrangement to give (105). Here again reac-

tion of (90) and (105) with Nal should give FpI, cycloheptene (81) and

1,3-cycloheptadiene (82), as observed.
Since the treatment of (72) with Me3SiOSO2CF3 did not give rise to
any cycloheptanone (80) or any organic compounds with oxygen present,

it appears that indeed the methoxy was clearly abstracted. The crucial

questions are whether the precursor to (90) and (105) is the allyl

cation (33) or the allene complex (35) and the structure of the pre-
cipitate initially formed. To address the latter, we undertook a low
temperature 1H NMR study of this material.

To prepare for this study, a search for suitable models revealed

that Olah and Liang46 had reported the preparation and properties of

(106a-c) in superacid. It was found that in the 1H NMR spectrum, the



2
3 R R


R
106(a-c) a=H b=CH3 c=C1


parent cation (106a) showed a doublet at 10.18 ppm (H1 + H3) and a

triplet at 8.34 (H2). Substituted allyl cations show vinyl resonances
slightly upfield from these values as seen in Table 4.
Foxman and co-workers22 reported the synthesis of (23) as a stable

crystalline solid whose 1H NMR revealed resonance at 4.45 ppm (H1),
6.50 (H3) and 5.80 (Cp), which we used as a model for the allene
complex (35).





47






Table 4. 1H NMR resonances for (106a-c)


R H1 H2 H3


a) H 6 10.18 6 8.34 6 10.18

b) Me 6 8.05 6 9.50


c) Cl 6 8.05 6 9.58





48









H Fp H






23



From these models clearly the carbocyclic allene complex (35) or

the carbocyclic allyl cation (33) should have very different and

characteristic H NMR spectra which should make it easy to distinguish

between them. A CD2C12 solution of the methoxy complex (72) was treated

with a slight excess of Me3SiOSO2CF3 at -780C in an NMR tube and the 1H

NMR spectrum recorded. This revealed a singlet at 5.70 ppm (Cp) and

two multiplets at 6.50 (H3) and 4.2 (H1) (Figure 7 ) which corresponds



+
Fp 2 Fp 2






35 23


* No resonances were observed from 7 to 15 ppm and 0 to -13 ppm.






49











c,
*r-






E
o
4-
4*r


0 C,
S-'-




fO
U



0
o -
4- C)








< 0
=_
U-
(-.)







-CD
U
0)0
C) 4-'




\ -4



z -
o
0r-







LL


I


C3
a0

0
oa








closely with (23) (Figure 8) as reported by Foxman and co-workers.22
Further evidence for the allene structure (35) would be the observation
of fluxional behavior22'47 as the temperature is changed. And indeed,
as the sample was slowly warmed from 00C to 400C, a coalescence of the
multiplets at 6.5 ppm (H3) and 4.2 ppm (H1) was observed (Figure 9)
occurring somewhere between 200 and 400C. After the sample was warmed
to 400C, it could be cooled back to 00C to reveal the multiplets at 6.5
ppm and 4.2 again. -As expected from earlier work, if the sample is
kept at room temperature in solution it slowly decomposes.
A characteristic property of Fp acyclic allene complexes is their
reactions with nucleophiles such as alcohols. We therefore decided to
examine the reaction of (35) with ethanol. Interest in nucleophilic
reactions with acyclic Fp allenes ran rather high about 10 years ago.
Lichtenberg and Wojcicki48 reported that treatment of (107) with most




+
Fp




R


107




* (35) Is stable for at least two hours at 0OC.





































*3



0.
E


tO


E
O
O
4->








0
CO




*r,

v


0
*c



4-
o

E



U

S J







'-4




5-


s-
























































o 0 0
m *r*


- c

'4-
0
L0
o




*r-





4-o
1-
S 0
r





CLI
S-




,-
r-
-^ f





:
e -
-1
0u
i-l
*r
CT
I
t "
01
L)_


j-J3







*
nucleophiles afforded attack at the terminal carbon with migration of

the metal to the central carbon. One exception was MeO- which prefer-

entially or exclusively attacks at the central carbon (Figure 10).

We found that the reaction of (72) was Me3SiOSO2CF3 at -78C

followed by the addition of a cold (00C) mixture of EtOH/Na2CO3

afforded (108)t in a 54% yield. To prove the structure assigned to

(108) an alternate synthesis was accomplished as seen in Scheme 4.


Me3SiOSO2CF3
Me3SiOSO^CF3


Fp Fp


or C


* Non completed allenes are inert to attack by nucleophiles.

( Addition of the alcohol either two minutes or 2.5 hours after the
initial addition gave the same product.

t This result is not only consistent with addition to the allene
complex but possibly to the allyl cation complex too.


EtOH
~-4


108















Fp R
+PPh3

R=Me
(40%)


R
Fp R
CH
3


R=Ph (40%)


acetone \Ph3


F



R I1
107


HN(Et),


OMe MeOH


jr


N(Et)2

R=Me (47%)

R=Ph (49%)


.-CR
Fp /
\---OMe
R=Ph (25%)

Fp-CH2-C-CH2R
0
R=Me (42%)
R=Ph (35%)


Figure 10. The addition of Nu- to (107).










Scheme 4


Ag
EtOH


1) n-BuLi
2) Co2


1U9


OEt


COC1


Fp
THF


hv
acetone


108


OEt


111


Br
Br








In this sequence, treatment of (40a) with AgNO3 in EtOH gave (109)

in a 75% yield. Treatment of (109) with n-BuLi at -780C followed by

addition of CO2 and acid work-up gave (110) in a 65% yield. To the

acid (110) was added SOC12 in benzene to give the acid chloride (111).

Addition of the acid chloride (111) to a suspension of Fp anion in THF

at -780C gave the desired acyl complex (112). The acyl complex (112)

was photolyzed for 2 hours at 00C in acetone to give (108) as a brown-

ish, air-sensitive oil, 28% from the acid chloride. The 1H NMR spectrum

of (108) is given in Figure 11, which is identical with that obtained

from the allene complex.

Up to this point, evidence for the carbocyclic allene structure

(35) has been based on the crude 1H NMR, the observation of its flux-

ional behavior and its reaction with EtOH. It would be desirable to

release the allene ligand and detect it as its dimer (113). A solution









113



of (72) in CD2C12 was therefore treated with Me3SiOSO2CF3 followed by

the addition of Me4N I-, which is soluble in CH2C12. Although Fpl was
formed the dimer (113) was not observed.

On searching the literature it was found that this result is not

inconsistent with the allene structure because Lichtenberg and

Wojcicki49 found that treatment of (107) with +NR41- gave Fpl as the





























E



r-
















m
-.
*
0












E
5-3
C-



0








r-
-o









-4
C r

U
Q-













3
i-hLL









major product; however no free allene was observed. An unstable

material (114) was characterized by IR which was believed to


4- Fp



R


-Na
Nal


107


R

Fp
\I


S Fpl + ?


114


*
spontaneously decompose to Fpl and a tarrish material at room tem-

perature. It has also been reported that (14) was released from (23)

with Fp anion.22 We therefore treated (35) with Fp anion in THF at

-780C but again no trace of the dimer (113) could be detected even

though Fp2 was isolated.



+


THF
Fp
FP"


+ Fp2


* A similar decomposition has been noted by Lukas and co-workers50 for
a Pt complex.








Since our attempts to release the carbocyclic allene were un-

successful, an attempt to isolate and further characterize the carbo-

cyclic allene complex (35) was next approached.

One of the major problems isolating (35) was its instability in

solution at room temperature; however, if the solution was kept at 00C

the allene complex seemed to be somewhat stable for at least two hours.

Therefore, after the initial generation of (35) at -780C the reaction

mixture was warmed to 00C at which time the solvent was removed in

vacuo. This afforded a tan solid (71%) which gave the 1H NMR spectrum

shown in Figure 12. This material,which is believed to be the allene

complex (35), appears to be stable indefinitely in the solid phase at

-780C under a N2 atmosphere; in fact it was sufficiently stable to

obtain a correct C,H analysis.

To further prove that indeed the new complex (35) had the allene

structure a 13C NMR spectrum (Figure 13) was taken at -200C. In this

spectrum the resonance for the allene carbons C1-C3 appeared at 150 ppm

(C2), 125.8 (C3) and 43.6 (C1). These compare quite well with the
resonances for the 1,2-cyclononadiene complex (23) which shows similar

resonances for carbons (C1-C3) at 148.5 ppm (C2), 122.3 (C3) and 51.3

(C1) as seen in Figure 14. This is strong evidence for the structural
similarity of complex (23) and (35).


+ Fp 2
Fp 2 1


1 3


35 23







60




























0
C:)
u
o














0
o

























E
I
4-)










C
r





94-















N
0
-4
tU





























L Ia
------ \ --- ar
01
i- I I

Ll












































0
o
0
CM
I




O
0











4-
0






E
0



CL
4,n
a_





v,
0

-







a-
C1
L
i-
cr)
e


E














































































E
E.

001

(C(1


cc
4-
0



1.-
CL









4-
0













C:--
0













S.
r-1
(0














C)
0












-r
L4-

Q.
VI







z:




63



In both cases the upfield shift of the C1 and C2 carbons as

compared with uncomplexed allenes suggests significant metallocyclo-

propyl character as depicted in (115) and (116). Furthermore, in



+






115 116


(35) the C1 resonance is ca. 8 ppm upfield from the C1 resonance in

(23) which indicates slightly more cyclopropyl character. This is

not surprising since the geometrical constraints opposing incorpora-

tion of the cyclopropyl ring in a structure such as (118) are less


118


than for a double bond as in (16). This relief of strain can be seen

best in the fact that (118)12,51,52 can be isolated whereas the more

strained allene (16) has been generated at low temperatures, but has

not been observed as the free molecule.17













Fp




35



At this point since the pure carbocyclic allene complex (35) was

in hand a more detailed examination of its fluxional behavior was

attempted. As discussed earlier the low temperature, at -39C, 1H NMR

spectrum of (35) exhibits two multiplets at 6.55 ppm (Ha) and 4.45

(Hb). As the temperature was raised the point of coalescence was ob-

served at 290C as seen in Figure 15. Here exchange of Ha and Hb became

rapid on the NMR time scale. Using Equation 1,53 the free energy of

activation (AGt) was obtained. In this equation, Tc represents the



AGt = R Tc(loge Tc/6v + 22.96)

Equation 1



temperature of coalescence and Sv is the distance between Hb and Ha in

Hz. The barrier for interconversion of isomeric allene complexes

(35a 35b) was calculated to be 13.9 0.2 kcal/mole with 6v equal to

215.6 Hz at -78C. This result corresponds to the activation barrier
















au p
E oO 0
I m m fcW a n Co 0)
I C C'3CUCUCU t- m


E

IL
"0


U.
a-







o



rQ

CV
-W




N-
N
S5


















35a 35b

of known acyclic allenes22 of 23.1, 18.0 and 16.3 kcal/mole for (107a),

(119) and (120), respectively.


Fp
107a


Fp
119



Fp+


Fp+



Fp+




Fp


120
Further support for the structure of (35) comes from an extremely

useful NMR technique known as spin saturation transfer,54-57 an NMR


Fp +

Ha


35a








technique which can be applied to systems that are in rapid equili-

brium. Since Ha and Hb havedifferent chemical shifts (6 6.50 and 4.45,

respectively; Figure 12) then either Ha or Hb could be specifically

saturated by applying a strong rf field at the appropriate frequency.

If the exchange rate between Ha and Hb is comparable to the relaxation

rate at both sites, then complete saturation of one resonance will

result in partial or complete saturation of the other resonance. If

the exchange process becomes sufficiently slow at low temperatures, then

saturation at Hb (or Ha) should result in no apparent saturation of Ha

(or Hb) since the relaxation process should take place before exchange

occurs. Conversely, if the exchange process is rapid at higher tempera-

tures then saturation of Hb should result in partial or complete satura-

tion of Ha since the relaxation process does not take place before ex-

change occurs.

Accordingly, the 1H NMR spectrum of (35) reveals a multiple at

6 6.55 (Ha) and 4.45 (Hb) as seen in Figure 16a. When a strong rf field

was applied at Ha (6 6.55 at -20C) the exchange process between Hb and

Ha apparently takes place without relaxation occurring in the transfer

process (Figure 16b) because the intensity of Hb was observed to de-

crease. However, at -60C the exchange process is significantly slower

than relaxation so complete relaxation occurs before exchange, Hb to Ha.

As a result, the intensity of Hb did not diminish when Ha was saturated.

At -400C, saturation of Ha results in partial saturation of Hb,(Figure

17b) thus resulting in an exchange process somewhat slower than that at

-200C.(Figure 16b) but faster than the exchange at -600C,(Figure 17c).

This is feasible for (35) since one would expect at high temperatures

(in this case -200C) a fast [1,2]Fp shift allowing Ha and Hb to exchange







68


















E








c o


o
0
CC 4-
-.0
0O


4-)















o-
O


0






uS



CL
C ,-








-^v ---.- 35- l-










to4-
*-
-0~











o 0
0 CJ













-1
oc











ru -
LL.






69



















*r-






0
L.


r-)


0I
0
Cl
-4J 4--

) U




r'- Ct



4-
O





C-

00 0


0




o
C -
OL
o r-








e-4
CI


















/ i .-
J -^ j |


\ ^\ -f3 i
m :1:--
'r ^s,
10 *i
4-

*I

*s *g
"' ? ^


u ja 1








whereas at lower temperatures the exchange is slowed down so that the

exchange between Hb and Ha is shown according to the NMR time scale.
At this point, we decided to reexamine some unanswered questions.

As mentioned before, addition of Nal to a crude reaction mixture of

(35) did not give the dimer (113) although Fpl was generated. Since the
allene complex (35) could now be obtained as a pure solid we decided to
reexamine this reaction.
A sample of the solid allene complex (35) was dissolved in a solu-

tion of Nal in d6-acetone at -78C. This mixture was then allowed to
stir for 2 hours at -780C followed by 4 hours at room temperature. An

examination of the 1H NMR spectrum (Figure 18) again revealed the pre-

sence of Fpl. A closer examination of Figure 18 also reveals the pre-
sence of cycloheptene (81) and cycloheptadiene (82). Analysis of the
mixture showed the amounts of (81) and (82) to be 20% and 49%,

respectively. From this result we conclude that the complex rearranges

to the corresponding r-complexes (90) and (105) faster than the allene
is released. The i-complexes then immediately react with Nal to give

the observed olefins (81) and (82).
In an attempt to determine if the precursor to the observed U-

complexes (90) and (105) is the allyl cation (33), we decided to see if
the addition of Ph3CH, a good hydride donor, would change the relative
amounts of (81) and (83). An excess amount of Ph3CHwas therefore added
to a solution of (35) in CH2C12 at -78C followed by warming for 3 hours
at room temperature. This gave a brownish oil after the removal of the

solvent in vacuo. The 1H NMR spectrum of this oil is seen in Figure 19.
Addition of Nal (Figure 20) followed by work-up gave Fpl, cycloheptene
(34%) and cycloheptadiene (51%). Decomposition under identical


























s-

4 -)



-o -E
=I-


a0


-- E
0
0
o



C

S.-
(o
















4-





O
c







a)
u





























cu
*r
































--I



a-





LL
s-






















u-






























E E
-o


0
--








-w
4-
0
s0



0

S--














4->
L) 0
C


O-
C






00






S-







K. LI
0






QW


tO 2







73





























E V



o
S-.



0






O

*r-



r(-










4-
S0




















-o
CU





























-r-
4-














*- I4
^^-^S:^ '' .ol
^\ ~ m S

1 \ n e

____ ^----- Ic
----------- i- r -

'^^--^








conditions in the absence of Ph3CH gave 1,3-cycloheptadiene (40%) and

a trace amount of cycloheptene, from this it appears that the presence

of a hydride donor increases the yield of cycloheptene (81) suggesting

that indeed the cycloheptene originates from a hydride abstraction

reaction.

The stability of the allene complex (35) is also of some import-

ance. While it was found that the complex (35) is stable under a N2

atmosphere as a solid at -780C for at least 6 weeks, exposure to the

air at ambient temperatures for 30 minutes affords a brownish oil.

The 1H NMR spectrum (Figure 21) of this oil in d6-acetone reveals a new

Cp resonance at 5.7 ppm. Furthermore, addition of Nal to this solution

followed by work-up afforded Fpl, 83% of cycloheptanone (80) and trace

amounts of cycloheptene (81) and 1,3-cycloheptadiene (82) by GC/MS.

One possible mechanism to rationalize this product is shown in

Scheme 5.

In this scheme the allene complex (35) reacts with H20 in the air

to afford the sigma complex (121) which can further react with H+ to

generate the carbocyclic carbene (122). This could then rearrange to

give the i-complex (123). Although formation of r-complexes of vinyl

alcohols58-60 are known, i.e. (124), it has not been reported whether




H H
H OH
Fp+

124
































E 4-





O
0


Q.
X





E

4-

u,


0

S-



S-
U
'-
O








oD




4--
0

ES-




LO
C4,)
U c
w -C

vu

-e0











-r> .OT
u.




76


Scheme 5


+ Fp


H 20


121


1


122a


122b


123


Nal acetone


0







or not Nal would release the n-complex to give the aldehyde or ketone.
Since the vinyl ether complex (86) is released by I- one would expect
the same to occur here.
Since it is clear that the carbocyclic allene complex (35) has
been generated we decided to explore whether or not the carbocyclic
allene complex (125) could be prepared. Therefore, the synthesis of the


+
Fp




125



sigma complex (126) was undertaken. The approach here is similar to
the approach used in the synthesis of (72) and is shown in Scheme 6.
6-Methoxy-l-bromocyclohexene (127) was prepared by the treatment


1) NaH/THF 00C
2) Mel 00C


OMe

$ Br


of (128) with NaH followed by Mel. Treatment of (127) with n-BuLi at
-780C followed by addition of CO2 and acid work-up gave the acid (129)


OH
IBr




128














OMe
$ Br


OH





128

OMe
COCI


126


Scheme 6


127

OMe


129

OMe


131












OMe
2 Br




127


1) n-BuLi THF -78C

21 CO- -780C


OMe
CO2H


129


in a 33% yield.


The acid (129) was then treated with SOC12 in benzene


OMe
C0O2H




129


to give the acid chloride (130). Addition of the acid chloride (130)


OMe


-780C THF


130


OMe
[0 COFp




131


benzene
A SOC12


OMe


- 0 COCi









to a suspension of Fp anion in THF at -78C gave an 8% yield of the

desired acyl complex (131) as an air-sensitive, brownish oil. The 1H

NMR spectrum of (131) is given in Figure 22. Photodecarbonylation of




OMe OMe
COFp Fp
hv 00C
acetone


131 126




(131) in d6- acetone at 00C gave an air-sensitive, brown oil (126) in a

70% yield. The 1H NMR spectrum of (126) is given in Figure 23.

Now with (126) in hand the question of whether or not it would

behave similarly to the reaction of (72) with Me SiOSO2CF3 remained to

be answered.

Here it was found that treatment of (126) with Me3SiOSO2CF3 at

-780C followed by warming to room temperature afforded a brownish oil

(Figure 24) after removal of the solvent in vacuo. When Nal was added

to a d6-acetone solution of this oil an immediate color change, brown

to purple, occurred. Work-up afforded Fpl, 30% of cyclohexene (132)

and 10% of 1,3-cyclohexadiene (133). A possible mechanism for forma-

tion of these products, which is similar to the C7 manifold, is seen

in Scheme 7.

In this mechanism addition of Me3SiOSO2CF3 to (126) gives the

allyl cation (134) which immediately hydride abstracts and rearranges

to the ir-complexes (96) and (137) via the same intermediate as seen in

the C7 manifold.






81



















E

C
0













T"





















E
cu





"L
< o-




L)

Q1
0
\1





tJ



'-
3
r-
LaI



























E
n.

-o















a

c






u-l
t 0




o



cv

Q.




I-



0)
r-i








o"
LL






83


























S0





t.-
-c







4-




Uc
S.u

o
---------- -- -- -C 4- -












C.) 0




I w-









--


L .-




84

Scheme 7


OMe
Fp Fp
Me 3Me3SiOSO2CF3
126 134


\-H +


aFp


135a 135b
I


136a
-1


a3Fp
136b


;Fp
96
Na acetone


0


Fp
137
NaI acetone


0


132


133








A further examination of the 1H NMR spectrum (Figure 24) reveals
resonances at 6 5.7 (Cp) and 5.45 (CH=CH) which is a good indication
of structure (96) since the resonances overlap with the known T-complex
(96) (Figure 25). The ir-complex (137) was not isolated; however, as
mentioned above addition of Nal to the reaction mixture (Figure 24)
afforded Fpl, cyclohexene, and 1,3-cyclohexadiene which is consistent
with previous work.
Although the products obtained here were similar to the products
obtained by the treatment of (72) with Me3SiOSO2CF3, we decided to see
if addition of Me3SiOSO2CF3 to (126) followed by addition of EtOH/Na2CO3


OMe
Fp
I


126


OEt


1) Me3SiOSO2CF3 -780C
2) EtOH/Na2CO3 -78C


138


would generate (138). In this case, and unlike (72), addition of
Me3SiOS2CF3 to (126) did not give (138) but rather (95) in a 15% yield.


1) Me3SiOSO2CF3 -780C

2) EtOH/Na2CO3 -78C


H
FP


126






86



















E

i o k





S -o -o -- O *- -. -

~-






-.,- (,









- ... ..
-- .. E I







-g_-.-- s------------------------- w





--a)
*1








This is, of course, the proposed cyclohexene precursor in Scheme 7.

From this result it would appear that in the six member ring (126)

very rapidly gives (95) which is protonated in a slow reaction. Thus,

addition of base stopped the reaction at this point. To further prove

the structure (95) an alternate synthesis was accomplished as seen

below:




COC1 COFp Fp

Fp THF hv O C
-780C acetone


139 140 95



Addition of the acid chloride (139) to a suspension of Fp anion

at -780C gave the acyl complex (140) in a 69% yield. The acyl complex

(140) was then photolyzed for 2.5 hours at 00C in d6-acetone to give a

yellow, air-sensitive solid (95) in a 97% yield, which is consistent

with the above work.

From these experiments it would appear that the allyl cation (134)

is generated; however, if it rearranges to the allene complex (125) as

seen in the C7 manifold, the latter must very rapidly convert back to

the cation to give the observed products.

In conclusion, the characterization and synthesis of the seven

membered carbocyclic allene complex (35) has been described within this

work. Further, it appears that this allene complex rather readily

converts to the cation to give the carbocation products. As expected if