A bicyclobutane-bridged diene irontricarbonyl complex. Synthesis, Ag⊛-catalyzed valence isomerisation and fluxional behaviour.

Tetrahedron Letters No. 27, pp 23e3 - 2386, 1976.

A BICYCMBUTANE-BRIDGED

DIENE

VALENCE

IRONTRICARBONYL

ISOmRISATION

Elzinga

J.

Department

Chemistry,

Groningen,

one-pot

synthesis'

makes

available

interestingfeature

functionalities,

catalyzed

of two interacting of reactions

in some cases,

reaction

methyl-o-xylylene. _

reaction

corresponding

Compound three complex

compound

concomitant

of -1 leads to a complex

to stabilize

from hexamethyl

(1). This highly _

-1 has been

reaction

(Dewar benzene)

strained

-viz. the butadiene

compound

possibly

the

and the bicyclobutane

of the bicyclobutane

mixture,

1,2,5,G-tetra-

possesses

shown to react at the butadiene

isomerisation

the diene

at the bicyclobutane

irontricarbonyl

(nitrogen

complex

atmosphere,

_2 in 40% yield

assignment at

2

-1 (5.0 gr, 31 mmoles)

days

The University,

part of the

fragment_

The Age-

via the intermediacy

of tetra-

2

We intended exclusive

BEHAVIOUR.

The Netherlands

2,6]hexane

with,

Ag@-CATALYZm

and H. Hogeveen

net~lyl-~,4-dimethylenetricyclo~3.1.0.0

molecule

SYNTHESIS,

in UK 12 May 1976; accepted for puhlioation 27 May 1976)

(Received

moieties. In a number

COMPLEX,

AND FLUXIONAL

of Organic

Zernikelaan,

A simple

Pergamon Press. Printed in Great Britain.

fragment.

of -1 in order

An obvious

in 800 mls benzene

Hanau high-pressure

(3,7 gr, 12 mololes) as an orange

to -2 is based

means

to open up the possibility to this end is to synthesize

of the

-2.

was irradiated Q-700

fragment

on the following

data:

correct

with a 2:l excess

Hg arc), yielding

oil b-p. 50°C/0.01 elemental

analysis

2060 and 1980 cm-I (Fe(C0)3), MS m/e 300 CM'), 272, 244, 216 (successive

2383

Fe(C0)5

during

the irontricarbonyl

mm Hg pressure. (H,C,Fe);

Structural

IR absorptions

loss of CO ligands);

PMR

(CCIq) 6 2.10

(d, J = 2.5 Hz, 2H), 1.58

is, 3H),

J = 2.5 HZ, 2H); CklR (CD2C12,'CS2 l:l, -89OC) 47.9,

44.7,

37.2, 7.9, 7.1, 2.5 ppm

of a new complex was obtained

with m-p.

in 60% yield

for two hours. (R,C,Fe);

-3

3

Structural

IR absorptions

loss of CO ligands);

PMR

moiety:

the precise

164.5-165.5OC

assignment

During

1980 cm

-1

(Fe(CO)3)

data:

(d,

116.7, 66.8,

of -2 yellow

crystals

The same compound

- on refluxing

on the following

2 in ethylbenzene

correct

elemental

analysis

; MS m/e 300 (Me), 272, 244, 216 (successive

from -2 by a thermal

of this valence

(basal CO's),

in the top of the column.

(d, J = 3.5 Hz, 2H), 2.03

1 is formed

(s, 6H), 0.40 ppm

distillation

to 40% hexamethylbenzene

(C6D6) 6 2.40

mechanism

sublimed

(s, 3H), 1.20

(apical CO), 210.9

to TMS).

to 2 is based

at 2050 and

(d, J = 3.5 HZ, 2H). Compound

6 216.5

(relative

- in addition

1.48

isomerisation

(s, 6~);

1.86

ring opening

(s, 611); -0.16 ppm

of the bicyclobutane

and the possible

role of the Fe-atom

are

unknown.

Treatment

of complex

three days at room temperature benzene following

-2

in CC14 solution

afforded

a reaction

4 (6%) _ Bulb to bulb distillation reaction

mechanism

accounts

in vacuum

with a catalytic

mixture

containing

afforded

for the formation

amount

-3 (9%1,

-4 as a yellow

of 4

(and -3).

(5moi %) of..AgClOq

during

4 (B5%) and hexamethyl-

oil in 70% yield.

The

5

-Ago

-Ho_

It should be pointed Fe(CO13 of

out that there

is no compelling

group in 4 are _ cis as indicated

_4 are based

on the following

data:

rather

correct

evidence

than trans. elemental

that the cyclopropyl

The remaining

analysis

structural

(H,C,Fe);

ring and the characteristics

IR absorptions

at 2080,

No.

27

2385

1’390 (Fe(CO)3) and 1640 cm -1 (C=C); MS m/e 300 (MO), 272, 244, 216 (successive (CC14) 6 5.03

PMR

(s, 3H), 1.17

(S, 3H), 1.10

(d, J = 3.0 Hz, 31.1,

(S, lH), 4.80

1H); CMR

(severely

distorted

6

we investigated

signals

interest

this process

(ratio 1:2) at d 216.5

start to line-broaden

d and q, 4H), 0.30 157.0,

122.2,

at higher

generated

spectra'

for various

By a least-squares

with

in complex

temperatures

values

CO

is associated

in the fluxional

(1 apical

6 212.8 ppm. The experimental. spectra

which

lH), 1.88

(d, J = 3.0 Hz, lH), 1.26

(d, J = 3.0 Hz, lH), 0.08 ppm

100.8, 99.8,

39.4,

34.8,

34.0, 31.9,

10.3, 9.8, 7.8 ppm_

complexes,

at

(d, J = 3.0 HZ,

(CDC13, 35O) 6 211.0,

In view of the recent

sharp

(5, IH), 2.06

loss of CO ligands);

rotation

CO) and 210.9 ppm

and coalesce

at various

k f 2k

diene-irontricarbonyl

CO

(2 basal

at about

temperatures

of the irontricarbonyl

fit of the Arrhenius-plot

of

2 by CMR line-broadening. -

of the rate constant

(basal)

8

behaviour

At about

CO's)

-20°C

-90°C two

are observed,

into one sharp

were compared

which

signal

with computer-

k of the interconversion

process

(apical)

group in -2.

(Figure) the activation

parameters

were

calculated

to

2306

30.

be Ea = 12.8 -+ 0.3 kcal/mole higher

and log A = 14.4 _ + 0.3. The energy

than that for butadiene

to rotation. complexes

We intend

in order

to extend

to other bi- and polycyclic

Drs. J.H. Wieringa

for assistance

3 kcal/mole

steric

diene

hindrance

irontricarbonyl

and W. Mellink

in obtaining

for recording

the computer-simulated

the CMR spectra

spectra.

and Notes.

l. H. Hogeveen

and P.W. Kwant,

2. H. Hogeveen

and W.F.J.

and E.P. Schudde,

manner

Tetrahedron

Huurdeman,

ibid.,

Sot., 98, 0000

3. The corresponding

products 5. Compare

(1976); R.F. Heldeweg

complex

metal

complexes

Huurdeman,

ibid.,

Lett.,

((!%N)2PdC12,

W.F.J.

Huurdeman

1975, 1517; J. Am.

unpublished

has been prepared

(1974).

results.

previously

in a different

1967, 2053. different

Rh2 (norbornadiene)2C121

are obtained.

6. a. L. Kruczynski b. C.G. Kreiter,

R.P. Henzel

and J. Takats, Sttier

S.

7. Computer-generated

spectra

and S.E. Wilson,

J. Am. Chem.

and L. Wackerle, were

obtained

J. Am. Chem. Sot., 94,

Sot., 96, 932

(1974);

J. Organomet.

Chem.,

on basis

of the NMREX-III

66, C49 -

7780

(1972).

(1974).

programme

by Dr. S. van der

by Dr. J. Runsink.

8. It has been pointed is likely

and H. Hogeveen,

and W.F.J.

Tetrahedron

39, 2624

1974, 1255; H. Hogeveen,

Lett.,

of the parent o-xylylene

e.g. L.A. Payuette,

adapted

1973, 3747; J. Org. Chem.,

1974, 4211; R.F. Heldeweg

transition

ratios

L&t.,

Tetrahedron

by W.R. Roth and J.D. Meier,

4. With different

Werf,

which may be due to an increased

these measurements

wish to thank

(XL-loo) and Dr. J. Runsink

Chem.

is about

to check this suggestion.

The authors

References

6a

irontricarbonyl,

of activation

27

to be more

out that actually complicated

the fluxional

(ref. 6).

process

in diene

irontricarbonyl

complexes