A transition metal-catalyzed dimerization of norbornadiene

TetrahedronLcattersNo. 11, pp. 368-372, 1961. Pergamon Press Ltd. Printed in Great Britain.

A TRANSITIONMETAL-CATALYZEDDIMBRIZATION OF NORBORNADIENE David hi.Lemal and Kyung S. Shim Departmentof Chemistry,University of Wisconsin Madison 6, Wisconsin (Received2 June 1961)

IRRADIATIONwith a sunlamp of a mixture of iron pentacarbonyland norbornadiene leads to a complex mixture of products includingthe tricarbonyliron complex of the diene, a number of ketones, and unsaturateddimers of

. the diene.' In addition to these we have found a saturateddimer to which we have assigned either of the novel structuresI or II. It should be

noted that several of the reaction products are formed in the absence of light,1,2 but we have been unable to obtain the saturateddimer by heating 1 R. Pettit, J.Amer.Chem.Soc,&l, 1266 (19591 3 L C.W. Bird, R.C. Cookson and J. Hudec, Chem. & Ind. 20 (1960). l

368

Dimerization

No.11 the reactants to yield

in the dark.

Irradiation

this compound,3 indicating

carbonyl are required

in t-butanol.

of norbornadiene alone also fails

that both light

saturated dimer was isolated

chromatography on alumina or silica

gel,

Calc.

and the iron penta-

(Found:

in 2-38 yield5

by sublimation

C, 91.03%; H, 9.00%; mol. wt.,

the melting 175, CryoscoPic

for CT4H16: C, 91.25%; H, 8.75%; mol. wt.,

In the mass spectrum, the relative

by

on both of which it was Only very

After further purification

point was 165-165.5’

369

for the dimerization. 4

Tne highly volatile

weakly adsorbed.

of norbornadiene

intensities

184.)6

of the peaks at 184, 185

and 186 agree within experimental error with the isotopic

distribution

Iv 3 Since this dimerization is successful even when performed In a soft glass vessel, it is apparent that the wavelength range of the effective radiation is outside of the region in which norbornadiene absorbs appreciably. See C.F. Wilcox, Jr., S. Winstein and W.G. McMillan, J.Amer.Chem.Soc. &, 5450 (1960). 4 Professor R.C. Cookson has kindly informed us that this dimer is

5 6

also formed by reaction of the diene with iron enneacarbonyl in the dark, so light is apparently required only for the transformation of the penta- to the enneacarbonyl. For the latter reaction, see R.K. Sheline and K.S. Pitzer, J.Amer.Chem,Soc. a, 1107 (1950). It is of interest that irradiation of a mixture of norbornadiene with its iron tricarbonyl complex does not yield the saturated dlmer. This yield is based upon the diene, which has been used as diluent as well as reactant, and hence in large molar excess (2.511).

Carbon-hydrogen analyses were performed by the Scandinavian Mlcrochemical Laboratory, Copenhagen, Denmark.

Dimerization

370 anticipated the

fact

t

for the that

any other

of norbornadiene

ion C H 14 16 ’

the parent

Consistent

peak at 184 is

with

several

No.11 a cagelike

times

structure

more intense

is

than

peak in the spectrum.

Evidence inertness

for

the saturated

to bromine

hydrogen

character

and potassium

over Adams’ catalyst

Moreover,

there

bond stretching

in the

infrared

spectrum

in the ultraviolet

permanganate

in acetic

is no absorption

of this

acid

and its

excludes

includes

failure

containing

corresponding spectrum,

molecule

to consume

perchloric

to carbon-carbon

and the

beyond doubt

lack

its

acid. double

of end absorption

the presence

of unsatur-

ation. Structures

III

two norbornadiene systems,

can

nuclei-

magnetic

carbon

tetrachloride 9.30,

spectrum

range

absorption),

derivatives

The most cogent

simple,

of the

3.49,

stretching spectrum

evidence&we

7.73,

8.10,

8.16,

and the Nujol

mull

7.62,

with

a highly

is no band in the

and nortricyclenes

a band characteristic

region. frequency

of cyclo-

More compelling

is the

below 3.37~~ and the

at higher

field

can adduce

for

and in

and IV, there

in which many tricyclenes nor is there

infrared

taken

consistent

to III

of

diene

The former

6.90, this

a fact

by the coupling

homoconjugated

165’ dimer.

Incidentally,

in the 9.8-l+

in the n.m.r.

of their

of the

With regard

(a region

sense

consideration

spectra

and 11.51~.

of a carbon-hydrogen absorption

termini

has maxima at 3.37,

10.51,

show prominen: propane

resonance

structure. ‘rl

in a formal

through

are both relatively

symmetrical 12.3-12.5

the

eliminated

‘be

proton

8.46,

and IV, derived

lack

absence of

than 8.2<.8 structures

I,

heptacyclo-

” L.J. Bellamy, The Infrared Soectra of Comolex Molecules pp. 17, 29, 30. John Wiley, New York (1959). 8 J.A. Pople, W.G. Schneider and H.J. Bernstein, Hiah Resol tio n Nuclear Maunetic Resonance pp. 236, 237. McGraw-Hill, New York (;959)& G.V.D. Tiers, Characte r is tic Nuclear Maanetic Resonance ‘Shieldinq Values’ for Hvdroaen in Oraanic Structures. Minnesota Mining and Manufacturing Company, St. Paul, Minnesota (1958).

Dimerization

No.11

(5 . 5 . 11.

of

norbornadiene

or II,

. 4r100.2~60.3~110.5~90.8~12)-tetradecane,

(7.4.1132’80.3’70.4~120.6’11010913)-tetradecane, resolution

n.m.r.

two sharp,

symmetrical

and methylene

peaks

protons,

is

3.1.

of

optimum resolution,

No fine

is

at 7.55xand

structure

is

8.21-c

discernible

whether

the

conceive

of

provided

by the high

corresponding

As expected,

respectively.8

heptacyclo-

at 60 mc the spectrum

In pyridine

spectrum.

371

peak under

be pyridine

of

to methine

the intensity

in either

solvent

consists

ratio conditions

or carbon

tetra-

chloride. It which

is

possible

are not

knowledge

all

it

rigorously

determination

II

that

a decision

molecule X-ray

(i.e.

unit

possess

cell

could

been successful

because

single

this

proved

I and II of

virtually

of

X-ray

demand that not

only

in I,

by

crystal

the probable all

our

improbable

be reached

might

distinguish

but to

highly

alone If

CUH16

symmetry lacking

them could

considerations symmetry.)

of

for

above,

only y&

through

The determination

elucidation.

as yet

group

structures

outlined

a center

between

space

of

studies

saturated

by the data

possesses

probable

a center

diffraction

structure not

of the

other

from norbornadiene

structure

was conceivable

examination

excluded

are derivable

Since

pathways.

to

the

to be the case,

through space

complete

group

the crystals

has

we have

9 examined have been twinned. The thermal this

substance

packed

of

the cagelike

in a stream

of

nitrogen

with Pyrex

the major of

stability

portion

the pyrolysis

helices of

the dimer

has been passed to

temperatures

has crystallized

comment. through

in excess

unchanged

Vapor of

a Pyrex of

tube

SOO’,

in the cooler

and part

tube.

In summary, the

s

and heated

dimer merits

low adsorbability,

high volatility,

relatively

high

9 L. deVries and S. Winstein, J.Amer.Chem.Soc. &, 5363 (15%0), have encountered similar problems with the birdcage hydrocarbon, crystals disordered.” of which are “highly

Dimerization

372 melting

point,

are indicative

chemical of its

and mass spectral distinction

inertness, cagelike

of norbornadiene and thermal

character.

No.11 of the 165’ dimer

stability

Infrared,

data powerful support structure

n.m.r.,

I or II,

ultraviolet, but permit no

between them.

- It is a pleasure for us to acknowledge the kind;. Seymour Meyerson of the American Oil Companywho measured the mass speb.trum of the 165O dimer and of Mr. Kenneth Kawano who determined the n.m.r. spectra. The X-ray photographs were taken by Professor Lawrence Dahl who, like Professor Peter Yates, has offered valuable suggestions. We are grateful also for financial assistance from the National Science Foundation.