Iron clusters containing the trifluoromethyl isocyanide ligand

17

I7 IRON CLUSTERS CONTAINING THE TRIFLUOROMETHYL ISOCYANIDE LIGAND

Dieter Lentz* and Robert Marschall Institut fiir Anorganische and Analytische Chemie der Freien Universitgt Berlin, Fabeckstr. 34 - 36, D-1000 Berlin 33 (F.R.G.)

Dodecacarbonyltriiron undergoes

rapid

Fe3 (CO)

posseses

a highly

of the

fluxional

carbonyl

bridging

trifluoromethyl

and becomes the carbon

completely

assignment atoms

is

even

which

at -150

from Fe3(CO)iz isocyanide

rigid

of the

molecule,

ligands

(CNCF3 ) , which can be prepared

I I

Nevertheless carbonyl

exchange

a rigid

temperature

is

on the

13C nmr resonances

OC [ll.

and CNCF3, however,

ligand

nmr time

in solution

even at ambient

scale

of the

at -100 eleven

OC f21.

different

ambiguous. CHzClz/CH3CN

Fe3 (CO)llL

+

(CH3)3NO

* Fe3 (CO) 10 (CH3CN)L

Fe3 (CO) 1 o (CH3CN)L + CNCF3

L = P(CH3)3,

+ Fe3 (Co)10 (CNCF3)L

P(OCH3)3,

P(C3Haj3,

heptane Fe3 (CO) 10 (CNCF3

reflux

-2 CO * Fe3 (CO) 8 (~3 -qz-CNCF3

)L + r.

To facilitate phosphite

CN-t-&H3

the

substituted

t.

+

assignment derivatives

of the

variable mechanism

temperature of the

been

nmr spectra

ligands

will

carbonyl

have been

Fe3 (CO) 1 D (CNCF3 ) P (CR3) 3 , two isomers Fe3 (CO)8 (CNCF3)P(OCH3)3 have

1L

2 CO resonances

synthesized.

phosphine

and

The structures

of

of Per (CO) I o (CNCF3 1P (OCH3) 3, and

investigated of the

by X-ray

compounds

crystallography.

and possible

migration

be discussed.

1 F. A. Cotton and D. L. Hunter, Inora. Chim. Acta, 11, L9 (1974). 2 I. Brtidgam, H. Hartl, and D. Lentz, mIlaturfocsch., 39b, 721 (1984); D. Lentz, Z. Naturforrch., Ilb, (1988) 839.

The