478
Organometallics 1985, 4, 478-485
and preparation and study of complexes with the Costa model containing CH2C(CH3)(C02C2H5)2 may elucidate the relative importance of steric and electronic contributions to instability. It is also possible that, during the catalysis, the organic intermediates do not form a direct Co to C b0nd.l Alternatively, a bond between Co and a secondary or tertiary carbon in the alkyl could provide the strain necessary to drive a carbon skeleton rearrangement. Increased strain was observed, as discussed above, in going from PPh3(DH)2(i-C3H7)to PPh3Co(DH)2(2-C4HS). The CH2C(CH3)(C02C2H6)2 ligandmtS2is interesting in that it is a bulky alkyl with electron-withholding substituents. The structural consequences of this have been mentioned above. The Co-P bond length in 3 is anomalouslv lone: and may reflect the steric bulk of the alkyl. Sterk intiractions -may be-made more serious by
