PREPARATION OF CATIONIC ETA-2-ALKENE AND ETA-2-ALKYNE COMPLEXES OF THE (ETA-5-C5H5)FE(CO)[P(OPH)3] SYSTEM AND REDUCTION OF THESE COMPLEXES TO SIGMA-ALKYL AND VINYL DERIVATIVES

New π-alkene and π-alkyne complexes of the type [η5-C5H5)Fe(CO) [P(OPh)3] (η2-un)] BF4 (un = unsaturated hydrocarbon) have been prepared in high yield from the reaction of (η5-C5H5)Fe(CO)[P(OPh)3]I and AgBF4 in CH2C12, followed by addition of 3 equiv of the alkene or alkyne. These complexes are much more stable in solution that the triphenylphosphine analogues reported previously. These new complexes can be reduced by hydride reagents to the corresponding alkyl and vinyl derivatives. The alkyl complexes in this system are very stable and do not thermally decompose by a β-elimination pathway. The sec-butyl complex formed from the hydride reduction of the cis-2-butene complex also shows no tendency to undergo alkyl isomerization on the metal to yield the n-butyl derivative. Thermal decomposition studies of the sec-butyl complex indicate that the diastereomer which forms preferentially is actually the less stable isomer. © 1979, American Chemical Society. All rights reserved.