KINETICS AND MECHANISM OF NUCLEOPHILIC SUBSTITUTIONS ON COORDINATED POLYENES AND POLYENYLS .1. REACTIONS OF TERTIARY PHOSPHINES WITH [RU(ETA(5)-C5H5)(ETA(4)-C5H4O)(L)]CF3SO3 (L=CH3CN, BENZONITRILE, THIOUREA, PYRIDINE)

Complexes of the type [Ru(eta(5)-C5H5)(eta(4)-C5H4O)(L)]CF3SO3 (L = CH 3CN (1a), benzonitrile (1b), pyridine (2), thiourea (3)) react with te rtiary phosphines to give either 1,1'- or 1,2-disubstituted ruthenocen es depending on the basicity of the entering phosphine and the nature of L. For 1a and 1b, only phosphines with a pK(a) value above 5 substi tute on the C5H5 ring while others substitute on the C5H4O ring. For c ompounds 2 and 3, the two rings are deactivated such that only the mos t basic phosphines react, and they attack only the C5H4O ring. In some cases of the reactions of 2 and 3, an intermediate is observed in whi ch the monodentate ligand has migrated to the C5H5 ring while the ente ring nucleophile coordinates to the metal center. The mechanism by whi ch phosphines attack a coordinated C5H4O ring has been established, an d detailed kinetic parameters have been obtained. For the reaction of 1a with PPh(3), PPh(2)Me, and P(p-PhOMe)(3) in acetone, the kinetics g ive a rate law indicating the reversible formation of an intermediate which goes irreversibly to the 1,2-disubstituted ruthenocene product. All three rate constants and their thermal activation parameters have been obtained for each of these reactions. For the P(p-PhOMe)(3) react ion, the volume of activation for each step has also been determined. The reaction of 2 and 3 with PBu(3)(n), PCy(3), PPhMe(2), and PMe(3) i n CD3CN give a long-lived intermediate which also goes to the 1,2-disu bstituted ruthenocene product. For the intermediates formed from 3, th e kinetics of this last step have been studied to determine the rate c onstants and their thermal activation parameters. In the case of PBu(3 )(n), the intermediate formed from 3 has been isolated and an X-ray st ructure determined, establishing that phosphine attack has occurred at the C5H4O ring.