Chemistry of vinylidene complexes. 6. Electrochemical reduction and UV spectra of vinylidene derivatives of cymantrene and complexes with an Mn-Pt bond

1. A comparative polarographic study of the phenylvinylidene compounds Cp(CO)2Mn=C= CHPh (I), Cp2(CO)4Mn2(Μ-C=CHPh) (II), and Cp (CO)2MnPt (Μ-CHPh)LL' (III–IX), where L and L′ may be P(OR)3 or CO, has shown that the coordination of the Mn=C bond to a second metal atom results in transposition of the electrophilic center from the α-C atom of the vinylidene group in I to the Mn atoms in II and the Pt atom in III–IX. 2. A correlation between the potential for the electrochemical reduction of the complexes Cp(CO)2MnPt(Μ-C=CHPh)LL' and the energy of the σ → σ* transition of the metal-metal bond in their UV spectra has been established. 3. The attachment of the donor substituents L and L′ to the Pt atoms in compounds III–IX results in an increase in the strength of the Mn-Pt bond. The donor interaction between the Pt atom and the semibridging carbonyl group causes the opposite effect.