Formation of palladium- and platinum-substituted fulvenes by activation ofa cyclopentadienyl or indenyl ligand

The stepwise, low-temperature reaction of {Pd[CH(SiMe3)(2)](mu-Cl)(PMe3)}(2 )(1) with CNBu-t and NaCp' (Cp' = C5H5, C5H4Me) or LiInd (Ind = C9H7) affor ds metal-substituted fulvenes of composition Pd[C(NHBu-t)=C(C4H3R)][CH(SiMe 3)(2)](CNBu-t)(PMe3) (R = H, Me) and Pd[C(NHBu-t)=C(C8H6)][CH(SiMe3)(2)](CN Bu-t)(PMe3), of which the C5H4Me-derived complex 5a has been characterized by X-ray crystallography. The mononuclear species Pd[CH(SiMe3)(2)]Cl(CNBu-t )(PMe3) (2) has been isolated as an intermediate of this reaction. An alter native synthesis of the palladabenzofulvene complex 6 involves the reaction of the 16 electron indenyl derivative (eta(3)-Ind)Pd[CH(SiMe3)(2)](PMe3) ( 7) with 2 equiv of CNBu-t. In this case an eta(1)-indenyl intermediate of c omposition (eta(1)-Ind)Pd[CH(SiMe3)(2)](CNBu-t)(PMe3) (8) can be observed b y low-temperature NMR spectroscopy. The complex Pt[CH(SiMe3)(2)]Cl(CNBu-t)( PMe3) (12) has been synthesized by the comproportionation reaction of Pt[CH (SiMe3)(2)]Cl(PMe3)(2) (10) and Pt[CH(SiMe3)(2)]Cl(CNBu-t)(2) (11), in the presence of catalytic amounts of CNBu-t. Complex 12 reacts with CNBu-t and NaCp to give first the cationic species {Pt[CH(SiMe3)(2)](CNBu-t)(2)(PMe3)} Cl (13) and then a mixture of platinafulvene isomers related to the above-m entioned Pd complexes. The fluxionality of these metallafulvene derivatives and the mechanism of their formation are discussed.