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

Article abstract of DOI:10.1021/om9806500

The stepwise, low-temperature reaction of {Pd[CH(SiMe₃)₂](/≤-Cl)(PMe₃)}₂ (1) with CNBu-t and NaCp′ (Cp′ = C₅H₅, C₅H₄Me) or Lilnd (Ind = C₉H₇) affords metal-substituted fulvenes of composition Pd[C(NHBu-t)=C(C₄H₃R)][CH(SiMe₃) ₂](CNBu-t)(PMe₃) (R = H, Me) and Pd[C(NHBu-t)=C(C₈H₆)][CH(SiMe₃) ₂](CNBu-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 alternative synthesis of the palladabenzofulvene complex 6 involves the reaction of the 16 electron indenyl derivative (η³-Ind)Pd[CH(SiMe₃)₂](PMe₃) (7) with 2 equiv of CNBu-t In this case an η¹-ndenyl intermediate of composition (η¹-Ind)Pd[CH(SiMe³)²](CNBu-t)(PMe ₃) (8) can be observed by 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-mentioned Pd complexes. The fluxionality of these metallafulvene derivatives and the mechanism of their formation are discussed.