Reactivity of an early-late heterobimetallic complex toward phosphines: Synthesis, structure, and reactivity of a cationic tantalum-palladium compound with a free cyclopentadienyl counteranion

Article abstract of DOI:10.1021/om00035a005

Treatment of Cp₂Ta(CH₂)(CH₃) with CpPd-(C₃H₅) led to Cp₂Ta(μ-CH₂)₂PdCp(1). Reaction of 1 with 1 equiv of either PMe₃ or P(OMe)₃ in CH₂Cl₂ resulted in the formation of Cp₂Ta(μ-CH₂)₂Pd(PR₃)(Cl) (R = Me, 2; R = OMe, 3) and 0.5 equiv of Cp₂(CH₂). The reaction of 1 with 2 equiv of PMe₃ or P(OMe)₃ or 1 equiv of Me₂P(CH₂)₂PMe₂ (DMPE) led to the isolation of [Cp₂-Ta(μ-CH₂)₂PdL₂]Cl (L₂ = 2 PMe₃, 4; L₂ = 2 P(OMe)₃, 5; L₂ = DMPE, 6). Addition of P(OMe)₃ to 1 in CH₃CN gave the product Cp₂Ta(μ-CH₂)₂Pd(P(OMe)₃)(CH ₂CN) (7). Each of these reactions of 1 with phosphorus compounds implicates the intermediacy of free cyclopentadienyl onion. In support of this hypothesis, the stable naked Cp complex [Cp₂Ta(μ-CH₂)₂Pd(DMPE)]Cp (8) was isolated from the reaction of 1 with DMPE in CH₃CN and was characterized by X-ray crystallography. The shortest distance between the free anionic Cp group and the bimetallic fragment in 8 is 3.46(3) A. Addition of FeCl₂ to 8 resulted in the formation of 1/2 equiv of Cp₂Fe and 6. Treatment of 8 with 1,2-dibromoethane led to the quantitative formation of 1/2 equiv of spiro[2.4]hepta-4,6-diene together with the bromide salt of 8.