REACTIVITY OF AN EARLY-LATE HETEROBIMETALLIC COMPLEX TOWARD PHOSPHINES - SYNTHESIS, STRUCTURE, AND REACTIVITY OF A CATIONIC TANTALUM-PALLADIUM COMPOUND WITH A FREE CYCLOPENTADIENYL COUNTERANION

Treatment of Cp2Ta(CH2)(CH3) with CpPd(C3H5) led to Cp2Ta(mu-CH2)2PdCp (1). Reaction of 1 with 1 equiv of either PMe3 or P(OMe)3 in CH2Cl2 resulted in the formation Of CP2Ta(mu-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 [Cp2Ta(mu-CH2)2PdL2]Cl (L2 = 2 PMe3, 4, L2 = 2 P(OMe)3, 5; L2 = DMPE, 6). Addition of P(OMe)s to 1 in CH3CN gave the product CP2Ta(mu-CH2)2Pd(P(OMe)3)(CH2CN) (7). Each of these reactions of 1 with phosphorus compounds implicates the intermediacy of free cyclopentadienyl anion. In support of this hypothesis, the stable naked Cp complex [CP2Ta(mu-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) angstrom. 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.