Platinum Complexes of a Borane-Appended Analogue of 1,1′-Bis(diphenylphosphino)ferrocene: Flexible Borane Coordination Modes and in situ Vinylborane Formation

A bis(phosphine) borane ambiphilic ligand, [Fe(eta(5)-C5H4PPh2)(eta(5)-C5H4PtBu{C6H4(BPh2)-ortho})] (FcPPB), in which the borane occupies a terminal position, was prepared. Reaction of FcPPB with tris(norbornene) platinum(0) provided [Pt(FcPPB)] (1) in which the arylborane is eta(BCC)-B-3-coordinated. Subsequent reaction with CO and CNXyl (Xyl= 2,6-dimethylphenyl) afforded [PtL(FcPPB)] {L= CO (2) and CNXyl (3)} featuring h 2BC-and eta B-1-arylborane coordination modes, respectively. Reaction of 1 or 2 with H2 yielded [PtH(m-H)(FcPPB)] in which the borane is bound to a hydride ligand on platinum. Addition of PhC2H to [Pt(FcPPB)] afforded [Pt(C2Ph)(m-H)(FcPPB)] (5), which rapidly converted to [Pt(FcPPB')] (6; FcPPB'=[Fe(eta(5)-C5H4PPh2)(eta(5)-C5H4PtBu{C6H4(BPh2)-ortho}]) in which the newly formed vinylborane is eta(BCC)-B-3-coordinated. Unlike arylborane complex 1, vinylborane complex 6 does not react with CO, CNXyl, H-2 or HC2Ph at room temperature.