Nickel Complexes Containing New Carbon−Phosphorus Unsaturated Ligands: First Examples of Phosphavinylidene−Phosphorane [R3PCPR‘] and Phosphavinyl Phosphonium [C(H)(PR3)P(R‘)]+ Ligands

摘要: Oxidative-addition reactions of Cl2CPN(SiMe3)2 with 1:2 Ni(COD)2/PPh3, Ni(PPh3)4, or (Ph3P)2Ni(C2H4) initially yields the phosphavinyl phosphonium complex Cl(Ph3P)Ni[η2-C(Cl)(PPh3)PN(SiMe3)2] (IIa). Addition another equivalent Ni(0) reagent to IIa results in formation novel, dinuclear, phosphavinylidene−phosphorane Ni2Cl2(PPh3)2[μ2-η2:η2-C(PPh3)PN(SiMe3)2] (IIIa); structure IIIa was established by X-ray diffraction and contains a Ph3PCPR‘ ligand bridged between two four-coordinate, planar nickel atoms butterfly arrangement Ni−Ni distance that is too long for significant bonding interaction. The ligand, which may be viewed as phosphavinylidene (CPR) phosphine-donor substituent, acts six-electron donor atoms. This contrasts known diphosphaallene compounds types R3PCPR3 RPCPR act two-electron ligands. When reaction performed Cl2CPMes* (Mes* = 2,4,6-t...