Dinuclear Ni(I)Ni(I) Complexes with Syn-Facial Bridging Ligands from Ni(I) Precursors or Ni(II)/Ni(0) Comproportionation

The previously reported mononuclear d9 complex (iPr3P)2NiCl (1) provides a convenient entry into a series of dinickel complexes with syn-facial bridging ligands. Cyclopentadienyllithium or indenyllithium react with 1 in in n-pentane to provide [(iPr3P)­Ni]2(μ-Cl)­(μ-C5H5) (3a) and [(iPr3P)­Ni]2(μ-Cl)­(μ-C9H7) (3b). Complexes 3a,b are also accessible by comproportionation of the mononuclear Ni­(II) complexes (iPr3P)­NiCl­(η5-C5H5)] (4a) and (iPr3P)­NiCl­(η3-C9H7) (4b) with the Ni(0) precursor [(iPr3P)2Ni]2(μ-N2) (2). The bulkier Ni­(II) complex (iPr3P)­(η5-C5Me4H)­NiCl (5) does not undergo clean reaction with 2, and the methyl complex (iPr3P)­(η5-C5H5)­Ni­(CH3) (6) does not react with 2. Reaction of 1 with NaBPh4 provided [(iPr3P)­Ni]2(μ-Cl)­(μ-PhBPh3) (7). The dinuclear complexes 3a,b and 7 all feature structurally similar [(PiPr3)­Ni]2(μ2-Cl) fragments, with an approximate planar arrangement of the X and PiPr3 ligands and a perpendicular organic cyclopentadienyl, indenyl, or phenyl π system.