Alkyl and acyl derivatives of nickel(II) containing tertiary phosphine ligands

Abstract

The interaction of complexes [NiCl₂L₂](L = PMe₃ or PMe₂Ph) with Grignard reagents derived from Me₂PhCCH₂Cl and Me₃SiCH₂Cl yields thermally stable monoalkyl derivatives of the type [NiR(Cl)L₂], which, when L = PMe₃, afford upon carbonylation at room temperature and pressure the corresponding acyls [Ni(COR)Cl(PMe₃)₂]. Metathesis reactions with KX give [NiR(X)(PMe₃)₂] and [Ni(COR)X(PMe₃)₂](X = Br, I, NCS, or NCO), while with Tl[C₅H₅], [Ni(CH₂CMe₂Ph)(η-C₅H₅)(PMe₃)] and [Ni(COCH₂CMe₂Ph)(η-C₅H₅)(PMe₃)] can be isolated. The synthesis of [Ni(COCH₂CMe₂Ph)Cl(PMe₂Ph)₂] is also reported. The acyls, [Ni(COR)X(PMe₃)₂], readily carbonylate solutions of the alkyl complexes, [NiR′(X)(PMe₃)₂], providing under certain conditions [NiR(X)(PMe₃)₂] and [Ni(COR′)X(PMe₃)₂] in almost quantitative yields. Structures for the new compounds are proposed on the basis of i.r. and ¹H n.m.r. spectroscopic studies. Those of [Ni(CH₂SiMe₃)Cl(PMe₃)₂] and [Ni(COCH₂SiMe₃)Cl(PMe₃)₂] have been confirmed by single-crystal X-ray determinations. Thus [Ni(CH₂SiMe₃)Cl(PMe₃)₂] crystallizes in the monoclinic space group Pc with a= 15.419(3), b= 6.406(2), c= 18.711(3)Å, β= 92.02(3)°, Z= 4, and R 0.031 based on 1 906 independent observed reflections. The phosphine ligands are trans[P–Ni–P 164(2)°] in a square-planar arrangement. The complex [Ni(COCH₂SiMe₃)Cl(PMe₃)₂] belongs to the orthorhombic space group Pbca with a= 12.668(3), b= 21.312(4), c= 28.925(4)Å, Z= 16, and R 0.049 for 1 394 independent observed reflections. The oxyzen atom is not co-ordinated to the nickel atom [Ni ⋯ O 3.121(4)Å].