Synthesis and properties of dialkyl complexes of nickel(II). The crystal structure of bis(pyridine)bis(trimethylsilylmethyl)nickel(II)

Abstract

Dichlorotetrakis(pyridine) nickel(II), [NiCl₂(py)₄](py = pyridine), reacts with trimethylsilylmethylmagnesium chloride, Mg(CH₂SiMe₃)Cl, in the presence of excess of pyridine, to yield the unstable dialkyl derivative [Ni(CH₂SiMe₃)₂(py)₂], for which an X-ray crystal-structure determination shows a cis pyridine configuration with an N–Ni–N angle of 87.5°. Interaction of this complex with unidentate (L) or bidentate ligands (L–L) gives [NiR₂L₂] or [NiR₂(L–L)](L = PMe₃ or PMe₂Ph; L–L = Ph₂PCH₂CH₂PPh₂, 2,2′-bipyridyl, 1,10-phenanthroline, or NNN′N′-tetramethylethylenediamine), while PMePh₂ and PPh₃ cause reductive elimination to [NiL₄]. Some neophyl analogues, [Ni(CH₂CMe₂Ph)₂(L–L)] are also described. Structures for the new compounds are proposed on the basis of i.r., ¹H, and ³¹P n.m.r. spectroscopic studies. Complexes [Ni(CH₂SiMe₃)₂(PR₃)₂](PR₃= PMe₃ or PMe₂Ph) exist in solution as mixtures of cis and trans isomers, but single-crystal X-ray studies (to be reported separately) of [Ni(CH₂SiMe₃)₂(PMe₃)₂] show trans phosphines with a P–Ni–P angle of 147°.