Bis(pyridyl)-silane and -methanol ligands IV. Catalytic application of nickel(II) complexes in the Kumada cross-coupling reaction

Article abstract of DOI:10.1016/0022-328X(90)87185-G

Treatment of the bis(2-pyridyl)silane ligands MeRSi(2-C5H4N)2 with (MeCN)2 NiBr2 afforded NiBr2 (3a, R = Me; 3b, R = Ph) in excellent yield.The latter complexes were bright purple crystalline solids with paramagnetic line broadening in the NMR spectra; although, no ESR signal could be detected in solution or in the solid state.Complex 3a was found to be an effective catalyst for the cross-coupling of Grignard reagents with aryl and vinyl halides.The catalytic system also coupled alkyl Grignard reagents with chlorobenzene provided a dipolar aproticsolvent such as HMPA was employed.Optically pure ligands, <6-alkoxy-2-pyridyl>(Ar)CH(OMe) (5), were employed in the asymmetric cross-coupling reaction of (1-phenylethyl)magnesium chloride and bromoethene.Conversion of the Grignard reagent ranged from 73 to 88percent with ca. 50percent chemical yields of 3-phenyl-1-butene with optical yields ranging from ca. 0 to 11percent.