Lewis base complexes of methyldihalobismuthines BiMeX2 (X = Cl or Br)

Methyldihalobismuthines, BiMeX2 (X = Cl or Br) prepared from MeLi and a stoichiometric amount of BiX3 in thf, react with 1,10-phenanthroline, 2,2′-bipyridyl or Me2NCH2CH2NMe2 (L−L) in thf or MeCN to give [BiMeX2(L−L)], which are poorly soluble in non-polar solvents. X-Ray structures of [BiMeBr2(L−L)] and of [BiMeCl2(Me2NCH2CH2NMe2)] show discrete square pyramidal molecules with apical methyl groups, and no intermolecular contacts within the sum of the appropriate Van der Waals radii. The structure of BiMe2Br is a 1-D polymer chain with bromine bridges containing a pseudo-trigonal bipyramidal geometry at bismuth. The reactions of BiMe2X with the bidentate N-donor ligands result in disproportionation to also form [BiMeX2(L–L)]. An unusual [BiMeBr4]2− anion in the salt [Li(H2O)(1,10-phen)2][Li(1,10-phen)2(μ-Br)BiMeBr3]·thf, was isolated as a by-product and shows a Li−Br−Bi bridge to one of the Li cations. BiMe2Br disproportionates on reaction with [M(CO)5(thf)] (M = Cr or W) to form [M(CO)5(BiMe3)].

BiMeX2 form Lewis base adducts with N-donor ligands, whereas BiMe2X disproportionate on reaction with the same ligands to give BiMeX2 adducts and with metal carbonyls they form BiMe3 complexes.Figure optionsDownload as PowerPoint slideHighlights
► X-ray structural authentication of N-base adducts of methylhalobismuthines.
► Dimethylhalobismuthines disproportionate on reaction with bidentate N-bases.
► Dimethylhalobismuthines form trimethylbismuthine on reaction with metal carbonyls.