2,2′-Bipyridine complexes of the lithium chalcogenolates Li(EPh) and Li(NC5H4E-2)(E = S or Se)

Abstract

2,2′-Bipyridine (bipy) forms stable crystalline co-ordination complexes with lithium benzeneselenolate and lithium pyridine-2-selenolate. The compounds are insoluble in aromatic hydrocarbons, slightly soluble in pyridine, and extremely soluble in tetrahydrofuran, from which they can be crystallized in ca. 70% yield. Both complexes have been characterized by elemental analysis, NMR, IR, and single-crystal X-ray diffraction. Compound [{Li(bipy)(SePh)}₂]1[space group p2₁/m, a= 9.493(4), b= 16.866(5), c= 10.112(9), β= 114.53(6)° and Z= 4] is a dimer containing two lithium ions bridged by a pair of symmetric benzeneselenolate ligands, with bidentate bipy ligands bound to each lithium ion. In compound [{Li(bipy)(NC₅H₄Se-2)}₂]2[space group P2₁/n, a= 10.361(5), b= 13.521(4), c= 11.062(5)Å, β= 117.21(4)° and Z= 4] each lithium ion is bound to a bidentate bipy ligand, one bridging selenium atom, and the nitrogen atom from the second bridging pyridine-2-selenolate ligand, thus forming an eight-membered Li–Se–C–N–Li–Se–C–N ring. The analogous lithium thiolates have also been prepared in 70% yield; they are not isostructural with the selenolates.