Anionic, four-co-ordinate, ten-electron bismuth complexes: aspects of synthesis, structure and bonding

Abstract

The reaction between [BiCl{Fe(CO)₂(η-C₅H₅)}₂]1 and 1 equivalent of [N(PPh₃)₂]Cl afforded the ionic complex [N(PPh₃)₂][BiCl₂{Fe(CO)₂(η-C₅H₅)}₂]2. The [NMe₄]⁺ salt, [NMe₄][BiCl₂{Fe(CO)₂(η-C₅H₅)}₂]3, was prepared similarly. An analogous bromide derivative, [PPh₄][BiBr₂{Fe(CO)₂(η-C₅H₅)}₂]4, was prepared from the reaction between [BiBr{Fe(CO)₂(η-C₅H₅)}₂]5 and [PPh₄] Br. The reaction between [BiCl{Mo(CO)₃(η-C₅H₅)}₂]7 and 1 equivalent of [N(PPh₃)₂]Cl afforded the complex [N(PPh₃)₂][BiCl₂-{Mo(CO)₃(η-C₅H₅)}₂]8; that between [PPh₃(CH₂Ph)]Cl and 7 afforded [PPh₃(CH₂Ph)][BiCl₂{Mo(CO)₃(η-C₅H₅)}₂]9. In tetrahydrofuran (thf) solution some degree of dissociation of [Mo(CO)₃(η-C₅H₅)]^– is observed for 8 and 9. The bromide complexes [PPh₄][BiBr₂{Mo(CO)₃(η-C₅H₅)}₂]10 and [NBuⁿ₄][BiBr₂{Mo(CO)₃(η-C₅ H₅)}₂]11 were prepared from the reactions between [BiBr{Mo(CO)₃(η-C₅H₅)}₂]12 and 1 equivalent of [PPh₄]Br and [NBuⁿ₄] Br respectively. The tungsten complexes [N(PPh₃)₂][BiCl₂{W(CO)₃(η-C₅ H₅)}₂]13 and [PPh₃(CH₂Ph)][BiCl₂{W(CO)₃(η-C ₅H₅)}₂]14 were similarly prepared. Spectroscopic data for the complexes [N(PPh₃)₂][BiCl₃{Mo(CO)₃(η-C₅ H₅)}]16 and [N(PPh₃)₂][BiCl₃{W(CO)₃(η-C₅H₅)}]17 are also presented. The structures of compounds 2, 8, 9(as a thf solvate) and 13 were determined by X-ray crystallography. The structures of all of the compounds comprise a four-co-ordinate bismuth centre bonded to two chlorine atoms and two ML_n fragments. The precise co-ordination geometries, however, vary from close to an idealised equatorially-vacant trigonal bipyramid (disphenoidal), 2 and 9, with axial chlorines and equatorial metal centres, to nearly tetrahedral, 8 and 13. These results are incorporated into a general discussion of the structures found for AB₄E complexes, i.e. four-co-ordinate with ten valence electrons, and some ideas are advanced on possible electronic factors which determine the particular geometry adopted.