Synthetic and structural studies on organomolybdenum and organotunsten complexes containing bismuth. X-Ray crystal structures of [BiCl{Mo(CO)3(η-C5H5)}2] and [BiCl{Mo(CO)2(CNBut)(η-C5H5)}2]

Abstract

The reaction between BiCl₃ and 3 equivalents of Na[Mo(CO)₃(η-C₅H₅)] affords the trimolybdenum–bismuth complex [Bi{Mo(CO)₃(η-C₅H₅)}₃], (1), which has been characterised by spectroscopic methods. The corresponding reaction involving 2 equivalents of Na[Mo(CO)₃(η-C₅H₅)] affords the disubstituted product [BiCl{Mo(CO)₃(η-C₅H₅)}₂], (3), which has been characterised by X-ray diffraction. The molecular structure comprises a trigonal pyramidal bismuth atom bonded to one chlorine and two Mo(CO)₃(η-C₅H₅) fragments and containing a stereochemically active lone pair at the apex of the pyramid. The two crystallographically independent molecules have similar conformations but a weak intermolecular Bi ⋯ Cl interaction, which is present for both molecules, is significantly different in each case. Treatment of a solution of compound (1) with 0.5 equivalent of BiCl₃ affords (3) and when pure samples of (3) are treated with 1 equivalent of BiCl₃ a redistribution reaction is also observed forming [BiCl₂{Mo(CO)₃(η-C₅H₅)}]. A similar range of compounds has been synthesised containing the methylcyclopentadienyl ligand. The analogous tungsten chemistry has also been investigated and similar tri-, di-, and mono-tungsten–bismuth compounds have been synthesised. Slight differences between the molybdenum and tungsten systems are observed, however, under the reaction conditions employed and these are discussed in terms of the possible mechanisms involved. Finally, the reactions between BiCl₃ and 2 equivalents of the carbonyl-substituted anions [Mo(CO)₂L(η-C₅H₅)]^–(L = Bu^tNC, MeNC, or PPh₃) have been examined. These result in the dimolybdenum–bismuth complexes [BiCl{Mo(CO)₂L(η-C₅H₅)}₂], L = Bu_tNC (15), MeNC (16), or PPh₃(17). The first two complexes exist as mixtures of isomers, viz, cis, trans and trans,trans with regard to the stereochemistry at the molybdenum centres, whilst the latter exists as the trans,trans form. The cis,trans form of (15) was characterised by X-ray diffraction. The structure is similar to that observed for compound (3) except that no short intermolecular Bi ⋯ Cl interactions are present. Spectroscopic and analytical data for the complexes are presented.