Crystal structure of tetraethylammonium bis(tetracarbonylmolybdenum)-tetrathiotungstate, [Et 4N] 2[(OC) 4MoS 2WS 2Mo(CO) 4] and synthesis, infrared spectra, 95 Mo NMR spectra and cyclic voltammetry of new linear trinuclear Mo(W)–S carbonyl clusters containing mixed-valence metal atoms [(OC) 4MS 2M′SM(CO) 4] 2− (M, M′=Mo or W)

Abstract

Four trinuclear molybdenum(tungsten)-sulfur carbonyl cluster compounds, [Et 4N] 2[(OC) 4Mo-S 2MoS 2Mo(CO) 4] (1), [Et 4N] 2[(OC) 4WS 2WS 2W(CO) 4] (2), [Et 4N] 2[(OC) 4MoS 2WS 2Mo(CO) 4] (3), [Et 4N] 2[(OC) 4WS 2MoS 2W(CO) 4] (4) have been prepared by both reaction of [M(CO) 4(S 2CNEt 2)] − with M′S 4 2− in MeOH and reaction of MeCN solution of M(CO) 6 with M′S 4 2− in MeOH (M=Mo, W; M′=Mo, W). These complexes has been characterized by routine elemental analysis and spectroscopy and the structures of 1 and 3 have been determined by X-ray crystallography. The structure study reveals that the anion of 3 contains a heteronuclear Mo–W–S trimetallic core, [MoS 2WS 2Mo] 2−, consisting of two perpendicular rhombic MoS 2W units sharing a tungsten atom. The Mo–W bond distances are 3.028(2) and 3.031(2) Å and the Mo–W–Mo angle is 176.04(5)°. The average bond lengths of W–S and Mo–S are 2.21 and 2.54 Å, respectively. The X-ray, structure, IR, CV (cyclic voltammetry) and 95 Mo NMR studies on these four cluster complexes indicated that these cluster complexes possess wide separated oxidation states of metal atoms and exhibit the charge transfer, M L→M HS 4 (M L represents a low-valance metal atom and M H a high valence metal atom), between the two different valence metallic centers in the cluster complexes. It has been found that the charge transfer, M L→M HS 4, in the complexes are: 1>4, 3>2, 1>3, 4>2, 1>2 and 3∼4 implying the electron-donation ability of low-valence metal atoms in the complexes is Mo 0>W 0 and the electron-accepted ability of the high valence metal atoms in the complexes is Mo VI>W VI.