Reactions of di- and poly-nuclear complexes. 17. Isolation and reactivity of μ-oxo dinuclear molybdenum(IV) thiolato-bridged complexes containing terminal and bridging chloride or bromide groups [(η-C5Me5)MoX]2(μ-X)(μ-O)(μ-SMe) (X = Cl, Br); crystal structure of [(η-C5Me5)MoBr]2(μ-Br)(μ-O)(μ-SMe)
Résumé
The reaction of [ η-C5Me5Mo(CO)3 ]2 with allyl chloride in refluxing THF gives the mononuclear complex [ (η-C5Me5)MoCl2(η3-C 3H5) (CO) ] (1). Thermolysis of complex 1 in THF or toluene in presence of dimethyldisulfide affords the unexpected complex [ (η-C5Me5)MoCl ]2(μ-Cl) (μ-O) (At-SMe) (2). Similar reactions are observed with allyl bromide and give the analogous bromide complex 3. X-ray analysis establishes that complex 3 contains a Mo2(μ-Br) (μ-O) (μ-SMe) core and that the C5Me5 ligands are cis with respect to the Mo-Mo axis, as are the terminal Br groups. The formally double Mo-Mo bond is relatively long (2.755(1) Å). An approximate plane of symmetry normal to the Mo-Mo bond passes through the bridging O, Br and S donor atoms and relates the two C5Me5MoBr units. Complexes 2 and 3 react with HSMe to afford the μ-oxo-bis(μ-thiolato) products [ (η-C5Me5)MoX ]2(μ-O)(μ-SMe)2 (X = Cl (4), Br (5)) and the replacement of the chloride bridge in complex 2 by HSCH2CH2SH leads to [ (η-C5Me5)MoCl ]2(μ-O) (μ-SMe) (μ-SCH2CH2SH) ] (6).