Synthesis, structure and mechanism of formation of chalcogen -stabilised mixed-metal clusters featuring acetylide bridging and acetylide coupling

Mild thermolysis of a toluene solution of [(η5-C5H5)Mo(CO)3(CCPh)] and [Fe3(CO)9(μ3-E)2] (E = S, Se) resulted in the formation of mixed-metal clusters, [(η5-C5H5)2Mo2Fe3(CO)8(μ3-E)2{μ5-CC(Ph)CC(Ph)}] (E = S, 1; Se, 2), [(η5-C5H5)2Mo2Fe4(CO)9(μ3-E)2(μ4-CCPh)2] (E = S, 3; Se, 4) and [(η5-C5H5)2Mo2Fe3(CO)7(μ3-E)2{μ5-CC(Ph)C(Ph)C}] (E = S 5; E = Se 6) which feature head-to-tail coupling of two acetylide groups, two acetylide groups which remain uncoupled and a tail-to-tail coupling of two acetylide groups, respectively, on the chalcogen-bridged Fe/Mo cluster framework. Under similar conditions, the reaction of [(η5-C5H5)W(CO)3(CCPh)] and [Fe3(CO)9(μ3-E)2] formed the clusters [(η5-C5H5)2W2Fe3(CO)7(μ3-E)2(μ3-η2-CCPh)(μ3-η1-CCH2Ph)] (E = S, 7 or Se, 8) and [(η5-C5H5)WFe2(CO)8(μ-CCPh)] (9). All compounds have been characterised by IR and 1H and 13C NMR spectroscopy. The Se-bridged compounds have been further characterised by 77Se NMR spectroscopy. The crystal structures of 1, 3 and 5–9 were elucidated by X-ray diffraction methods.