Two modes of C-H bond activation of tris(2-thienyl)phosphine in trinuclear osmium carbonyl clusters

The phosphine-substituted clusters [Os3(CO)11{P(C4H3S)3}] (1), [Os3(CO)10-{P(C4H3S)3}2] (2) and [Os3(CO)9{P(C4H3S)3}3] (4) and the C-H activated product [Os3(μ-H)(CO)9{μ2-P(C4H2S)(C4H3S)2}{P(C4H3S)3}] (3) were obtained from the reaction of tris(2-thienyl)phosphine with [Os3(CO)12] at 110 °C. The bridging phosphothienyl ligand in 3 is equatorially coordinated via both the phosphorus and carbon atom. The unsaturated precursor [Os3(μ-H)2(CO)10] gave the substitution product [Os3(μ-H)2(CO)9{P(C4H3S)3}] (5) and the addition product [Os3H(μ-H)(CO)10{P(C4H3S)3}] (6) at ambient temperature whereas at elevated temperature the cyclometallation products [Os3(μ-H)(CO)9{μ3-P(C4H2S)(C4H3S)2}] (7) and [Os3(μ-H)(CO)8{μ3-P(C4H2S)(C4H3S)2{P(C4H3S)3}] (8) were obtained.