Reactivity of triosmium clusters with 3,4-dimethyl-1-phenylphosphole and cyanoethyldi-tert-butylphosphine ligands: X-ray crystal structures of [Os3(CO)9(μ-OH)(μ-H)(η1-PhPC4H2Me2)] and [Os3(CO)11(η1-tBu2PC2H4CN)]

Reaction of [Os3(μ-H)2(CO)10] with 3,4-dimethyl-1-phenylphosphole in refluxing cyclohexane affords two substituted triosmium clusters: [Os3(CO)9(μ-H)(μ3:η1:η1:η2-PhPC4H3Me2)] (1) and [Os3(CO)9(H)(μ2-η1:η2-PhPC4H4Me2)] (2), of which cluster 2 exhibits two chromatographically non-separable isomeric forms attributed to terminal and bridging coordination of the hydride ligand, respectively. When this reaction is performed in refluxing THF, the only product is the cluster [Os3(CO)9(μ-OH)(μ-H)(η1-PhPC4H2Me2)] (3). Crystallographic information obtained for cluster 3 shows the phosphole ligand occupying an equatorial position, as expected, while the OH group is asymmetrically bridging unlike previously reported similar compounds. Additionally, interaction of the labile cluster [Os3(CO)11(CH3CN)] with cyanoethyldi-tert-butylphosphine in dichloromethane at room temperature was found to give [Os3(CO)11(η1-tBu2PC2H4CN)] (4) as the only product; its crystallographic characterization shows that the phosphine ligand coordinates by means of the phosphorus atom in an equatorial fashion, analogous to compound 3.