The reaction of triphenylphosphine selenide with triosmium clusters: a facile cluster coupling through a selenium atom

Abstract

The room temperature reactions of Ph₃PSe with the triosmium clusters Os₃(CO)₁₁(CH₃CN), Os₃(CO)₁₀(CH₃CN)₂ and Os₃(μ-H)₂(CO)₁₀ have been investigated. The reaction with an equimolar amount of Os₃(CO)₁₁(CH₃CN) afforded the known clusters Os₃(μ₃-Se)₂(CO)₉, 1, and Os₃(CO)₁₁(PPh₃), 2, and the new cluster Os₃(μ₃-Se)(CO)₉(PPh₃), 3. The analogous reaction with Os₃(CO)₁₀(CH₃CN)₂ gave 1 and 2; reaction with 0.5 equivalent of the cluster gave 1 quantitatively. The reaction with Os₃(μ-H)₂(CO)₁₀ gave two new clusters, viz. Os₃(μ₃-Se)(μ-H)₂(CO)₈(PPh₃), 4a, and Os₆(μ₃-Se)(H)(μ-H)₃(CO)₁₈(PPh₃)₂, 5a. Single crystal structures of 3, 4a and 5a have been obtained. Cluster 3 possesses bridging carbonyls; these appear to have been lost on elongation of the osmium–osmium bonds by bridging hydrides in 4a. The structure of 5a is novel and comprises a naked μ₃-Se atom bridging two triosmium moieties; an Os₃(μ-H)(CO)₁₀ unit and an Os₃(H)(μ-H)₂(CO)₈(PPh₃)₂ unit.