Reactivity of the unsaturated triosmium cluster Os-3(CO)(8)(mu(3)-eta(2)-Ph2PCH2P(Ph)C6H4)(mu-H) with benzothiophene: Activation of a P-C bond in diphosphine and a C-H bond in benzothiophene

Treatment of the electronically unsaturated cluster Os-3(CO)(8)(mu(3)-eta(2)-Ph2PCH2P(Ph)C6H4)(mu-H) (1) with benzothiophene in refluxing m-xylene afforded Os-3(CO)(7)(mu-PPh2)(mu-PMePh)(mu(3)-eta(2)-C6H4) (2), Os-3(CO)(7)(mu(3)-eta(2)-PPh(C6H4)CH2PPh)(mu(3)-eta(3)-SC8H5)(mu-H) (3), and Os-3(CO)(8)(mu-CO)(mu(3)-eta(2)-PPh(C6H4)CH2PPh) (4). Thermolysis of 1 in refluxing toluene for 35 h afforded only 4, whereas in refluxing m-xylene it gave both 4 and 2. Compound 4 can also be obtained from the thermolysis of Os-3(CO)(9)(mu(3)-eta(2)-PPh(C6H4)CH2PPh2)(mu-H) (5) in refluxing toluene. All the complexes have been structurally characterized. Compound 3 contains a unique example of a mu(3)-eta(2) benzothienyl ligand coordinated through the sulfur atom and the C-C double bond of the five-membered ring in a sigma,pi vinyl fashion. This coordination mode results in the rupture of one osmium-osmium bond, whereas the basic triangular metal framework is retained in the case of 2 and 4, which are derived from the activation of P-C and C-H bonds of 1 and do not contain any benzothiophene-derived ligand.