A comparative study of the reactivity of the lightly stabilized cluster [Os3(CO)8{μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] towards tri(2-thienyl)-, tri(2-furyl)- and triphenyl-phosphine

Reactions of the lightly stabilized triosmium cluster [Os-3(CO)(8){mu(3)-Ph2PCH2P(Ph)C6H4}(mu-H)] with tri(2-thienyl)phosphine (PTh3) and tri(2-furyl)phosphine (PFu(3)) are described and compared to analogous reactions with PPh3. At room temperature, a number of products are isolated: [Os-3(CO)(10)(mu-dppm)] from CO addition, [Os-3(CO)(8)(PR3){mu(3)-Ph2PCH2P(Ph)C6H4}(mu-H)] from phosphine addition, [Os-3(CO)(9)(PR3)(mu-dppm)] from phosphine and CO addition and [Os-3(CO)(8)(PR3)(2)(mu-dppm)] from addition of two equivalents of phosphine. The latter are shown by NMR and X-ray diffraction to exist as 1,2-isomers, whereby one phosphine is bound to the non-dppm-substituted center and the second shares an osmium atom with one end of the diphosphine. Heating 1,2-[Os-3(CO)(8)(PTh3)(2)(mu-dppm)] at 100 degrees C results in its clean isomerization to the 1,1-isomer in which both monodentate phosphines are located on the same osmium atom. Prolonged heating of [Os-3(CO)(8)(PR3)(2)(mu-dppm)] (R = Th, Ph) at 110 degrees C gives [Os-3(CO)(9)(PR3)(mu-dppm)] and the new lightly stabilized clusters [Os-3(CO)(7)(PR3){mu(3)-Ph2PCH2P(Ph)C6H4}(mu-H)], the latter being formed by loss of phosphine and CO with concurrent metalation of a phenyl ring. Heating [Os-3(CO)(8)(PFu(3))(2)(mu-dppm)] at 110 degrees C gives [Os-3(CO)(9)(PFu(3))(mu-dppm)] together with the carbon-phosphorus bond cleavage products [Os-3(CO)(7)(mu-PFu(2))(mu(3)-eta(2)-C4H2O)(mu-H)(mu-dppm)] and [Os-3(CO)(7)(mu-PFu(2))(mu(3)-eta(2)-C6H3CH3)(mu-H)(mu-dppm)]. All new compounds were characterized by analytical and spectroscopic techniques together with single crystal X-ray diffraction analysis of nine clusters. Density functional theory (DFT) calculations have been carried out on isomers of [Os-3(CO)(8)(PR3)(2)(mu-dppm)] in order to understand the observed isomer ratios. (C) 2013 Elsevier B.V. All rights reserved.