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

•A comparative study of the reactivity of an unsaturated triosmium cluster towards various phosphines.•Reactivity of the unsaturated [Os3(CO)8{μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] towards phosphines.•Synthesis and characterization of a variety of phosphine addition products.•Formation of isomeric clusters due to disposition of phosphines at different coordination sites.•Different reactivity exhibited by isomeric clusters upon heating.

Reactions of the lightly stabilized triosmium cluster [Os3(CO)8{μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] with tri(2-thienyl)phosphine (PTh3) and tri(2-furyl)phosphine (PFu3) are described and compared to analogous reactions with PPh3. At room temperature, a number of products are isolated: [Os3(CO)10(μ-dppm)] from CO addition, [Os3(CO)8(PR3){μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] from phosphine addition, [Os3(CO)9(PR3)(μ-dppm)] from phosphine and CO addition and [Os3(CO)8(PR3)2(μ-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-[Os3(CO)8(PTh3)2(μ-dppm)] at 100 °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 [Os3(CO)8(PR3)2(μ-dppm)] (R = Th, Ph) at 110 °C gives [Os3(CO)9(PR3)(μ-dppm)] and the new lightly stabilized clusters [Os3(CO)7(PR3){μ3-Ph2PCH2P(Ph)C6H4}(μ-H)], the latter being formed by loss of phosphine and CO with concurrent metalation of a phenyl ring. Heating [Os3(CO)8(PFu3)2(μ-dppm)] at 110 °C gives [Os3(CO)9(PFu3)(μ-dppm)] together with the carbon-phosphorus bond cleavage products [Os3(CO)7(μ-PFu2)(μ3-η2-C4H2O)(μ-H)(μ-dppm)] and [Os3(CO)7(μ-PFu2)(μ3-η2-C6H3CH3)(μ-H)(μ-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 [Os3(CO)8(PR3)2(μ-dppm)] in order to understand the observed isomer ratios.

Graphical abstractReactions of the lightly stabilized triosmium cluster [Os3(CO)8{μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] with various monodentate tertiary phosphines having different electronic properties are described. A number of new triosmium clusters have been isolated and characterized from these reactions which are formed by addition of phosphines to the parent cluster.Figure optionsDownload full-size imageDownload as PowerPoint slide