Multiple carbon–carbon bond cleavage on a heptaosmium cluster: synthesis and structural characterisation of [Os7(CO)18(µ3-CPh)2] and [Os7(CO)15(µ3-CPh)4]

Abstract

The cluster [Os₇H₂(CO)₂₀] reacts with excess of Ph₂C₂ in refluxing toluence to produce first the brown species [Os₇(CO)₁₈(µ₃-CPh)₂]2 and then, over a longer period, the purple cluster [Os₇(CO)₁₅(µ₃-CPh)₄]4. These clusters have been shown by X-ray crystallography to possess monocapped octahedral and unprecedented bicapped square-pyramidal metal cores, respectively. In each case the crystallographic data clearly show that in the course of this reaction carbon–carbon multiple-bond cleavage has occurred and ‘carbyne’(CPh) units have been generated and stabilised by interactions with triangulo-Os₃ structural units. Crystal data: for 2, triclinic, space group P, a= 11.379(5), b= 18.525(5), c= 9.886(2)Å, α= 106.43(2), β= 113.61(3) and γ= 82.22(3)° for 4, monoclinic, space group C2/c, a= 15.953(5), b= 19.816(4), c= 14.383(2)Å and β= 94.51(6)°.