Synthesis and crystal structure of [NiOs3(η-C5H5)(µ-H)2{µ-Cu(PPh3)}(CO)9]. Hydrogenation–dehydrogenation reactions of dienes and alcohols with heterogeneous catalysts derived from [NiM3(η-C5H5)(µ-H)2(µ-X)(CO)9][M = Ru, X = H; M = Os, X = Cu(PPh3)]
Abstract
The complex [NiOs3(η-C5H5)(µ-H)2{µ-Cu(PPh3)}(CO)9] has been synthesized in tetrahydrofuran (thf) by reaction of the anion [NiOs3(η-C5H5)(µ-H)2(CO)9]–, generated in situ from [NiOs3(η-C5H5)(µ-H)3(CO)9] and NaH, with [{Cu(PPh3) Br}4]. Its structure has been determined by X-ray methods. Crystals are triclinic, space group P![[1 with combining macron]](https://www.rsc.org/images/entities/char_0031_0304.gif)
with Z= 2 in a unit cell of dimensions a= 13.643(7), b= 14.120(6), c= 9.504(4)Å, α= 94.88(3), β= 105.77(4), and γ= 102.15(3)°. The structure has been solved from diffractometer data by direct and Fourier methods and refined by full-matrix least squares, to R= 0.0462 for 2 191 observed reflections. The metal cluster can be described as a NiOs3 tetrahedron with an Os–Os edge bridged by the Cu atom from the Cu(PPh3) group. This complex, supported on Chromosorb and thermally activated under H2, forms a heterogeneous catalyst for the hydrogenation–dehydrogenation of several substrates, in particular alcohols. The behaviour of this catalyst is significantly different from that of systems derived from the parent cluster [NiOs3(η-C5H5)(µ-H)3(CO)9] or from [NiRu3(η-C5H5)(µ-H)3(CO)9]. In particular, it shows high dehydrogenation ability.
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