The partial hydrogenation of small unsaturated molecules by osmium cluster compounds. The reaction of diispropylcarbodiimide with H2Os3(CO)10 |
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| Authors: | Richard D. Adams Dean A. Katahira John P. Selegue |
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| Affiliation: | Department of Chemistry, Yale University, New Haven, CT 06511 U.S.A. |
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| Abstract: | The products (μ-H)[μ-η2-(CH3)2CHNHCNCH(CH3)2]Os3(CO)10, I, and (μ-H)- [μ-η2-(CH3)2CHNHCO]Os3(CO)9[CNCH(CH3)2], II have been obtained from the reaction of H2Os3(CO)10 with diisopropylcarbodiimine. Both products have been investigated by infrared and 1H NMR spectroscopies, and by single crystal X-ray diffraction analyses. For I: Space group, P21/c, a12.840(4), b 15.724(4), c 12.638(4) Å, β 106.91(2)°, V 2441(2) Å3, Z4, ? calc 2.66 g/cc. For 2869 reflections, R 0.051 and Rw 0.052. I contains an N-hydrido, N-isopropylamidinyl ligand bridging one edge of a triangular cluster of three osmium atoms. It was apparently formed by the incorporation of one carbodiimide molecule into the coordination sphere of the cluster followed by the transfer of one hydride ligand to one of the nitrogen atoms. For II: Space group P2 1/n;a 13.936(7), b 12.146(2), c 15.509(6) Å, β 105.20(4)°, V 2533(3) Å, Z 4, ?calc 2.57 g/cc. For 3065 reflections, R 0.052 and Rw 0.057. II contains an N-hydrido, N-isopropylformamido ligand bridging one edge of a triangular cluster of three osmium atoms and an isopropylisocyanide ligand. The molecule appears to have been formed by the cleavage of an NCH(CH3)2 moeity from one carbodiimide molecule and the transfer of it together with one hydride ligand to the carbon atom of a carbonyl group. The resultant formamido ligand bridges an edge of the cluster. The remaining fragment of the carbodiimide molecule bonds to one of the metal atoms of the cluster as a terminal isocyanide ligand. When heated, I loses one mole of carbon monoxide and forms the new cluster complex (μ-H)[μ3-η2-(CH3)2CHNHCNCH-(CH3)2]Os3(CO)9 III. On the basis of electron counting schemes, III is believed to contain a triply-bridging amidinyl ligand serving as a five electron donor. Most importantly, no II was formed from I indicating that it is not a precursor -to II. A mechanism for the formation of I and II is presented and discussed. |
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