The homoleptic amides [M(NMe2)5] (M = Nb 1 or Ta 2; the latter is characterised by a structural study) reacted with the carborane nido-C2B9H13 to eliminate two equivalents of HNMe2 and generate the dicarbollide half-sandwich tris(dimethylamide) complexes [M(C2B9H11)(NMe2)3] (M = Nb 3 or Ta 4). The crystal structures of isomorphous 3 and 4 have been determined and reveal two NMe2 ligands in a vertical orientation and the third one in a horizontal orientation with respect to the η5-co-ordinated face of the C2B9H11 ligand. The electronic factors responsible for the amide ligand orientations in these complexes are explored using qualitative MO arguments. Complexes 3 and 4 reacted with CO2 and CS2 to yield the tris(carbamate) [M(C2B9H11)(O2CNMe2) 3] (M = Nb 5 or Ta 7) and tris(dithiocarbamate) [M(C2B9H11)(S2CNMe2) 3] (M = Nb 6 or Ta 8) complexes, respectively. The crystal structures of 6 and 7 show two (dithio)carbamate ligands in horizontal and one in vertical orientation, demonstrating the similarity between the σ,π-donor frontier orbitals of the ligands NMe2 and X2CNMe2 in 4 and 6 or 7 respectively.
|Number of pages||9|
|Journal||Journal of the Chemical Society - Dalton Transactions|
|Publication status||Published - 7 Nov 1999|
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