A carbon-13 NMR study of some metal carbonyl compounds containing one-electron ligands |
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Authors: | LJ Todd JR Wilkinson JP Hickey DL Beach KW Barnett |
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Institution: | Department of Chemistry, University of Missouri-St. Louis, St. Louis, Missouri 63121 U.S.A. |
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Abstract: | Carbon-13 NMR spectral data for complexes having the general formula CpM(CO)nX (Cp = η5-C5H5; M = Mo or W, n = 3; M = Fe, n = 2; X = halogen, methyl or acetyl) and their phosphine and isocyanide substitution products are reported. For CpM(CO)3X complexes two carbonyl resonances (1 : 2 ratio) are observed in all cases, consistent with the retention of the “piano-stool” geometries observed in the solid state. Substituted complexes CpM(CO)2(L)X (M = Mo or W; L = PR3 or cyclohexyl isocyanide) are unequivocally assigned cis or trans geometries on the basis of the number of observed carbonyl resonances and values of 2J(PC) for the phosphine substituted derivatives. Spectral data for M(CO)5X]? (M = Cr, Mo or W; X = Cl, Br or I) and η7-C7H7Mo(CO)2X and the halide derivatives above generally show an increase in the shielding for carbonyls adjacent to the halide ligand in the order Cl < Br < I. Carbonyl resonances are more shielded in isostructural complexes in the order Cr < Mo < W (triad effect). |
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