Molecular and electronic structures of three pyridine- and piperidine-substituted chromium carbonyl compounds: Cr(CO)5(C5H5N), Cr(CO)5(C5H10NH) and cis-Cr(CO)4(C5H10NH)[P(OMe)3]
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The problem of metal-ligand bonding in Cr(CO)5L compounds, and related ones, where L is an aliphatic amine or an aromatic amine, has been addressed by X-ray work on a novel crystalline solid containing equimolar amounts of Cr(CO)5NHC5H10 and Cr(CO)5NC5H5 and on cis-cr(CO)4(HNC5H10) [P(OMe)3] as well as by Fenske-Hall calculations on Cr(CO)5NH3 and other data collected from the literature. The theoretical results show that in the Cr(CO)5L compounds the b1dx2-y2) orbital lies above the a1(dz2) orbital in agreement with some but contrary to other previous proposals. The structures show that the replacement of an aliphatic by an aromatic amine has no significant effect on the structure of the Cr(CO)5 group and that the two substituents C5H10NH and P(OMe)3 exert their structural effects on the Cr(CO)4 residue essentially independently. The crystals containing the Cr(CO)5(C5H10NH) and Cr(CO)5(C5H5N) molecules belong to space group P21/n and have the following unit cell parameters: a = 13.851 (2) Å, b = 11.026 (1) Å, c = 17.693 (2) Å, β = 109.93 (2)°, V = 2540 (1) Å3, and Z = 4. The structure was refined with use of 2209 data to R1 = 0.041 and R2 = 0.049. The compound cis-Cr(CO)4(C5H10NH)[P(OMe)3] crystallized in space group P212121 with a = 8.088 (1) Å, b = 11.587 (2) Å, c = 18.431 (2) Å, V = 1727.4 (5) Å3, and Z = 4. Refinement using 1326 data converged with R1 = 0.043 and R2 = 0.054 for the preferred enantiomorph. © 1981, American Chemical Society. All rights reserved.
author list (cited authors)
Cotton, F. A., Darensbourg, D. J., Fang, A., Kolthammer, B., Reed, D., & Thompson, J. L.