CRYSTAL AND MOLECULAR STRUCTURES OF [N,N-BIS(2-DIPHENYLPHOSPHINOETHYL)ETHYLAMINE]-TRICARBONYLCHROMIUM

The crystal and molecular structure of [N,N-bis(2-diphenylphosphinoethyl)ethylamine]tricarbonylchromium, [(C6H5)PCH2CH2N(CH2CH3)CH2CH2P(C6H5)2Cr(CO)3, have been determined by single-crystal X-ray diffraction techniques. The crystals belong to the monoclinic system, space group B21/c with the dimensions a = 14.884, b = 18.826, c = 21.274 Å; 7beta; = 94.05. The calculated density assuming Z = 8 is 1.353 g/cc; the observed density is 1.35 g/cc. The final value of the conventional R factor is 7.5 % for 2547 independent nonzero reflections measured at 21° with a manually operated General Electric counter diffractometer. The least-squares refinement employed anisotropic temperature factors for all nonhydrogen atoms. The structure is a distorted octahedron, with the N and the two P atoms in mutually cis positions. The Cr-C(carbonyl) distances trans to phosphorus atoms (1.83 and 1.82) are almost as short as the Cr-C(carbonyl) distance (1.80 Å) trans to a nitrogen atom. Also, the Cr-N distance is anomalously long (2.31 Å). It appears that there are severe strains in this molecule as a result of the formation of fused chelate rings, with perhaps additional strain resulting from nonbonded repulsions. Because of the strains and distortions involved, it is unwise to base discussions of Cr-C multiple bonding or correlations of such bonding with structural and spectroscopic parameters on data obtained from this or similarly strained molecules. © 1969, American Chemical Society. All rights reserved.