A comparison of room-temperature single-crystal neutron and x-ray diffraction studies of the bis(triphenylphosphine)iminium salt of the .mu.-hydro-decacarbonyldichromate(1-) monoanion
| Autor: | Jeffrey L. Petersen, Jack M. Williams, Paul L. Johnson, Lawrence F. Dahl, James E. O'Connor |
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| Rok vydání: | 1978 |
| Předmět: | |
| Zdroj: | Inorganic Chemistry. 17:3460-3469 |
| ISSN: | 1520-510X 0020-1669 |
| Popis: | A combined room-tempepature x-ray and neutron diffraction study of the bis(triphenylphosphine)iminium salt of the (Cr/sub 2/(CO)/sub 10/(..mu..-H))/sup -/ monoanion has been performed to investigate the effects of crystal packing on the anion and Cr--H--Cr geometry. A comparison with the earlier work on the (Et/sub 4/N)/sup +/ salt has shown that the pseudo-D/sub 4h/ geometry of the anion's nonhydrogen framework is maintained. This result indicates that the (Cr/sub 2/(CO)/sub 10/(..mu..-H))/sup -/ anion is considerably less susceptible than the tungsten analogue to a twisting deformation from a linear, eclipsed to a bent, staggered configuration. ((Ph/sub 3/P)/sub 2/N)/sup +/(Cr/sub 2/(CO)/sub 10/(..mu..-H))/sup -/ crystallizes with four molecules in a monoclinic unit cell of symmetry C2/c with x-ray-determined lattice parameters of a = 21.377(6) A, b = 16.285 (4) A, c = 16.186 (5) A, and ..beta.. = 128.68 (2)/sup 0/. The ((Ph/sub 3/P)/sub 2/N)/sup +/ cation lies along the twofold rotation axis which bisects the P--N--P bond angle of 154.8 (4)/sup 0/; the (Cr/sub 2/(CO)/sub 10/(..mu..-H))/sup -/ anion resides on the crystallographic center of symmetry. Only one position for the bridging hydrogen atom was resolved from the neutron diffraction data with the corresponding maximum negative nuclear density at the center of symmetry. However, themore » highly anisotropic character of its thermal ellipsoid strongly favors our interpretation that the observed anion structure is consistent with the slightly bent (Cr/sub 2/(CO)/sub 10/(..mu..-H))/sup -/ anion of C/sub 2v/-2mm geometry (previously observed for the (Et/sub 4/N)/sup +/ salt) being disordered among four equivalent sites and with the off-axis placement of the bridging hydrogen atom. 48 references, 4 figures, 7 tables.« less |
| Databáze: | OpenAIRE |
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