7327
Structural Characterization of { [ (C,H,) ,PI ,N 1 [Cr, ( CO ) ,,I]. Stereochemistry and Bonding of the Bis ( triphenylphosphine ) iminium Cation and of a Monohalogen-Bridged Dinuclear Metal Carbonyl Anion Larry B. Handy,laJ John K. Ruff,lb and Lawrence F. Dahl'"?'
Contribution from the Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, and the Department of Chemistry, University of Georgia, Athens, Georgia 30601. Received June 3, 1970 Abstract: An X-ray crystallographic analysis of the [PPN][Cr2(CO)loI]salt (where PPN represents the [(C6&)3P=N-P(CsH&] + cation) has provided unequivocal proof that the halodecacarbonyldimetalate anion, [Cr2(CO)loI]-, possesses a "bent" Cr-I-Cr framework rather than a linear one initially proposed from infrared analysis. Hence, the formal replacement of the bridging hydrogen atom in the [(OC),Cr-H-Cr(CO),]- anion of D4h-4/ m2/m2/m geometry, which contains a linear Cr-H-Cr segment held together by a three-center electron-pair bond, by a bridging halogen atom results in a drastic geometrical transformati,(CO),and Fe4(h5-C5H5)4S4, are described in terms of a qualitative molecular orbital model which successfully relates their molecular geometries, including the absence of direct cobalt-cobalt bondingoin C O ~ ( C O ) ~in~ accord S ~ ~ , with an observed average nonbonding Co . .Co internuclear compound crystallizes in the tetragonal system with cell dimensions distance of 4.115 (4) A. The C94(C0)12Sb4 a = 14.561 (3), c = 10.507 (4) A, and with centrosymmetric space group symmetry Z41/amd. Each of the four molecules per cell possesses crystallographic site symmetry DPd-42m. The application of the symbolic-addition method in space group Z41/amdto determine this crystal structure is briefly outlined. Full-matrix least-squares refinement of the structure yielded RI = 5.0% and RP = 5.2z for the 282 independent reflections with \F,I > 44FJ.
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T
he synthesis and study of transition-metal complexes containing metal-metal bonds has shown a meteoric rise in the last few Prior to about
* Address correspondence to this author. (1) Previous paper in this series: A. S. Foust, M. S. Foster, and L. F. Dahl, J . Amer. Chem. Soc., 91, 5633 (1969). (2) This paper is based in part on a dissertation submitted by A. S . F. to the Graduate School of the University of Wisconsin in partial fulfillment of the requirements for the Ph.D. degree, Jan 1970. (3) F. A. Cotton, Accounts Chem. Res., 2, 240 (1969), and references contained therein. (4) E. W. Abel and F. G . A. Stone, Quart, Rev., Chem. Soc., 23, 325 (1969), and references contained therein.
10 years ago, metal-metal bonding was primarily a curiosity, and the deliberate synthesis of a compound containing a metal-metal bond was virtually unknown. The recent preparation and characterization of Co2(C0)6AS2in our laboratory led to the postulation of the existence of an As-As multiple bond of T order near ( 5 ) P. Chini, Inorg. Chim. Acta Rea., 2, 31 (1968), and references contained therein. (6) B. R. Penfold in "Perspectives in Structural Chemistry," Vol. 11, J. D. Dunitz and J. A. Ibers, Ed., Wiley, New York, N. Y., 1968, p 71. ( 7 ) M. C. Baird, Progr. Inorg. Chem., 8 , 1 (1968). and references contained therein.
Foust, Dahl
Organometallic Pnicogen Complexes
