2654
Organometallic Pnicogen Complexes. VI. Synthesis, Structure, and Bonding of a New Iron-Antimony Cluster Complex, { [Fe( h6-C,H,) (CO) ,SbCl] [FeCl,] CH,Cl,; Geometry of the Tetrachloroferrate( 11) Anion and Its Stereochemical Relationship with Other Tetrachlorometalate Anions’ Trinh-Toan and Lawrence F. Dahl* Contribution f r o m the Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706. Received August 12, 1970 Abstract: A new kind of antimony-(transition metal) cluster system has been isolated as a cation of the dark reddish purple crystalline salt { [Fe(h5-C5H5)(C0)2]aSbC1) 6FeCl4].CH2Clz by the reaction of Na[Fe(h5-C5H5)( C 0 ) J with SbC13. The characterization of this trimetal-substituted derivative of the nonisolatable tetrachlorostibonium cation was achieved from a three-dimensional X-ray diffraction analysis. Crystalline { [Fe(hW5HS)(C0)2]3SbCl]2[FeC14].CHzClz is constructed of discrete { [Fe(h5-C5H5)(C0)2]3SbC1) + cations, [FeC14] 2- anions, and CHzClzsolvent molecules. In the cation the one chlorine and three [Fe(hj-C6H5)(CO)2]ligands are markedly distorted from a regular tetrahedral arrangement about the central antimony atom; the orientations of two of the three [Fe(hj-C5H~)(C0)2]ligands approximately conform to threefold symmetry about the Sb-Cl bond, with the disposition of the third one differing from this pseudothreefold geometry primarily by a rotation of approximately 143’ about its Fe-Sb axis coupled with a small but significant angular distortion of the Fe,SbCl fragment from a n idealized C3,-3m geomepy to a n experimentally observed C,-m o$e. The hitherto unknown Fe-Sb bond length is of average value 2.54 A, while the Sb-C1 bond length is 2.401 (4) A. A detailed comparison of the stereochemical features of this cation with those of electronically equivalent, neutral tin-(transition metal) cluster molecules is made, including a discussion of the nature of the Sb-C1 and Sb-Fe bonding. The structural data of the [FeCld] *- anion (of crystallographic site symmetry Cz-2) are compared to those of the other tetrachlorometalate anions [MCL] 2(M = Mn, Co, Ni, Cu, Zn), and rationalizations of the observed trends in average M-C1 bond lengths in this series and in the [Fe$14]--[FeC14]2- pair are made in terms of bonding arguments. The fact that the determined mean value of 2.30 A for the Fe(I1)-C1 bonds in the [FeClaI2- anion is 0.11-0.14 A longer than the average values for Fe(II1)-C1 lengths found in several salts containing [FeC14]- anions illustrates that the placement of the one extra electron of the [FeCl4I2-anion in a n antibonding M O (of doubly degenerate representation e under assumed cubic Td-33msymmetry) and the interdependent size expansion of the appropriate iron valence orbitals due to a less positive charge o n the Fe(I1) nucleus produce a drastic enlargement of the Fe-C1 bonds: The significant difference in the two crystallographically distinct Fe-C1 bond lengths of 2.284 (4) and 2.320 ( 5 ) A in the [FeC1412- anion together with its observed angular distortion are attributed in part to the interaction of two of the four chlorine atoms of the [FeC14]2- anion with the hydrogen atoms of the CHzClzmolecule. Crystalline { [Fe(hj-CsH5)(C0)~13SbCI) 2[FeClh] CHzClzforms monoclinic crystals, with four formula species in unit cell of centrosymmetric space group 12/c and of dimensions a = 19.360 (2), b = 17.111 (l), c = 16.850 (2) A, and 0 = 94.06 (1)’; the calculated and observed densities are 1.979 and 1,986 g/cma, respectively. An anisotropic-isotropic full-matrix least-squares refinement of the nonhydrogen atoms yielded final discrepancy values of R1 = 7.1 and Rz = 6 . 4 z for the 2040 independent data ( I 2 2 4 ) ) collected with a Datex automated General Electric diffractometer.
A
l t h o u g h a large n u m b e r of transition m e t a l cluster c o m p o u n d s c o n t a i n i n g tin a t o m s h a v e been s t r u c turally c h a r a c t e r i z e d , 2-17 s t r u c t u r e s of (transition
(1) (a) Previous paper in this series: A. S . Foust and L. F. Dahl, (b) presented in part at the Inorganic Symposium on “Structure and Chemistry of Compounds with Metal-Metal Bonds,” Joint Conference of the Chemical Institute of Canada and the American Chemical Society, Toronto, Canada, May
J . Amer. Chem. Soc., 92, 7337 (1970);
I 97n. ._ _.
(2) B. T. Kilbourn and H. M. Powell, Chem. Ind. (London), 1578 (19 64). (3) (a) R . D. Cramer, R. V. Lindsey, Jr., C. T. Prewitt, and U. G. Stolberg, J. Amer. Chem. Soc., 87,658 (1965); (b) L. J. Guggenberger, Chem. Commun., 512 (1968). (4) 3. D. Cotton, J. Duckworth, S . A. R. Knox, P. F. Lindley, I. Paul, F. G. A. Stone, and P. Woodward, ibid., 253 (1966). (5) H . P. Weber and R. F. Bryan, ibid., 443 (1966); Acta Crystallogr., 22, 822 (1967). (6) (a) R. F. Bryan, J . Chem. Soc. A , 172 (1967); (b) ibid., A , 192 (1967); (c) Chem. Commun., 355 (1967). (7) R . F. Bryan and A. R. Manning, ibid., 1220 (1968). (8) R. Mason, G. B. Robertson, P. 0. Whimp, and D. A. White, ibid., 1655 (1968). (9) R. IC. Pomeroy, M. Elder, D. Hall, and W. A. G. Graham, ibid., 381 (1969).
Journal of the American Chemical Society 1 93:11 June 2, 1971
metal)-antimony cluster c o m p o u n d s are a s yet unreported. R e c e n t d e v e l o p m e n t s i n o u r l a b o r a t o r i e s i n t h e field of (transition metal)-arsenic cluster ~ y s t e m s * ~ ~ ~ ~ (10) (a) B. P. Bir’yukov, Yu. T. Struchkov, IC. N. Anisimov, N. E. Kolobova, 0. P. Osipova, and M. Ya. Zakharov, ibid., 749 (1967); (b) B. P. Bir’yukov, Yu. T, Struchkov, IC. N. Anisimov, N. E. Kolobova, and V. V. Skripkin, ibid., 750 (1967); (c) B. P. Bir’yukov, YU. T. Struchkov. I3~ Only signs with a probability factor of 2 4 4 . This procedure yielded a total of 2040 observed and 788 P 2 0.99 were accepted. After several cycles, 321 symbolic signs unobserved independent reflections (besides the sytematic absences were determined. By then, it seemed obvious that the two letter required by the space group). The linear absorption c ~ e f f i c i e n t , ~ ~ symbols A and B must have the same sign. p , for Mo K a radiation is 32.2 cm-l. Based on this absorption A computed three-dimensional Fourier synthesis, based on the coefficient together with the previously mentioned dimensions of revealed initial positions for one anticombination A = B = the regularly shaped crystal, the calculated transmission coefficients mony, four iron, and two chlorine atoms, the coordinates of which ranged from only 0.38 t o 0.43. 3 1 Since these extreme values of the were transformed to coordinates based on the initial unit cell of absorption correction31 caused only a & 2 - 3 x fluctuation in IFl’s, 12/c symmetry. One cycle of full-matrix least-squares refinement absorption corrections were neglected. No extinction corrections of these seven atoms with individual isotropic temperature factors were made. was carried out with a local version of the Busing-Martin-Levy The atomic scattering factors used for all atoms are those based ORFLS program.38 This refinement based on the minimization of on Hartree-Fock-Slater calculations as compiled by Hanson, et a / .3 2 Bw,AFC2with the weights assigned according to the relationship Dispersion corrections for atomic scattering factors were made for w = l/a,2(Fo), yielded R1 = [Z(]Fo] - IFcl)/ZIFo/l X 100 = 32.2% antimony, iron, and chlorine atoms. * 3 and R2 = [Zw(lF,l - ~F,1)2/ZwIFo12]’/2 X 100 = 39.4x. After two Unit Cell and Space Group. The measured lattice constants successive Fourier syntheses all nonhydrogen atoms were located ( 2 5 ” ) and estimated standard deviations for the monoclinic unit including those of a solvated CHzClz molecule, which was estabcell of { [Fe(h6-C6Hs)C0)z]3SbCl}z[FeCla] .CH2C12are a = 19.360 lished on the basis of the positions and relative peak heights of the chlorine and carbon atoms. The discrepancy factors at this point ( 2 ) , b = 1 7 . 1 1 1 ( 1 ) , c ~16.850(2)A,B = 94.06(1)”; thevolumeof were R1 = 1 1 . 4 z and Rz = 11.0%. Four cycles of least-squares the unit cell is 5568 A 3 . The density of 1.979 g/cm3 calculated on the basis of four of the above formula species per cell agrees well refinement were carried out with anisotropic thermal parameters with the experimental value of 1.986 g/cm3 measured by the flotafor the antimony, iron, and chlorine atoms and isotropic ones for
+ +
+
+
+
+,
(26) T. C. Furnas, Jr., “Single Crystal Orienter Instruction Manual,” General Electric Co., Milwaukee, Wis., 1966. (27) A. S. Foust, Ph.D. Thesis (Appendix), University of Wisconsin (Madison), 1970. (28) Argonne National Laboratory, “Orientation and Angle Setting Generation Program,” Program B-101, 1965. (29) V. A. Uchtman and L. F. Dahl, J . Amer. Chem. Soc., 91, 3756 (1969). (30) “International Tables for X-Ray Crystallography,” Vol. 111, Kynoch Press, Birmingham, England, 1962, p 157. (31) J. F. Blount, DEAR, an absorption correction program based on the methods of W. R. Busing and H. A. Levy, Acta Crystallogr., 10, 180 (1957). (32) H.’P. Hanson, F. Herman, J. D. Lea, and S. Skillman, ibid., 17, 1040 (1964). (33) Reference 30, p 213.
Journal of the American Chemical Society / 93:11
June 2, 1971
(34) Reference 30, Vol. I, 2nd ed, 1965, p 101. (35) (a) G. H. Stout and L. H. Jensen, “X-Ray Structure Determination,” Macmillan, New York, N. Y . , 1968, p 321; (b) I. L. Karle, K. S. Dragonette, and S . A. Brenner, Acta Crysfallogr., 19, 713 (1965). (36) (a) H. Hauptman and J. Karle, “Solution of the Phase Problem. I. The Centrosymmetric Crystal,” American Crystallographic Association Monograph No. 3, Polycrystal Book Service, Pittsburgh, Pa., 1953; (b) cf, I. L. Karle and J. Karle, Acta Crystallogr., 16, 969 (1963). (37) R. B. K. Dewar and A. L. Stone, “Fame and Magic, Fortran Computer Programs for Use in the Symbolic Addition Method,”
University of Chicago, 1966; cf, E. B. Fleischer, R. B. K. Dewar, and A. L. Stone, Abstracts of Papers, American Crystallographic Association, Winter Meeting, Atlanta, Ga., 1967, p 20. (38) W. R. Busing, Ihe cyclopentadienyl carbon. .carbon separations, 3.7 A for the chlorine. . chlorine contacts, 3.2 A for the oxygen. . .carbon sepcation by less than 0.01 A (
