4840
Figures 2 and 3 between the guanidyl and phosphate groups within the asymmetric unit resembles very closely the hydrogen bonding interaction between the guanidyl moiety of arginine-35 and the 5’-phosphate group of the deoxythymidine 3 ‘,5 ’-diphosphate (pdTp) inhibitor observed in the high-resolution structure of staphylococcal nuclease and shown in Figure 1. Additionally, in the enzyme the third guanidyl nitrogen atom
of this arginine forms bridging hydrogen bonds to backbone carbonyl oxygen atoms. In methylguanidinium dihydrogenphosphate, the third nitrogen atom, Nz,hydrogen bonds weakly through its two hydrogen atoms (Hn21 and Hnzz)to oxygen atoms of phosphate groups in two other asymmetric units. The remaining guanidinium hydrogen atom, Hn31,also hydrogen bonds to a phosphate oxygen in another asymmetric unit.
Organometallic Chalcogen Complexes. XXVII. Structure and Bonding of a Metal Carbonyl Tetramer, Go4(CO)4(~2-SC2H5)8, Containing a Planar Tetrametal Cluster System. A Direct Stereochemical Appraisement of Strong Me tal-Metal Interactions in a Ligand-Bridged Complex1,2 Chin Hsuan Wei,3&Laszl6 Mark6,3b Gyorgy BO^,^^ and Lawrence F. Dahl*3d
Contribution f r o m the Biology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, the Department of Organic Chemistry of the University of Chemical Engineering, Veszprkm, Hungary, Laboratory of the Chemistry and Technology of the Radioelements of the C N R , 35100-Padova, Italy, and the Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706. Received January 22, 1973 Abstract: A structural characterization of Co4(CO)4(p2-SC2H& has not only revealed a new kind of organometallic X)S a planar array of four metal atoms but also has afforded cluster system of general formula M ~ L ~ ( F ~ -containing from the determined molecular parameters a direct assessment of the effect of localized metal-metal interactions upon the molecular geometry of a ligand-bridged complex. The four cobalt atoms are situated at the corners of a rectangle with each pair of cobalt atoms connected by two bridging mercapto sulfur atoms. Each chemically equivalent cobalt atom has a distorted (tetragonal-pyramidal)-like environment of four bridging sulfur atoms in the basal plane and the carbonyl ligand at the apex. An electron-pair metal-metal bond may be assumed to complete an octahedral-like coordination about each cobalt atom. The basic C O ~ ( C O ) ~ ( framework ~ ~ - S ) ~ of the molecule ideally conforms to D2h symmetry which is lowered by inclusion of the sulfur-attached ethyl groups to the crystallographically required C, symmetry. The seuere orthorhombic Dlh distortion of the COSScore from a tetragonal Ddhmodel is ascribed to the energy stabilization of the tetramer by the formation of two localized electron-pair cobalt-cobalt bonds such that each Co(I1) attains a closed-shell electronic configuration. The considerable bond strength of these localized metal-metal ban$ is directly gauged in this molecule per se through (1) the resulting short Co-Co bonding distance of 2.498 (5) A for one qpposite pair of cobalt atoms in the tetracobalt rectangle us. a normal nonbonding Co. . .Co distance of 3.312 (9) A for the other opposite pair, and (2) the sharply acute Co-S-Co bond angles of 67.8” (av) for the two (metal-metal)-bonded Co2S2fragments compared to the normally obtuse Co-S-Co bond angles of 94.0” (av) for the other two Co2S2fragments without the cobalt-cobalt bonds. The architecture of the C O ~ ( C O ) ~ ( ~ ~ - Smolecule C ~ H ~ )isScompared with those of the structurally related Feltetramer, and its (C0)&2-SC2H5)2-type dimer and of the structurally analogous Ru~(NO)~(~~-C~),(~~-P(C~H~)~)~ metal-metal bonding is discussed relative to that for a hypothetical tetragonal D4hmodel. One salient feature is that, whereas the two S-CH2 bonds in each (cobalt-cobalt)-bonded Co2(SC2H&fragment are “equatorial-axial” anti, the two S-CH2 bonds in each Co2(SC2HJ2fragment without the Co-Co bond are “bisequatorial” syn (relative to the tetracobalt plane); the fact that this latter arrangement is unprecedented in the dinuclear Fe2(C0)6(p2-SR)2 molecules is rationalized fromastereochemicalconsiderations. C O ~ ( C O ) ~ ( ~ ~ - S Ctriclinic; ~ H & : Pi ; a = 9.22 (2), b = 10.55 (2), C = 10.84 (2) A ; = 61’ 21 (lo)’, p = 79’ 10 (lo)’, = 66’ 12 (10)’; p o b s d = 1.63 GS. Pcaiod = 1.69 g ~ m for - 2 ~ = 1. Least-squares refinement gave Rl(F) = 8.3% and R2(F) = 7.4% for 1575 independent photographically collected data.
D
uring the last 10 years considerable effort has been directed toward preparative and structural studies
(1) (a) The research a t the University of Wisconsin was financially made possible by the National Science Foundation (Grant No. GP19175x1, while the research at Oak Ridge was supported by the U. S. Atomic Energy Commission under contract with the Union Carbide Corporation. (b) Presented in part at the Winter Meeting of the American Crystallographic Association, Atlanta, Ga., Jan 25-28, 1967.
Journal of the American Chemical Society J 95:1.5
of organometallic sulfur clusters in order to elucidate the detailed nature of metal-metal interactions in these complexes and especially to systematize the influence of (2) Previous paper in this series: G. L. Simon and L. F. Dahl, J . Amer. Chem. Soc., 95,2164 (1973). (3) (a) Biology Division, Oak Ridge National Laboratory; (b) University of Chemical Engineering, Veszprim, Hungary; (c) CNR, Padova, Italy; (d) University of Wisconsin.
July 25, 1973
4841
from each other only by the necessity of an electron-pair valence electrons upon molecular geometries. This work interaction in one as opposed to none being required was largely catalyzed by an extensive investigation of in the other in order for each of the metal atoms to the reactions of dicobalt octacarbonyl with elemental achieve a so-called closed-shell electronic ground-state sulfur and sulfur-containing reagents4 which have configuration. This latter kind of systematic analysis yielded a wide variety of polynuclear cobalt carbonyl which showed the drastic effects of metal-metal intersulfur complexes. Crystallographic studies of these actions on ligand-bridged organometallics was first complexes, which include C O ~ ( C O ) , ( ~ &FeCoz(CO)9~ from structural investigations16 of two (~3-s [CO,(CO>,(~~-S)]Z(~~-S~),’ )~~ C03(CO)3{( P Z - S C ~ H ~ ) ~demonstrated dimeric complexes Mz(h5-CjH6)z(pz-P(C6H5)2)2 (where ( ~ z - C O ) } ,Cos(C0)6(p2-CO)s(p2-SCzH5)(p3-SCzH5)3(p3~ s))’c o ~ ( ~ ~ ) S ( ~ Z ~ ~ ~ )~ 2~ ( 6~ ( ~~ ~~ ~) >1 ,4 , (1 ~0 2 ~ ~ ~ M ) ( ~=3 Co, 3 - ~Ni) ) ~ and more recently was obtained by an alteration of valence electrons either through replaceCSz,11j12and co6(co)16c2s3,12’13have revealed highly ment of difterent metal atoms and/or different ligands20 unusual structures l 4 containing new metal-sulfur linkor through redox reactions.21z22 This paper reports the ages of biological importance as well as of considerable details of the stereochemistry and bonding of cOq(c0)4theoretical interest. (pZ-SC2H&, which have been briefly communicated In 1965 Mark6 and Bor l5 reported the preparation of earlier. Ib an additional cobalt carbonyl-sulfur complex, Co4(CO),(SC,H,),, which was obtained by the reaction of Experimental Section hydrated cobalt dichloride with sodium hydroxide, ethyl Single-Crystal X-Ray Data. Black air-stable crystals of Cor(CO)amercaptan, and carbon monoxide in methanol at room (qLZ-SC2H&, were recrystallized from petroleum ether solution, from temperature. The formulation of this compound as a which a needle crystal of length 0.38 mm and width 0.12 mm was tetramer was based on a molecular weight determinaisolated and used for the collection of intensity data. The crystal, tion in benzene. An infrared examination was also sealed in a thin-walled glass capillary tube, was mounted for rotation about the needle axis which corresponded to the b axis of an arcarried out, but no possible structural models were probitrarily chosen A-centered triclinic unit cell. The lattice paramposed at that time. l 5 eters of this A-centered triclinic cell were determined from Okl and Our interest in elucidating the stereochemical nature hkO precession photographs. Multiple-film equiinclination Weisof this new type of complex resulted in the structural senberg data were obtained for reciprocal levels h01 through hlOl determination of Co4(C0)4(SC2H& which revealed a with Zr-filtered Mo Ka! radiation. In order to eliminate systematic new basic polyhedral unit for an organometallic M4L4- errors due to spot compaction o n the lower half of Weissenberg film,13 the intensities of only the upper half of the Weissenberg film ( P ~ - Xsystem. )~ This complex also has a unique stereowere determined. This required two separate sets of film data for chemical feature in that it affords from the determined the nonzero reciprocal levels corresponding to a 360” rotation architecture of one complex a direct measurement of the range. In addition, multiple-exposure precession data were collected for the hkO, Okl, lkl, and 2kl reciprocal levels. The intensideformation of the molecular geometry of a ligandties of all films were visually estimated by comparison with calibridged complex due to a metal-metal interaction. brated sets of standard spots. Absorption corrections were not Previous a s ~ e s s m e n t s ’ ~of - ~ ~the influence of metalmade since for Mo KCY radiation the estimated pR,,, was only 0.37, metal interactions on the molecular geometries of orand hence the maximum variation in intensity due to absorption is ganometallic ligand-bridged complexes have arisen from estimated to be less than 1 2 z . After correction of the intensities for Lorentz-polarization effects and spot extension,z4 all indices comparisons of two corresponding complexes differing were transformed from the A-centered triclinic unit cell to the re-
duced primitive triclinic unit cel125 according to the a < b < c (4) (a) L. Marko, G. Bor, and G. Almlsy, Chem. Ber., 94, 847 (1961); convention. z 6 Reflections common to both sets of Weissenberg (b) L. Marko, G. Bor, and E. Klumpp, Chem. Ind. (London), 1491 films and the precession data then were utilized in a least-squares (1961); (c) L. Mark6, G. Bor, E. Iclumpp, B. Mark6, and G. Almasy, Chem. Ber., 96, 955 (1963); (d) L. Marko, G. Bor, and E. Iclumpp, merging programz7 which placed all 1575 independent diffraction Angew. Chem., 75, 248 (1963); (e) E. Idumpp, L. Marko, and G. Bor, maxima on a single common scale. Standard deviations of the obChem. Ber., 97, 926 (1964); (f) S. A. Khattab, L. Marko, G. Bor, and served structure amplitudes were assigned as follows. If I, < B. Marko, J. Organometal. Chem., 1, 373 (1964); (9) E. Iclumpp, G. 4Zo(min), u(F,) = [F,/20][41~(min)/I,]2; if I, 2 410(min), u(F,) = Bor, and B. Marko, Chem. Ber., 100, 1451 (1967); (h) G. Bor and G. F0/20. Neither extinction nor dispersion corrections were Natile, J . Organometal, Chem., 26, C33 (1971); (i) E. Iclumpp, G. Bor, made.28’29 and L. Marko, ibid., 11, 207 (1968); (j) L. Mark6, Acta Chim. (BudaCrystal Data. The reduced primitive triclinic unit cell with pest), 59, 389 (1969); (k) G. Natile, S. Pignataro, G. Innorta, and G. Bor, J . Organometal. Chem., 40, 215 (1972). lattice parameters a = 9.22 i 0.02, b = 10.55 f 0.02, c = 10.84 f (5) C. H. Wei and L. F. Dahl, Znorg. Chem., 6,1229 (1967). (6) D. L. Stevenson, C. H . Wei, and L. F. Dahl, J. Amer. Chem. SOC., 93, 6027 (1971). (20) P. D. Frisch and L. F. Dahl, J. Amer. Chem. SOC.,94, 5082 (7) D. L. Stevenson, V. R. Magnuson, and L. F. Dahl, J. Amer. Chem. (1972), and references cited therein. SOC.,89, 3727 (1967). (21) (a) N. G. Connelly and L. F. Dahl, J. Amer. Chem. Soc., 92, (8) C. H. Wei and L. F. Dahl, J . Amer. Chem. SOC.,90,3960 (1968). 7470, 7472 (1970); (b) Trinh-Toan, W. P. Fehlhammer, and L. F. (9) C. H. Wei and L. F. Dahl, J . Amer. Chem. SOC.,90, 3977 (1968). Dahl, ibid.,94, 3389 (1972), and references cited therein. (10) This molecular complex is isostructural with C O ~ C O ) S ( ~ Z - C O ) Z - (22) G. L. Simon and L. F. Dahl, J. Amer. Chem. Soc., 95, 2175 (1973), and references cited therein. (p:-Te)z: C. H . Wei, E. Rodulfo de Gil, and L. F. Dahl, to be submitted for publication. (23) Cf.M. J. Buerger, “X-Ray Crystallography,” Wiley, New York, (11) J. F. Blount, L. Marko, G. Bor, and L. F.Dahl, to be submitted N. Y., 1942, pp 227-229. for publication. (24) D. C. Phillips, Acra Crystallogr., 7, 746 (1954). (12) Initially formulated from elemental analyses as C O ~ ( C O ) I O C S Z . ~ ~ (25) Cf.L. V. Azaroff and M. J. Buerger, “The Powder Method in (13) C. H. Wei and P. A. Agron, to be submitted for publication. X-Ray Crystallography,” McGraw-Hill, New York, N. Y., 1958, (14) The preparation, structure, and bonding of another stereoChapter 11. chemically related mercaptocobalt carbonyl cluster, CO~(CO)~(L(Z-CO)~- (26) V. Balashov, Acta Crystallogr., 9, 319 (1956). C. H. Wei and L. F. Dahl, ( ~ z - S C Z H ~ ) ~ ( ~ ~ - Swere CZH reported: ~)Z, (27) P. W. Sutton and M. D. Glick, “A Crystallographic Data CorJ . Amer. Chem. SOC.,90, 3969 (1968). relation Program,” University of Wisconsin (Madison), 1964. (15) L. Marko and G. Bor, J. Organometal. Chem., 3 , 162 (1965). (28) For Mo K a radiation the values of the dispersion corrections to (16) J. M. Coleman and L. F. Dahl, J . Amer. Chem. SOC., 89, 542 the atomic scattering factors are Af’ = 0.4 and Af” = 1.1 for cobalt; (1967). Af’ = 0.1 and Af” = 0.2 for sulfur.29 Since CO~(CO)~(~Z-SCZHS)S (17) R. H. B. Mais, P. G. Owston, and D. T. Thompson, J. Chem. possesses a centrosymmetric space group, these relatively small disperSOC.A , 1735 (1967). sion corrections do not affect significantly the atomic coordinates. (18) S . F.Watkins, J. Chem. SOC.A , 1552 (1969). (29) D. H. Templeton in “International Tables for X-Ray Crystallog(19) G. L. Simon and L. F. Dahl, J . Amer. Chem. Soc., 95, 783 raphy,’’ Vol. 111, Kynoch Press, Birmingham, England, 1962, p 215; (1973), and references cited therein. D. H. Templeton, Acra Crystalbgr., 8, 842 (1955). 81
Wei,
Mark;, Bor, Dahl
1 Organometallic
Chalcogen C o m p l e x e s
4842 Table I. Final Atomic Parameters ( X l O 4 P t b Atom Co(1) Co(2) S(2) '(') S(4) s(3) C(1T) O(1T) C(2T) O(2T) C(1E) C(2E) C(3E) C(4E) C(5E) C(6E) C(7E) C(8E)
X
Y
2
4540 (2) 4731 (2) 5961 (4) 2568 (4) 6631 (4) 3094 (4) 4245 (18) 4060 (17) 4578 (16) 4463 (14) 8097 (15) 8937 (18) 2478 (17) 1793 (29) 7049 (16) 8533 (17) 2471 (17) 1437 (17)
3039 (2) 5247 (2) 2839 (4) 4370 (4) 2848 (4) 4283 (4) 1214 (21) 61 (14) 6171 (17) 6679 (14) 2249 (17) 2083 (20) 3470 (17) 2078 (30) 1067 (16) 876 (18) 2859 (15) 3596 (19)
6683 (2) 6847 (2) 8091 (4) 7897 (4) 4895 (4) 4877 (4) 7468 (19) 7908 (14) 7909 (18) 8683 (15) 7517 (17) 8654 (21) 9830 (15) 10505 (22) 4748 (17) 3555 (18) 4787 (16) 3654 (18)
Pll
P22
P33
PI2
P13
127 (3) 117 (3) 142 (6) 129 (5) 124 (5) 130 (5) 184 (28) 520 (39) 177 (26) 323 (26) 14 (22) 222 (32) 246 (30) 559 (66) 173 (26) 207 (30) 229 (28) 191 (26)
107 (3) 113 (3) 125 (6) 150 (6) 118 (5) 119 (5) 218 (34) 188 (23) 177 (28) 279 (25) 214 (28) 262 (37) 217 (29) 532 (63) 150 (26) 200 (31) 175 (26) 283 (33)
81 (3) 74 (3) 85 (5) 89 (5) 94 (5) 91 (5) 175 (32) 182 (24) 149 (29) 215 (24) 153 (27) 196 (34) 54 (20) 139 (33) 172 (29) 152 (27) 95 (22) 147 (27)
-49 (3) -39 (2) -38 (5) - 56 (5) -39 (4) -57 (4) -45 (26) -214 (25) -63 (22) -85 (19) 10 (20) -77 (27) -117 (25) -394 (54) -64 (21) 3 (24) -94 (21) -83 (24)
-7 (2)
P23
-35 -41 -29 -48 -45 -38 -101 -21 -71 -149 -110 -72 -42 -110 -92 -99 -31 -99
-8(2) -27 (5) 5 (4) -10 (4) -7 (4) -43 (23) -45 (23) -32 (21) -62 (19) -66 (20) -31 (26) 23 (20) 60 (38) 31 (21) 8 (23) -51 (20) -58 (22)
(2) (2) (5) (5) (4) (4) (27) (19) (23) (20) (22) (27) (19) (38) (22) (23) (19) (24)
a Least-squares derived standard deviations of the least significant figures are given in parentheses in all tables and in the text. Since no absorption corrections were applied, these values represent a lower limit for the true standard deviations. See W. C. Hamilton and S. C. The form of the anisotropic temperature factor is exp[-(Pllh2 &k2 p d 2 4Abrahams, Acta Crystallogr., Sect. A , 26, 18 (1970). 2Pishl 2Pzskl)l. 2Pizhk
+
+
+
+
Figure 3. Arrangement of the C O ~ ( C O ) ~ ( ~ ~ - Smolecule C ~ H ~ ) in ~ the triclinic unit cell stereochemically viewed down the center of the cell. The origin of the unit cell is in the upper-left rear corner with the right-handed axial system oriented such that the a axis is UP. Figure 1. View of the CO,(CO)&Z-SCZH~)~ molecule approximately perpendicular to the tetracobalt plane. The entire molecule four sulfur, ten carbon, two oxygen, and ideally twenty hydrogen possesses crystallographic site symmetry Ci-7; the C O , ( C O ) , ( ~ ~ - S ) ~ atoms. fragment ideally has D~h-2/m2/m2/m symmetry. The hydrogen Determination of the Structure. Initial coordinates for the cobalt atoms are not shown. and sulfur atoms were obtained from an interpretation of a threedimensional Patterson function, and the positions of the carbon and oxygen atoms were established from successive Fourier synthesis. Isotropic least-squares refinement of the 18 nonhydrogen X 100 of 9.7% and atoms yielded an R1 = [21Fol - /F,//ZIIF,/] R2 = [ZwIIFo1 - /F,~~~!~wIF,/~]'/? X 100 of 9 . 2 2 after three cycles. In order to obtain a more realistic thermal crystal model, anisotropic least-squares refinement was continued for four additional cycles until all parameter shifts converged within 4 % of their corresponding standard deviations at R1 and RZ values of 8.3 and 7.4%, respectively. A final difference Fourier map showed no irregularities. Although peaks characteristic of approximately 10 of the 20 independent hydrogen atoms were resolved at the expected positions on this map, no further attempt was made to locate them. ~H,), Figure 2. A stereoscopic view of the C O ~ ( C O ) ~ ( ~ ~ - S Cmolecule All least-squares refinements30 were based on the minimization of (without the hydrogen atoms) for whicht hermal ellipsoids of 50z Z\v!IIF.l - lFcll* with the individual weights wi = 1/u(Fd2. Scatprobability are shown for each atom tering factors used for cobalt were those of Thomas and Umeda;31 for sulfur, those of Dawson;32 and for carbon and oxygen, those of Berghuis, et nl.33 Final positional and thermal parameters with 0.20 A , a = 61" 21 & lo', /3 = 79" 10 i lo', = 66" 12 i 10' their estimated standard deviations, obtained from the output of contains one formula of C O , ( C O ) ~ ( ~ ~ - S C ~ The H ~ ) ~volume . of the unit cell is 825 A 3 . The total number of nonhydrogen electrons per unit cell equals 388. The observed density of 1.63 g (30) W. R. Busing, I
