22 J.C.S. DaltonCrystal and Molecular Structure of Di-pcarbonyL(tricarbonylcoba1tio)-carbonyl (x-cyclopentadienyl) ironBy Ian L. C. Campbell and Frederick S. Stephens,"t Department of Chemistry, University of Essex, ColchesterThe crystal structure of the title compound has been determined by X-ray diffraction methods by use of counterdata and refined to R 0.055 for 1240 unique reflections by a full-matrix least-squares procedure. The monoclinicunit cell, space group P2,lm. has dimensions a = 7.008 f 0.009. b = 10.941 f 0.1 07. c = 8.605 f 0.01 6 8,= 104.7 f 0.1 O , for Z = 2. The molecule possesses m symmetry (a requirement of the space group) and hasa non-planar Fe(CO),Co bridging system, the angle between the two Fe(C0)Co planes being 143.5". Fe Coi s 2.545(1) A.The terminal carbonyl groups lying on the mirror plane are in a cis-configuration. The metal tobridge-carbon distances are: Fe-C 1.882(7), Co-C 2.036(7) 8. The cobalt is in a square-based pyramidalen vi ron men t.C04 3SQINFRA-RED studies of compounds of the type [(x-dienyl)FeCo(CO),] have shown the presence of carbonyl-bridged species, both in solution and the solid state.lThe interpretation of the spectra suggested the carbonylbridges would be non-planar with interplanar bridgeangles of ca. 14OO.l The structure of the compound forwhich the dienyl ligand is indenyl (C,H,) has been shownto possess a distorted bridging systems2 The crystalstructure of the title compound was undertaken with aview to explaining the distortions observed in the bridg-ing system of the indenyl compound.EXPERIMENTALCrystaE Data.-C,,H,CoFeO, M = 347-9, Monoclinic,u = 7.008 f 0.009, b = 10.941 f 0.017, c = 8.605 f 0.016A, p = 104.7 f O s l o , U = 638.3 Hi3, D, = 1-80 (by flot-ation), 2 = 2, D, = 1.81, F(000) = 344.h'lo-&radiation,A = 0.71069 A, p(Mo-K,) = 24.2 cm-1, for cell parametersand intensity measurements. Systematic absences OOk fork = 2n + 1. Space group 2'2, (Ci, no. 4) or PB,/m (Cih,no. 11).The complex crystallises as dark brown plates lying on thet Present address: School of Chemistry, Macquarie University,North Ryde, N.S.W. 2113, Australia.A. R. Manning, J . Chem. SOC. ( A ) , 1971, 2321.F. S. Stephens, J.C.S. Dalton, 1974, 13.(001) face, elongated along a, with pinacoids (100) and{ 0 lo}.Unit-cell parameters were determined from single-crystal precession photographs by the use of Mo-K, radiation.Systematic absences indicated the space group to be P2, orP2,/nz. The intensities were collected on a PhilipsPAILRED diff ractometer by use of monochromatisedMo-K, radiation. Each reflection in the O-1OkE layersfor sin 0 < 0.54 was recorded. 1240 reflections gavecounts for which a(l)/I < 0.5, and these were used forthe structure analysis. Intensities were corrected forLorentz and polarisation effects, but no correction forabsorption or extinction was applied.The scattering factor curves for all atoms were taken fromref. 4, the values for cobalt and iron atoms being correctedfor the effects of anomalous dispersion. Calculations werecarried out on a PDP 10 computer of the University of Essexusing programmes written by one of us (F.S. S.).Structure Determination.-From the systematic absences,the space group is P2, or P2,/m. With two molecules perunit cell, there are no symmetry restrictions on the moleculargeometry imposed by the non-centric space group P2,.However, for the centric space group P2,/m, the moleculesmust possess either a centre of symmetry or a mirror plane.Only the latter is feasible for the present compound. Aa M. Mack, Norelco Reporter, 1966, 12, 40.4 ' International Tables for X-Ray Crystallography,' vol. 111,Kynoch Press, Birmingham, 19621975 23statistical analysis of the intensity data “(2) test] indicatedthe centric space group.5 The three-dimensional Pattersonsynthesis was consistent with this space group, and readilygave the positions of the metal atoms, The centric groupwas assumed therefore and confirmed subsequently by thesuccessful structure analysis. A series of Fourier anddifference syntheses, each phased by an increased number ofatoms, gave the positions of all non-hydrogen atoms.Refinement of the structure was carried out by a full-matrix least-squares procedure in which the functionminimised was CwA2.The weight for each reflection, w, wasinitially unity and in the final refinement given by zu =(5.0 - O.llFol + 0*0041F,,12)-1. For this latter weightingscheme the average values of wA2 for ranges of increasinglFol were almost constant.Reflections for which the calcu-lated structure factors were less than one-third of the ob-served values were omitted from the least-squares analysis.Initial refinement used a procedure in which positionaland individual isotropic thermal parameters for each atomwere refined. A difference synthesis, calculated when themaximum shift in any parameter was of the order of its a,showed no unusual features, and gave the approximatepositions of all the hydrogen atoms. These were included insubsequent calculations with positions calculated assumingC-H 1.0 and thermal parameters of B 6.0 Hi2.Final refinement was carried out with anisotropic thermalparameters for all non-hydrogen atoms. After severalcycles the positional parameters of the hydrogen atoms wereincluded in the least-squares matrix.The refinement wasterminated when the maximum shift in a parameter was< 0- la. 1225 reflections were included in the final cycle ofrefinement. The final value of R, based on 1240 reflections,was 0.055 and for R’{ = [Zw(IFol - IFcI)2/IcwlFo12]*) was0.057.Final atomic co-ordinates and thermal parameters aregiven together with their estimated standard deviations inTables 1 and 2. Observed and calculated structure factorsare listed in Supplementary Publication No. SUP 21149(8 pp., 1 microfiche) .*TABLE 1Atomic co-ordinates (fractional) with estimatedstandard deviations in parenthesesxla Y lb Z i t0.4441 (1)0-1457( 1)0-2652(8)0-5548( 10)0.6281 (7)0.268618)0.5043( 10)0.5 5 39 ( 7)0.0281 (12)0.1832 ( 15)0.3 707 (22) 0-3470( 11) 0-1006(20)c o 0.1 4 9 6 ( 2) fFe 0- 13 55 (2) tO W )O(T11) -0.2116(11) aO(T21) -0*2602(13) iC(B1)C(T11) -0.0766(13) *C(T21) -0*1077(17) a0*4329( 19) * C(1)C(2)0-510(9) a C(3)0.347( 14) 0*090( 9)H!1)0.1 77( 11) 0- 146 (8)H(2)H(3)Figure 1 shows a perspective drawing of the moleculeFigure 2 shows theThe molecules* See Notice to Authors No.7 in J.C.S. Dalton, 1973, IndexE. R. Howells, D. C. Phillips, and D. Rogers, Acta Cryst.,0.02 13( 13) 0.4786(6)O(T12) 0.3 9 6 4 ( 1 0) 0*4406( 6)0*0712( 11) 0.3 786( 7)0.3 0 1 3 ( 1 0) 0.367 9 (7)- 0*0556( 11)C(T12)0*2500( 13) 0*3107(8) -0*0386(10)0-2 80 (7)0*088( 12)- 0.1 19 ( 10)DISCUSSIONand the labelling of the atoms.6packing of the molecules in the crystal.6issue (items less than 10 pp.are supplied as full size copies).1950, 3, 210.TABLE 2Thermal parameters ( x lO4),* with estimatedstandard deviations in pa.renthesesb l l b22 b33 bl, b,, b2300Co 246(3) 95(1) 98(1) 0 5 2 P )Fe 234(3) 113(1) 87(1) 0 39P)O(B1) 107(36) 161(7) 293(12) 277(14) 261(17) 8:(8)O(T11) 362(20) 268(13) 269(15) 0 164(14)O(T12) 699(26) 215(9) 281(12) 199(13) 143(14) 9:(9)O(T21) 262(21) 751(35) 221(16) 0 19(15)C(B1) 447(22) 140(9) 177(10) 87(11) 119(12) 1:(8)C(T11) 257(21) 160(12) 143(12) 0 56(13)C(T12) 386(19) 134(8) 144(8) 58(10) 80(10) 0:(7)C(T21) 295(28) 355(26) 157(15) 0 84(17)C(l) 204(24) 733(76) 135(15) 0 47(16) 0C(2) 701(51) 199(17) 563(38) 233(27) 469(39) 209(23)For all hydrogen atoms B 6.0 Hi2.C(3) 456(24) 186(11) 226(13) -79(13) 189(15) -105(10)* Anisotropic thermal parameters in the form : exp - (h2h,, +k2b,, + Pb,, + 2hkbl, + 2hlb1, + 2kZbZ3).FIGURE 1 A perspective drawing of the molecule and the label-Thermal ellipsoids are scaled to include 307; ling of the atoms.probabilityn nFIGURE 2 The packing of the molecules in the crystal.As aconsequence of the mirror plane, only the labelled atoms ofFigure 1 are included in the diagram (i.e. mirror images areomitted)6 C. K. Johnson, 1965, ORTEP, A Fortran Thermal EllipsoidPlot Program for Crystal Structure Illustrations, Report ORNL3794, Revised 1971, Oak Ridge National Laboratory, Oak Ridge,Tennessee24 J.C.S.Daltonare held in the crystal by van der Waals forces. Theclosest intermolecular contacts are O(T12) - - O(T12) at1 - x, y, 1 - x (3.21 A), O(B1) * - C(3) at -x, -y, -z(3.29 A) and O(T21) - - - C(l) at -1 + x, y , x (3-33 A).All other non-hydrogen contacts are >3.37 A. Bonddistances and angles, together with their estimatedstandard deviations derived directly from the least-squares inverse matrix, are given in Table 3. The C-HTABLE 3ori id lengths (A) and angles ('), nit11 estiniatcclstandard deviations in parentlieses(a) DistancesFe * * .CoFc-C(B1)FeC('r21)Fc-cp *C(€31)-O(B1)Fc-C ( 2 )1;e-q 3)C( 1)-H(1)(b) AnglesCo-l;c-C(Bl)C(T2)-O(T21)Fe-C ( 1)C(B l)-Fe-C( I3 1')C(Bl)-Fe-cp *C( Bl)-Fe-C( T2 1)C(TBl)-Fecp *FcC ( B l)-CoI;c-C( B1)-0 (Bl)Co-C( B 1 )-0 (B 1)C(2)-C( 1)-H( 1)C (2)-C ( 3)-H ( 3)C( 3')-C( 3)-H (3)C( 2')-c ( 1)-C( 2)C( 2)-C( 3)-c (3')2*545( 1)1*748( 13)1*729( 11)1 - 147 ( 8)1.1 28 ( 12)?027( 13)1"*078( 10)2*060( 6)0*87( 6)1 *883 (7)52.2 (2)89.3 (3)80.9 (3)96.8(3)124-7( 3 )l22*0(3)144-5( 6)134*6( 6)1 10.7 (5)124*7( 7)107-3(5)130(6)122(6)Co-C( B 1)co-c (T 1 I ) co-c (T12)C(l)-C(2)C(3)-C(3 )c (3)-H( 3)C(T1 1)-O(T11)C( T12)-O(T12)C(2)-C(3!C( 2)-H ( 2)l?e-Co-C( B 1)C (B 1 )-Co-C( ?' 1 1)C (T 1 l)-Co-C( T 1 2 )Co-C(Tll)-O(Tll)Co-C( T 12)-0( T12)C( €3 1)-co-C( El')C( R1)-Co-C( 'r 12jc (T 12)-co-C( T 12')r;C-c (1-2 1)-o (-r 2 1 )C(l)-C(2)-C(3)C( 1)-C( 2)-H( 2)C ( 3)-C( 2)-H( 2)?036( 5)1.78 1 (9)1*783( 7)1 * 142 ( 10)1 - 1 27 (8)1*290( 18)1.340( 16)1 m 7 ( 17)O.71( 10)0*88( 8)46*9(2)155-0(3)92.7 ( 3)87-5(3)!t7*1(3)1 0 7 *4 (3)174.8 (8)177*6( 6)176.9( 10)1 0 7.3 ( 10)156(9)95( 9)Primed atoms refer t o the equivalent position at x,* cp is the centroid 01 the cyclopentadienyl ring.- y , z,relative t o atoms at x , y , z.J.1XBLE 4Least-squares plancs and their equations gi\-cn b\- 2-Y' -;-ml" +- ?zZ' - p =: 0 wlierc X', I-', and %' are ortho-gonal co-ordinates related to tlie atomic co-ordinates-Ti, Y , and Z by X' = S sin p, 1'' = I-, Z' =: Z 4- A'cos p. Tlic deviations (A) of the most relevant atonisfroiii the planes are gi\-cii in sqmre brackets.I 1 u 91 PPlane (1)C(1), C(2), C(3), C(3'), C(2') 0.7816 0 -0.6237 1.8154[C( 1) - 0.028, C(2) 0.0%, C(3) - 0.007]Plane (2)Fc, Co, C(Bl), O(B1) 0.9491 0.3130 -0.0360 1.6886[Fc 0.003, CO 0.002, C(R1) -0.012, O(B1) 0.007]Plane (3)C(Bl), C(Ul'), C(Tl.'), C(T13') -0.7953 0 0.6002 0.9406[CO 0.408Jdistances are appreciably shorter than accepted values,'but this is realistic since the hydrogen positions ob-tained are those of electron-density maxima rather thannuclei.Cheni. SOC.Specid Publ., So. 11, 1959; So. 18, 1965. * R. I;. Bryan and P. T. Grcene, J . Client. Soc. (A), 1970, 3064.The molecules possess 31z (C,J symmetry, which isspace-group imposed, and has the expected Fe (CO),Cobridging system, with the cyclopentadienyl ligand X -bonded to the iron atom.The terminal carbonyl groupslying on the mirror plane are in a cis-configuration withrespect to the bridging system. The cyclopentadienylring is planar (Table 4) with equal C-C distances roundthe ring (mean 1.32 A). The iron to ring-carbon dis-tances are 2.03-2-08 A, mean value 2.06 A. The ironatom is 1.73 A from the ring centroid, and the anglebetween this direction and the Fe - - - Co direction is126.5".The centroids of the cyclopentadienyl system and ofthe bridging carbonyl groups lie on opposite sides of theline Fe - - - Co, and the angle between the tn-o Fe(C0)Coplanes is 143.5" (Table 4). This agrees well cvitli thatpredicted from the spectral study and also with that of148" observed in the related indenyl compound i(x-C,H,)-I;eCo(CO),] ., This value is intermediate between thatof 164" observed in the iron parent compound cis-;((x-C,H,)Fe(CO),),], and that of 127" in CO,(CO),.~A comparison of the metal to bridge-carbon distanceswith those of the parent compounds cis-[{ (x-C,T-€,) Fe-(CO),},] and CO,(CO), shows an apparent movementof the bridge-carbon atoms towards the iron atom.TheFeC(br) (br = bridge) distance is reduced from 1-92 to1-88 A, while the Co-C(br) bond has lengthened from 1-92to 2.04 A. This is accompanied by an opening of tlicFe-C(B1)-O(B1) angle, the planar environment of C(B1)being maintained by an equivalent closure of the Co-C(B1)-O(B1) angle. ?I similar geometry has been ob-served for one of the carbonyl bridges of the relatedindenyl compound.2The geometrical environment about the cobalt atomcan be described in terms of a square-based pyramid withthe apical direction defined by the Co-C(Tl1) direction.The angle between this direction and the normal to tlieplane of the carbon atoms in the basal plane is 64". Tliecobalt atom lies 041 -81 from this plane (Table 4). Thiscontrasts with the analogous indenyl compound in whichthe cobalt atom environment is intermediate between thesquare-based pyramidal and trigonal bipyramidal.,Observations from the present compound suggest thatthe distortion in the bridging system of the indenyl com-pound involves the bridge carbon atom which isdirected over the benzene fragment of the indenyl ligand.It is probable that tlie short intramolecular contacts in-volving this carbon371 group are responsible for this dis-tortion, and may account at least in part for tlic inter-mediate geometry about tlie cobalt atom.\Ye thank JJr. A. K. Manning for supplying a sample of theconipouncl mid tlie S.1t.C. for tlic award of a researchstudentsliip (to I. I,. C. C.),[4/1365 Received, 8th JZLIJJ, 19741G. G. Suinner, 11. 1'. Iilug, and I,. 1;. Alexander, Actn Cryst.,1964, 17, 732