1975 1473 Metallaborane Chemistry. Part 11.l Molecular and Crystal Structure of I '1 - B is( d i met hyl phenyl phosph i ne) -2'4-d imet hyl-2,4-d ica r ba-1 -plat ina-closo-dodecaborane By Alan J . Welch Department of Inorganic Chemistry University of Bristoi Bristol BS8 1 TS The structure of the title compound has been determined by single-crystal X-ray diffraction methods and refined to R 0.033 for 4073 independent observed reflections collected on a diffractometer. Crystals are triclinic space group P7 witha = 9.324(3),b = 10.285(4),andc= 14.208(8)A,cr= 100.40(4),p= 94.32(4),andy= 98.95(3)". The carbaboranefragment has a distorted icosahedral geometry with the carbon atoms at positions 2 and 4 (relative to the metal a t 1). The platinum atom is ca. 1.81 A above a (non-planar) C,B face which in turn is nearly per-pendicglar to the PtP plane.Pt-P Distances are 2.249(2) and 2.303(2) 8. All the hydrogen atoms in the molecule have been located and positionally refined. HEREIN is reported a full structural analysis of EXPERIMENTAL [Pt (Me2C2B,H,) (PMe,Ph),J one of several compounds prepared 1-5 by the direct reaction of a heteroborane cage with a nucleophilic NiO Pdo or Pto species. Pre-liminary crystallographic details have appeared else-~ h e r e . l * ~ A sampIe of the compound was recrystallised from methylene chloride-methanol to constant m.p. ( ~ a . 187 oc in vacuo). Individual crystals pow as pale yellow trans-parent irregular blocks which may be freed from cohesive M. Green J. A. K. Howard J. L. Spencer and F. G. A.Stone, J.C.S. Chem. Comm. 1974 153. * M. Green J. L. Spencer F. G. A. Stone and A. J. Welch, J.C.S. Chem. Comm. 1974,571. .5 M. Green J. L. Spencer F. G. A. Stone and A. J. Welch, J.C.S. Chem. Comin. 1974 794. 1 Part I M. Green J. L. Spencer F. G. A. Stone and A. J. 2 J. L. Spencer hl. Green and F. G. A. Stone J.C.S. Chem. Welch J.C.S. Dalton 1975 179. Cotnnm. 1972 1178 1474 J.C.S. Dalton crystallites by rolling gently between the fingers. That chosen for analysis was multifaceted and very nearly spherical (' diameter ' ca. 0.02 cm). It was mounted on a glass fibre with an epoxy resin glue set on a Syntex P2, four-circle diffractometer and the unit-cell constants their standard deviations and one asymmetric set of diffracted intensities recorded via a procedure already described.$ Details pertinent to the present experiment were as follows 15 reflections (14.5 < 28 < 24.5) were chosen from a 10 min rotation photograph and an accurately defined cell was obtained from these alone; graphite-monochromated Mo-K radiation (51 = 0.71069 A) and a 96-step 8-28 scan procedure were used; the scan rate was determined from a preliminary 2 s peak-count and varied from 0.0337 (for counts \<1 500) to 0.9765 O s-l (for counts 25 000) ; the 28 range for data collection was 2.9 < 26 < 50.0" ; 3 check reflections monitored periodically showed no significant crystal decomposition or machine variance during data collection ; preliminary data treatment was carried out by use of local programs.' Of 4 269 intensities recorded 4 073 having I > 2.50(1) were used to solve and refine the structure 188 having I < 2.50(1) being discarded.For 8 having measured counts in excess of 50 000 s-1 at the peak maximum the linear correction for counter coincidence effects (applied to all intensity steps with counts >5 000 s-l) is considered invalid and the offending data were automatically deleted from the observed set. Unfortunately these were not re-recorded a t reduced voltage and remain absent; no absorption correction was considered necessary since the maximum difference in absorption factors was calculated to be (2%. CrystaE Data.-C,,H,,B,P,Pt M = 63 1.844 Triclinic, n = 9.324(3) b = 10.285(4) G = 14.208(8) A a = 100.40(4), (by flotation) 2 = 2 D = 1.593 F(000) = 620.Ago-K, radiation 51 = 0.71069 A; ~(Mo-K,) = 57.3 cm-1. The 4 073 observed data were corrected for Lorentz and polarisation effects and a three-dimensional Patterson map computed. Examination revealed one maximum dis-tinctly larger than all others this was taken as the Pt - * Pt vector. Consideration of peaks within 5 A of the origin revealed only one set of two that might be Pt - * P vectors implying the centric space group. Since inspection failed to locate a P - - P (intramolecular) vector and a P-Pt-P angle near 90" was expected there existed four reasonable possibilities for the orientation of the PtP moiety and thus the location of the metal atom alone was used to calculate the first set of phases. Full-matrix least-squares refinement (2 cycles) with an arbitrary isotropic variable of 0.04 A2 gave a first R of ca.0.23. A difference electron-density synthesis computed after the second cycle revealed all the non-hydrogen atoms. In-clusion of these atoms and the assignment of anisotropic temperature factors to Pt and P converged R to 0.044 after four cycles. Examination of the variation of A2F over ranges of IFo/ and sin 0 suggested a Hughes-type 8 weighting * Whilst the hydrogens attached to boron atoms seem reason-ably well defined some rather unexpected molecular parameters are calculated from the positions of those bound to C(21) C(4l), C(135) and C(232). Since the offending hydrogens are not in-volved in close interligand packing (see later Table 7) they were removed from Fa calculations at one stage in the refinement only to reappear on a difference synthesis in the same positions.Partly for this reason and also because neither the C-H H-C-H nor H-C-C parameters of any one carbon atom do not differ signifi-cantly from the expected value i t is felt the ' suspect ' hydrogens should be included in the final model. p = 94.32(4) 7 = 98.95(3)O U = 1316(1) A, D = 1.58 scheme of the form w* = 1 for F < F* and z e f i = F*/Fo for Fo > F* with F* set at 190.0 (absolute scale). In allowing all the (non-hydrogen) atoms to refine aniso-tropically the variable parameters were divided into four similarly dimensioned blocks. Three cycles converged to R 0.036 and from an accompanying difference synthesis all hydrogen atoms were located. For subsequent Fc calcu-lations these were assigned an isotropic temperature factor TABLE 1 Final atomic positions (fractional co-ordinate x lo4; for Pt x lo5) of the non-hydrogen atoms with estimated standard deviations in parentheses X 19 946(3) 1543(2) 4 503 (2) 796(9) 1852(9) 1238(8) 16(10) 437( 11) 751 (1 1) -281(9) - 51 7( 11) - 1 495( 10) - 993( 10) - 1 053(11) 1 324(10) 2 274( 11) 1177(10) 2 908(8) 3 780(9) 4 835( 10) 5 081(10) 3 131(10) 5 379(10) 5 305(8) 6 524(9) 7 137(11) 6 530(12) 5 351(12) 4 700(10) - lOO(9) 4 200(11) 5 453(9) Y 46 199(3) 6 682(2) 5 166(2) 3 155(7) 2 48619) 2 365(8) 3 394(9) 3 927(9) 1483(10) 1012(10) lGll(l0) 2 597( 10) 2 404( 10) 1 038( 10) 3 741(10) 2 204( 10) 7 631(8) 6 718(9) 7 772(7) 8 914(8) 9 690(9) 9 358(10) 8 252(10) 7 471(9) 4 037(9) 6 743(8) 7 571(9) 8 715(10) 8 998(10) 8 184(10) 7 044(9) 5 199(10) 2 2 4057(2) 2 315(1) 2 649(2) 3 403(6) 2 652(7) 1436(6) 2 761(7) 1885(9) 1178(8) 1948(8) 3 142(8) 2 186(9) 4 462(7) 642(7) 3 465(7) 1856(6) 2 049(7) 1103(8) 518(7) 895(7) 1655(7) 3 207(8) 3 462(6) 3 276(7) 3 969(9) 4 807(8) 5 005(7) 4 321(6) 1 453(7) 3 119(9) 1545(7) 2 439(7) set a t 110% that of the attached ' heavy ' atom a t its isotropic convergence but the hydrogen thermal para-meters were not subsequently refined.Incorporating the hydrogen-atom positions into a fifth block mixed isotropic-anisotropic refinement of the whole molecule * converged at R 0.033 and R' 0.040 (R' == [Cw(lFol - IF,l)2/lCmlFo12])).In the final cycle the mean shift-to-error of refined parameters was 0.003 and in a final difference synthesis the largest peak was ca. 0.45 e A-3. Atomic scattering factors for neutral atoms were taken from ref. 9 for platinum and boron ref. 10 for phosphorus and carbon and ref. 11 for hydrogen. Those of platinum and phosphorus were corrected for both components of anomalous dispersion.12 Tables 1-3 list the final atomic parameters. Details of molecular planes parameters in-volving hydrogen atoms and observed and calculated * A. G. Modinos an P. Woodward J.C.S. Dalton 1974 2065. A. G. Modinos DRSYN,' a Fortran program for data 8 E. W. Hughes J . Amev. Chem. Soc. 1941,63 1737.D. T. Cromer and J. T. Waber Actu C~yst. 1965 18 104. lo D. T. Cromer and J. B. Mann Actu Cvyst. 1968 A24 321. l1 R. F. Stewart E. R. Davidson and W. T. Simpson J . Chem. l3 ' International Tables for X-Ray Crystallography,' vol. 111, analysis . Phys. 1966,42 3175. Kynoch Press Birmingham 1962 1975 1475 structure factor amplitudes are listed in Supplementary Publication No. SUP 21267 (24 pp. 1 microfiche).* All calculations were performed on the University of London CDC 7600 computer with the ' X-Ray '72 ' crystallo-graphic computing system,l3 except where otherwise stated. Final anisotropic thermal parameters * (A2 P X lo4) of the non-hydrogen atoms, standard deviations in parentheses TABLE 2 ~ 1 0 3 ; Pt and with estimated u13 u28 32(1) -l(l) 37(8) 37(8) 43(8) 19(8) -4(3) 1(3) -5(4) 914) -3(3) -12(3) O(4) -7(4) 5(4) 4(4) 5(5) W5) 2(5) -3(5) -3(5) -7(4) -3(4) 2(4) O(5) 9(5) 3(4) 13(4) lO(4) 15(5) 15(5) -26(4) 19(4) -2(4) -1(4) 16(4) 4f3) 8(3) 1(4) 3(4) 1(5) 13(4) 6(5) 32(5) 3(4) 4(4) -7(3) 4f3) 114) 3(4) 1415) 19(5) 15(5) -6(6) -1(5) l6(5) -12(5) 6(5) -22(6) -9(6) -7(5) -6(4) -2(4) 5(4) * The anisotropic thermal parameter is defined as expl- 2x2-( Ul,a*2h2 + U2,b^*2k2 + U,,C*^~~~ + 2U12a*b*hk + 2U$*;*hl+ 2U,,b*c*kE)).DESCRIPTION AND DISCUSSION OF THE STRUCTURE The compound exists in the solid state as discrete, neutral monomer molecules with no crystallographically imposed symmetry. Interatomic distances (not cor-rected for thermal motion) and interbond angles appear in Tables P - 6 with in each case the estimated standard deviation in parentheses.Figure 1 is a perspective ORTEP l4 plot of a single molecule showing the atomic numbering scheme adopted [hydrogen atoms not shown take the same number as the atom (C or B) to which they are bound]. The Platinacarbaborane Fragment.-The analysis con-firms that the metal atom co-ordinates three boron and two carbon atoms to complete a 2,4-dicarba-I-platina-closo-icosahedron. Least-squares planes data show that the platinum * See Notice to Authors No. 7 in J.C.S. Dalton 1974 Index l3 Technical Report TR 192 of the Computer Science Centre, l* C. K. Johnson ORTEP Report ORNL 3794 Oak Ridge issue. University of Maryland June 1972. National Laboratory 1965.TABLE 3 Final positional (fractional co-ordinates x lo3) and thermal * parameters (AS x lo3) of the hydrogen atoms Hydrogen H(3) €3 (6) H(6) H(7) H(8) H(9) H(10) W1) H(12) H(21) H(22) H(23) H(41) H(42) :[%) H(112) H(113) H(121) H(122) H(123) H(131) H(f32) H(133) H(134) H(135) H(211) H(212) H(213) H(221) H(222) H(223) H(231) H(232) H(233) H(234) H(235) X 300(8) - 15(8) - 75(8) 70(9) 116(9) -80(9) -267(9) - 176(9) -185(10) 66(10) 218(10) 107( 10) 266(10) 187(10) 337( 10) 37(9) 81(9) - 9(9) -93(9) 243(9) - 29(9) 367(9) 545( 10) 590( 10) 407(10) 274(9) 53 3 ( 10) 642( 10) 495(10) 648(10) 530(10) 492 (1 0) 68 7 ( 10) 782 ( 1 1) 697(11) 497(10) 329(9) Y 229(8) 391(8) 489(8) 85(9> 16(8) 108(9) 277(8) 242(8) 314(9) 488(9) 305( 10) 1 72 ( 10) 207(9) 709 (9) 843 (9) 787(8) 635(9) 620(9) 912(8) 1039(9) 804( 10) 686(9) 589 ( 10) 523 (9) 454(10) 436(9) 322(9) 390(9) 751(9) 9 18 (1 0) 97 1 ( 10) 833 ( 10) 653(9) 53x9) 377(9) 757(9) 997(7) z 286(6) 300(5) 368(6) 161(6) 177(6) 366(6) 212(6) 491(7) 456(7) 455(6) 86(6) 38(6) 27(7) lO(7) 95(7) 373(6) 336(6) 395(6) 188(6) l55(6) 311(6) 248( 7) 82(6) 79(7) 72(6) -26(7) 140(7) 174(7) 116(7) 328(7) 283(7) 383(7) 272(6) 372(7) 532(7) 562(7) 452(6) * Isotropic thermal parameters given by the u, 35 37 34 61 48 49 45 46 64 66 56 56 59 59 69 47 47 47 50 60 60 46 67 62 64 51 58 58 58 58 58 68 53 70 69 65 48 expression expi- 8x2 Uj(sin2B)/h2) were estimatecfat 110% of the converged isotropic parameter of the atom bound t o the hydrogen atom, and were thereafter held invariant in the final refinement (see text).TABLE 4 Bond lengths (A) (a) Within the polyhedron Pt(l)-C(2) 2.452(8) Pt( 1)-B(3) 2.270(9) Pt(l)-C(4) 2.442(7) Pt(1)-B(5) 2.261(8) Pt(1)-B(6) 2.255(9) 1.64( 1) 1.69( 1) 1.67(1) C( 2)-B (1 1) 1.7 1 (1) B(3)-C(4) 1.76(1) B(3)-B(7) 1.79(1) B( 3)-B(8) 1.81 (1) 1.67(1) 1.65( 1) 1.68(1) C(21-B(3) C(2)-B(6) W)-B(7) C(4)-B(5) C(4)-B(8) C(4)-B(9) (b) Exo-polyhedral bonds Pt(1)-P(1) 2.249(2) Pt(1)-P(2) 2.303(2) C(2)-C(21) 1.53(1) C(4)-C(41) 1.54( 1) P( 1)-C( 11 0) 1.829(9) P(l)-C(120) 1.820(9) P( 1)-C( 130) 1.802( 8) P( 2)-C ( 2 10) 1.809 ( 10) P( 2)-C( 220) 1.816( 11) P(2)-C(230) 1.828(7) B(5)-B (6) B(5)-B(9) B (5)-B( 10) B (6)-B ( 1 0) B( 6)-B( 1 1) B( 7)-B( 11) B( 7)-B( 12) B (8)-B( 12) B (9)-B ( 1 0) B (9)-B( 1 2) B( lO)-B( 1 1) B( 10)-B(12) B( ll)-B( 12) B(7)-B(8) B(8)-B(9) C( 130)-C(131) C( 131)-C( 132) C( 132)-C( 133) C( 133)-C( 134) C(134)-C(135) C( 135)-C(130) C(230)-C(231) C(231)<(232) C( 232)-C( 233) C(233)-C(234) C( 234)-C( 235) C(235)-C(230) 1.89( 1) 1.79(1) 1.77(1) 1.80( 1) 1.79(1) 1.80( 2) 1.75(2) 1.79(2) 1.75 (2) 1.77 (2) 1.76 (2) 1.72( 2) 1.78(2) 1.80(2) 1.76(2) 1.40(1) 1.38(1) 1.37(2) 1.38( 1) 1.38( 1) 1.38(1) 1.38(1) 1.40(1) 1.36(2) 1.36( 2) 1.40(1) 1.39(1 1476 J.C.S.Dalton atom is 1.814 A above the C,B face (which is non-planar with the carbon atoms bent back into the cage .and away from the metal). Although individual TABLE 6 Bond length and angle summary Type TABLE 5 Inter-bond angles (") la) Within the polyhedron C (2)-Pt ( 1)-B( 3) B(3)-Pt( 1)-C(4) C(4)-Pt( 1)-B(6) B( 5)-Pt( 1)-B(6) B(6)-Pt( 1)-C(2) Pt( l)-C(2)-B(3) B(7)-C(2)-B( 11) B( 1 1)-C( 2)-B( 6) B (6)-C (2)-Pt (1) Pt ( 1)-B (3)-C(2) C( 2)-B( 3)-B( 7) B (7)-B (3)-B (8) C( 4)-B (3)-Pt ( 1) Pt( l)-C(4)-B(q B13)-C(2)-B(7) €3 (8)-B (3)-c(4) B(3)-c(4)-B (8) B(8)-c(4)-B19) B(9)-C(4)-B@) B (5)< (4)-Pt (1) Pt( l)-B(5)-C(4) C(4)-B (5)-B (9) B( 9)-B (5)-B( 10) B( lO)-B (5)-B( 6) B( 6)-B( 5)-Pt (1) Pt ( 1)-B (6)-C( 2) C( 2)-B( 6)-B( 1 1) B( 1 1)-B (6)-B( 10) B ( 10)-B( 6)-B (6) B(6)-B (6)-Pt( I) (b) Other angles P( 1)-Pt( 1)-P( 2) P( 1)-Pt( I)-€( 2) P( 1)-Pt( l)-c(4) P(2)-Pt( l)-C( 2) P(2)-Pt( 1)-c(4) C(21)<(2)-Pt(l P( 1)-Pt( 1)-B(3) P( 1)-Pt ( 1)-B (5) P( 1)-Pt( 1)-B(6) P(2)-Pt( I)-B( 3) P ( 2)-Pt ( 1 )-B ( 5 ) P(2)-Pt( 1)-C(6) C( 2 I)<( 2)-B( 3) C( 2 l)-C(Z)-B( 7) C(21)-C(;?)-B( 11 C( 21)-C( 2)-B( 6) C(41)-C(4)-Pt( 1) C( 41)-C( 4)-B( 3) C( 4 l)-C(4)-B( 8) C(41)<(4)-B( 9) C( 41)-Cf4)-B(5) C( 110)-P( 1)-Pt( 1) C( 120)-P( 1)-Pt( 1) C( 130)-P(l)-Pt(l) C( 1 1O)-P( 1)-c ( 120) 40.4(3) 43.6(3) 4 1.3 (3) 49.6( 3) 41.7(3) 63.8(4) 65.5(6) 62.4(6) 63.8(6) 62.9(4) 75.8(5) 58.0( 5) 59.6 (6) 55.0(5) 73.4 (4) 63.0(4) 64.2(6) 63.3(6) 64.4 (5) 63.5 (4) 75.1(4) 58.2(5) 59.2(6) 58.7(5) 65.0(3) 7 5.4 (4) 57.3 (5) 58.7 (6) 59.3(6) 66.4f4) 97.30(7) 125.2( 2) 1 64.5 (3) 1 35.8 (2) 98.7( 3) 92.8(2) 1 17.4 (2) 96.3(2) 110.6(2) 147.0( 3) 157.1( 3) 109.1 (5) 1 2 2 4 7) 1 16.2( 8) 11 6.7( 7) 120.8(7) 107.3 (5) 121.7( 7) 115.1 (7) 1 18.7( 7) 122.3(8) 1 13.3( 3) 115.1(3) 117.I (3) 101.3(4) C( 2)-B ( 7)-B ( 3) B (3)-B(7)-B( 8) B (8)-B( 7)-B ( 12) B( 12)-B(7)-B(11) B(ll)-B(7)-C(2) B (3)-B(%-C 14) C(4)-B( 8)-B ( 9) B( 9)-B( 8)-B( 1 2) B( 12)-B( 8)-B( 7) B (7)-B( 8)-B (3) C(4)-B( 9)-B (5) B (5)-B( 9)-B ( 10) B( lO)-B (9)-B( 12) B ( 1 2) -B (9)-B (8) B(8)-Bt9)-c(4f B (5)-B( 1O)-B (6) B( 6)-B( 1O)-B ( 1 1) B( 1 1)-B( 10)-B (1 2) B ( 12)-B( 1 Of-B (9) B( 9)-B( lO)-B (5) C (2)-B( 1 1)-B (6) B( 6)-B( li 1)-B( 10) B( 10)-B( 11)-B( 12) B( 12)-B(ll)-B( 7) B( 7)-B (1 l)-C( 2) B( 7)-B( 12)-B( 8) B (8)-B ( 12)-B (9) B( 9)-B ( 12)-B( 10) B( 1 O)-B( 12)-B ( 1 1) B( 1 1)-Bf 12)-B(7) C( 1 10)-P( 1)-C( 130) c ( 1 20)-P ( 1 )-c ( 1 3 0) C( 210)-P( 2)-Pt (1) c (220)-P( 2)-P t ( 1) C(230)-P(2)-Pt( 1) C(21O)-P(2)-C(220) C( 220)-P( 2)-C( 230) C (2 10)-P( 2)-C( 230) 56.5 (5) 60.9(6) 59.2(6) 59.6(6) 60.0 (5) 60.8 (5) 58.7(7) 60.4 ( 6) 59.3 (5) 59.5 (5) 57.5(5) 60.1 (5) 62.2(7) 61.2 (7) 57 * 4 (5) 64.0(5) 60.2(5) 59.0 ( 6) 57.9(6) 60.7 (6) 57.6 (5) 60.6(6) 61.1(6) 61.3 (6) 67.6 (5) (a) Bonds (A) P t-B Pt-c P t-P B-R B-c C(cage)-C P-c C (Ph)-C( Ph) B-H C-H (b) -4ngles (") P-Pt-P R-Pt-B B-Pt-C Pt-B-B Pt-B-C B-B-C B-B-B H-B-Pt H-B-B H-B-C Pt-C-B B-C-B Pt-c-c B-C-C H-C-C( cage) H-C-H H-C-P Pt-P-c c-P-c P-c-c c-c-c 60.5(6) H-C-C(pheny1) No.(N) 3 2 2 17 8 2 ti 12 9 28 1 1 4 2 4 12 27 3 34 8 4 6 2 8 6 18 12 6 6 4 12 20 Range Mean * 2.255(9)-2.270(9) 2.262(8) 2.442(7) 2.452(8) 2.249( 2) 2.303 (2) 1.71(1)-1.8911) 1.78(4) 1.64( 1)-1.76 ( 1) 1,68 (4) 1.802(8)-1.829(9) 1.817(11) 1.35 (2) -1.40( 1) 1.04( 9)-1.16( 9) 0.68(8)-1.27(8) 0.98( 13) 1.53(1) 1.54(1) 1.38 (2) 1.1 1 (5) 97.30(7) 46.6 (3) 65.0(3) 65.4(4) 40.4( 3)-43.6 (3) 73.4 (4) -75.8 (5) 55.0(5)-60.8(5) 57.3 (5)-64.0( 6) 106 (4)-109 (4) 1 1 1 (4)-13 1 (5) 113(4)-130(4) 62.9 (4) -63.8 (4) 62.4 (5) -65.5 (6) 115.1(6)-122,6(7) 103 (4)-12 2 (5) 90 ( 8) - 1 20 ( 8) 1 02 ( 5 ) - 1 1 6 (5) 113(3)-117.8(3) 98.7 (4) -1 06.3 (4) 117.216)-122.9(6) 1 1 7.8 (7)-121.5 (8) 106( 8)-132(8) 107.3 (5) 109.1 (6) 42P) 75(1) 5 W ) 60P) 107(2) 122(4) 121(5) 63.3(4) 6401 119(3) 112(6) 109(4) 116(2) 103(3) 121(3) 120(7) 109(8) 120(1) - _ .6o.i(7j 59.9 (6) 60.0(6) 59.1(6) and the mean af N similar types. * The u of the mean of several similar types is given by the expression o2 = {xi== (xi - k)2)/(N - l ) where xi is the ith 106.3(4) 102.0(4) 11 4.4( 3) 1 16.5 (3) 117.8(3) 10 1.8 (5) 105.3 (4) 98.7 (4) P(l)-C(130)-C( 131) 122.9(6) P(l)-C(13O)-C(136) 119.4(5) C(131)-C(130)-C(135) 117.8(7) C( 13 O)<( 13 1)-C( 132) 120.f (8) C( 13 1)-C( 132)-C( 133) 121.5( 8) C( 132)-C( 13 3)-C( 134) 1 18.8( 9) C( 133)-C( 134)-C(136) 120.2(9) C (1 3 4 w ( 135)-C( 1 30) 12 1.6 (7) P( 2)-C( 23O)-C( 23 1) 1 22.5 (7) P(2)-C(230)-C(235) 117.2(6) C(231)-C(23O)-C(235) 120.1(7) C(23O)-C(231)-C(232) 118.9(9) C (2 3 1)-C( 23 2)-C( 233) 120.3 (9) C( 232)-C( 233)-C( 234) 121.4( 9) C(234)-C(235)<(230) 119.5(8) c ( 233)-c ( 234)-C( 235) 1 1 9.8 ( 1 0) members of the R-B and Pt-C bond types do not mutually differ significantly the geometry of the C,B, face is not regular with the B(3)-C distances differing onto the C,B face is 0.134 A from its centre This may by ca.go. The point of projection of the metal atom FIGURE 1 ORTEP plot of a single enclosing 30% electron probability except for hydrogen atoms which have an artificial radius of 0.1 A for clarit f975 1477 be compared with the corresponding distance of ca. 0.15 A in the bis-(3)-l,7-dicarbollylnickelate(11) dianion,15 the only other 2,4-dicarba-l-(ds)-metalla-dodecaborane reported as structurally characterised. Bf61 ''(2\ FIGURE 2 Co-ordination about platinum; 23% == 360.7' Tables 4 and 5 demonstrate that the overall distortion of the twelve-atom polyhedron from ideal icosahedral geometry is due almost entirely to the greater covalent radius of the metal atom.Pentagonal-prismatic faces not containing this atom are appreciably less distorted (with the exception of the C2B face). Further the dihedral angle between planes (1) and (2) (1.1') lies well below the range (2.2-6.4') for other near-parallel face sets where one face contains the platinum. The boron-boron distances [1.72(2)-1.89(1) mean 1.78(4) A] boron-carbon distances [1.64( 1)-1.76( I), mean 1.68(4) A] and their associated angles are all as expected for icosahedral carbaboranes. The Metal Co-ordinati0n.Tt.e plane containing the PtP moiety intersects the C2B face nearly perpendicu-larly and almost symmetrically. Thus the co-ordination about the platinum atom is best described in terms of an approximately square planar geometry with the mutually cis-phosphorus atoms P(l) and P(2) lying trans to B(3) and the midpoint of the B(5)-B(6) bond respectively (Figure 2).The existence of an appreciable trans-influence is apparent with the metal hybrids over-lapping less strongly with the single atomic orbital of B(3) than with the two of the B(5),B(6) unit. This geometry allows the cage carbon atoms to bond only weakly to the platinum and to tend towards their preferred cage co-ordination number of four.16* l7 [The Pt-C are longer than the Pt-B bonds by ca. 0.19 A, though the covalent radius of (tetrahedral) carbon is 0.11 A less than that of (tetrahedral) boron.ls] The Pt-B bond lengths [2.270(9) 2.261(8) and 2.255(9) A] agree well with those found in [Pt(H)-(B,H,,S)(PEt,)J (2.20-2.25 [Pt(B,H,) (PMe,Ph)J (2.13-2.38 [Pt(B6Hl0),C1,] (two of 2.27 A),21 and in several compounds 4 9 5 * 2 2 we have studied.Although the Pt-P lengths differ by ca. 270 neither lies outside the range usually observed (see e.g. Table 7 of ref. 20). l6 R. M. Wing J . Amer. Chem. SOC. 1970 92 1187. l6 R. E. Williams Progv. Boron Chem. 1970 2 37. l7 W. J. Evans G. B. Dunks and M. F. Hawthorne J . Amev. L. Pauling 'The Nature of the Chemical Bond,' Cornell A. R. Kane L. J. Guggenberger and E. L. Muetterties J . Chem. SOC. 1973 95 4565. University Press Ithaca New York 1960. Amer. Chem. SOC. 1970 92 2571. The Plzosplzine Ligands.-An effective C axis bisect-ing the P-Pt-P angle relates the two dimethylphenyl-phosphine ligands and as might be predicted from intramolecular steric considerations the phenyl groups are directed away from both the metalla-carbaborane unit and its associated methyl groups.The length of all pairs of bonds related by the axis agree within statistical error with the exception of the P-C(Ph) bonds (A ca. 3.250). The C-C bond lengths and all the angles of the phosphine ligands are as expected. In agreement with previous results,23 inter-bond angles at the phosphorus atom are greater if one bond involved is the co-ordinate bond. The C(130)-C(135) and C(230)-C(235) rings are planar with the phenyl hydrogen atoms showing maximum deviations of -0.263 [H(134)] and 0.125 [H(231)] out of the respective planes. For the molecule as a whole mean bond lengths involving hydrogen atoms [B-H 1.11(5) C-H 0.98(13) A] are predictably 24 shorter than the accepted l8 inter-nuclear separations of ca.1.2 and ca. 1.1 A. Non-bonding Contacts end Crystal Packing.-Figure 3 Itcsinp P FIGURE 3 The unit-cell contents looking down the a axis. Hydrogen atoms are omitted for clarity is a molecular packing diagram viewed along a. Table 7 lists the short contacts between non-bonded centroids TABLE 7 Interligand H H contacts <2.4 A H(3) * * H(222) 2.21(12) H(113) * * H(235) 2.31(13) H(3) - H(223) 2.40(11) H(21) * * H(1111) 2.25(13) H(6) * * * H(111) 2.35(10) H(5) - * * H(121'1) 2.39(12) H(6) * * H(122) 2.26(13) H(10) * * H(134II) 2.37(12) Roman numeral superscripts denote the following equivalent positions relative to the reference molecule a t x y z I f 1 - y, 1 - 2; I1 x 1 - y P. of electron density around the hydrogen atoms (true internuclear H - H contacts could be up to 0.2 A less) .24 Of particular interest are the first four (intramolecular) 2o L. J. Guggenberger A. R. Kane and E. L. Mutterties J . Amer. Chem. SOC. 1972 94 5665. 21 J. P. Brennan R. Schaeffer A. Davidson and S. S. Wreford, J.C.S. Chem. Comm. 1973 345. 22 A. J . Welch unpublished work. 23 U. A. Gregory J. A. Jarvis B. T. Kilbourne and P. G. Owston J . Chem. SOC. (A) 1970 2770. 24 See e.g. 31. R. Churchill Inorg. Clzem. 1973 12 1213 and refs. therein 1478 J.C.S. Dalton contacts which may be responsible for the slight twist I thank Dr. J. L. Spencer for supplying the crystalline (l0,l5*) of the PtP plane towards C(4) and B(6) ex- sample Dr. A. Quick (Imperial College London) for the hibited by the molecule in the solid state. (The 1H ORTEP plot and Dr. P. Woodward and Professor F. G. A. n.m.r. spectrum implies a molecular plane of symmetry Stone for helpful discussion-containing the PtP m0iety.l) [4/2063 Received 7th October 1974