摘要:
1972 1189Crystal and Molecular Structure of Tetramethylammonium Triacetatodi-phenylplumbate(iv) : An Eight-co-ordinate Lead ComplexBy N. W. Alcock, Department of Molecular Sciences, The University of Warwick, Coventry CV4 7ALThe crystal structure of the title complex has been determined. The crystals are orthorhombic, space-groupPcan. a = 17.772. b = 9.397. c = 14.324 8, Z = 4. 886 Intensities above background were measured by countermethods and refined to a final R of 0.037. The crystal contains discrete cations and anions. The lead atom iseight-co-ordinate with approximately hexagonal bipyramidal geometry. The Pb-C(axia1) bonds are of normallength, 2.1 6(3) A. The equatorial Pb-0 bonds are very long, 2.55 (mean). The structure is compared withthat of the uranyl triacetate anion.The unit cell of the corresponding caesium salt has been determined as cubic,a = 13.21 8.As a ligand, the acetate ion can bind in three ways:unidentate, bidentate chelating, and bidentate bridging.This makes it very difficult to determine the co-ordinationof a metal acetate from the formula. For this reason,and because it potentially shows a high co-ordinationnumber, the structure of the triacetatodiphenylplumbate-(IV) ion has been determined by single-crystal X-raymet hods.EXPERIMENTALCrystal Data.-C,2H31N0,Pb, &I = 61 2.2, Orthorhombic,a = 17.772(6), b = 9-397(4), c = 14.324(6) A, U = 2392-1 Hi3,Dl,, = 1.5 (by flotation), 2 = 4, D, = 1-6, F(000) = 1128.Systematic absences: Ilk0 with h + k = 2n + 1, h0Z with?I = 2n + 1, Oh2 with 2 = 2n + 1 indicate space-groupPcan (No.60, with x and y exchanged, positions [x, y, x;&fo-Ka X-radiation, h = 0.7107 A; p(Mo-K,) = 69.8 cm-l.There is a strong pseudo-systematic extinction withh + k = 2n + 1 generally weak. The well formed colour-less chunky crystals show faces of form (110) and (001).The unit-cell constants and standard deviations weredetermined by least-squares fit to the reflecting positions of12 high-angle reflections using the standard program of aPicker FACS-I. The final data set was collected on thisinstrument equipped with a graphite monochromator using8-28 scan, 4" take-off angle, no attenuators; the crystalswere enclosed in a Lindemann glass tube. Data wascollected to 28 = 50".Data CoZ2ection.-The initial data were taken with a Stoetwo-circle goniometer, and the structure mas solved (seelater) but could not be satisfactorily refined.The reasonfor this was probably crystal decomposition, because whenthe data were re-collected reflections were monitored morecarefully, and very variable rates of decomposition wereobserved for different crystals at different times. Duringthe final collection three crystals were used and the datawere further grouped into 7 sections, in all, with a separatescale-factor for each, depending on the rate of decomposition.It should be noted that the subdivisions correspond approxi-mately to increasing 11, and so the anisotropic B,, tempera-ture factors may not be as well determined as the others.The decomposition seemed to show no angle dependence,was approximately linear within each group and was com-pensated for by multiplying the net intensity of the Nthreflection in the j t h group by (1.0 + KjN) where K j waschosen to fit the rate of decomposition in the group.Qi-., & + y , 8 - 2 ; * + % a-r, 2 ; x,-y, * - z 3 ) .F.Huber and E. Schonafinger, Angew, Cliem., 1968, 80, 79.a ABSCOR, an analytical absorption program in the ' X-RAY63 ' system.Lorentz and polarisation corrections were applied, assumingthe monochromator to be perfectly mosaic, and the datawere corrected for absorption with the program ABSCOR;maximum and minimum transmission factors were 0.5 and0.3. 886 Reflections with Ilcr(1) > 3.0 were taken to beobserved.Prelimimary investigations were also made on very smallcrystals of caesiuni triacetatodiphenylplumbate(1v) whichwere optically isotropic and usually formed as hexagonalprisms (forms { 110) and { 111)) or dodecahedra ({ 110)).The data obtained were : C,,H,,CsO,Pb, cubic, primitive,a = 13.21 A, U = 2305 A3, D, = 1.9 (by flotation),The Laue group is probably w&n, but the weak photo-graphs did not allow systematic absences to be identified.The anion must lie on a special position with the phenylgroups disordered, and the most likely choices of space-group are P4,32, P4,32, or P4,32, with special positionsymmetry 32.Structure SoZulio?z.-In space-group Pcan both cation andanion lie on special positions on either a two-fold axis or aninversion centre ; both the pseudo-systematic absence,h + h # 2n, and the formula of the anion indicate that thelead atom must be on the two-fold axis.With the originaldata set this atom was readily located by a Pattersonsynthesis. Although a Fourier synthesis phased on thelead atom shows false mirror symmetry (i.e. special positionsymmetry 2mrn instead of 2) the other atoms of the anionwere located without great difficulty, by assigning Fourierpeaks either to phenyl ring atoms or to acetate atoms. Thenitrogen of the tetramethylammonium group was alsolocated, again on the two-fold axis, but the carbon atomsseemed to be disordered. Although the atomic positionswere reasonable, least-squares refinement did not reduceR below 0.18.Because the data quality was suspect, datawere then re-collected (see earlier). Starting from the pre-vious positions, refinement with all atoms isotropic rapidlyconverged to R 0.066. The tetramethylammonium groupwas located, not ordered on the two-fold axis, but with onecarbon atom on the axis and the other three occupying twoalternative sets of positions. With all atoms anisotropic,R was reduced to 0-050. 22 Reflections which showed largediscrepancies, perhaps due to extinction or the lack ofattenuators were removed and final refinement gave R 0.037.Unit weights were found to be satisfactory (with the re-flections including duplicate measurements of standardreflections in different scale groups). Scattering factorswere from ref. 3 and anomalous dispersion was correctedfor.3 The only significant features on the final difference' International Tables for X-Ray Crystallography,' vol.3,Z = 4, D, = 1.93.Kynoch Press, Birmingham, 19621190TABLE 1J.C.S. DaltonAtomic co-ordinates and 2nisotropic * temperature factors ( x 1 0 4 )X1487*1(6)2836( 12)369(10)1384( 10)8385( 12)3177 (20)4009(20)706 ( 14)278(15)1490( 15)1980( 16)197 8( 15)1466( 17)976( 15)975(12)75 1 6 (25)891 7( 98;8555 (40)8 744 (3 0)Y08 10 (22)853(19)155 l(2 1)0001483 (26)2 14 1 (27)1 835 (2 8)1837( 30)3052(33)41 60( 27)4105( 27)2926(24)0745 (90)934( 107)1331 (63)z25003044( 15)3375( 12)3957( 16)2500250025003983(16)4802 (1 5 )1596( 17)862(17)247 (1 7)400( 16)1157(17)1747( 17)25001 753 (55)3379(60)2226 (32)Pl 143(8)35(6)26(9)22(9)21(10)39(13)40(10)66(12)45( 11)45(10)40(10)34(14)151( 199)65(27)48(18)2 1 -2 (8)29(7)42(9)3003)B.22120.1 (1 -3)270(37)205(28)21 6( 32)170(47)238(67)117(46)114(35)163 (40)166(39)185(46)246(57)194(37)165(38)120( 35)535( 123)300( 136)6 85 (2 80)252(88)with standard deviations in parentheses39*3(4) 0 0 -4-2(3.7)loo( 15) 1(13)833 812 (913 P23102( 15) 12(14) -5(10) -64(19)68(11) -17(11) 1(7) -24(15)68(16) 09(18) 65(13) - 8(15) 6 (9)44(14) - 7(20) 14(11) 4(21)49(13) -24(20) - 2(9) 8(24)55(12) 6(21)66(14) 7(17)46(17) 0 0 60(82)339(64) 0 0 207(61)-8(20) 57(14) 24( 17) 30(10)59(12) -24(18) -23(11) 17(19)17(19)'(12) 19(21)lO(10) 4(11) 15(18)0 3 13 (83)70(16) -$15)289(54)64(48) 34(120) lOS(S0) -49(68)124(44) -79(75) 62(32) - 269(96)63(43) - 12(32) -7(19) 125(48)The acetate group on the two-fold axis contains atoms 0(11), C(11), and C(12) ; the acetate group in a general position is 0(21),0(22), C(21), C(22); the benzene ring is C(31)-(36) : the tetramethylammonium group is N ( l ) and C(41)-(44) (disordered, 0-6population parameter).* In the form exp [- (h2pl1 + k2& + Z2P3, + 2hkp12 i- 2hZp13 + 2kZ823)].Fourier synthesis were a few ripples around the lead atomposition; no hydrogen atom peaks could be found, and sothese were not included in the calculations. The finalTABLE 2Bond lengths (A) and angles (") with standard deviationsA primed atom is related to the corre- in parentheses.sponding unprimedatom by the two-foldPb-O(l1) 2*63(2) O( 1 1)-PbO( 11')Pb-O( 2 1) 2.48 (2) 0 (2 1 )-Pb-0 (22)Pb-0 (22) 2*55(2) O( 1 l)-Pb-O(22)O(11) * * * O(22) 2*98(3) C( 3 1)-Pb-c(3 1')(a) Lead environmentPb-O( 3 1) 2*16( 3) 0(21)-Pb-O( 2 1')O( 17)-Pb-C( 3 1)O(21) - * * O(21') 2*98(3) 0 (2 l)-P&C(31)0 (22)-Pb-C(3 1)(b) Acetate groupsaxis48.9(7)49.1 (6)70*0(6)73*7(6)1 7 9.7 ( 1.0)86*8(9)92.7( 8)92*0(8)C( 11)-O( 11) 1.25(3) 0 ( 1 1)-C( 1 1)-O( 1 1') 12 1*7( 3.2)C( 21)-O( 21) 1.21(3) 0 (21)-C( 21)-O(22) 1 19.8 (2.4)C( 21)-0( 22) 1*21(3) 0(21)<(21)-C(22) 120*3(2*3)C( 2 1)-C( 22) 1 * 53 (3) 0 (22)-C (2 l)-C(22) 1 19*9( 2.3)C( 1 1)-C( 12) 1.38(5) O( 1 I)-€( 1 1)-C( 12) 119.1 (1 *8)(c) Benzene ringC( 3 l)-C( 32) 1 2 3 (2)C (32)-C ( 3 3) 1-44(4) C(31)-C(32)-C(33) 118(3)C(33)-C(34) 1 -40 (4) C(32)-C(33)-C(34) 120(2)C (35)-C (36) 1-39(3) C( 34)-C( 35)-C( 36) 120( 2)C (36)-C (3 1) 1*39(4) C( 35)-C( 36)-C( 31) 1 ZO(2)1 *3 7 (4) C (36)-C( 3 1)-C( 32)C (34)-C( 36) 1*40(4) c (33)-C( 34)-C( 35) 120( 2)( d ) Tetramethyl ammonium groupN(l)-C(41) 1.54(5) Mean of six tetrahedral angles 108.6',N( 1)-C(42) 1.59(12) o 2-5'; none departs significantlyN(l)-C(43) 1.57(8) from the normal value.N( 1)-C(44) 1-46(6)atomic co-ordinates and temperature factors are given inTable 1, and the final structure factors are listed in Supple-mentary Publication No.SUP 20318 ( 5 pp., 1 microfiche).*In this listing scale-group changes occur after the following* For details of Supplementary Publications see Notice toAuthors No.7 in J. Chem. SOC. (A), 1970, Issue No. 20 (itemsless than 10 pp. will be supplied as full size copies).reflections: 6, 0, 10; 6, 0, 14; 8, 6, 11; 12, 2, 6 ; 15, 7, 5;8, 0, 1. All computing was carried out with the X-RAY63 ' system of programs * on an IBM 7094 or on the S.R.C.Atlas.RESULTS AND DISCUSSIONThe structure determination shows that the crystalcontains discrete tetramethylammonium and triacetato-diphenylplumbate ions. Both ions lie on the two-foldaxis x , 0, a. In the environment of the lead atom, itbisects one acetate group and relates the second acetategroup to the third and the two phenyl groups to eachother.In the tetramethylammonium group the nitrogenand one carbon atom are on the axis and the other threecarbon atoms have a two-fold disorder. Bond lengthsand angles are given in Table 2. For all the organicmoieties the values are normal.Co-ordination of the Lead Atotn.-The lead atom iseight-co-ordinate, with its ligands forming an approxi-mate hexagonal bipyramid (Figure 1). Two phenylgroups are in the axial positions and three bidentateacetate groups take up the equatorial positions. Thedetails of various mean planes are given in Table 3.The lead atom deviates by 0.04 from the plane of thephenyl carbon atoms, a value which is probably notstatistically significant. One phenyl ring is rotated by73" relative to the other, which excludes the possibilityof T; orbital conjugation through the lead atom.Theacetate groups do not lie precisely in a plane. If theirmean plane is defined by their central carbon atoms, thelargest deviations are by O(11) and O(ll'), (plus andminus 0.209 A), while C(22) deviates by 0.13 A. Thesedeviations do not seem to be of chemical importance.The lengths of the bonds from the lead atom do not allcorrespond to expected values. For Pb-C, the follow-4 ' X-RAY 63 ' system of programs, J . M. Stewart, Uhiversityof Maryland Technical Report TR 64 61972 1191ing values (A) have been reported: 5 9 6 2.20 (&O-Ol) and2.25 (&0.06) in PbMe, and Pb2Me6, 2.27 (h0.03) in[(x-C,H,)F~(CO),],P~M~, (ref.7), and in [Ph,PbBr],C L c"" O(11)FIGURE 1axis.The anion viewed almost parallel to the C-Pb-CThe two-fold axis passes through C(11) and C(12).2-25 (mean) to the central carbon atom and 2.20 to thephenyl ring.8 The observed distance of 2.16A is notsignificantly different from this last value, and reinforcesthe previous evidence that C(sp2)-Pb is shorter thanC(sP3)-Pb. The only PbIV-O distances which have beendetermined are in PbO, and range from 2.16 to 2.22 A(octahedral co-ordination) . This compares satisfactorilywith estimates obtained by (i) subtracting from thePb-C distances the difference between the covalent radiusTABLE 3Equations of mean planes (in orthogonal I$ co-ordinates)and deviations (A) of relevant atoms from the planesPlane (1): C(31)-(36) 0.676X + 0.469Y + 0.5782 = 3-89[C(31) -0.011, C(32) 0.008, C(33) -0.005, C(34) 0.006,C(35) -0.009, C(36) 0.012, Pb 0.0351Plane (2): Pb, C(11), C(21) - 0.836Y + 0.6492 = 1.965[0(11) 0.209, O(21) -0.017, O(22) 0.073, C(22) -0.1271Angles (") between planes:* (1)-(2) 86.2* Planc (1') is related to plane (1) by the two-fold axis.(1)-( 1') 72.7of carbon and that of oxygen,1° or (ii) adding the dif-ference between the covalent radii of tin and lead (ca.0.06 A) lo to the Sn-0 distances of 2-12 and 2.14 A intwo tin acetates.ll However, in the triacetatodiphenyl-plumbate ion, the mean Pb-0 distance is 0.35 longer5 C.-H.\Vong and V. Schomaker, J . Chem. Phys., 1958, 28,1007.H. -4. Skinner and L. E. Sutton, Trans.Favaday SOC.,1940, 36, 1209.B. P. Biryukov, Yu. T. Struchkov, R. N. Anisimov, N. E.Kolobova, and 1'. V. Skripkin, Zhur. strukt. Khim., 1968, 9, 922. * J: Kroon, J. B. Hulscher, and A. F. Peerdeman, J. Organo-metallzc Chmi., 1970, 23, 477.than this (2.55 A, with individual values rather scatteredbut a t most 40 from this value), The implications of thiscan be seen in relation to the overall geometry.Acetate groups can be considered as either trulybidentate or as occupying only one co-ordination posi-tion. Taking the first view, the only other compoundswith hexagonal bipyramidal co-ordination are uranyl(and neptunyl, plutonyl, and americyl) derivatives c.g.UO,(OAc), (ref. 12). Very similar bonding schemes arepossible for both the lead and uranium compounds, thelatter (UVI) using two electrons for each U=O(axial)bond, and the former (PbTV) using one electron for eachPb-C(asia1) bond.In the uranyl compounds, the equa-torial are very much longer than the axial bonds,12longer than would be expected for the replacement ofc'=O with U-0. This is precisely the behaviour of thelead compound and clearly the two have a strong re-semblance.9aFIGURE 2 Packing of the molecule viewed down c, showing thelayer with Pb and N atoms a t z 0.25. One of the two orient-ations of the NMe,+ ion is shown dotted. There is a gapbetween this layer and that a t z 0.75, which has Pb atomsclose to the x,y positions of the N atoms in the z 0.26 laver andvice versaIf the acetate groups were considered to occupy onlyone co-ordination position, the compound would be five-co-ordinate with trigonal-bipyramidal geometry.How-ever, in trigonal-bipyramidal species with some alkyl oraryl ligands, it is well established that these groupsoccupy the equatorial positions. A notable example isA. I. Zaslavskii and S. Tolkachev, Zhur. j i z . Khim., 1952,26, 743.lo A. I;. Wells, ' Structural Inorganic Chemistry,' 3rd edn.,Oxford, 1962, p. 696.l1 N. W. Alcock and R. E. Timms, J . Chem. SOC. ( A ) , 1968,1876.l2 W. H. Zachariasen and H. A. Plettinger, -4cta Cryst., 1959,12, 5261192 J.C.S. DaltonCl,SbPh, which has two phenyl groups and one chlorineatom around the equator.13 In triacetatodiphenyl-plumbate on this model the phenyl groups are in theaxial positions. This implies that a five-co-ordinatemodel does not give a satisfactory representation of thestructure.Molecular Packing.-All significant intermolecularcontacts are likely to be between unlocated hydrogenatoms and so cannot usefully be discussed. A generaldescription of the packing can be given in terms of layersperpendicular to c with a centred arrangement in eachlayer (Figure 2). One layer has Pb and N atoms atheight x 0-25 and there is a considerable gap to thenext with x 0-75. Each ion has three neighbours ofopposite charge in the same layer and two others aboveand below it.I thank Dr. F. Huber for the crystals, Professor C.Ballhausen and Dr. K. Watson for hospitality and use ofequipment during part of the investigations, and D. Bevanand B. Taylor for much assistance during the initial workon the compound.[1/1934 Received, 21st October, 19711l3 T. N. Polynova and M. A. Porai-Koshits, J . Struct. Ckem.,1961, 2, 445
ISSN:1477-9226
DOI:10.1039/DT9720001189
出版商:RSC
年代:1972
数据来源: RSC