摘要:
1974 1545Crystal and Molecular Structure of Tetraphenylarsonium Aquotetra-chlorohydroxotellurate( iv)By Paul H. Collins and Michael Webster," Department of Chemistry, The University, Southampton SO9 5NHThe structure of the title compound has been determined by single-crystal X-ray diffraction using diffractometer dataand refined to a final R of 5.1%. Crystals are monoclinic, a = 18.71 f 0.03, b = 7.31 h 0.02, c = 19.29 f0.03 8, p = 92.03 f 0.05", with Z = 4, space group either C2/c or Cc. The structure has been refined in both spacegroups and a chemically similar structure obtained although the evidence favours a disordered model in thecentrosymmetric space group C2/c. Tetraphenylarsonium ions, whose bond lengths and angles agree well withearlier studies, are present.The anion consists of a square pyramidal [TeCI,O] group with an apical oxygen atombut it is not possible to distinguish between the [TeCI,(OH)]- and [TeC1,0I2- formulations [Te-CI 2.484(2).Te-0 1.74(1) 81. Adjacent anions are weakly linked through water molecules interacting with the Te and 0(or OH) groups to form an infinite chain structure.THERE is considerable interest in the stereochemistryof compounds of the main-group elements with a formallone-pair of electrons, which may be stereochemicallyactive or inactive. Whereas the [TeF,]- ion is a discretesquare pyramid in KTeF,,l the [TeCl,]- ion in thecompound [PCl,][TeCl,j has been shown by two in-dependent X-ray studies 2 y 3 to contain a polymericanion with each tellurium atom being approximatelyoctaliedrally co-ordinated.The factors which promotethis polymerisation are at present not clear and wethought it important to know whether changing the[PCl,]' for a larger cation would radically alter theanion structure. A recent n.q.r. study on the hexa-chlorotellurate(1v) ion indicated that changes in thecation had little effect on its ~ t r u c t u r e . ~ Inspection ofthe literature showed few, if any, compounds apparentlycontaining the [TeCl,]- ion and we examined the systemPh,AsCljTeCl, in an attempted synthesis of [TeCl,]-.On carefully concentrating an equimolar mixture oftetraphenylarsonium chloride and tellurium tetra-chloride in methylene dichloride, colourless crystals wereisolated in low yield. The composition was eventuallyestablished as [Ph,As]TeCl,(OH) (H20) by a combinationof elemental analysis and the X-ray structure deterrnin-ation where the oxygen atoms presumably arise fromeither the reagents and/or the solvent.Further con-centration of the solution gave a precipitate of theknown yellow [Ph,A~],Tecl,.~*~ No other tellurium-containing species were isolated from the reactionmixture. Very recently the [Te,Cl,,j- ion has beenestablished from the reaction between triplienylmethylchloride and tellurium tetrachloride.No other compounds of the type [Ph,As]TeCl,-(OH) (H,O) have been established previously and wereport now our X-ray results on this unusual structure.E S PE RI M E N T AI,Synthesis of Compound and *4 naZ~ts~s.-TelluriuIii tetra-chloride was prepared from tellurium and chlorine.8l'etraphenylarsonium chloride (Schuchardt) ancl inethylenedichloride were reagent grade.To a boiling solution ofA. J . Edwards and hI. A. Mouty, J . Chenz. Soc. ( A ) , 1969,703; S. H. Mastin, R. R. Ryan, and L. R. Asprey, Irzovg. Chewt.,1970, 9, 2100.P. H. Collins and $1. Webster, Acta Cvyst., 1972, B28, 1260.B. Krebs, B. Buss, and W. Berger, 2. anorg. Chem., 1973,397, 1.T. N. Brill and W. A. Welsh, J.C.S. Dalton, 1973, 357.TeCl, in methylene dichloride was added an equimolarquantity of Ph,AsCl dissolved in a small volume of the samesolvent. A clear yellow solution formed immediately andon slow cooling in a stoppered vessel deposited, in smallyield, colourless needle crystals (A) (m.p.21 1-213 "C).On some occasions no crystals formed, and solvent was thendistilled off before cooling, but if too much were removedyellow crystals of [Ph,As],TeCl, were deposited (map. ca.285 "C).was prepared by mixing Ph4,4sC1 andTeC1, (2 : 1 mole ratio) in hot methylene dicliloride, whenthe yellow crystalline compound was precipitated [Found :C1, 19-4 (mean). Calc. for [Ph,As],[TeCl,] : C1, 19-227/,,m.p. 281-286 "C). By use of dry-box procedures thecolourless crystals (A ) were separated from the motherliquor, pumped in vacuo, and subsequently analysed forC1, Te, and the Ph,Asf ion by techniques describedlater. The results obtained on two separate preparationsare shown in Table 1. The atomic ratios of I'h,As : Te : C1[Ph,As],TeCl, 5,TABLE 1Analyses (yo )C1 Te Ph,As RemainderFound [prep.(I)] 20.8 18.65 65.85 4.7Calc. for [Ph,As] [TeClJ 25.76 18-54 55-70 0.00Found [prep. ( 2 ) ] 20.45 18.3 54.8 6-40Calc. for [Ph,As]TeCl,- 20.62 18-66 55-74 5.082.54(OH) (H2O)Calc. for [Ph,As]TeCl,- 21.18 19.05 57.23(OH)is 1 : 1 : 4. The unaccounted for elements must carry asingle negative charge and the analytical evidence favoursa compound containing both OH- and H20, rather thanonly the hydroxo-ion.Subsequent experiments on the reagent Yh,-\sCl estab-lished unambiguously that i t is approximately the mono-hydrate (Found: C1, 8-15. Calc. for Ph,AsCl: C1, 8.46.Calc. for Pli4-4sC1,H,0 : C1, 8.12%) ; the i.r. spectrum(hTujol and hexachlorobutadicne mull) showed an intenseband a t ca.3500 cni-l. This no doubt is the origin, a t leastin part, of the oxygen content of compound ( A ) .The analyses for the three components were performedon the same weighed sample (ca. 0-05 g). After hydrolysiswith NaOH solution (10 ml, 2 ~ ) , the solution was made upto 100 ml (IM in SaOH). Aliquot portions (10 nil) of thisD. Rl. Adatns and D. M. Morris, J . Chem. SOC. ( A ) , 1967,2067.&I. L. Unland, J . C h e w Plzys., 1968, 49, 4514.€5. Krebs and V. I'aulat, Angrw Chrm. Irttevizat. Edn., 1973,* J. F. Suttle and C. R. F. Smith, Iwovg. Synth., 1950, 3, 140.12, 6661546 J.C.S. Daltonsolution were used for the subsequent determinations.Chlorine was estimated by potentiometric titration againststandard silver nitrate after acidification with nitric acid.Tellurium( IV) was estimated spectrophotometrically as the[TeC1J2- ion at 295 nm in ca.5~-hydrochloric acid.Tellurium dioxide was used to set up the calibration graphand to verify Beer's Law for the system, and a telluriumanalysis for TeCl, gave good agreement with the theoreticalvalue. The tetraphenylarsonium ion was estimated spectro-photometrically using the bands at 263 and 270 nm, and acalibration graph constructed by use of tetraphenyl-arsonium chloride. Experimental conditions were carefullystandardised during the analyses and qualitative andquantitative spectra recorded on Unicam SP 800 andSP 500 spectrometers. Attempts to estimate tellurium(1v)colorimetrically using ammonium pyrrolidine dithio-carbaniate !I were unsatisfactory.Crystals for X-ray examination were grown frommethylene dichloride and mounted in capillaries underglove-box conditions.Crystal Data.-C,,H2,AsC1,0,Te, M = 687.8, Monoclinic,u = 18-71 & 0.03, G = 19-29 & 0.03 A,/3 = 92.03 & 0.05", U = 2636.6 A3, D, = 1.73 & 0.02 (byb = 7.31 & 0.02,flotation), 2 = 4, D, = 1.732 g ~ m - ~ .Systematic absences:la + k = 2n + 1 for hkl, and I = 2n + 1 for h01, consistentwith space groups CG (No. 9) or C2/c (No. 15). p(Cu-K,) =148.3 and ~(Mo-K,) = 29-0 cm-l.Preliminary cell dimensions, diffraction symmetry, andsystematic absences were obtained from Weissenberg andprecession photographs. For data collection, a crystal(max.) 0.5 x (min.) 0.1 mm was mounted about the b axisin a Lindemann glass capillary (0-3 mm diam.).Data werecollected by use of a General Electric XRD 6 manualdiffractometer in the stationary-crystal-stationary-countermode with zirconium-filtered Mo-radiation, take-off angle3"). Counting for 10 s, 2324 independent reflections wererecorded up to 20 (max.) 50". A general backgroundwas measured as a function of 28 by offsetting w by &lofrom a number of observed reflections, and was subtractedfrom the measured peak intensity to give the correctedintensity, I,,,,. 457 Reflections having I,,,, (1.2 xbackground were considered unobserved.lO Three medium-intensity reflections were monitored and used as standardst o correct for the observed deterioration (ca.7%) in thediffracted intensities. Lorentz and polarisation factorswere applied together with an absorption correction by themethod of de Meulenaer and Tompa.* Scattering factorsfor neutral atoms were taken from ref. 11 and a dispersioncorrection l1 for tellurium, arsenic, and chlorine wasapplied in the structure-factor calculations.Structuve Deter~ination.-Examination of the three-dimensional Patterson function gave plausible positionsfor the tellurium and arsenic atoms. In space group Cc,two general positions were occupied, while in space groupC2/c the tellurium was in position 4(c) and the arsenic in4(e). Apart from the different choice of origin, these twosolutions were the same and the structure solution wasinvestigated in both space groups.A structure-factor calculation basedC .A. Watson, Monograph, No. 74, Hopkin and Williams,lo (a) G. J. Palenik, Acta Cryst., 1972. B28, 1633; (b) ' X-Rayl1 ' International Tables for X-Ray Crystallography,' 1101. 111,(a) Space group Cc.* Using the program ABSCOR in ref. lo@).1971.'63 ' system of programs,Kynoch Press, Birmingham, 1962.on the Te and As positions, followed by an electron-densitysynthesis, revealed four chlorine atoms. On adding theseinto the model, repetition of this procedure gave theposition of 24 carbon atoms associated with the tetra-phenylarsonium group. Because of the insensitivity of thechemical analysis to the oxygen content of the moleculeit was not clear at this stage whether we were looking forone or two oxygen atoms per molecule, although thechemical analysis and density measurements favoured twooxygen atoms.One cycle of least-squares refinement [unit weights, fixedcarbon atoms, refinement of scale factors and heavy atom(Te, As, CI) positional and isotropic thermal parameters]reduced R to 16.8~, and further refinement to include thecarbon atoms (positional and isotropic thermal parameters)reduced R to 12.8y0 with reasonable temperature factors.An electron-density map calculated from this modelshowed only four small unaccounted peaks.The absorptioncorrection was applied at this stage.A number of calculations were undertaken t o establishwhich, if any, of the unassigned Fourier peaks should beregarded as genuine oxygen atoms.One peak [O(l)] atca. 1.96 A from the tellurium atom was considered to be anoxygen atom on the basis of its position, peak-height, andbehaviour on least-squares refinement. Inclusion of thisatom in the refinement reduced R to 9.2% and a subsequentelectron-density synthesis showed only one unaccountedpeak which was taken as the second oxygen atom [0(2)].In space group C2/c the tellurium atoms would occupy sitesof 1 symmetry but there was no evidence for a secondoxygen atom centrosymmetrically related to O( 1). Anempirical weighting scheme was derived from a plot ofus. F, for various ranges of F, [w(obs.) = 1/(A +BFO2 - CF,); A = 4.75, B = 4.0 X C = 7.0 X10-4; w(unobs.) = 0.81 x ~(obs.)]. Further refinement[ 179 parameters ; calc.weights, scale factors, positionalparameters for all atoms (fixing only the x and z co-ordinatefor Te) , isotropic carbon and oxygen atoms, anisotropicthermal parameters for chlorine, arsenic and telluriumatoms] reduced R to a final value of 5.1%. No hydrogenatoms were included in the structure-factor calculations.Inspection of the correlation matrix derived from theleast-squares routines showed, as might be expected, largecorrelation coefficients (0.8-0-9) between the correspond-ing parameters of the pseudo-centrosymmetrically relatedchlorine atoms. Similarly the carbon atoms related by theapproximate two-fold axis passing through the arsenicatom and parallel to b show large (ca. 0-75) correlationcoefficients. The origin of this effect is clearly the space-group ambiguity since the correlated atoms are just thosewhich would be symmetry related in the higher symmetrygroup C2/c.We experienced no difficulty with the least-squares refinement program (CRYLSQ) except that theisotropic temperature factor for two pseudo-symmetry-related carbon atoms showed marked oscillations fromcycle to cycle although the other refined parameters showedlow shift-to-error values indicating satisfactory con-vergence. A number of authors have experienced similarproblems with pseudo-symmetry and space-group am-biguities.l2.l3 The bulk of the scattering material in the12 J. D. Lee and &I. W. R. Bryant, Acta Cryst., 1969, B25,2497; B. Van Dijk and G. J . Visser, ibid., 1971, B27, 846;H. Einspahr and J .Donohue, ibid., p. 846; J. D. Lee, ibid., p.847.13 L. K. Templeton and D. H. Templeton, Acta Cryst., 1971,B27, 16781974 1547cell is approximately centrosymmetric and thereforechoosing the enantiomorph may present difficulties. Theleast-squares calculation was repeated for the enantio-morphic structure and gave a small decrease in the un-weighted and weighted R factors (see Table 2).TABLE 2Comparisons of selected bond lengths (A) and angles(") in space groups Cc and C2/cCC CC(1st (2nd(a) Distancesenantiomorph) enantiomorph) C2/cTe-Cl(1) 2*466(10) 2*457( 10) 2.484(2)Te-Cl(2) 2*490( 10) 2 -476 ( 1 0) 2*483(2)Te-Cl(3) 2 -472 ( 10) 2.487(10) *Te-C1 ( 4) 2.505 (10) 2 -5 14(09) *Te-0 ( 1 ) 1.740 ( 12) 1*736( 12) 1*741( 11)Te-0 (2) 2 -9 12 (23) 2*914(25) 2 * 8 86 [ 1 5)0(1)-0(2)19 t 3*020(26) 3.0 1 5 (2 7) 3*042( 19)(b) Angles0 ( 1)-Te-CI (1 ) 8 9.1 (5) 8 9.4 (5) 8 9.9 (4)O(l)-Te-Cl( 2) 90.2(5) 91*3(4) 90*6(4)O(l)-Te-C1(3) 90-3(5) 89.2 (5) 89*4(4) *O(l)--Te-C1(4) 90.9(5) 90*3(4) 90*2(4) *R (observed only) 5.09, 5.04 5.12%R' 5.30 5.26 5.43 yoNo. of refined 179 179 108parameters* Cl(1) and Cl(4) are related by the centre of symmetry inspace group C2/c and similarly for atoms Cl(2) and Cl(3). t See footnote to Table 5.( b ) Space gvoup C2/c.A similar analysis in space groupC2/c was undertaken. Tellurium is on a centre of sym-metry (&,$,O) and arsenic on a two-fold axis (O,y,&). Thechlorine and carbon atoms were readily located and least-squares refinement [ 100 variables, calculated weights, atompositional parameters, atom isotropic (C) and anisotropic(Cl, As, Te) thermal parameters] reduced R to 7.9%.Thesame weighting scheme was used and an examination ofAF as a function of sin 0 and Fo showed no gross abnor-malities. An electron-density synthesis showed two addi-tional peaks ascribed t o oxygen atoms. Various modelswith ordered and disordered oxygen atoms were exploredand the model in which both oxygen atoms were presentwith population parameters of 0-5 was found t o give themarkedly lowest R factor of 5.1% on refinement. Lowshift-to-error values in the full-matrix least-squares analysisindicated satisfactory convergence and an electron-densitysynthesis on the final parameters gave peak electrondensities of 4.5-6.5 e k 3 for carbon and 2.7 and 2.5 eAM3for oxygen atoms 0(1) and O(2).A final differenceelectron-density synthesis showed no prominent featureson the map, particularly where atoms are located, and inaddition showed a number of small peaks (0-3-0-6 eAV3).The position of ten of these was found to be in the correctposition for hydrogen atoms bonded to the carbon atomsof the phenyl rings and their peak heights were consistentwith this inter~retati0n.l~ A few other small peaks wereobserved close to the oxygen atoms but these did not allowa clear decision on the hydrogen positions. No hydrogenatoms were included in the structure-factor calculation.(c) Comparison of structure solutions.-In gross chemicalterms the structural solutions found for the two spacel4 G.H. Stout and L. H. Jensen, X-Ray Structure Deter-mination,' Macmillan, New York, 1968.TABLE 3Final positional ( x lo4) and isotropic thermal ( x lo3)parameters with standard deviations in parentheses(space group C2/c)xla Y lb %/C u pTe 2500 2500 0"(') 3002( 1)c1(2) * 2912(6) :[:\ * 2581(7)As 0 4961(1) 2500'(I2) 1034( 5)'(' 3, 07 12 (5)0180(5)4236(4) 8400( 10)3575(4) 8520(11)1427(1) 36 17 (4) 0593( 1)1347(4) 1126( 1)0 142 (6) 4608(16)6443(2 1) OOll(7) 113(4)59(3)C(11) t 0281(4) 6505 (10) 1761(4) 45 (2)081 9(5) 7794( 12) 1 9 1 3 (4) 58(2)1383(5) 70 (3)8804( 14) 0 7 18 (5) 68(3)7536( 13) 0578 (5) 63(2)C(14)6348(12) 1103(4) 54(2)C(15)2197(4) 41 (2)2505(4) 50(2)W1)7330(13) 2269(4) 60(2)6023(13) 1770(5) 65(2)5910( 13) 1474(5) 65(2)895 7 (1 4)C(16) -0044(4)c(22) 3028 (5)c(23) 3155( 5)c(24) 3833(5)C(26) c(25) 4371 (5) 7 102 (12) 1 692 (4) 60(2)* Population parameter of 0.5.t Carbon atoms are num-bered C(ij) ; i = 1,2 and refers t o the ith phenyl ring, j = 1-6and refers to the carbon atoms of the ith ring numberedcyclically.TABLE 4Heavy-atom anisotropic temperature factors * ( x lO4),with standard deviations in parentheses (space groupC 2 / 4ull u2Z u33 u12 u13 u23Te 705(5) 557(5) 496(19) 137(4) 131(4) 75(4)Cl(1) 692(14) 824(17) 687(23) 117(13) 165(11) -33(13)Cl(2) 779(15) 792116) 555(22) 87(13) -2(11) 106(12)As 375(5) 462(6) 436(19) 0 t 5(4) 0 t* In the form: T = exp[-2~~2(U,,h~a*~ + U22k2b*2 +U3312c*2 + 2U12hka*b*cos y* + 2U13hla*c*cos @* + 2U2,klb*c*cos .*)I, t Constrained to be zero by the atom site symmetry(H.A. Levy, Acta Cryst., 1956, 9, 679).TABLE 5Pertinent bond lengths (A) and angles ( O ) , with standarddeviations in parentheses (space group C2/c)(a) AnionTe-Cl( 1) 2*484(2) C1( 1)-Te-Cl( 2) 89-8(1)Te-Cl(2) 2.483 (2) C1 (l)-Te-C1(2I) 90*3( 1)Te-0 (1) 1-74(1) O(1)-Te-Cl(1) 89-9(4)Te-0 (2) 3*89(2) 0 (1)-Te-C1(2) 90.6 (4)0(1)-0(211) 3.04(2) O(1)-Te-C1( 11) 89*4(4)O( 1)-Te-C1(21) 90.2 (4)(b) CationAs-C(11) 1 *90 7 (7) C( 1 1)-As-C (21) 110-4(3)As-C(2 1) 1 -905 (7) C(ll)-As-C(llIII) 107-4(3)C(21)-As-C(21III) 106.4(3)C(ll~~~)--A~--C~21) 111*1(3)C(ll)-C( 12) 1*40(1) c (2 1 )-c (22) 1*39(1)C( 12)-C( 13) 1-40 (1) C(22)-C( 23) 1*41(1)C( 13)-C( 14) 1 -40 (1) C(23)-C(24) 1-38(1)C(14)-C(15) 1*38(1) c (2 4)-c (25) 1*41(1)C (1 5)-C( 16) 1 -4 1 (1) C(25)-C(26) 1*39(1)C( 16)-C( 11) 1*39(1) C (26)-C (2 1) 1 *39(1)Atoms superscripted are related by a symmetry operationto those with no superscript.Atoms with superscripts I and I1are related by a centre of symmetry (at &&,O and &,$,O re-spectively), and those with I11 by the two-fold axes passingthrough the arsenic atom (O,y,$ and $,& + y,&)..(c) Equations for the least-squares plane through the carbonatoms of the phenyl rings (where x , y , and z are the fractional co-ordinates in direct space)Plane (a) : C(l1)-(16) 13.141~ - 4.868~ - 5.3272 = -33.737Plane (b) : C(21)-(26) 5.062~ - 4.772~ + 13.4562 = 1.101548 J.C.S. Daltongroups are very similar and Table 2 shows some pertinentbond lengths and angles for the two space groups.Insuch situations Harniltonl5 has suggested the use ofstatistical tests based on the R factor ratio for the two spacegroups. Comparing the second enantiomorph in Cc withC2/c using either the weighted or unweighted R factorsindicates that at better than the 25% significance level thespace group C2/c is preferred.Final positional and thermal parameters for the analysisin C2/c, together with the standard deviations derived fromthe least-squares analysis, are shown in Tables 3 and 4.Table 5 lists chemically interesting bond lengths and angles.c> c> Te CL.--- - , I Iperpendicular to the plane.This oxygen atom is dis-ordered (in the space group C2/c) and the atoms thusform a disordered square-pyramidal group with an axialoxygen. As expected, for a disordered model, the bondangles involving the apical oxygen are close to 90" (seeTable 5 ) and we are thus not able to comment on thevalue for any one TeC1,O group. The Te-Cl bondlengths can be compared with the mean of 2-44 for theterminal bonds in PC&,TeCl, and 2.53 A in octahedraltr~uts-TeC1,,2(tetrarnetliylthiourea).~~ There are nodirectly comparable Te-0 bond lengths in related3 0 0As 0 CI,-- 1.FIGURE 1 View of the unit cell looking in the --x direction (The +,+,O related positions have been omitted for clarity.ordered oxygen atom is shown as a full and clashed circle, the former making one and the latter the other chain.oxygen-oxygen and oxygen-tellurium distances are drawn with broken lines for the full-circle oxygen atoms only.)Each dis-The longObserved and calculated structure factors are listed inSupplementary Publication Xo.SUP 21012 (3 pp.).*All calculations except for the absorption correction werecarried out on an ICL 1906A computer at Harwell, using theX-ray system of programs devised by J. 31. Stewart.DISCUSSIONDiagrams of the structure are presented in Figures 1and 2. The arrangement of ligands around the telluriumatom shows four chlorine atoms lying in a square-planararrangement with a tellurium oxygen bond (1.74 A)* See Notice to Authors No.7 in J.C.S. Dalton, 1973, Indesl5 W. C . Hamilton, Acta Cvyst., 1965, 18, 502.le S. Husebye and J. W. George, Inovg. Chem., 1969, 8, 313.l7 0. Lindqvist, Acta Chevn. Scand., 1970, 24, 3178.0. Lindqvist, Acta Chem. Scmzd., 1972, 28, 4107.issue (items less than 10 pp. are supplied as full size copies).molecules but the Te-0 distances in a number of TeVroxides and hydroxides fall in the range 1%----1-99 &l7-lgand in [SeOC1,I2- (ref. 20) and SeOCl, the Se-0 distanceis 1.61 A.The second (disordered) oxygen atom in the structure[0(2)] is 3.04 A from the oxygen atom bound to the Teand 2-89 A from an adjacent Te atom, the whole structureforming an infinite chain parallel to b (see Figure 2).The 3.04 A 0 - - - 0 distance must be regarded as arather long hydrogen bond 21*22 and the 2.89 A distancemay indicate a weak interaction between the oxygenand tellurium atoms.19 0.Lindqvist and M. S. Lehmann, Acta Chewz. Scaitd., 1973,27, 85.20 B. C . Wang and A. W. Cordes, Irtovg. Clcem., 1970, 9, 1643;*l G. C. Pimentel and A. L. McClellan, ' The Hydrogen Bond,1960, Freeman, San Francisco.22 W. C. Haillilton and J. A. Ibers, ' Hydrogen Bonding inSolids,' Benjamin, New York, 19681974 1549We cannot distinguish between the two formulations[TeCl,(OH)]-(H,O) and [TeC1,0I2-H3O+ and indeedbecause of (almost certain) hydrogen bonding betweenIIFIGURE 2 The anion and associated atoms (see caption toFigure 1)the oxygen atoms the distinction between these two maybe somewhat artificial.The i.r. spectrum of the com-pound (4000-650 cm-l) showed clear evidence for thepresence of the tetraphenylarsonium group, but a clearlyrecognisable absorption in the OH stretching region wasnot apparent. I t is known that the i.r. absorptionspectra of hydrogen bonded systems are often broad and23 K. Nakamoto, M. Margoshes, and R. E. Rundle, J . Amer.24 B. Zaslow and R. E. Rundle, J . Phys. Chem., 1957, 61, 490.26 F. A. Cotton and S. J. Lippard, jun., Inorg. Chem., 1966, 5,26 J . G. Bergman and F. A. Cotton, Inorg. Chem., 1966,5, 1208.27 J . G. Bergman and F. A. Cotton, Inorg. Chem., 1966,5, 1420.28 J . E. Hopkin, A. Zalkin, D. H. Templeton, and M. G.29 F. A. Cotton and C. B. Harris, Inorg. Chem., 1968, 7, 2140.Chem.Soc., 1955, 77, 6480.416.Adamson, Inorg. Chem., 1966, 5, 1427.of low inten~ity.~Z In view of the large amount ofscattering by heavy and not-so-heavy atoms, thehydrogen atoms observed in the difference electron-density synthesis were not considered adequate for theestablishment of the appropriate formulation.The dimensions of the tetraphenylarsonium ion agreewell with previous crystallographic studies on moleculescontaining this The mean C-C distances in thephenyl rings are 1.40 A and the angles around thearsenic atom are close to the tetrahedral value. The ionis required to have two-fold symmetry, although itexhibits approximately S, point-group symmetry.Tellurium( 1v) in its compounds is capable of displayingor not displaying a stereochemically active lone-pair ofelectrons. Square-pyramidal arrangements have beenfound in [TeF,]-,l [MeTeI,]-,83 and the polymericchlorine-bridged RTeCl, (R = CH,*CH,Cl) 34 whereaswith six-co-ordinate species, e.g. [TeC1,I2-, octahedralsymmetry is found in the solid The trisoxalato-antimonate(II1) ion 36 is one of the few well-defined six-co-ordinate species with a stereochemically activelone-pair and other less clear-cut examples in telluriumchemistry are known.37 Indeed an alternative view-point of the present structure is to give the long Te-0interaction structural significance and regard the anionas involving six bonds to the central tellurium. Anon-octahedral arrangement of these bonds arises on theSidgwick-Powell model from the st ereochemically activelone-pair of electrons on the central atom.We thank the S.R.C. for a maintenance grant (to P. H. C.),the Royal Society and I.C.I. for financial support, and thestaff of the Atlas Laboratory, Harwell, for help with theX-ray system on the 1906A computer.[3/1656 Received, 6th .4ztgust, 1973130 See refs. in G. Ferguson and E. W. Macauley, J . Chem. SOC.3l J. Drummond and J . S. Wood, J . Chem. SOC. ( A ) , 1970, 226.32 B. D. Faithful1 and S. C. Wallwork, Acta Cryst., 1972, B28,33 F. Einstein, J. Trotter, and C. Williston, J . CIzeiiz. SOC. ( A ) ,34 D. Kobelt and E. F. Paulus, Axgew. Chem. Internat. Edn.,35 M. Webster and P. H. Collins, J.C.S. Dalton, 1973, 588.36 M. C. Poore and D. R. Russell, Claem. Comm., 1971, 18.37 I<. J . Wynne, J . Chem. Educ., 1973, 50, 328.( A ) , 1969, 1.2301.1967, 2018.1971,10, 74
ISSN:1477-9226
DOI:10.1039/DT9740001545
出版商:RSC
年代:1974
数据来源: RSC