摘要:
J. CHEM. SOC. DALTON TRANS. 1982 2313Complex Formation between Antimony Trifluoride and Alkali-metalSulphates : The X-Ray Crystal Structure of K2SO4-SbF, andAntimony-121 Mossbauer Studies of Some Related Compounds tThomas Birchall *Department of Chemistry and Institute of Materials Research, McMaster University,7280 Main Street W., Hamilton, Ontario, Canada L8S 4MlBernard Ducourant, Robert Fourcade, and Guy MascherpaLaboratoire des Acides Mindraux, Universitb des Sciences et Techniques du Languedoc,Place Eugene Bataillon, 34060 Montpellier Cedex, FranceThe X-ray crystal structure of K2S04*SbF3 is reported. It crystallizes in the orthorhombic space groupP2,2121, with a = 5.601 (2), b = 9.072(4), c = 14.180(6) A, and Z = 4 and a final R = 0.035. Theantimony environment is that of a distorted octahedron, SbF302E, where E represents the non-bondingelectron pair of Sb? The 121Sb Mossbauer data of this and other M2SO4=SbF, complexes areinterpreted in terms of SbX5E and SbX6E environments. In all cases the non-bonding electron pair isstereoc hemically active.Antimony trifluoride is a strong fluoride-ion acceptor and avariety of fluoroantimonate(r~~) complexes have been examinedby antimony-121 Mossbauer spectro~copy.'-~ 0x0-anions alsoform complexes with SbF3 and lZ1Sb Mossbauer and X-raycrystallographic studies have been reported for a number ofthese c~mplexes.~-~ This paper presents the X-ray crystalstructure of KZSO4-SbF3 to further extend this series.In allof these compounds the antimony(rrr) is in a distorted environ-ment indicating that the non-bonding electron pair is stereo-chemically active.Alkali-metal sulphates form strong com-plexes with antimony trifluoride and in order better to under-stand the bonding in these complexes we have measured the'''Sb Mossbauer spectra of a number of complexes formedwith SbF3. These spectra are discussed here with reference tothe known structural data.ExperimentalThe complex K2S04*SbF3 was prepared by the simultaneousdissolution of stoicheiometric quantities of KzSO4 and SbFJin water followed by slow evaporation of the solution at20 "C. This procedure resulted in fine colourless needleswhich were used for the subsequent studies.Antimony- 121 Mossbauer spectra were recorded using anElscint drive system in conjunction with a Promeda multi-channel analyzer.The source was nominally 0.5 mCi Balzl"-Sn03, purchased from New England Nuclear, and togetherwith the sample was cooled to 80 K in a cryostat designed byB. Ducourant and manufactured by Aire Liquide. The windowof the single-channel analyzer was set on the escape peak ofthe 37-keV (ca. 5.9 x lo-'' J) y-ray. Samples contained ca.15 mg Sb cm-2 and all isomer shifts were measured withrespect to InSb at 80 K. The velocity range was calibratedperiodically using a 57C0 source and a standard iron foil.About lo5 counts per folded channel were accumulated andthe data were computer fitted using the program describedby Ruebenbauer and Birchall which incorporated the fulltransmission-integral procedures which are necessary for thesuccessful refinement of lZ1Sb Mossbauer spectra.Crystal Data.-K2S04*SbF3, M = 352.95, Orthorhombic,space group P212121, a = 5.601(2), b = 9.072(4), c =t Supplemmtary duta mailable (No. SUP 23402, 10 pp.): thermalparameters, structure factors.See Notices to Authors No. 7, J.Cheni. Soc., Dalton Trans., 1981, Index issue.14.180(6) A, CI = 720.52 A3, Dm = 3.22 g ~ m - ~ , 2 = 4,D, = 3.25 g ~ m - ~ , F(OO0) = 656, h (Mo-Ka) = 0.7107& andp(MO-Ka) = 52.95 cm-'.A preliminary examination of a single crystal using aWeissenberg camera allowed us to determine the cell para-meters and establish the space group as P212121. The cellparameters were refined from powder diffraction data usingthe method of least squares according to Norbert.lo Theobserved bands and their relative intensities are given inTable 1 up to a value of 8 = 20" for Cu-K, radiation.Theequivalent positions for P2,2,2, are: x , y, z : 3 - x , - y ,3 +z; * f x , 3 -y, -2; - x , + f y , 3- -z.X-Ray Intensity Measurement.-A fine needle-like crystal ofdimensions 0.20 x 0.05 x 0.02 mm was mounted on a fibreand h,k,Z intensity measurements obtained by means of anautomatic Nonius CAD4 diffractometer, until the value of(sin B)/h = 0.70. In view of the small size of the crystal,absorption corrections were not made.Structure Determination and Refinement.-The location ofthe antimony atom in the unit cell was obtained from a three-dimensional Patterson synthesis using 1 01 6 reflectionspreviously corrected for Lorentz and polarization factors.Successive refinements by a difference-Fourier synthesisallowed the other atoms to be located.Using isotropicthermal parameters R was 0.055 (R = ZlkF, - ~Fo]]/XCkFo andk = C~F,~/XIFoI). A final refinement with varying anisotropicthermal parameters gave R 0.035. The final difference syn-thesis showed peak maxima corresponding to 2 e in theneighbourhood of the antimony atoms. Programs used inthe refinement of the structure were DATAP2, DRF, LINUS,DISTAN, and ORTEP." Scattering factors used in the cal-culation of F, were those of Doyle and Turner.12 Table 2summarizes the final positional co-ordinates of the atoms.DiscussionThe Structure.-A representation of the structure in the1 0 0 plane is shown in Figure 1 where the SbF3 and [S0412-units are clearly distinguishable. Each antimony of the SbFj isbonded to two sulphates by Sb-0 bonds of intermediatelength. Each of the two sulphate groups have the samerelationship to two antimony atom.The groups form ahelix which stretches out along the z axis and this is repre-sented in Figure 2. The helices, of formula (SbF3*S04)x2X-, ar2314 J. CHEM. SOC. DALTON TRANS. 1982Table 1. Powder pattern data for K,SOI.SbF3h k l0 1 10 0 20 1 21 0 11 1 01 1 10 2 10 1 31 1 20 2 20 0 41 2 01 2 11 1 30 1 4dcalc. 18,7.6427.0905.5865.2094.7664.5174.3204.1923.9553.8213.5453.5253.4213.3563.302dob.lA7.6227.0865.5625.2054.7664.5254.3504.1793.9583.8273.5503.5253.4213.3533.302Intensity3943201243210410055314220h k l1 2 21 0 40 3 11 1 41 2 32 0 00 2 40 1 51 3 10 3 31 2 40 2 50 0 60 3 4dc, Ic ./A3.1562.9952.9572.8442.8252.8002.7932.7072.6152.5472.5002.4042.3632.301dobs. 18,3.1552.9952.9572.8412.8252.7912.7102.61 52.5442.4972.4022.3632.301Intensity17101377772210331024814Table 2. Atomic co-ordinatesAtom Xla0.473( 1)0.020 O(4)0.495 7(4)0.246( 1)0.215(1)0.461( 1)0.069( 1)0.241 (1)0.070(2)0.844(2)0.022 3(4)Ylb0.057 76(6)0.313 6(2)0.490 7(2)0.206 4(2)0.077 3(6)0.573 6(7)0.906 2(6)0.120 3(8)0.224 5(9)0.852 O(8)0.134(2)Zlc0.022 44(4)0.388 9(1)0.191 2(1)0.161 5(1)0.461 2(4)0.035 4 ( 5 )0.124 3(4)0.075 7(5)0.214 2(5)0.368 4(5)0.218 l(8)Table 3.Environments of the potassium atoms and of the sulphategroup (distances in A, angles in degrees)2.693(6)2.750(7)2.762(7)2.802(6)2.828(6)2.87 l(9)2.884(9)3.032( 6)3.081(11)2.639(11)2.7 1 7( 6)2.737(6)2.8 1 3(7)2.849(9)2.866(6)2.9 12(9)O(l)-S-0(2)O( 1)-S-O(3)0(1)-S-0(4)0(2)-S-0(3)O(2) -S -0(4)O( 3) -S -0(4)1.44(1)1.444(9)1.469(9)1.480(7)109.7(6)107.5(4)110.0(6)110.0(4)110.0(6)109.0(5)held together in the crystal by co-ordination of fluorine andoxygen atoms to the two potassium cations K(1) and K(2).One of the potassium cations is nine-co-ordinate while theother is seven-co-ordinate.The main interactions to thepotassium are listed in Table 3 along with the bond lengthsand angles in the sulphate anions. The sulphate groups arenot distorted by their co-ordination to the antimony. This is incontrast to the situation in MSbF2*S04 (M = Rb or Cs)whose significant distortion of the sulphate tetrahedron isobser~ed.'~Of most interest is the environment about the antimony(Figure 3) where, based on the criteria defined by Alcock,14there are three short Sb-F bonds and two longer Sb-Obonds. Based upon an analytical model developed by Four-#Figure 1. Projection of the structure of K2S04*SbF3 on the 1 0 0planeFigure 2. A representation of a fraction of the (SbF3S04),2X-helixcade and Mascherpa for co-ordination polyhedra aboutatoms having an oxidation state two less than the groupmaximum, the geometry about the Sb"' must be considered asbeing of the AX3Y2E type.'" From an examination of FigurJ.CHEM. SOC. DALTON TRANS. 1982 2315Table 4. Mossbauer data for some alkali-metal sulphate complexes with antimony trifluoride6 eQ V,, rCompound mm s-' T A X21d M aNa,SO,.S b F, -5.68 f 0.01 15.62 f 0.12 1.16 f 0.03 3.79 f 0.101.90 f 0.05 K,SO,.SbF, -5.53 i 0.02 14.84 0.18 1,.41 f 0.04KZS04.2SbF3 -5.20 f 0.01 16.89 f 0.15 1.26 f 0.04 1.84 f 0.05RbSbF*.SO, -6.41 f 0.01 16.38 & 0.17 1.64 f 0.04 2.14 f 0.05CSSbF,.SO, -6.18 i 0.02 17.71 f 0.16 1.55 f 0.04 1.92 f 0.05InSb 0.0 f 0.01 0.0 1.05 i 0.04 2.68 f 0.02SbF, -6.29 19.1 - 0.75Ref.3. ' Misfit defined as in S. L. Ruby, ' Mossbauer Effect Methodology,' eds. I. J . Gruverman and C.York, 1973, vol. 8, p. 263.2.202.172.352.462.331.271.25W. Seidel,0.220.420.380.380.380.340.23Plenum, NewFigure 3. A representation of the SbF302E octahedron. Additionalangles are O(l)SbF(3) 84.5 and 0(3)SbF(2) 84.0'; in the basal planethe Sb lies 0.371 8, below while 0(1), F(3), F(2), and O(3) lie0.105, 0.072, 0.123, and 0.071 8, above the plane3 it is apparent that the non-bonding electron pair of Sb"'must occupy the vacant position of the octahedron approxi-mately opposite to Sb-F( I), the shortest antimony-fluorinebond. The longest antimony-fluoride bond, Sb-F(3) isopposite to the shortest antimony-oxygen bond, Sb-0(3),with the bonds of intermediate length also being opposed.The differences observed in the bond angles about the anti-mony are just what one would expect from an SbF302Earrangement based on the ideas of Gillespie.16Comparison of this structure with K2S04.2SbF3 andNa2SO4.SbF3 shows some interesting differences. Theaverage Sb-F primary contact distance is 1.973 A in the titlecompound compared to an average value of 1.95 A in therelated corn pound^.^^^ More significant differences are foundin the Sb-0 distances which are 2.346 and 2.45 A in K2SO4.SbF3 while the average Sb-0 distance in the other twocompounds is longer at 2.508,.7-8 This lengthening of the Sb-0distances is undoubtedly caused by the additional fluorinecontact to antimony in the last two compounds.This occurson the side of the polyhedron away from the three shortSb-F bonds and is 2.972 8, in Na2S04*SbF3 and 2.799 A inK2S04-2SbF3. This lengthening of the Sb-0 bonds and thegreater distortion of the antimony polyhedron is necessaryin order to accommodate this additional fluorine contact.There are no long Sb-F interactions of this kind in the titlecompound.lz1Sb Mossbauer Spectra.-Antimony- 121 spectra wererecorded for the compounds discussed above together withtwo related compounds MSbF2*S04 (M = Rb or Cs). Thesecompounds all have a high recoil-free fraction and goodspectra could be obtained at liquid-nitrogen temperature.The XZ/d values are somewhat on the high side for the com-puter fits but the misfit values indicate that these spectra areof good quality.These spectra showed a broad absorptionenvelope to high negative velocity of the source with theenvelope tail at negative velocity relative to the peak minimum.This indicates that the quadrupole coupling constant ispositive and since eQ for '"Sb is negative the sign of V,, mustalso be negative. The negative isomer shift indicates a highs-electron density at the antimony, since 6 R / R for 12'Sb isnegative. This is typical for antimony(1rr) fluorine com-plexes l-' where the non-bonded electron pair is stereo-chemically active. We have summarized the Mossbauer datain Table 4 and included data for SbF3 for comparison.Table 4 shows that the sodium and potassium compoundshave isomer shifts which are less negative than those for therubidium and caesium compounds and antimony trifluoride.This indicates a significantly lower s-electron density in thesodium and potassium compounds compared to the others.This is either the result of an increased participation of theantimony(Ir1) 5s electrons in the bonding or increased shieldingof the s electrons from the nuclear charge by an increase inthe strength of the secondary interactions compared to thesituation in SbF3.The latter factor is probably the moreimportant one since the average primary Sb-F distance isshorter in SbF, than in the compounds discussed here, whilethe secondary contacts to oxygen are quite strong in thesulphate-antimony trifluoride cases.The increased s particip-ation may be significant only for K2S04*SbF3 since this isthe only compound in which there are only five bondingcontacts to antimony. Here the geometry can be described asbeing AXsE rather than AX6E.The quadrupole coupling constants are not as negative as inSbF3 indicating a more regular environment. This again is aconsequence of the longer primary interactions and shortersecondary ones. The sign of the coupling constant indicatesthat V,, is dominated by the stereochemical activity of thenon-bonding electron pair of Sb which must have some 5pcharacter and that the principal component of the electricfield gradient tensor must be through the lone-pair orbitaland the cone made by the three primary Sb-F bonds. TheK2S04*SbF3 compound has the smallest quadrupole couplingconstant and X-ray crystallography shows that the antimonyindeed does have the most regular structure, i.e.closest tooctahedral. The most distorted antimony environment of thesethree compounds occurs in K2S04*2SbF3 which shows thelargest variation in Sb-F bond lengths, from 1.91 7 to 1.963 A,and has the shortest secondary fluorine contact at 2.799 A. Itshould also be pointed out that in this compound there arealso two crystallographically different antimony environ-ments and that the Mossbauer spectra were fitted to only oneabsorption envelope2316 J. CHEM. SOC. DALTON TRANS. 1982The rubidium and caesium salts have a different composi-tion from that of the sodium and potassium compoundseven though the method of preparation was the same.13They have significantly more negative isomer shifts than thesodium and potassium salts indicating a much larger s-electron density at the antimony.In RbSbF2*S04 there areonly two fluorine contacts to the antimony, 1.91 and 1.93 A,and this is very similar to the situation in other fluoroantimonycomplexes containing an [SbF2]+ unit.17 In these lattercompounds the [SbF2] + is co-ordinated by two additionalfluorines from each of two [SbF6]- anions to give a [Sb3F14]-anion and the co-ordination number is completed by fourmuch longer Sb"'-F interactions. These interactions arehowever rather weak and result in rather large negative isomershifts ranging from -6.5 to -7.6 mm s-'.17 The implicationfor the MSbF2*S04 compounds is that the SbFz unit here hasmuch less positive charge residing on the antimony thusaccounting for the somewhat less negative isomer shifts.A further difference between the [SbF2] +-containing com-pounds is that the Sb"' in the [Sb3Fl4]- anions all have verylarge asymmetry parameters whereas in the MSbF2*S04compounds the spectra were fitted with q values which werenot significantly different from zero.It is clear then that wecannot consider the [SbF2]+ unit in the sulphate complexesto exist as a cation and that other strong interactions mustoccur to give the antimony a pseudo-three-fold symmetry.This is indeed the situation and a Sb-0 contact at 2.1 1 Acomprises the third strong bond to the Sb"' in RbSbF2*S04.Three other longer oxygen contacts complete the SbX6Egeometry and a quite distorted antimony environment.Theobserved quadrupole coupling constant is large and negativeindicating that the lone-pair axis is coincident with thepseudo-three-fold axis through the SbF20 cone. The caesiumsalt has a less negative isomer shift but a more negativequadrupole coupling constant. This suggests that the primarySbF2-0 contact is stronger in this compound than in therubidium case while the secondary oxygen contacts are cor-respondingly weaker.AcknowledgementsThe Natural Sciences and Engineering Research Councilof Canada are thanked for funds which enabled T. B. toparticipate in the Canada-France Cultural Exchange Scheme.This work was carried out at U.S.T.L. Montpellier.References1 T.Birchall and B. Della Valle, Can. J . Chem., 1971, 49, 2808.2 J . D. Donaldson, J. T. Southern, and M. J. Tricker, J. Chem.3 J. G . Ballard, T. Birchall, R Fourcade, and G. Mascherpa,4 T. Birchall and B. Ducourant, J. Chem. SOC., Dalton Trans.,5 P. Escande, D. Tichit, B. Ducourant, R. Fourcade, and G.6 M. Bourgault, R. Fourcade, B. Ducourant, and G. Mascherpa,7 B. Bonnet, B. Ducourant, R. Fourcade, and G. Mascherpa,8 M. Bourgault, B. Ducourant, B. Bonnet, and R. Fourcade, J .9 K. Ruebenbauer and T. Birchall, Hyperfine Interact., 1979, 7 ,SOC., Dalton Trans., 1972, 2637.J. Chem. SOC., Dalton Trans., 1976, 2409.1979, 131.Mascherpa, Ann. Chim. (Paris), 1978,3, 117.Rev. Chim. Miner., 1979, 16, 151.Rev. Chim. Miner., 1980, 17, 88.Solid State Chem., 1981,36, 183.125.10 A. Norbert, Reu. Chim. Miner., 1969, 6, 687.1 1 DATAPZ, P. Coppens, L. Lizerowitz, and P. Robinovich;DRF, A. Zalkin; LINUS, P. Coppens and W. C. Hamilton;DISTAN, A. Zalkin; all adapted by E. Philippot.12 P. A. Doyle and P. S. Turner, Acta Crystallogr., Sect. A , 1968,24, 390.13 M. Bourgault,Thesis, Maitre &s Sciences, Universitk des Scienceset Techniques du Landguedoc, 1980.14 N. W. Alcock, Adv. Inorg. Chem. Radiochem., 1972, 15, 1 .I5 R. Fourcade and G. Mascherpa, Rev. Chim. Miner., 1978, 15,16 R. J. Gillespie, ' Molecular Geometry,' Van Nostrand Reinhold,17 J. F. Ballard, T. Birchall, R. J. Gillespie, E. Maharajh, D. Tyrer,295.Princeton, New Jersey, 1972.and J. E. Vekris, Can. J. Chem., 1978, 18, 2417.Received 26th February I982 ; Paper 2135
ISSN:1477-9226
DOI:10.1039/DT9820002313
出版商:RSC
年代:1982
数据来源: RSC