摘要:
J. CHEM. SOC. DALTON TRANS. 1992 193Structural Studies on Organotransition-metal-BismuthComplexes tWilliamNicholas C. Norman.*rs Nicholas A. L. Williams,lb Susan E. Stratford,lb Stephen J. Nichols,lbPenelope S. Jarrettb and A. Guy Orpen * s ba Department of Chemistry, The University, Newcastle upon Tyne NEl 7RU, UKNeville A. Compton,a R. John Errington,8 George A. Fisher,a David C. R. Hockless,"Department of inorganic Chemistry, The University, Bristol BS8 7 TS, UK~ ~ ~ ~ ~~ ~~ ~ ~~The X-ray single-crystal structures are reported for [BiX{M(CO),(q-C,H,)},] ( M = W, X = CI 2; M = Mo,X = Br 3; M = Mo, X = I 4). Compounds 2 and 3 exhibit linear polymeric structures involvingintermolecular Bi X interactions and are isomorphous with the previously reported [BiCI(Mo(CO),(q-C5H5)}.J 1.In contrast, the iodide derivative 4 exists in the solid state as a weakly bound dimer. Analysis ofBi-L,,,-edge and M-K-edge or L,,,-edge extended X-ray absorption fine structure (EXAFS) spectra for[BiCI{M(C0),(q-C,H5)}J (M = W or Mo; y = 3 2, 1: M = Fe; y = 2 5) and [Bi{M(CO),(q-C,H5)}3](M = W 6 or Mo 7 ) in solid (1, 2, 5, 7 ) and solution (1, 5) phases also shows evidence for oligo- orpoly-merisation through Bi CI interactions in solid 1, 2 and 5. In tetrahydrofuran (thf) solutions of1 and 5 these interactions are disrupted, and the monomeric species formed show co-ordination ofsolvent to bismuth. The BiM, species 6 and 7 show metal-metal distances consistent with apyramidal geometry at bismuth. EXAFS data for BiCI, 8 in the solid and in thf solution showed onlyindirect evidence for disruption of the weaker Bi CI contacts present in the solid o n solvation.As part of our interest in organotransition-metal-bismuthcomplexes, we have determined several structures by X-raycrystallography 1-3 and more recently we have examined, inboth the solid state and in solution, a number of compounds byextended X-ray absorption fine structure spectroscopy(EXAFS).4 The latter technique has proven extremely useful instudying structures in the solid state where crystals suitable forX-ray diffraction are not available but, and of perhaps greaterimportance, it has also enabled us to study the nature ofcomplexes in solution.All of these data provide valuablestructural information and, in addition, they often allow us tounderstand better much of the chemistry of these compounds.Herein we describe further results obtained by X-raycrystallography and EXAFS and comment on the nature of thebismuth centre in these complexes particularly with regard to itsLewis acidity.Results and Discussion(i) A'-Ray Crystallography.-In ref.2 we described thestructure of [BiCl{ Mo(CO),(q-C,H,)},] 1. Compound 1crystallises with two molecules, A and B, in the asymmetric unit;these, although similar in their molecular structures,2 exhibitlarge differences in their intermolecular interactions. Thus for Asubstantial Bi Cl interactions exist between adjacent sym-metry-related molecules such that, whilst the primary Bi-Clbond distance is 2.746(2) A, the secondar , intermoleculardistance is only ca.0.29 A longer at 3.039(3) i. For molecule Bmuch weaker intermolecular interactions are present; theprimary Bi-CI distance is 2.612(3) 8, whereas the secondarydistance is ca. 0.98 A longer at 3.596(4) A. These data show thatas the secondary Bi C1 distance decreases the primary Bi-CIdistance increases. Moreover, the Cl-Bi-Cl angles [ 15 1.6( 1)" forA and 141.6(1)" for B] show that the secondary chlorinet Supplemeniury duta uvrrilable: see Instructions for Authors, J. Cheni.Soc., Dalton Trans., 1992, Issue I , pp. xx-xxv.O(111)Fig. 1Hydrogen atoms omitted for clarityA view of the molecular structure of molecule A of complex 2.interaction is approximately trans to the primary Bi-CI bond.We shall return to and discuss these observations later.The complexes [BiC1{W(C0),(q-C5H,>),1 2 and [BiBr{ Mo-(CO)3(q-C5H5)}2] 3 are isomorphous with 1.The synthesis of 2was described in ref. 2; 3 was prepared in exactly the same wayas 1 but using BiBr,, although an alternative preparation of thiscomplex involving the reaction between Na[Mo(CO),(q-C,H,)] and BiBrMe, has been reported by Panster andMalisch.'A view of molecule A of complex 2 is shown in Fig. 1, selectedbond lengths and angles are given in Table 1 and atomicpositional parameters in Table 2. For molecule A the primaryBi-Cl distance is 2.752(6) 8, and the secondary Bi*.-Clinteraction is ca. 0.27 A longer at 3.017(6) A. For molecule B therelated distances are 2.604(7) and 3.620(6) 8, (the latter 1.02 Alonger).The Cl-Bi-Cl angles are 151.9(4)O for A and 141.8(4)*for B.A view of molecule A of complex 3 is shown in Fig. 2, selectedbond lengths and angles are given in Table 3 and atomicpositional parameters in Table 4. The primary and secondar194 J. CHEM. SOC. DALTON TRANS. 1992Bi-Br distances are, for molecule A, 2.938(2) and 3.104(2) Arespectively and, for B, 2.773(2) and 3.71 8(2) A respectively. TheBr-Bi-Br angles are, for A, 148.2(1)" and, for B, 140.7(1)". Aview of part of the unit cell of 3 (Fig. 3) illustrates theintermolecular interactions.The iodide complex [BiI(Mo(C0),(q-C5H5)),1 4, incontrast to 1-3, is a weakly bound dimer. A view of 4 is shown innUO(113). .O(l23)Fig.2Hydrogen atoms omitted for clarityA view of the molecular structure of molecule A of complex 3.Table 1 Selected bond lengths (A) and angles (") for complex 2Molecule A Molecule BBi( 1)-W( 11) 2.964( 2) Bi( 2)-W (2 1 ) 2.9 I5(2)Bi( 1)-W( 12) 2.935( 1) Bi( 2)-W( 22) 2.98 l(2)Bi( 1 )-Cl( 1 ) 2.7 5 2( 6) Bi(2)-CI( 2) 2.604(7)Bi(1) 0 . . Cl(1b) 3.017(6) Bi(2) - Cl(2d) 3.620(6)W(l l)-Bi(l)-W(l2) 117.7(1) W(21)-Bi(2)-W(22) 115.9(1)W( I 1 )-Bi( I t C l ( I ) 102.2(2) W(2 1 )-Bi(2)-C1(2) 96.3( 2)W(l2)-Bi(l)-Cl(l) 91.0(2) W (22)-Bi( 2)-C1( 2) 1 06.4( 2)W( ll)-Bi( l)-Cl( 1 b) 95.7(2) W(21)-Bi(2)-C1(2d) 86.8(2)W( 12)-Bi( 1)-CI( 1 b) 99.8(2) W(22)-Bi(2)-C1(2d) 106.3(2)Cl( I )-Bi( 1 )-Cl( 1 b) 1 5 1.9(4) C1(2)-Bi(2)-C1(2d) 141.8(4)Bi( 1)-C1( 1 )-Bi( 1 a) 147.6( 1) Bi(2)-C1(2)-Bi(2c) 136.5( 1)Symmetry operations: a $ - x, -4 + y 7 2 - - 1 -.b 2 - x 9 2 + y 3 2 - -3 -.c 1 - .,- 1 + 1 9 L - -. d 1 - -x, -$ +y, 4 - 2.2 * 2 . 3 2 - 7 2Fig. 4 and one of the dimeric units is shown in Fig. 5. Selectedbond lengths and angles are given in Table 5 and atomicpositional parameters in Table 6. The primary Bi-I bond lengthis 2.949( 1) A whereas the secondary Bi - I interaction is over1 A longer at 4.152(1) A.(ii) EXAFS.-Transmission EXAFS data were collected onsolid samples of complexes 1, 2, [BiClfFe(C0)2(q-C5H5)),1 5,CBi{W(Co)3(77-C,H,))31 6, CBi(Mo(CO),(q1-C,H,)),1 7 andBiCI, 8 and on tetrahydrofuran (thf) solutions of 1,5 and 8 asdescribed in the Experimental section. The results of the EXAFSdata analyses are summarised in Table 7.Typical Fouriertransform (quasi-radial distribution function) and EXAFSfunction plots are shown in Figs. 6-8.For complexes 1 and 5 the principal conclusions to be drawnconcern the intramolecular geometry of the [BiCI{M(CO),(q-C5H5))J units, and the Lewis-acid interactions of the bismuthatom, either with the chlorine of another [BiCl(M(CO),(q-C5H5)l2] moiety or with the oxygen of the solvent. The solid-state structures of 1 and 5 had been known for some time priorto this work 1 * 2 * 6 and that of 2, obtained after the EXAFS workreported in Table 7, is described in the preceding section. Thesolid-state structures of 1 and 5 as determined by EXAFS arefully consistent with the X-ray determined structures.Thus for 1Table 3 Selected bond lengths (A) and angles (") for complex 3Molecule A Molecule BBi( 1)-Mo( I 1) 2.963(1) Bi(2)-Mo(21) 2.987( 1)2.939( I ) Bi(2)-Mo(22) 2.927( 1) Bi( 1)-Mo( 12)Bi( 1 )-Br( 1 ) 2.938(2) Bi(2)-Br(2) 2.773(2)Bi( 1) . Br( 1 b) 3.104(2) Bi(2) - - Br(2d) 3.71 8(2)Mo(1 l)-Bi(l)-Mo(l2) 118.9(1) Mo(21)-Bi(2)-Mo(22) 116.2(1)Mo( ll)-Bi( 1)-Br( 1) 102.3(1) Mo(21)-Bi(2)-Br(2) 107.3( 1)Mo( 12)-Bi( 1)-Br( 1) 91.9( 1) Mo(22)-Bi(2)-Br(2) 96.8( 1)Mo(l1)-Bi(1)-Br(1b) 98.5(1) Mo(21)-Bi(2)-Br(2d) 105.4(1)Mo( 12)-Bi( 1)-Br( 1 b) 99.0( 1) Mo(22)-Bi(2)-Br(2d) 87.7( 1)Br( 1)-Bi( 1)-Br( 1 b) 148.2( 1) Br(2)-Bi(2)-Br(2d) 140.7( I )Bi( 1)-Br( 1)-Bi( la) 142.2( 1) Bi(2)-Br(2)-Bi(2c) 132.6( I )Symmetry operations: a 1 - s, -: + y, - :; b i - s, t + y, 3 - z;c : - .~ , - : + y , : - - ' ; d : - . ~ , : + r . , : + - - .Table 2 Atomic coordinates ( x lo4) for complex 2AtomBi( 1 )W(11)W( 12)CN 1 )C(I11)O ( l l 1 )C( 112)O(112)C(113)O( 113)C( 114)C(115)C( 116)C( 117)C(118)C( 121)O( 121)C( 122)O( 122)C( 123)O( 123)C( 124)C( 125)C( 126)C( 127)C( 128)Y7210(1)7352( 1)5741(1)7050( 5)6666( 15)6280( 15)6559( 16)6083( 13)6917(14)6680( 13)8529( 12)82978227841686035567( 16)5394( 1 1 )6075( 18)6183( 10)4807( 18)4278( 14)5372( 16)50745677634761 58).'1759(1)1744( 1)2301(1)1487(23)1338(21)2967(22)3669( 17)74( 24)2546(23)3219235911541270I295(23)691(19)3972(2 1 )495 1 ( 1 5)2995( 24)3371 (1 8)2686( 2 1 )151968513362573- 740( 5)- 895( 15)Z2680( 1 )4213(1)1759(1)235 l(4)4794( 14)5 166( 14)3846( 13)3685( 13)39 10( 13)3863( 10)41 99( 10)47295258505544002525( 16)2946( 12)2 180( 16)2330( 12)19 14( 18)2032( 16)554( 10)69 3939952714AtomBi(2)W(21)W(22)C U )C(211)O(211)C(212)O(2 12)C(213)O( 2 I 3)C(214)C(215)C(216)C(217)C(218)C(221)O(221)C( 222)O( 222)C(223)O( 223)C( 224)C( 225)C( 226)C( 227)C(228)Y2501(1)1030( 1 )3498( 1 )2054( 5)1 7 16( 14)2 106( 15)1114(16)1096( 14)565( 16)283( 13)790( 12)10715 64109- 302561(2 1)2 1 14( 1 3)3410( 17)3355( 15)3217(25)3 132( 19)4404( 16)40974280470 147781'3253( 1 )2154(1)3128(1)5561(6)872(20)16(17)342 1 (2 1 )4202( 16)1343(23)889(21)1275( 16)24923367269013972214(22)1663( 16)356 l(2 1 )3778( 19)4900( 24)5969( 16)16 13(22)14812567337027803062( 1 )2890( 1 )4502( 1 )2870(5)3275( 14)3509( 10)3649( 15)4037( 1 1 )3583( 1 1 )3957( 1 1 )1783( 1 1)17231888204919844580( 12)4742( 10)5501 ( 1 5)5982( 10)4380( 15)4410(11)4874( 15)414238064330499J.CHEM. soc. DALTON TRANS. 1992 195Table 4 Atomic coordinates ( x lo4) for complex 3AtomBi( I )Mo( 1 I )Mo( 12)Br(1)C(111)O(111)C( 112)O(112)C( 113)O(113)C( 114)C( 115)C( 116)C( 117)C( 118)C(121)O(I21)C( 122)O( 122)C( 123)O( 123)C( 124)C( 125)C( 126)C( 127)C( 128)\-2816(1)2658( 1 )4262( 1)3038( 1 )3123(6)3389(5)3447(6)39 lO(5)3329(6)3714(6)I702(9)1777(7)I583(7)1403( 7)1456(9)5 I86(6)5 720( 5)3907(6)3769( 5)4474(5)4659( 5)4595( 10)3797( 10)3651(7)4333(8)4909(8)1'6639( I )6727( 1)7250( 1)4020( 1 )5110(11)4159(8)7930( I 1)8656(8)6542( 10)6393(9)8 133( 14)7376( 19)61 85( 14)6247( 17)7402( 27)7987( 1 1)8403 (9)8883( 10)9858(7)62 59( 9)7567( 17)6235( 14)5662( 14)6463( 15)5734(9)7459( 17)7273( I )5753( 1 )8210(1)7575( 1)60 14(6)607 1 (5)6136(5)6308(5)5 124( 6)4769(5)5319( 12)4785(7)4937(9)5564(10)5778(9)8065(6)798 l(6)7829(6)7676( 5)743 8 (6)9398(7)9194(8)8968(7)9022(7)9277(7)7009( 5)AtomBi(2)Mo(21)Mo(22)Br(2)C(211)O(211)C(212)O(212)C(213)O(213)C(214)C(215)C(216)C(217)C(218)C(221)O(221)C(222)O(222)C(223)O(223)C(224)C(225)C(226)C(227)C(228)Y25 17( I )1513(1)3018(1)2429(6)2894(4)1762(7)1832(6)1603(6)1674(6)308(8)256(7)594(8)888(8)701(9)3 244( 5)2846(5)4457(6)4729(5)392 t ( 5 )3 953( 6)4203(8)488 l(8)5039(6)4438(7)3979( I )3955(7)I'6724( I )6876( 1)7869( 1)4334( 1)7731(11)828 l(8)51 16(11)407 5( 8)6466( 1 1 )6267( 10)6697( 14)7262( 16)83 14( 15)8474( 19)7460(23)9 15 1( 10)9946(8)8689( 1 1)9 148(9)6598( 1 I )5897( 10)7 570( 14)87W( 13)8632( 13)741 7( 15)6699( 13)1914(1)487( I )2109(1)21 t4(1)402( 5)262(4)588(6)569(5)-465(6)- 1009(5)659( 1 1)158(10)849( 1 1)36(9)1169(8)1722(5)1495(5)1433(6)1050(5)1385(6)968(5)3273(6)3229(6)3044( 7)2966(6)31 16(6)Table 5 Selected bond lengths (A) and angles (") for complex 4Bi-Mo( 1 ) 2.963( 1) Bi-M o( 2) 2.928( 1)Bi-I 2.949( 1) Bi .. . I' 4.152( 1)Mo( 2)-Bi-I 103.2(1) I-Bi-I' 95.2( 1)BI-I-Bi' 84.8( 1)Mo( 1 )-Bi-Mo(2) I t8.2( 1) Mo( 1 )-Bi-I 101.8(1)Symmetry operation for primed atoms: -x, 1 --y, 2 - 2.Fig. 4atoms omitted for clarityA view of the molecularFig. 3 A view of part of the crystal structure of complex 3 showing theintermolecular Bi - - - Br contacts.Each Mo(CO),(C,H,) fragment isrepresented as a circle and three lines to the carbonyl carbons. Thecyclopentadienyl ligands are omitted for claritythe crystallographic Bi-Mo distances range from 2.921( 1) to2.983(1) A (mean 2.951 A) c:f: 2.951(3) A by EXAFS (N.B. thephase shifts for Mo were adjusted to obtain this fit). TheBi - CI distances in the crystal were 2.612(3), 2.746(2), 3.039(3)and 3.596(4) a and those by EXAFS 2.599(8), 2.689(5) and3.41( 1 1 ) A although it was not possible to refine four separateBi C1 separations. Of these distances only the secondEXAFS Bi C1 contact differs significantly from the X-raycystructure of complex 4. Hydrogend" VFig. 5 A view of the dimeric unit in the crystal structure of complex 4values being 0.057 A shorter than the lower crystallographicvalue.This discrepancy arises at least in part because of thesimilarity of these Bi*.-Cl and Bi-Mo distances and theconsequent overlaps in this region of the quasi-radialdistribution function. The possibility of accuracy substantiallybelow precision for such overlapping shells is one that must b196 J. CHEM. SOC. DALTON TRANS. 1992Table 6 Atomic coordinates ( x lo4) for complex 4X417(1)159(1)- 2078( 1)- 1389(8)- 1102(8)- 1 134(8)- 646(8)-271 l(9)- 3087(9)-3103(9)- 3962(8)- 3897(9)- 3 0 3 ( 10)- 25 19(8)2272( 1)1306( 10)876(9)1273(8)789(8)2181(11)2 176( 13)4021(8)4363(9)408 8( 9)3 549( 8)3507(8)Y5353( 1)6983(1)5165(1)6327(7)7022(7)3938(8)3217(6)4955(10)4829( 1 1)4 3 82( 9)4700(9)5763(10)6M7( 8)5218(9)6131(1)81 12(5)5195(8)4636(9)6893(8)7355(9)5 157(9)61 52( 10)6664(8)5987(8)5057(8)7360(7)z85OO( 1)9807( 1)6918(1)6467(7)6 132(8)6898(8)6877(9)5420(8)4556(7)78 1 9( 9)6856(8)686 1 ( 1 0)7796(9)8382(7)7874( 1)7883(9)7 894( 9)6749(7)6094(6)6643( 10)5957( 10)8435( 10)8477(9)9 176(8)91 85( 10)96w8)XM = Mo, X = C11; M = W, X = C12M = Mo,X = Br3;M = Mo,X = I 40 2 4 6r /AFig.6 (a) Observed (-) and calculated (- - ~ -) /?-weighted Bi-L,,,-edge EXAFS spectra for complex 5 as a solid at low temperature.(6) Observed (----) and calculated (- - - -) Fourier transformmagnitudes (quasi-radial distribution function) of (a)M = W6orMo7taken seriously in several of the studies reported here.As aconsequence, some of the distances reported must be viewedwith caution. Nevertheless significant qualitative conclusionsmay safely be drawn as we shall see, even if some quantitativeaspects of these results have to be taken less seriously. TheMo-K-edge data for 1 are in reasonable agreement with boththe Bi-LIII EXAFS and the crystallographic values [Mo-Bi3.139(8) and Mo Mo 5.05(2) A]. The latter dimensionimplies a Mo-Bi-Mo angle of 119(1)" in good agreement withthe crystal structure values [118.3( 1) and 116.4(1)"].On dissolution of complex 1 in thf significant changes occurin the EXAFS spectrum (see Fig. 7), especially in the range k =5-8 A-'.In the model fitting these changes can be seen to beassociated with the contraction of the Bi-CI distance [to2.551(7) A] and the disappearance of the long Bi CI contact,together with the appearance of a Bi-0 contact [2.23(4) A]associated with a shoulder on the low r side of the main peak inthe Fourier transform at cu. 3 8, [see Fig. 7(b)]. While the lengthof the Bi-0 contact should not be taken too seriously the2.933(2), Mo-C(O) 1.992(3), Mo-C(C,H,) 2.367(4), MO 01.01- 0.02 0.6e.E 0.4- 0.20.0Ec L1 0 LI0 1 2 3 4 5 6r / AFig. 7 ( a ) Observed k3-weighted Bi-L,,,-edge EXAFS spectra for com-plex 1 as a solid (-) and as a 0.050 mol dm-3 thf solution (- - - -). (h)Fourier transform magnitudes (quasi-radial distribution function) of (aJ.CHEM. SOC. DALTON TRANS. 1992 197Table 7 EXAFS analyses for [BiC1,{M(CO),(q-C,H5)}3~x] (x = 3; x = 1 or 0, y = 3, M = W or Mo; x = 1, y = 2, M = Fe) complexes"Shell number (n)1 [BiCl{ Mo(CO)~(~-C~H,)),]solid 1.t.solutiond 50 mmol dm-3solution 64 mmol dm-38 BiCI,solid 1.t.solution 300 mmol dm-3Mo-K-edge datakmaxl A-15.917.619.019.813.018.31819.017.016.018.419.018.01 2 3 4 5 6 7Bi-M Bi-CI Bi...CI Bi...Bi Bi.0-C B i . . - OR R' ( N = 2)' ( N = 1) ( N = 1) ( N = 2) ( N = 4 ) ( N = 1)0.10 0.06 2.958(3) 2.688(6) 3.167(8) 3.870(10) 3.397(11) -0.008(3) O.OOS(2) 0.009(2) 0.019(3) 0.043(5)rl:r3 0 . 6 8 ; ~ ~ : ~ ~ 0 . 8 9 , ~ ~ : ~ ~ 0.69, Eo:rl -0.89, E0:r2 -0.83, Eo:r4 -0.56, Eo:r5 -0.71Bi-Cl( N = 0.5) ( N = 0.5)0.12 0.06 2.951(3) 2.599(8) 3.41(11) - 3.36(4) - 2.689( 5)Eo:rl -0.87,a5:r30.79,a5:a3 -0.92,a,:r3 -0.59,a5:r5 -0.55,a,:r7 -0.59,a7:a2 0.800.006( 1) 0.007(2) 0.027(3) 0.023(2) O.OlO(1)0.21 0.13 2.944(5) 2.551(7) - - 2.93(4) 2.23(4)0.016(1) O.Oll(1) 0.047(7) 0.048( 17)Eo:rl -0.91, E0:r2 -0.66, Eo:r6 -0.73, r2:rl 0.52, r6:r1 0.74, u6:r1 0.54, a6:r2 0.510.1 1 0.05 2.689(2) 2.939(4) 3.077(9) 3.985(12) 3.36(10) -0.007(1) 0.004(1) 0.012(2) 0.019(3) O.llO(22)Eo:rl -0.83b1-0( N = 1)0.05 0.03 2.761(2) 2.426(18) - - 3.280(9) 2.373(3) 3.451(5)0.018(2) 0.062(12) 0.027(3) 0.007(1) O.O03( 1)Eo:rl -0.80, a2:r1 0.54, ul:r2 -0.55, Eo:r5 -0.71, u2:r6 -0.61(N=3)0.23 0.19 3.002(3)0.009(3)Eo:rl -0.86Bi-Mo(N = 1 ) (N = 3)0.005(1) 0.008(1) - 1 0.008(2)0.32 0.14 3.008(5) 2.884(9) - - 3.301(11)rl:r5 0.86, rl:r2 0 .5 4 , ~ ~ : ~ ~ 0.78, Eo:r, -0.89, Eo:r5 -0.65, E0:a2 0.58, Eo:a5 -0.62(N = 3)0.24 0.16 - 2.505(4)0.0 1 5(2)Eo: r2 - 0.860.06 0.03 2.489(1)0.008( 1)W-Bi W-C W-C W 9 . - 0 W - - We( N = 1) ( N = 3) ( N = 5 ) ( N = 3) ( N = 2)0.22 0.15 2.923(2) 1.996(4) 2.321(5) 3.1 14(9)0.005(1) 0.007(1) 0.007(1) 0.012(1)0.12 0.08 2.946(4) 1.960(3) 2.330(4) 3.095(5) 4.55(10)O.OO8( 1) 0.005(1) O.O9( 1) 0.008( 1) 0.04(3)Mo-Bi Mo-C Mo-C M o * . - O Mo-..Mo( N = 1) ( N = 3) ( N = 5 ) ( N = 3) ( N = 1)0.15 0.1 1 2.933(2) 1.992(3) 2.367(4) 3.139(8) 5.05(2)O.OO6( 1) O.W( 1) 0.005(2) 0.009(1) 0.01 5(2)0.22 0.12 2.940(3) 1.989(3) 2.347(6) 3.126(9)0.008(1) O.W(1) 0.012(1) 0.016(1198 J.CHEM. SOC. DALTON TRANS. 1992Table 7 continuedShell number (n)CompoundFe-K-edge data1 2 3 4 5 6 7Fe-Bi Fe-C Fe-C Fe...O Fe... Fe kmaxl A-' R R' ( N = 1) ( N = 2) ( N = 5) ( N = 2) ( N = 1)5 CBiCl(Fe(CO),(I1-C,H,)),Isolid 1.t. 17.6 0.32 0.26 2.685(5) 1.750(6) 2.106(6) 2.915(5) 4.318(11)solution 64 mmol dm-3 16.0 0.06 0.05 2.636(5) 1.766(2) 2.098(2) 2.896(4) -O.oOS(2) O.O06( 1) 0.006( 1) O.OlO(3) 0.009(3)0.013(2) O.oOS(1) 0.008(2) O.OlO(1) -"The estimated standard deviation in the least significant digit as calculated by EXCURV 90 model fitting is given in parentheses, here andthroughout this paper. We note that such estimates of precision are likely to be underestimates of accuracy and particularly so in cases of highcorrelation between parameters (see footnote h below).Residual index R was calculated asR = 4 k 3 ( f b s j i - y c a 1 c i ) ) 2 ~ ~ ~ 3 ~ 0 b 5 j ) * ;R was calculated as for R, with final model parameters, but with data Fourier filtered with rmax = ca. 6-7 A to remove noise. For each shell n thedistance ( r , in A) is given above the Debye-Waller factor (a, in A'); correlation coefficients >0.5 between E,, r, and a, are listed below the parametervalues. E, is the refined correction to the threshold energy of the absorption edge. ' 'Co-ordination' numbers, N (i.e. the number of contacts in a givenshell) as assigned (on chemical grounds) are given below the appropriate contact. All solution spectra were measured in thf at ambient temperature(298 K) for the given concentration; low-temperature (1.t.) spectra were measured at liquid-nitrogen temperature (78 K).This shell significant at the95% level only.42Y,- 0- 2- 4hxYCICI-6; I - I I . I I I i3 5 7 9 11 13 15 17k IA-'CI0 1 2 3 4 5r l AFig. 8 ( a ) Observed k3-weighted Bi-L,,,-edge EXAFS spectra forBiCl, 8 as a solid (-) and as a 0.30 mol dm-3 thf solution (- - ~ -).(h) Fourier transform magnitudes (quasi-radial distribution function)of (4cumulative evidence for the dissociation (i.e. disruption of theBi-CI Bi chains) and solvation of the [BiCl{ Mo(CO),(y-C5H5))J monomers is strong (Scheme 1). This behaviour ISvery similar to that noted for [BiCI(Mn(CO)S)2]4 and for 5below. It is particularly noteworthy that while the EXAFS in theregion k = 8-1 1 A-1 is very similar for 1 in solid and solution, itScheme 10is in the low k region, where 0 is athe most dramatic changes are tostrong back-scatterer, thatbe seen.In the medium kregion where the metal (and chlorine) back scattering would beexpected to be dominant there is little change on dissolution,reflecting the maintenance of the Bi-CI and Bi-Mo co-ordination sphere. At high k the higher temperature at whichthe solution spectra were acquired is reflected in the decreasedamplitude of the EXAFS for this sample. In contrast the Mo-K-edge data for 1 are relatively insensitive to these solvationeffects, as might be expected if the Mo-Bi bonds are essentiallyunaffected by dissolution.For complex 5 the Bi-LI,, EXAFS interatomic distances are inreasonable agreement with the crystallographic values [Bi-Fe2.689(2), Bi-CI 2.939(4) and 3.077(9) A,6 c;f: Bi-Fe mean2.687(7), Bi-Cl 2.84(2), 2.98(3) A] although the Bi-CI distancesare ca.0.1 A larger than X-ray values. Also fitted was theBi Bi distance which is strongly indicative of a cyclicoligomeric structure for 5 [Bi - Bi 3.985( 12), c:f: mean 3.97 J. CHEM. SOC. DALTON TRANS. 19922.82.62.4199-t" .--b .b2.4 2.6 2.8 3.0 3.2 3.4 3.6r (Bi.. * .CI)/AFig. 9 The C1- - Bi and Bi-Cl distances (A) for trans-CI - Bi-Clbonds in [BiCl(ML,),] complexes determined by crystallography ( + )and EXAFS (@)by crystallography]. In marked contrast the Bi Bi distancesin linear chain polymers (as in crystalline 1 and 2) are ca.5.5 A.The Fe-K-edge data for 5 are in reasonable agreement with boththe Bi-L,,, EXAFS and the crystallographic values [Fe-Bi2.685(5), Fe-C(0) 1.750(6), Fe-C(C,H,) 2.106(6), Fe 02.91 5(5) and Fe Fe 4.32(1) A]. The latter dimension impliesan Fe-Bi-Fe angle of 107( 1)" in good agreement with the crystalstructure values [ 109.7( 1)-110.0( l)"]. The effects of solvation onthe EXAFS spectra and model fitting for 5 are broadly similar tothose for 1 (and for [BiC1(Mn(C0),},]4). In summary,therefore, the Bi-CI Bi bridges are broken and the CI Bicontact replaced by a Bi-O(thf) contact. In this case theB i - 0 - Bi contacts clearly fitted in solid 5 are absent (andunfittable) in the EXAFS for the thf solution of 5.For BiCI, 8 the effect of dissolution in thf on the EXAFSspectra is rather different from the pattern of behaviourestablished for 1 and 5 (see Fig.8). The EXAFS is substantiallyhigher in amplitude and similar in frequency for the solutionstate as compared with the solid. This may be understood byreference to the solid-state crystal structure' which shows quitevariable Bi-CI distances (2.468-2.518, mean 2.500 A) and arange of five longer Bi CI interactions (3.216-3.450 A). In theabsence of such secondary interactions (as, eg., in solution) onemight imagine that rather shorter and more regular primaryBi-CI bond lengths would result. Such a picture is consistentwith the observed Bi-CI distances and Debye-Waller factors[solid 2.505(4), a = 0.015(2) A2; solution 2.489(1), a =0.008(1) A,].No successful fits of Bi-0 contacts were possiblefor these solution data. This may reflect rather diffuse andirregular bonding of thf to BiCI, in this solution. In this contextwe note the wide range of Bi O(ether) distances observed bycrystallography for a BiCI, complex of 18-crown-6 (1,4,7,10,1 3,-16-hexaoxacyclooctadecane) (Bi 0 2.77-3.16 A).8 Also ofnote in that crystal structure is the presence of a Bi-OH, contact[2.50(3) A] and the average Bi-CI distance [2.503(11) A]. Thelatter is close to our EXAFS-determined Bi-Cl distances forBiCI, in both solid and solution phases. The relative shortnessof the Bi-OH, contact might imply that the short Bi-0distances observed for thf solutions of 1 and 5 above could resultfrom water contamination of these solutions.This is hard to ruleout on the basis of the available data. All that can be said is thatdried and degassed solvent was used, the samples were preparedand sealed in a glove-box and were stable over much longerperiods than the EXAFS experiment (according to IR spectros-copy), there being no indication of the decomposition thatwould be expected if these solution samples did containsignificant amounts of water. When deliberately wet thf (1equivalent of H,O per BiCl,) was used the EXAFS spectraobtained were indistinguishable from those reported for BiCI,in Table 7, and a white precipitate was formed (presumably ofBiOCl).In the cases of complexes 2, 6 and 7 the objective of theEXAFS studies was structure analysis of unknown solid-statestructures, although in the event the crystal structure analysis of2 was subsequently achieved (see above).Two sets of solid-stateBi-L,,, and W-L,,, EXAFS spectra were collected for 2. Thebetter-quality (as judged by reproducibility and signal to noise)data sets were collected for a sample that did not containcrystals of suitable quality for X-ray crystal structure analysis,and it is the analysis of these data that is presented in Table 7.The bonded distances (Bi-W, Bi-CI, W-C, see Table 7) weremuch as to be expected and not dissimilar to the correspondingvalues for the molybdenum analogue, complex 1. However astriking feature of the model fitted to the Bi-L,,, EXAFS data isthe presence of a Bi .. Bi contact ca. 3.87 A. As noted abovethis distance is characteristic of a cyclic trimer structure ratherthan the linear-chain form observed in the crystal structure of 2.In contrast, for the poorer data collected for a crystalline sampleof 2 (from which the crystal used for X-ray structure analysiswas taken), no Bi Bi distance ~ 4 . 5 A could be fitted(although the poor quality reduces the significance of thisobservation). Our tentative conclusion is that there may existtwo solid forms of 2 one of which contains a cyclic oligomer(possibly a trimer) in addition to the form whose crystalstructure is reported in this paper.In the cases of complexes 6 and 7 the Bi-L,,,-edge EXAFSdata are dominated by the Bi-M (M = W or Mo) contributionat ca.3.0 A. The primary objective of the EXAFS study of 6 and7 was the assessment of the co-ordination geometry at Bi(planar or pyramidal) as reflected in the M-Bi-M bond angles.The good agreement between EXAFS results and crystallo-graphy for such bond angles obtained for 1 and 5 indicates thatsuch information is obtainable with care from the M (M = Feor Mo) EXAFS data by triangulation of Bi-M and M Mdistances. The major difficulty is in the reliable identification ofthe M - . * M contact, since such non-bonded distances areparticularly prone to substantial distance variation which mightdrastically reduce their impact on the EXAFS data. In practice,features at distances corresponding to such contacts wereobserved for both 6 [W-L,,, data, W - - - W fitted at 4.55( 10) A]and 7 (Mo-K data, Mo - Mo observed, but nut significantlyfitted, at ca.4.2 A). These distances correspond to M-Bi-Mangles of lOl(3) and 91" (unfitted) for 6 and 7 respectively. Thesevalues seem likely to be underestimates but also seem clearly tosupport a pyramidal geometry at Bi in both 6 and 7. Otherdimensions obtained from the EXAFS analyses (see Table 7) areas would be expected from crystallography.(iii) C1 Bi-CI Contacts.-A graph of mutually transC1 Bi-CI distances, determined from both crystallographicand EXAFS studies of [BiCI(ML,),] complexes, is shown inFig. 9 (N.B. CI-Bi-CI > 140" for all crystallographic data). Anumber of points emerge from this graph.First reasonable (butimperfect!) agreement between the two sources of data is visible.The general curvature of the plot is clear and may be taken toillustrate the effect of primary and secondary interactions onone another. Taking the Burgi-Dunitz' view of such a plot, thedistribution of points maps the S,2 displacement of onechlorine by another in these formally three + one co-ordinatebismuth species. The form of this plot is broadly similar to thoseobtained for other associative nucleophilic substitution modelsstudied in this way.' Thus the sum of Bi C1 distances for thesymmetrical intermediate geometry (where the two Bi-CIdistances are equal) is ui. 5.9 A, cf: ca. 6.2 at the extremes of theplot for a highly asymmetric CI Bi-CI system which modelsthe initial stages of the substitution process.(A standard Bi-C200 J. CHEM. SOC. DALTON TRANS. 1992Table 8 Crystallographic dataCompoundFormulaMCrystal systemSpace groupalAbIAC I API"u/A3ZD,/g ~ m - ~jtlrnm-' F(owCrystal size/mmMaximum indices hklTransmission factorsReflections measuredUnique reflectionsObserved reflectionsWeighting parameters ARintExtinction parameter xRR' = (C wA2/Z w FO2)fGoodness of fitNo. of parametersMean, maximum shift/e.s.d.Maximum, minimum electron densityle A-321820.8Monoclinic18.559(10)1 0.708( 6)19.683(11)104.29(6)3790.583.19021.7832160.10 x 0.27 x 0.2722, 12,230.007-0.0401 1 958673748780.039C16H 1oBiCIO6W2n l l n2.2(4) x l@'0.0780.1011.054340.007,0.0384.5, -2.63C16H loBiBrM0206779.0Monoclinic18.55 l(2)10.950(2)10.866(3)104.29(1)3910.682.64612.2428480.15 x 0.15 x 0.1922, 13, 230.085-O.1409390686047050.033Qln- 18,489, - 967,13,101, - 13266(2) x 1C80.0400.0371.094700.004,0.0201.22, -1.114CI6H loBiIMo,06826.0Monoclinic12.148( 1)13.223(2)14.268(2)114.01( I)2093.642.62011.0014960.15 x 0.23 x 0.3814, 15, 160.096-0.1424514368030030.03933, -54,258,- 72,50,48p2 1 In2.8(4) x lo-'0.0300.0321.122360.001,0.0040.96, -0.79single bond value for this type of molecule is found in[BiCl{ MO(CO)~(CNBU')(~-C,H,)),~ Bi-CI 2.610(2) A2 whichis monomeric with no close Bi C1 intermolecular contacts.)Such behaviour has, in other cases, been interpreted in terms ofconservation of total bond order.' Further discussion of thedetails of this system and related arylbismuth halide systemswill be deferred to a later paper. We note, however, that theintermolecular Bi C1 interactions are an example of thesecondary bonding described by Alcock" and that thecorrelation between the primary and secondary Bi-CI bonddistances is fully consistent with the view that the acceptororbitals on the bismuth centre, which give rise to its Lewisacidity, are Bi-CI o* orbitals., This model also accounts for theapproximately trans disposition of the chlorides with respect tothe bismuth centre although, as we described in ref.3, otherfactors may also influence this angle.Further studies on thestructures of four-co-ordinate [Six 2( M LJ2] complexes,including the molecules described herein, will also be the subjectof a future paper.ExperimentalFor standard general procedures, see ref. 4.Preparations.-Compound 2 was prepared as described inref. 2. Dark red-purple X-ray-quality crystals were obtained bysolvent diffusion of hexane into CH2CI2 solutions of 2 at- 30 "C over a period of days.Compound 3 was prepared as described for l 2 but usingBiBr,. Typical yields of 90% were obtained and dark greenX-ray-quality crystals were grown from thf-hexane mixtures at- 30 "C. The infrared spectrum (thf solution, Nicolet 20 SXBFTIR spectrometer, CO stretching region) showed signals at2009s, 1978m, 1969(sh) and 1909m cm-'.The appearance of thespectrum is similar to that shown for 1 in thf in ref. 2.Compound 4 was isolated from the reaction between [Bi-{MO(CO),(~-C,H,))~] 7 and I, according to the followingprocedure. Samples of red 7 (0.154 g, 0.163 mmol) and purpleiodine (0.041 g, 0.163 mmol) were combined as solids anddissolved in thf (15 cm3). This resulted in a deep green solutionwhich was stirred for 30 min after which time all volatiles wereremoved by vacuum. The crude solid was washed with hexane(5 x 15 cm') to remove [MoI(CO),(q-C,H,)] then redissolvedin fresh thf (10 cm3) and filtered through Celite. The resultingdark green solution was layered with hexane (30 cm3) andsolvent diffusion over a period of days at - 22 "C afforded shinydark green crystals 4 (0.052 g, 39%).A second recrystallisationby the same method produced single crystals of 4 suitable forX-ray diffraction. Infrared: v(C0) (thf) 2009s, 1979m and1916m cm-', similar to 1 (Found: C, 23.5; H, 1.2. Calc. forC16HloBiIMo206: C, 23.3; H, 1.2%). NMR (CD,Cl,); 'H, 65.50; 13C-{'H), 6 94.0.X-Ray Crystallography.-Crystallographic data are sum-marked in Table 8 for compounds 2-4. Crystals were examinedon a Stoe-Siemens diffractometer with graphite-monochrom-ated Mo-Ka radiation (h = 0.710 73 A), at room temperature(295 K). Cell parameters were refined from 20 values of 32reflections in the range 2&25", measured at & o. Intensitieswere measured in a w 0 scan mode with on-line profile fitting.' 'In each case, the maximum 28 was 50" and a complete uniqueset of data was collected (indices f h, + k, +I), together with apartial set of equivalent reflections.Semiempirical absorptioncorrections were applied, and no significant change wasobserved in the intensities of three periodically monitoredstandard reflections.The structures were determined from reflections withF > 4oc(F), where oc was derived from counting statistics only.Compounds 2 and 3 are isostructural with 1;, the knownatomic coordinates of 1 were used for refinement of 3, but thestructure of 2 was actually solved independently from aPatterson synthesis and a different choice of asymmetric unitand origin was made. The heavy atoms of 4 were located bydirect methods, and remaining atoms by difference syntheses.Refinement was by blocked-cascade least-squares methods tominimise CwA2 with A = IF,,] - IFcI.The weighting scheme wasw-' = oC2(F) + 0.007 31F2 for 2 and w-' = 0 2 ( F ) = oc2(F) J. CHEM. SOC. DALTON TRANS. 1992 20 1A , + A,G + A,C2 + A,H + ASH2 + A,GH for 3 and 4,where C = FJF,,,,, and H = sine/sinemax.13 Atomic scatteringfactors were taken from ref. 14. Non-hydrogen atoms wererefined anisotropically; H atoms were constrained on ring-angleexternal bisectors, with C-H 0.96 A, U(H) = 1.2Ue,(C). For 2the C5H, rings were additionally constrained as idealpentagons of side 1.420 A. An isotropic extinction parameter xwas refined, such that F,' = FJ(1 + xFc2/sin20)*. The majorfeatures of residual difference syntheses were close to heavyatoms in each case.EXAFS-All EXAFS data were collected at the DaresburySyncrotron Radiation Source (SRS) on station 7.1 intransmission mode, using samples prepared in a glove-boxunder nitrogen.Solid samples were typically of ca. 1 mmthickness and were diluted in boron nitride in order to achievechanges in log(lo/I) in the range 1-2 at the absorption edge.Solution spectra were measured in cells of thickness ca. 3 mmand summed to provide the data to be analysed. Raw data werecorrected for dark currents and converted to k-space (withEXCALIB 5 ) , and backgrounds subtracted (with EXBACK 15)to yield EXAFS function xobSi(k). These were Fourier filtered toremove features at distances below ca.1.2 A but not to removelong-distance features of the quasi-radial distribution function(i.e. no noise removal was attempted). Model fitting was carriedout with EXCURV 90," using curved-wave theory allowing formultiple scattering to third order for near-linear atomarrangements (M-C-0). Except where noted, only shellssignificant at the 99% level l 6 were included in final models, i.e.shells added to the model caused reduction in the R indices by>6% of their previous value. Details of the final modelsemployed are listed in Table 7, which gives interatomicdistances ( r J , Debye-Waller factors (a,) and the 'co-ordination'numbers (N), i.e. the numbers of atoms in a given shell n. Abinitio phase shifts and back-scattering factors using sphericalwave theory with 25 1 values were used throughout.The phaseshift for chlorine in bismuth data was checked using fits to Bi-L,,,-edge data for the compounds [SiCl{ Mo(CO),(q-C,H ,)} 2 ]1 and BiCI, 8 in the solid state. The calculated molybdenumphases, cp(k), for the Bi-L,II-edge data were modified accordingto the equation cp'(k) = (1.0 + bk)cp(k), where b = -0.049(10),by refinement to obtain Bi-Mo distances in agreement with theX-ray crystal structure of 1. The values used throughout for theproportion of absorption leading to EXAFS ('AFAC' = 0.8)and the magnitude of inelastic effects modelled by an imaginarypotential ('VPI' = -4.0 eV, ca. -6.4 x J), wereconfirmed for Bi-L,,,-edge data by fits to 2 and 6 and for dataat other edges by similar methods. Multiple scattering effectswere allowed for in the cases of W, Mo and Fe data for theCO ligands.AcknowledgementsWe thank the SERC for financial support, the staff of theDaresbury SRS for technical support and BP Research(Sunbury) for CASE Awards (to N. A. C. and G. A. F.).References1 W. Clegg, N. A. Compton, R. J. Errington and N. C. Norman,J. Chem. Soc., Dalton Trans., 1988, 1671.2 W. Clegg, N. A. Compton, R. J. Errington, N. C. Norman, A. J.Tucker and M. J. Winter, J. Chem. Soc., Dalton Trans., 1988,2941.3 W. Clegg, N. A. Compton, R. J. Errington, G. A. Fisher, D. C. R.Hockless, N. C. Norman and A. G. Orpen, Polyhedron, 1991,10,123.4 N. A. Compton, R. J. Errington, G. A. Fisher, N. C. Norman, P. M.Webster, P. S. Jarrett, S. J. Nichols, A. G. Orpen, S. E. Stratford andN. A. L. Williams, J. Chem. Soc., Dalton Trans., 1991,669.5 P. Panster and W. Malisch, J. Organomet. Chem., 1977,134, C32.6 J. M. Wallis, G. Muller and H. Schmidbaur, J. Organomet. Chem.,7 S. C. Nyburg, G. A. Ozin and J. T. Szymanski, Acta Crystallogr.,8 M. G. B. Drew, D. G. Nicholson, I. Sylte and A. Vasudevan, Inorg.9 H. B. Burgi and J. D. Dunitz, Acc. Chem. Res., 1983, 16, 153.1987,325, 159.Sect. B, 197 1,27, 2298.Chim. Acta, 1990,171, 11.10 N. W. Alcock, Ado. Inorg. Chem. Radiochem., 1972, 15, 1 .11 W. Clegg, Acta Crystallogr., Sect. A, 1981,37, 22.12 G. M. Sheldrick, SHELXTL, an integrated system for solving,refining, and displaying crystal structures from diffraction data,University of Gottingen, 1985, revision 5.13 Wang Hong and B. E. Robertson, Structure and Statistics inCrystallography, ed. A. J. C. Wilson, Adenine Press, New York, 1985,p. 125.14 International Tables for X-Ray Crystallography, Kynoch Press,Birmingham, 1974, vol. 4, pp. 99, 149.15 EXCALIB, EXBACK and EXCURV 90, N. Binstead, S. J. Gurmanand J. W. Campbell, SERC Daresbury Laboratory, 1990.16 R. W. Joyner, K. J. Martin and P. Meehan, J. Phys. C, 1987,20,4005.Received 26th June 1991; Paper 1/03216
ISSN:1477-9226
DOI:10.1039/DT9920000193
出版商:RSC
年代:1992
数据来源: RSC