摘要:

J. CHEM. SOC. DALTON TRANS. 1991 3243Synthesis and Crystal Structure of two StereochemicalIsomers of the trans-Dichloro(1.4,8,1 I -Tetraazacyclotetra-decane)chromium(iii) Cation tLuisa M. Flores-Velez,a Javier Sosa-Rivadeneyra,a Martha E. Sosa-Torres,**aMaria J. Rosales-Hoz*,b and R. A. Toscanoha Division de Estudios de Posgrado, Facultad de Quimica, Universidad Nacional Autonoma de Mexico,Ciudad Universitaria, Co yoacan 045 70, Mexico D. F., MexicoUniversitaria, Co yoacan 045 70, Mexico 0 . F., Mexicolnstituto de Quimica, Universidad Nacional Autonoma de Mexico, Circuit0 Exterior, CiudadTwo stereoisomers of the cationic trans- [Cr(cyclam)CI,] + complex (cyclam = 1,4,8,11 -tetraazacyclo-tetradecane) were prepared and isolated as the nitrate and tetrachlorozincate salts and their structuresdetermined by X-ray diffraction studies of the rnonoclinic crystals of the nitrate salt, a = 6.480(2),b = 18.862(12), c = 13.628(6) A, p = 100.28(3)", and tetragonal crystals for the tetrachlorozincate salt,a = 16.377(4), c = 6.821 (2) A.The two complexes show an octahedral geometry about the metal atomswith the RSSR configuration but with differences in the conformations of the six-membered rings.The relationship between molecular shape and chemical re-activity in macrocyclic compounds is a well known feature andseveral studies ' L ~ have been carried out on the kinetics of base-catalysd hydrolysis of cis and trans isomers of [M(cyclam)-Cl,] + (cyclam = 1,4,8,11 -tetraazacyclotetradecane) complexes,to determine the effects of isomerization on the mechanism andvelocity of this reaction. However, the scope for isomerism ismuch larger than that arising from different combinations ofconfigurations of the nitrogen atoms.4In the first reaction of chromium(u1) chloride and the ligandcyclam Ferguson and Tobe readily prepared the derivative cis-[Cr(cyclam)Cl,] + and occasionally found the trans isomer as aside product, which was described as grey-pink.Later Poonand Pun' reported the isomerization of the cis to the transderivative, and described it as red-pink. This same product waslater prepared by Sosa and Tobe.' We observed that when thelast technique was carried out with some changes a greenproduct is obtained.As part of a study on the structure and reactivity of severalpolyamine, cyclic and non-cyclic metal complexes, we nowdescribe the synthesis and structural characterization of thegreen species as well as the structural characterization of thepink product.The two compounds proved to be stereoisomersof the cation [Cr(~yclam)Cl,]~ in the form of their tetra-chlorozincate (green) and nitrate (pink) salts.ExperimentalPreparations.-The ligand 1,4,8,11 -tetraazacyclotetradecanewas prepared as described in the literature.' trans-Dichloro-(1,4,8,1l-tetraazacyclotetradecane)chromium(11I) nitrate, 1was prepared as reported in ref. 1 (Found: C, 32.95; H, 6.70;N, 18.2. Calc. for C,,H,,CI,CrN,O,: C, 31.15; H, 6.25; N,18.20%). Crystals were obtained from an aqueous nitric acidsolution.chrorniurn(111) tetrachlorozincate, 2.The ligand cyclam (0.37 g)was dissolved in dry methanol (75 cm3) and anhydrous CrCl,trans-Dichloro( 1,4,8,11 -tetraa,7ac~clotc~tradecane)-j. Supplenientary dcrta available: see Instructions for Authors, J. Chem.Sot., Dalton Trans., 1991, Issue 1 , pp. xviiikxxii.(0.25 g) was added followed by zinc amalgam (3 g, prepared asfor use in a Clemmensen reduction).8 The mixture was refluxedfor 3 h, during which a pink precipitate was observed while thesolution became violet. When the reaction was over and air wasallowed to enter the flask the precipitate redissolved and thesolution changed to a red-wine colour. The solution was filteredand the filtrate concentrated to 25 cm3. Acetone (25 cm3) wasadded and the final solution was concentrated to half its volume.The brown-purple precipitate formed was recrystallized from 1mol dmP3 HCl as green needles (0.16 g) (Found: C, 28.20; H,N, 13.10%).5.70; N, 13.00.Cak. for C20H48Cl8Cr2N8Zn: c , 28.10; H, 5.65;Crystal and Molecular Structure Determinations.-Thecrystals of both compounds were air stable and were mountedon glass fibres.Crystal data. Compound 1. CIoH,,Cl2CrN,O3, A4 = 385.0,monoclinic, space group P2,/c, a = 6.480(2), b = 18.862(12),c = 13.628(6) A, = 100.28(3)", C; = 1638.97 A (by least-squares refinement from 25 automatically centred reflections inthe range 3 d 28 < 20"), 2 = 4, D, = 1.56 g ~ m - ~ , D, notmeasured, F(000) = 804, Mo-KX radiation, h = 0.710 69 A,~(Mo-Kx) = 10.3 cm-'.Compound 2.C,oH,8C18Cr,N,Zn, M = 845.4, tetragonal,s ace group P4,/n, a = 16.377(4), c = 6.821(2) A, U = 1830(2) l3 (by least-squares refinement from 25 automatically centredreflections in the range 3.5 d 28 < 23.6"), 2 = 2, D, = 1.55 g~ m - ~ , D, not measured, F(OO0) = 876, Mo-KX radiation,h = 0.710 69 A, ~(Mo-Kx) = 18.52 cm-'.Data collection and processing. Both sets of data werecollected on a Nicolet R 3m four-circle diffractometer using a 28scan width 2.0", and a variable scan rate of 4-30' min-' usinggraphite-monochromated Mo-KX radiation. In the case of 1,2911 reflections were measured (3.0 < 28 < 50.0') of which2367 were unique [ I > 30(1)]. In the case of 2, 1906 reflectionswere measured and 1201 unique. After corrections for absorp-tion, 2 showed transmission factors of 0.8641 and 1.1481.9 Noabsorption corrections were made in the case of 1.Structure analyses and refznernent.The structures were solvedby direct methods and Fourier difference syntheses. Blocked-cascade least-squares refinement with all non-hydrogen atomsassigned anisotropic thermal parameters. Hydrogen atom3244 J. CHEM. SOC. DALTON TRANS. 1991Table 1 Atomic coordinates ( x lo4) for compound 1Y47 1 O( 1 )7034( 1 )2383( 1)5234(5)3328(7)2590( 7)2255(4)1831(7)15 12(7)3444( 8)4203(5)6163(7)691 l(7)7 1 80( 5)7862(7)1646(6)75 57( 7)5937(7)121 l(8)574(7)3223(8)Y6227( 1)6591(1)5851(1)7 17 l(2)7607(2)7525(2)676 1 (2)6582(3)5798(3)5334(3)5278(2)4864(2)4938(2)5 707( 2)5 8 60( 3)6655(3)7 121(3)3666(2)3 185(3)4188(2)3595(3)2770( 1)1744( 1)3786( 1)3 5 3 3( 3)3 2 3 O( 4)21 33(4)190 l(2)819(3)640( 3)909(4)1995(3)2279(4)3380(4)3639( 3)4716(3)49 16( 3)4628(3)2064( 3)1453(4)2ow4)271 l(4)Table 2 Atomic coordinates for compound 2Y1 /40.176 79(6)1 I20.550 57(5)0.51 5 8(2)0.449 O(2)0.371 3(2)0.386 4(2)0.31 7 9(2)0.336 l(2)0.402 3(2)0.509( 3)0.389(2)I’1 /40.1 58 94(5)1 /20.420 OO( 5)0.405 4(2)0.346 l(2)0.392 8(2)0.450 6(2)0.508 3(2)0.567 l(2)0.631 O(2)0.422( 2)0.424(2)1 /40.428 3(1)00.258 4( 1)- 0.198 4(4)-0.154 3(5)-0.1 12 8 ( 5 )0.051 O(4)0.085 l(6)0.251 5(6)0.211 7(6)0.150(6)-0.282(6)Table 3 Infrared spectra of the different isomers of the cation[Cr(cyclam)CI,] + with various counter ions (in parentheses)acis (Cl) trnns (Cl) frans (ZnCI,) trans (NO,) trans (CIO,)Deep red Purple Green1460vs 1460vs 1465vs1440w 1450m(d) 1450vw1390vw 1385w(d)1370vw 1345vw 1320m1310m 1335vw 1300m1285m 1320m1300m1425m 1425sPurple Dark pink1465w 1470(br, s)1430vw 143 5mb 138Ovw1335vw 1345vw1320vw 1335vw1300m 1320w130OmEstimated relative intensities: s = strong; m = medium; w = weak;br = broad; and d = doublet.In KBr disks. It is not possible to distinguish any other absorbancepeak in this region, due to the presence of a broad nitrate peak.bonded to nitrogen atoms were located directly in an electron-density map while methylene hydrogen atoms were placed ingeometrically idealized positions.The weighting scheme w =[aZ(Fo) + oF2]-l gave satisfactory agreement analyses. FinalR and R’ values were 0.053 and 0.056 for 1, and 0.03 1 and 0.045for 2. The structures were solved and refined using theSHELXTL set of programs l o on a Nova 4 s computer for 1, andwith the TEXSAN-TEXRAY structure-analysis package l 1 in aVax Station I1 for 2. Complex neutral-atom scattering factorswere employed. l 2 The atomic coordinates for compounds 1 and2 are listed in Tables 1 and 2 respectively.c0 .- c e0 v) 2400 500 600 70031 InmFig. 1tran~-[Cr(cyclam)C1,]~[ZnCI,I (- - -) in the solid stateElectronic spectra of trans-[Cr(cyc1am)C1,]NO3 (-) andAdditional material available from the Cambridge Crystal-lographic Data Centre comprises H-atom coordinates andthermal parameters.Analyses.-Elemental analyses were carried out on a Perkin-Elmer 240B instrument at the Chemistry Faculty (Universidadde MCxico) and at University College London.Infrared spectra of KBr pellets of the complexes, in the rangeof 4000-200 cm-’, were recorded on a Perkin-Elmer 599Bspectrometer, electronic absorption spectra in aqueous solutionon a Schimatzu UV-240 spectrophotometer. The solid-stateelectronic spectra were measured on a Cary 17D spectro-photometer.Results and DiscussionThe two isomeric complexes 1 and 2 can be isolated by changingthe reaction conditions from those used to prepare 1, namelythe solvent, methanol instead of ethanol, and the zinc amalgamwhich this time was used as a solid in direct contact with thereactants in solution, instead of the use of Soxhlet apparatus.Complex 2 is apparently stabilized by the presence of the[ZnC1,I2- anion, when the reaction is carried out in methanol.In order to see whether other large counter ions could stabilize2, the chloride salt was dissolved in methanol with a smallamount of water and a perchlorate salt was added; a pinkprecipitate was obtained.When a hexafluorophosphate salt isadded to the same solution no precipitation is observed. Whentetrabutylammonium or tetraethylammonium tetrafluoro-borate is added a grey-pink precipitate is obtained in eachcase.Both compounds 1 and 2 show in their infrared spectra thecharacteristic pattern for the trans isomer described by Poon,’at 800-1000 cm-’, although there are slight differences around1300-1400 cm-’ (see Table 3).There have been other examples of a similar behaviourreported by Gibson and McKenzie l 4 in cis-dichlorobis( 1,10-phenanthroline)chromium(IIr) compounds.For instance, cis-[Cr(phen),Cl,]CI~xH,O (x = 2 4 ) has been obtained asdifferent polymorphs. Their colours in sunlight range from red-brown to various shades of green, but all have a reddish colourin tungsten light and all give the same species in solution. Theauthors proposed a cis configuration for all the complexes.The electronic spectra of compounds 1 and 2 in the solid state(Fig. 1) have maxima at h = 550 and 570 nm respectivelyJ.CHEM. SOC. DALTON TRANS. 1991 3245( b )Fig. 2trcms-[Cr(cyclam)CI2] [ZnCl,] (6)Molecular structures of ~rans-[Cr(cyclarn)Cl,]NO~ (a) andHowever, in aqueous solution the green species convertsinstantaneously into the pink complex, showing almost twicethe absorbance value. In order to determine whether thesecompounds were truly isomeric, X-ray crystal structuredeterminations of both complexes were undertaken.The molecular structures of both [Cr(cyclam)C1,] -+ cationsare illustrated in Fig. 2 along with the numbering schemeadopted. Associated bond lengths and angles are given inTables 4 and 5. In both cases the structures consist of trans-[Cr(cyclam)CI,] + cations linked via hydrogen bonds withthe corresponding anions which in turn interact with othermolecules of the cations.This can be observed in the packingdiagrams, Fig. 3. The macrocyclic ligands adopt, both in 1 and2, a planar configuration with the four nitrogen atoms co-ordinated to the metal atom. Two chloride anions in the axialpositions complete the overall octahedral geometry about themetal atoms.In both complexes 1 and 2 the angles about the octahedronare within 5" of the regular angle of 90"; N-Cr-N which arepart of five-membered rings form angles smaller than 90°,while in six-membered rings the N-Cr-N angles are larger than90". This behaviour had been previously observed in trans-[Ru(cyclam)CI,] +.'The Cr-CI bond lengths are very similar in 1 and 2 and alsopractically equal to the corresponding value of cis-[Cr(cyclam)-CI,] + .I 6 However, the Cr-N distances are significantly longerin both derivatives of cis-[Cr(cyclam)C1,] + than in the transcornplexe~.~~ Significant differences in Cr-N bond lengthsTable 4 Bond lengths (A) and angles (") for compound 1Cl( l)-Cr-Cl(2)Cl( 2)-Cr-N(4)C1( l)-Cr-N(8)N( 1 )-Cr-N(8)C1( 1)-Cr-N(l1)N( 1 )-Cr-N( 1 1)N@)-Cr-N( 11)Cr-N( 1 )-C( 14)N( l)-C(2)-C(3)Cr-N(4)-C( 3)C(3)-N(4kC(5)C(5)-C(6)-C(7)Cr-N(8)-C( 7)C(7)-N(8)-C(9)C1(2)-Cr-N( 1 )C(9)-C( 10)-N( 11)N( 1 1)-C( 12)-C( 13)N( 1 )-C( 14)-C( 13)O( 1)-N-O(3)Cr-N( 1 1 )-C( 12)2.334( 1)2.060( 3)2.073(3)1.480(5)1.494(6)1.490( 5 )1.51 8(7)1.483(6)1.495(6)1.530(7)1.229(6)I .232(6)179.4( 1)91.6( 1)88.6( 1)9 0 3 1)1 7 9 3 1)88.1 (1)94.6( 1)85.3( 1)116.5(3)108.9(4)106.4(2)1 15.2(3)1 16.3(4)116.3(3)114.5(4)109.3(4)1 16.9(3)11 1.3(4)1 12.8(4)117.8(5)C1( 1)-Cr-N( 1)Cl( l)-Cr-N(4)N( 1)-Cr-N(4)C1(2)-Cr-N( 8)N(4)-Cr-N( 8)C1(2)-Cr-N( 1 1)N(4)-Cr-N( 11)Cr-N( 1)-C(2)C(2)-N(l)-C( 14)C(W33)-N(4)Cr-N(4)-C(5)N(4)-C(5)-C(6)C(6t-C(7)-N(8)Cr-N( 8)-C(9)N(8kC(9)-C( 10)Cr-N( 1 1)-C( 10)C( 10)-N( 1 1 )-C( 12)C( 12)-C( 13)-C( 14)O( 1)-N-0(2)0(2tN-0(3)2.333( 1)2.067( 3)2.062( 3)1.483(5)1.483( 5 )1.505(8)1.478( 6)1.499(7)1.472( 5 )1.520( 7)1.208(6)89.0( 1)91.5(1)84.8( 1)8 8 4 1)95.3( 1)9 1 4 1)179.2( 1)106.6( 2)114.0(4)108.8(3)116.3(3)1 12.3(4)1 13.3(4)105.8(2)108.7(4)106.2(2)114.7(4)116.6(4)123.4(4)1 18.7(5)Table 5 Bond lengths (A) and angles (") for compound 2C1( 1)-Zn-Cl( 1)N (4)-C r-N (4A)N(4)-Cr-N( 1A)N(4)-Cr-C1(2A)N( 1 )-Cr-C1(2A)C(7)-N( 1 kC(2)C(2)-N( 1 )-CrN(4)-C(3)-C(2)C(5)-N(4)-CrN(4kC(5kC(6)N(1 )-C(7)-C(6)115.1 l(5)180(3)94.0( 1)9 1.56(8)8 8.34( 9)114.7(3)105.2( 2)108.8(3)1 17.4(2)1 1 1.9( 3)112.3(3)C1( 1 )-Zn-CI( 1 A)N(4)-Cr-N( 1)N(4)-Cr-CI( 2)N( l)-Cr-C1(2)C1(2)-Cr-C1(2A)C(7)-N( 1 )-CrN( 1 )-C(2)-C(3)C(5)-N(4)-C(3)C(5)-C(6)-C(7)C( 3)-N(4)-Cr2.3472(9)2.074(3)1.494( 5 )1.486(4)1.5 18( 5)106.73(2)86.0( 1)88.44(8)9 1.66(9)180 (4)117.2(2)109.0(3)113.4(3)105.9(2)116.1(3)were observed between the chloride and perchlorate salts of cis-[Cr(cyclam)CI,] + and were explained in terms of the hydrogen-bond system present in the first complex.Complexes 1 and 2, asmentioned above, also show hydrogen bonds between amineprotons and oxygen or chlorine atoms in the correspondingcounter ions: H(l) O(1) 2.43, H(8) O(2) 2.616 andH(4) C1( 1) 2.57 A. Therefore this does not seem to be thedetermining factor that causes the differences between the twocomplexes.Another, very likely reason is the greater distortion of themacrocycle in the cis isomer which then produces longer Cr-Ndistances. To our knowledge, Ru"' is the only other metal ionfor which both cis l 7 and trans ' cyclam derivatives have beenstructurally characterized and it can be seen than the Ru-Ndistances are longer in the cis than in the trans isomer.The ring conformation in molecules is described by th3246 J .CHEM. SOC. DALTON TRANS. 1991Table 6 Selected torsion angles (") for [Cr(cyclam)C1,]N03N( l)-Cr-N(4)-C(3)Cr-N( 1)-C(2)-C(3)N(4)-Cr-N(8)-C(7)N( 8)-Cr-N(4)-C(5)N( 1 )-C(2)-C( 3)-N(4)N( 4)-C( 5)-C( 6)-C( 7)C( 3)-N(4)-C( 5)-C( 6)C(7)-N(S)-C(9)-C( 10)Cr-N(8)-C(9)-C( 10)N( 1 I)-Cr-N(8)-C(9)C(9)-C( 10)-N( 11)-CrN(l l)-Cr-N(l)-C(l4)Cr-N( 1 1 )-C( 12)-C( 13)C( 10)-N( 1 1 )-C( 12)-C( I 3)C( 2)-N( 1 )-C( 14)-C( 13)14.8(3)55.9(5)34.7(3)- 35.6(3)- 4 1.2(4)70.7(5)179.9(4)172.0(4)42.6(4)3 9.2( 4)- 16.5(3)- 37.1(3)- 55.9(4)178.8( 3)178.5(4)N(4)-Cr-N( 1)-C(2) 14.7(3)C(2)-C(3)-N(4)-Cr - 4034)C(2)-C(3)-N(4)-C(5) - 171.1(4)Cr-N(4)-C( 5)-C(6) 54.3( 4)C( 5)-C(6)-C(7)-N(8) - 70.1(5)C(6)-C(7)-N(S)-Cr - 52.5(5)C( 6)-C( 7)-N( 8)-C( 9) - 176.5(4)N(8)-Cr-N( 1 1)-C( 10) - 12.2( 3)N(8)-C(9)-C( 10)-N( 1 1) - 56.2(3)Cr-N( 1 )-C( 14)-C( 1 3) 5 3.7(4)N(1 l)-C(12)-C(13)-C(14) 69.7(5)C(9)-C( 10)-N( 1 1)-C( 12) 170.0(4)C(12)-C(l3)-C(14)-N(l) -68.9(5)C( 14)-N( 1)-C(2)-C(3) - 17 1.2(3)Table 7 Selected torsion angles (") for [Cr(cyclam)C1,],[ZnC14]C(2)-N( 1 )-Cr-N( 4) 165.8(2)N(4)-C( 5)-C(6)-C(7) 69.5(4)Cr-N( 1 )-C(2)-C( 3) 40.8(3)N ( 1 )-Cr-N( 4)-C( 3) - 14.9(2)C( 3)-N( 4)-C( 5)-C( 6) - 179.2(3)N(4)-Cr-N( 1 A)-C( 7) - 142.9(3)N( lA)-C(7)-C(6)-C(5) - 69.5(4)C(2)-N( l)-C(7A)-C(6A) - 178.4(2)C( 2)-C( 3)-N(4)-C(5)Cr-N(4)-C( 3)-C(2)C(2)-N( 1 )-Cr-N(4)Cr-N(4)-C(5)-C(6)Cr-N( 1A)-C(7)-C(6)N( lA)-Cr-N(4)-C(S)N( l)-C(2)-C(3)-N(4)C(3)-C(2)-N( 1)-C(7A)17 1.6(3)41 3 3 )- 56.8(4)- I4.2(2)17 1.0(3)-55.1(4)54.3(3)37.4(3)t b n1Fig.3[Cr(cyclam)CI,] ,[ZnCI,] 2Packing diagrams of ~run~s-[Cr(cyclam)C1,]N03 1 and truns-endocyclic torsion angles (signs in accord with the definition ofKlyne and Prelog"), and some simple rules have beenproposed in order to determine conformational types. Theserules have been extended by Boeyens and Dobson 2o and can beapplied to define the corners of macrocycles. The torsion anglesfor complexes 1 and 2 are given in Table 6 and 7 respectively.According to these rules, for planar arrangements of cyclamthe conformations 133133 or 3434 are the most frequentlyf o ~ n d . ' ~ * ~ ' Both 1 and 2 show the 133133 arrangement.Thisconformation is compatible with the molecular symmetryshown by the torsion angles: a mirror plane in 1 and an inversioncentre in 2. It must be mentioned that the metal atom incomplex 2 sits on a crystallographically imposed centre ofsymmetry.An analysis of the chelate rings shows that the five-memberedrings in both 1 and 2 have half-chair conformations. Both six-membered rings in 1 have sofa conformations, but 2 shows adistorted conformation that does not fit with any of the exactsymmetry arrangements. Structural differences between 1 and 2are observed in the conformations of the rings.The enantiomeric forms in the unit cell of complexes 1 and 2have RSSR (and SRRS) configuration.We have thereforecharacterized two different conformations in the trans con-figuration for the octahedral complexes.The nitrate and tetrachlorozincate anions in 1 and 2respectively show the expected triangular and tetrahedralstructures. The Zn atom in 2 is placed in a crystallographicallyimposed four-rotofold axis.AcknowledgementsWe thank Mr. Abelardo Cuellar and Mr. Ricardo Acosta fortechnical assistance. M. E. S.-T. would like to express hergratitude to Professor M. L. Tobe for his encouragement andsupport.References1 M. E. Sosa and M. L. Tobe, J. Chem. Soc., Dalton Trans., 1986,427.2 J. Lichtig, M. E. Sosa and M. L. Tobe, J. Chem. Snc., Dalton Trans.,3 J. Lichtigand M. L.Tobe, innrg. Chem., 1978, 17,2442.4 D. A. House and V. McKee, Inorg. Chem., 1984,23,4237.1984,581J. CHEM. SOC. DALTON TRANS. 1991 32475 J. Ferguson and M. L. Tobe, Inorg. Cliini. Actu, 1970,4, 109.6 C. K. Poon and K. C. Pun, Inorg. Chem., 1980, 19, 568.7 E. K. Barefield, F. Wagner, A. W. Herlinger and A. R. Dahl, Inorg.8 A. I. Vogel, Tc\-thook of Pructicul Orgunrc Chemi.stry, 4th edn.,9 N. Walker and D. Stuart, Actu Crystullogr., Secr. A, 1983,39, 158.10 G. M. Sheldrick, SHELXTL, Version 3, An Integrated System forSolving, Refining and Displaying Crystal Structures from Diffrac-tion Data, University of Gottingen, 1981.1 1 TEXSAN-TEXRAY, Structure Analysis Package, Molecular Struc-ture Corporation, 3200A. Research Forest Drive, The Woodlands,TX, 1985.12 htornutionul Tuhlm for X- Ruj, CrJ~stullography, Kynoch Press,Birmingham, 1974, vol. 4.13 C. K. Poon, Inorg. Chirn. Acta, 197 1, 5, 322.SJw/h.. 1976, 16, 223.Longman, London, 1978, p. 318.14 E. G. Gibson and E. D. McKenzie, J. Cliem. Soc. A, 1969,2637.15 D. D. Walker and H. Taube, Znorg. Chem., 1981,20,2828.16 E. Forsellini, T. Parassasi, G. Bombieri, M. L. Tobe and M. E. Sosa,17 M. Che, S. Kwong, C. K. Poon, T. F. Lai and T. C. W. Mak, Inorg.18 W. Klyne and V. Prelog, E.qwrientia, 1960, 16, 521.19 W. L. Duax, C. M. Weeks and D. C. Rohrer, Top. Stereochem., 1988,9, 271.20 J. C. A. Boeyens and S. M. Dobson, Stereochemistry of Organo-mc~tcillic und Inorganic Compounds, vol. 2, ed. I. Bernal, Elsevier,Amsterdam, 1987, p. 2.21 B. Bosnich, R. Mason, P. J. Pauling, G. B. Robertson and M . L.Tobe, Chem. Cornmun., 1965,97.Actu Cry.ytullogr., Sect. C, 1986, 42, 563.Clicwr., 1985, 24, 1359.Received 2nd April 1991; Puper 1101539

ISSN:1477-9226    

DOI:10.1039/DT9910003243

出版商:RSC    

年代:1991

数据来源: RSC