摘要:

J. CHEM. SOC. DALTON TRANS. 1991 163X-Ray and Potentiometric Studies on a PentanuclearCopper( 11) Complex with p-Alaninehydroxamic Acid tBarbara Kurzak,**e Etelka Farkas,b Tadeusz GlowiakC and Henryk Kozlowski * Xa Institute of Chemistry, Pedagogical University, Siedlce, PolandDepartment of Inorganic and Analytical Chemistry, University of Debrecen, H-40 I0 Debrecen, HungaryInstitute of Chemistry, University of Wroclaw, 50-383 Wroclaw, PolandPotentiometric and X-ray studies on the system copper(i1)-L-P-alaninehydroxamic acid have shownthe formation of a very stable pentanuclear complex [CU,A,H_,]~+ at pH around 4. In this species alldonor atoms of the aminohydroxamic acid are involved in the metal ion co-ordination. Four peripheralmetal ions form an almost planar structure and the central metal ion is 0.4 A above this plane.Thereare twelve five- and six-membered chelate rings with different conformations. The X-ray structureresults support earlier suggestions based on potentiometric and spectroscopic data for the formationof oligomeric structures a t relatively low pH.Recent spectroscopic and potentiometric studies have shownthat copper(r1) ions may form a variety of complex species withaminohydroxamic acids. 1-4 At relatively low pH (4-6) adinuclear complex is formed with involvement of mixed donorsets as shown in Scheme 1. The co-ordination mode in thismolecule was proposed on the basis of spectroscopic data.4 Itsstability is relatively high though the monomeric MA2 andMAH-, complexes are the major species at pH >6.The highstability of these monomeric complexes results from veryeffective chelation by the two nitrogen donors of the amino andhydroxamic groups, which in a-amino acid derivatives form five-membered rings. The X-ray crystal structures of planarbis(glycinehydroxamato)nickel(n) complexes 5 * 6 and two trans-bis(glycinehydroxamato)copper(r~) complexes 7 , 8 provide clearevidence for such co-ordination. In the present work we havestudied the complex formation in the copper(I1)-L-P-alanine-hydroxamic acid (3-amino-N-hydroxypropanamide) system inwhich the amino and hydroxamic nitrogens are one morecarbon apart from each other than in the tl derivatives andpotentially they may form six-membered chelate rings.ExperimentalL-P-Alaninehydroxamic acid was prepared via the methyl esterof L-P-alanine as described in ref.9. Its purity and the exactconcentrations of the ligand stock solutions were determined byGran's method."Potentiometric Studies.-The concentration of the ligand inthe samples was varied in the range 1 x - 4 x lop3 moldm-3. The metal-to-ligand molar ratios were adjusted in therange 1 : 1 to 1 : 5 and measurements were performed s t sixdifferent ratios. Titrations were carried out with carbonate-freeKOH solutions of known concentration (ca. 0.2 mol dmP3). Theionic strength was adjusted to 0.2 mol dmP3 with KCI and thetemperature was 25 a 0.1 "C. Measurements were carried outon a Radiometer pH-M64 instrument with 62040B glass andK4040 calomel electrodes, using a TTA 80 titration unit.Theelectrode system was calibrated by the method of Irving et al.,' 'so that the pH-meter readings could be converted intohydrogen-ion concentrations. The calculations of the pH-metric?- Supplementary duta available: see Instructions for Authors, J. G e m .Soc., Dalton Trans., 1991, Issue 1, pp. xviii-xxii.. .*,Cy,* '.H 2 d 'OH2[CU2A2H-11+Scheme 1data were performed with the aid of the PSEQUAD computerprogram.'Crystallographic Measurements.-The approximate unit-celldimensions were determined from rotation and Weissenbergphotographs. A specimen of 0.38 x 0.40 x 0.47 mm wasselected for diffraction studies. More accurate unit-celldimensions and the orientation matrix used for data collectionwere obtained from a least-squares fit of the observed settingangles for 15 high-order Mo-Ksr reflections measured with aSyntex P21 computer-controlled four-circle diffractometer,equipped with a scintillation counter and graphite mono-chromator.The intensities of 4368 independent reflections were measuredat room temperature by the 8-28 scan technique up to 28,,, 50".Two standards were monitored after every 50 reflections.Themaximum variation of an intensity value was 6%. The intensitieswere corrected for Lorentz and polarization effects but not forabsorption; 3784 such data for which I > 3.50(I) were used inthe analysis.The structure was solved by direct methods using theSHELXS program,' and refined by full-matrix least squares.The positions of all hydrogen atoms were determined fromsuccessive Fourier difference maps.Several cycles of refinementof coordinates and anisotropic thermal parameters for non-Hatoms, fixed with coordinates and isotropic thermal parametersfor H atoms, reduced R to 0.038 and R' to 0.049. Neutral atomicscattering factors for all atoms were taken from ref. 14 and allcalculations were performed with a Syntex XTLjXTLEstructure determination system.' A summary of the datacollection and processing parameters is given in Table 1.Additional material available from the Cambridge Crystal-lographic Data Centre comprises H-atom coordinates, thermalparameters and remaining bond lengths and angles164 J. CHEM. SOC. DALTON TRANS. 1991Table 1 Summary of data collection and processing parametersFormulaMSpace group4h / ACIA4"PI"Yi"u l ~ 3zD, (flotation, CC1,-CHBr,)/g cm-,D,/g cm-,F(oO0)Ic( MO-K+~p(Mo-Ka)/cm-'Unique data collectedData with I > 3.50(I)Total variablesR = W F O I - l ~ c l ~ / ~ l f .o lR' = [Cw(lF0I - ( F c ( 2 / C ~ ( F , ) 2 ] ~Function minimized (w = 1/02)Final ApIe A-3Final (A/O),,,~~s = Cw<IFoI l y 2 / ( n - P>l+*C3,H24C14C~5N80.5H20101 5.5210.568(2)11.800(2)13.742(3)94.49(3)110.58(3)99.81(3)1563.0(7)22.15(2)2.1610180.710 6937.54368378443 30.0380.0494.56k0.35 At0.01PiCw(F0 - Fc)2* n = No. of observations, p = no. of parametersI 1 I .l I .L I0.2 0.4 0.6 0.8 1 .oVolume of KOH/cm3Fig.1 Titration curves for P-alaninehydroxamic acid and copper(I1)-P-alaninehydroxamic acid systems ( x on the horizontal axis denotes theconsumption of 2.40 equivalents of base per metal for the particularsample): cA = 4 x lo-, rnol dm-3 for all samples; cM = 0 (l), 1.9 x(2), 2.9 x lo-, (3) and 3.9 x lo-, rnol dm-3 (4)15 13 11 9 7 5PAFig. 2 Formation curves for the copper(i1)-P-alaninehydroxamic acidsystem: cA = 3.75 x lo-, mol dm-3 for all samples; cM = 3.0 x l 0 - j (a),2.0 x lo-, (h) and 1 x mol dm-3 (c)0.6 1.2%IcA1.8Fig. 3on metal-to-ligand molar ratio; cA = 5 xDependence of the absorbance of the d-d transition at 616 nmmol dm-3I .N(32)(733)Fig. 4 Perspective view, atom numbering and assignment of thechelate-ring conformations for the complex [Cu,A,H-,][C10,],~5H20.Thermal ellipsoids scaled to 50% probability.The letters indicate theapproximate conformations of the rings: E = envelope, T = twist, C =chair and HB = half-boat; P = planarResults and DiscussionPotentiometric Study in Aqueous Solutions.-The fully proton-ated form of the ligand (H3N+CH2CH2CONHOH) can releasetwo protons in the range 7.5-10.5, one from the amino groupand one from the hydroxamic acid group. These two dissoci-ation processes may overlap with each other. This means thatthe dissociation constants calculated from the pH-metric dataare macroconstants and they are equal to 8.45 ( p K , ) and 9.74Some of the titration curves registered for P-alaninehydrox-amic acid and for the copper(I1)-P-alaninehydroxamic acidsystem are shown in Fig.1. As can be seen each sample can betitrated without precipitation up to pH 11 even at 1 : 1 metal-to-ligand molar ratio. The colour of the solution becomes greenishabove pH 4.5. This finding, taking into account our previousresults obtained for copper(1r)-a-alaninehydroxamic acid andcopper(rr)-aspartic acid-P-hydroxamic acid,' suggests that inaddition to the nitrogens the oxygens of the hydroxamatemoiety take part in the co-ordination in the copper(Ir)-a-alaninehydroxamic acid system.In order to obtain more specific information about thestoichiometry of the species formed in the copper(II)-P-alaninehydroxamic acid solutions, formation curves have beencalculated. Some of them are depicted in Fig.2. A wide plateauis attained at n [= (c, - [A])/cM] ca. 1.20. This parameter(PKJ. CHEM. SOC. DALTON TRANS. 1991 165Table 2paren thesesFinal atomic coordinates for non-hydrogen atoms ( x lo4) of [CU,A,H~~][C~O~],~~H,O with estimated standard deviations (e.s.d.s) inX Z Y Atom I' Atom L' 71 074(1)1 239(1)2 025( 1)2 282( 1)1261(1)7 41 l(2)4 610(2)1 843(5)1012(4)893(4)705(4)2 237(4)1618(4)2 921(5)1411(4)315(5)4 374(6)4 206( 1 1)4 284(7)7 040(6)8 681(6)7 562(7)6 339(6)-1 263(5)4 805( I)2 987( 1)6 523( 1)8 355(1)5 688( 1)9 109(2)2 779(2)6 152(4)6 028(3)1 940(3)4 038(3)5 205(3)5 377(3)9 340(3)7 304(3)4 753(4)9 518(4)6 639(5)4 955(6)4 799(6)8 461(6)8 877(6)10 331(5)8 766(5)1 850(1)4 729( 1)6 754(1)4 003( 1)4 221(1)469(2)4 682(2)1331(3)2 847(3)3 449(3)3 71 l(3)7 516(3)5 602( 3)5 360(3)4 709(3)819(3)3 352(4)- 131(4)2 975(5)1013(5)1171(4)402(6)876(4)-521(3)5 972(6)3 731(5)4 233(7)4 436(9)3 383(5)1 140(6)1658(5)1 662(5)1941(5)2 773(6)2 106(6)2 958(6)2 871(7)837(6)910(7)311(7)2 006(6)2 093(7)2 634(7)2 679(6)3 239(7)3 847(7)1733(5)757(5)3 282(6)3 543(4)1735(5)2 482(6)7 156(4)9 466(4)3 620(4)3 622(4)4 242(3)1811(4)7 691(4)7 659(4)7 091(5)8 176(5)9 331(5)2 534(5)1933(5)2 446(5)4 263(5)3 148(5)2 292(5)8 753(4)9 331(5)8 620(5)5 298(6)4 764(4)5 075(5)3 620(4)2 784(3)2 742(4)767(4)5 869(3)5 687(3)5 809(4)8 049(4)1 800(5)2 288(5)2 684(4)1712(5)708( 5)6 876(4)7 320(5)6 758(5)6 042(4)7 169(5)8 OOO(5)3 445(4)1975(4)increases only at high ligand concentration (high pH) wherehydrolytic processes can take place.Thus bis(1igand) complexesare not formed in this system.Absorption spectra in the d-d region at pH < 3 exhibit atransition around 820 nm characteristic for the copper(r1) aquaion. An increase in pH above 3 leads to the appearance of a newd-d band at 616 nm which increases in intensity up to pH 9without any changes in energy (E = 55 at pH 4.2 and 67 dm3mol-' cm-' at pH 9). This indicates that the major species at pH4-9 is the same although its amount can vary slightly. Thecharge-transfer (c.t.) band centred at 325 nm is broad and mostlikely contains at least two transitions as was the case for thedimeric species reported earlier., In the latter case the circulardichroism spectra were resolved enough to show that the c.t.band observed in the absorption spectra around 330 nmconsists in fact of three transitions at 430,355 and 315 nm.Thefirst of these can be assigned as the hydroxamic oxygen to metalc.t. transition. The other two correspond to the hydroxamicnitrogen to Cu" c.t. transitions., Since the ligand is not opticallyactive the c.t. band at 325 nm remains, unfortunately,unresolved. The major complex formed at pH 4-9 does notshow any EPR spectrum at liquid-nitrogen temperature orabove.According to the experimental results outlined above, theformation of a polynuclear species at pH > 4 is stronglysuggested.It is obvious from the potentiometric results thatonly one complex species exists at measurable concentration inthe range pH 4.5-9 (see Figs. 1 and 2). At the same time, from thespectroscopic data (Fig. 3 ) a plot of absorption coefficient us.cM/cA indicates a metal-to-ligand ratio of 1:0.8 in this species.The contradiction between the pH-metric (6 = 1.2) andspectroscopic results (1igand:metal = 0.8: 1) can be resolved ifwe consider the jumping on the titration curves at 2.4equivalents of base consumption per Cu" ion. This suggests theoccurrence of 'extra' deprotonation of the hydroxamate groupby the copper(1r) ion already in acidic solution with theformation of the AH-, form of the ligands.,>l6 Polynuclearspecies have been found in which all of the three donor atoms ofthe hydroxamate group are co-ordinated.2"Consequently, the most likely explanation of our pH-metricresults is that the P-alaninehydroxamic acid in its polynuclearcopper(I1) complex may release three protons.Taking this intoaccount, a 1 :0.8 copper(I1) to AH-, ratio arises also from thepH-metric results. The simplest possible formula correspondingto this ratio is [CU,(AH_,),]~+ [A = NH,(CH,),CONHO-1.From the considerations presented above it is possible thatthe major species in solution at pH 4.5-9 is a pentanuclearspecies [Cu5A,H-J2+. The pH-metric data for this pH range(about 100experimental points) could be evaluated satisfactorilyby assuming this complex with a stability constant log P =46.66(7).The formation of other complexes has to be presumedbelow pH 4.5. A fairly good fit was found assuming the speciesCuA with log P = 12.85(3).X-Ray Studies.-From titrated solutions (pH around 9) leftto stand for some hours single crystals were obtained ofsufficient quality for the diffraction study. The X-ray structure(Fig. 4) confirms the formation of a pentanuclear species. All thedonor groups of four ligand molecules are involved in the metalion co-ordination. The nitrogen atoms chelate one copper ionwhile the oxygen donors are bound to another metal ion. Thisco-ordination leads to formation of the tetrameric unitCu,A,H-, having at its centre the fifth metal ion bound to fouroxygens of the hydroxamic groups.The latter oxygen donorsbridge the central metal ion and the four peripheral metal ions.The central metal ion fits very well into the space between thefour oxygens, being almost in their plane. The unusual structureconsists of 12 chelate rings. The NH,,N- co-ordination leads tothe formation of four six-membered rings which have distortedhalf-boat conformations (Fig. 4). The C0,O - donors form fourfive-membered chelate rings of which only that with Cu(3) isplanar while the others have envelope-like conformations. Theinclusion of copper ion at the central position of the pentamerleads to the formation of four further five-membered rings. Mostof these rings are twisted as indicated in Fig. 4.The crystallographic parameters are collected in Tables 1 4 .Besides the basic planar co-ordination (four donors) each metalion interacts with a fifth donor in apical position.All areoxygens of water, perchlorate ion, or vicinal aminohydroxamicacid ligand (Table 3) at distances between 2.363(5) and 2.675(5)A. In addition to the bonds in the ligand plane, Cu(5) shows along interaction with 0(51'), 2.787(7) A, and the latter alsointeracts, 2.884(7) A, with the adjacent Cu(4). Atom 0 ( 5 " ) ,located on the opposite side with respect to W(2) (W = wate166 J. CHEM. SOC. DALTON TRANS. 1991Table 3 Bond distances (A) and angles (") for [CU,A,H-~][C~O,],*~H,O *Copper environmentCU( 1)-O( 1 1) 1.960(4) Cu(2)-0(21) 1.95 l(4) Cu(3)-N(41) 1.959(5) Cu(4)-N(ll) 1.952(5)CU( 1)-O( 12) 1.936(4) Cu(2)-0(22) 1.942(4) Cu(3)-N(42) 1.966(5) Cu(4)-N( 12) 1.982(6)Cu(l)-N(21) 1.993(4) Cu(2)-N(3 1) 1.941(5) C~(3)-0(22') 2.675(5) Cu(4)-W(2) 2.6 19(5)CU( 1)-W( 1) 2.363(5) Cu(2)-0(6) 2.585(6) C~(5)-0(32) 1.879(4) Cu(5)-0(22) 1.934(4)Cu(3)-0(31) 1.943(4) Cu(4)-0(4 1) 1.948(4) C~(5)-0(5~') 2.787(7) Cu(5)-0(42) 1.932(4)CU( 3)-O( 32) 1.8 73(4) Cu(4)-0(42) 1.937(4)Cu(l)-N(22) 1.988(5) CU( 2)-N( 3 2) 1.9 84( 5) C~(5)-0(12) 1.898(4) Cu(4)-O( 5") 2.8 84( 7)P-Alaninehydroxamic acid ligandsn = l n = 2 n = 3 n = 4O(n1)-C(n1) 1.287(7) 1.299(7) 1.293 (7) 1.278(7)O(n2)-N(n 1) 1.441(6) 1.405(6) 1.420(6) 1.420(6)N(n1)-C(n1) 1.305(8) 1.297(7) 1.298(7) 1.307(7)N(n2)-C(n 3) 1.474(8) 1.489(8) 1.467(8) 1.485(9)C(nl)-C(n2) 1.52 l(9) 1.496(9) 1.49 7( 8) 1.506(8)C(n2)-C(n3) 1.503(9) 1.522(8) 1.525(10) 1.497(9)C1-0 av.1.421(7) range 1.384-1.443Copper environmentO( 1 1)-CU( 1)-O( 12)O( 1 l)-Cu( 1)-N(22)O( 1 l)-Cu( 1)-N(2 1)O( 1 ~)-CU( 1)-N(2 1)0(12)-C~(l)-N(22)N(2 l)-Cu( 1)-N(22)W( 1)-Cu( 1)-O( 11)W( 1)-Cu( 1)-O( 12)W( l)-Cu( 1)-N(21)W( l)-Cu( 1)-N(22)Cu( 1)-O( 1 1)-C( 1 1)CU( 1)-O( 12)-N( 1 1)CU( 1)-0(12)-cu(5)N(I 1)-0(12)-Cu(5)Cu(l)-N(21)-0(22)CU( I)-N(21)-C(21)CU( 1)-N(22)-C(23)O( 3 l)-Cu( 3)-O( 3 2)O(3 l)-Cu(3)-N(42)O( 3 l)-Cu( 3)-N(4 1)O( 3 ~)-CU( 3)-N (4 1 )8 1.2(2)95.6(2)163.9(2)90.7(2)176.5(2)92.8(2)9 5.7( 2)89.2(2)98.1(2)89.8( 2)110.8(4)112.7(3)1 17.0(2)11 6.1(3)116.7(3)130.6(4)11 3.5(4)82.3 (2)93.2(2)169.1(2)8 8.5( 2)P-Alaninehydroxamic acid ligandsO( 22)-Cu( 2)-N( 3 1)O( 22)-C~( 2)-N( 3 2)N( 3 1 )-CU( 2)-N( 32)0(6)-C~(2)-0(21)0(6)-C~(2)-0(22)O( ~)-CU( 2)-N( 3 1 )O(6)-C U( 2)-N( 32)CU(2)-0(21)-C(2 1)Cu(2)-0(22)-Cu( 5 )C~(2)-0(22)-N(21)N(2 1)-0(22)-Cu( 5 )Cu(2)-N(3 1)-O(32)Cu(2)-N(31)-C(31)Cu(2)-N( 32)-C( 3 3)O(4 l)-Cu(4)-0(42)0(41)-Cu(4)-N(12)0(41)-Cu(4)-N(ll)0(42)-Cu(4)-N( 1 1)0(42)-Cu(4)-N( 12)O( 5")-Cu(4)-0(4 1 )O( 5")-Cu(4)-0(42)90.3 (2)1 7 5.3 (2)93.5(2)84.7(2)88.4(2)90.5(2)94.3(2)1 09.9( 4)11 1.5(3)117.5(2)119.5(3)117.2(3)132.2(4)1 14.4(4)81.8(2)93.0(2)170.2(2)9 1.3 (2)1 72.8 (2)96.1(2)73.0(2)n = lO( n 1 )-C(n 1 )-N(n 1 ) 124.2(6)O(n 1 )-C(n 1)-C(n2) 1 17.4( 5)O(n2)-N(nl)-C(nl) 109.9(5)N(n 1)-C(n 1)-C(n2) 118.4(5)C(nl)-C(n2)-C(n3) 1 17.4( 5)C( n2)-C(n 3)-N(n2) 112.7(6)0-C1-0 av.109.7(4)* Symmetry codes: I -x, 1 - y, 1 - Z; I1 1 - X, 1 - y , 1 - Z.O( 3 ~)-CU( 3)-N( 42)N(4 l)-Cu(3)-N(42)0(22')-C~(3)-0(3 1)0(22')-Cu(3)-0( 32)0(22')-Cu(3)-N(4 1)0(22')-Cu(3)-N(42)Cu(3)-0(3 1)-C(3 1)O(2 l)-CU(2)-0(22)O(2 1 )-Cu(2)-N( 3 2)0(21)-Cu(2)-N(3 1)CU( 4)-O( 42)-N (4 1)CU(4)-0(42)-CU(5)N(4 1)-0(42)-C~(5)Cu(4)-N( 11)-O(12)Cu(4)-N( 1 1)-C( 11)Cu(4)-N( 12)-C( 13)O( 32)-C~( 5)-O(42)0(42)-C~(5)-0(12)0 (22)-C u (9-0 (42)O( ~")-CU( 5)-O(42)O( 5")-Cu( 5)-O( 32)170.0(3)95.0(2)89.3(2)83.3(2)95.4(2)105.6(2)110.3(4)80.8(2)95.6(2)170.0(2)111.0(3)112.7(2)118.6(3)116.8(3)1 3 1.9(4)114.1(4)89.1 (2)90.6(2)167.7(2)89.1(2)75.5(2)0(511)-Cu(4)-N(1 1)0(511)-Cu(4)-N( 12)0(5")-CU(4)-W(2)W(2)-CU(4)-0(41)w (2)-cu(4)-0(42)W(2)-Cu(4)-N( 11)W(2)-Cu(4)-N( 12)CU(4)-0(41)-C(41)Cu(3)-0(32)-Cu( 5 )N( 1 l)-Cu(4)-N( 12)C~(3)-0(32)-N(3 1)N(3 1)-0(32)-C~(5)Cu(3)-N(4 1 )-O(42)CU( 3)-N(4 1 )-C(4 1)CU( 3)-N(42)-C(43)O( 12)-C~(5)-0(22)0(22)-C~(5)-0(32)O( 12)-Cu(5)-0(32)0(5")-Cu(5)-0( 12)O( 5")-Cu( 5)-O(22)n = 2 n = 3 n = 4122.8(5) 122.9( 5 ) 123.6(6)117.7(5) 118.0(5) 118.1(5)11 1.5(5) 110.6(5) 111.3(5)119.5(5) 119.1(5) 118.3(5)11 1.3(5) 112.8(5) 11 1.3(5)116.2(5) 113.9(5) 1 17.4( 5)range 108.5-1 11.675.2( 2)102.7(2)169.1(2)93.2(2)87.4(2)9 7.4(2)1 00.5 (2)87.4(2)110.2(4)113.9(3)1 23.8 (2)122.3(3)1 18.4(3)126.9(4)1 1 1.0(4)9 1.1 (2)90.0(2)176.7(2)8 7.7(2)116.8(2)molecule) bridges Cu(5) and Cu(4) and completes the distortedelongated octahedral co-ordination of the latter.The distances between the central and peripheral metal ionsvary from 3.221(2) [Cu(5) Cu(4)] to 3.315(2) 8, KCu(5)Cu(2)].The distances between peripheral metal ions are in therange 4.638(2) [Cu( 1) - Cu(4)]-4.565(2) 8, CCu(3) Cu(4)].Four such ions form an almost planar structure (& 0.1 A) andthe central Cu" is 0.4 8, above this plane.The co-ordination via hydroxamic group oxygens suggestedearlier from the spectroscopic data for dimeric complexes is nowclearly seen also in the X-ray structure of the oligomericcomplex.In the solid state the complex does not give any EPRspectrum, owing most likely to the strong antiferromagneticcoupling within the oligomer and between the pentameric units.The distances between the metal ions of the vicinal moleculesare relatively short (3.5-3.9 A). The finding that the hydroxamicoxygens are bound strongly to metal ions had been suggestedpreviously for dimeric complexes formed at low pH with U-aminohydroxamic acids.*ConclusionThe solution and X-ray studies on copper(r1) complexes withP-alaninehydroxamic acid have shown that all donor atoms ofthe aminohydroxamic acids are very effective binding sitesfor metal ions. The binding of two copper centres through theNO- group is very strong and it is now evident that theearlier suggestions of its involvement in dimer formation iJ.CHEM. SOC. DALTON TRANS. 1991 167(Project MM 46/86), and the Polish Ministry of Education(Project RP.II.lO). Table 4 Hydrogen bond distances (A) and angles (") with e.s.d.s inparenthesesD-H . AW(1)-H(l) - O(11"')W( 1)-H(2) O(3 1')W(2)-H(3) O(21")W(2)-H(4) O(2")W(3)-H(5) - - 0(4?,W(3)-H(6) * W(5W(4)-H(7) O(6)W(4)-H(8) O(5")W(5)-H(9) - * W(3)W(5)-H(10) * W(4)lvN(12)-H(15) * * O(7 )N(22)-H(21) W(1"')N(32)-H(27) - W(2')N(42)-H(34) - W(3'"))D-H0.7700.9430.9101.0440.9651.01 11.0030.9930.9660.9620.9991 .ooo0.9991 .oooH - . * A2.2101.9451.9681.8661.9371.92 12.2592.1861.8191.7952.2492.1882.2191.973D - .* A2.873(6)2.820(6)2.80 1 (6)2.846(7)2.86 l(8)2.841(10)3.209( 10)3.1 lO(11)2.786(9)2.719(11)3.134(8)3.035(7)3.1 18(7)2.959(8)Angle1451531511551 60150158154179160147142149169Symmetry codes: I -x, 1 - y , 1 - z; I1 1 - x, 1 - y , 1 - z; I11 -x,1 - y, -z; IV x, 1 + y , z; v - 1 + x, y, z; VI 1 - x, 1 - y , -z; VIIx, y , 1 + z.corresponding a-aminohydroxamic acid systems were correct.This strong coupling of metal centres leads to the 'EPR silentspecies.'The results obtained in this work and in the earlier study withaspartic acid-0-hydroxamic acid l 6 indicate that when twoaminohydroxamate ligand nitrogen donors are in a position toform six-membered chelate rings the formation of theoligomeric species becomes favourable.AcknowledgementsThis work was supported by the Polish Academy of Sciences(Project CPBP 01.12), the Hungarian Ministry of EducationReferences1 N.Kurzak, K. Kurzak and J. Jezierska, Inorg. Chim. Acta, 1987,130,189.2 E. Farkas, J. Szoke, T. Kiss, H. Kozlowski and W. Bal, J. Chem. Soc.,Dalton Trans., 1989, 2247.3 B. Kurzak, K. Kurzak and J. Jezierska, Inorg. Chim. Acta, 1986, 125,77.4 B. Kurzak, D. Kroczewska, J. Jezierska and M. Huza-Koralewicz,Transition Met. Chem., 1988, 13,297.5 T. T. Pakkanen, T. A. Pakkanen, K. Smolander, D. A. Brown, W. K.Glass and A. L. Roche, J. Mol. Struct., 1987,162,313.6 M. Julien-Pouzol, S. Jaulmes, P. Laruelle, S. Carvalho and E. B.Paniago, Acta Crystallogr., Sect. C, 1985,41, 712.7 T. Glowiak and M. Koralewicz, School Symposium on InorganicBiochemistry and Molecular Biophysics, Wroclaw-Karpacz, 1985.8 C. 0. B. de Miranda-Pinto, E. B. Paniago, S. Carvalho, M. Tabakand Y. P. Mascarenhas, Inorg. Chim. Acta, 1987,137, 145.9 A. H. Blatt, Organic Synthesis Collection, Wiley, New York, 1943,vol. 2, p. 67.10 G. Gran, Acta Chem. Scand., 1950,4,599.11 H. Irving, M. G. Miles and L. D. Pettit, Anal. Chim. Acta, 1967, 38,475.12 L. Zekany and I. Nagypal, in Computational Methods for theDetermination of Stability Constants, ed. D. Leggett, Plenum, NewYork, 1985.13 G. M. Sheldrick, SHELXS 86, Program for Crystal StructureSolution, University of Gottingen, 1986.14 International Tables for X-Ray Crystallography, Kynoch Press,Birmingham, 1974, vol. 4.15 Syntex XTL/XTLE Structure Determination Systems, SyntexAnalytical Instruments, Cupertino, 1976.16 E. Farkas and P. Buglyo, J. Chem. Soc., Dalton Trans., 1990,1549.Received 7 t h September 1990; Paper 0104133

ISSN:1477-9226    

DOI:10.1039/DT9910000163

出版商:RSC    

年代:1991

数据来源: RSC