摘要:
1973 1729Transition-metal Complexes of Pyrrole Pigments. Part V1.t Some Bi-valent Metal Complexes of 3,3‘,4,4’-Tetrachloro-5,5’-d iet hoxycarb-onyidipyrrometheneBy Yukito Murakami,” Yoshihisa Matsuda, and Kazunori Sakata, Department of Organic Synthesis,Arthur E. Martell, Department of Chemistry, Texas A €t M University, College Station, Texas 77843, U.S.A.Faculty of Engineering, Kyushu University, Fukuoka 81 2, JapanThe cobalt( I!), nickel( I [ ) , copper( \I), and zinc( I!) complexes of 3,3’,4,4‘-tetrachloro-5,5’-diethoxycarbonyIdipyrro-methene were investigated by means of electronic, vibrational, and e.s.r. spectroscopy as well as X-ray diffractionmeasurements of powdered samples. 1.r. and visible spectral data proved the distorted tetrahedral co-ordinationof M-N4 type for the cobalt(l1) and zinc(l1) complexes.The nickel(l1) and copper(l1) complexes showed two kindsof carbonyl bands in their i.r. spectra, and the d --t d transition bands were consistent with the distorted octa-hedral (C,) co-ordination. E.s.r. spectra of the copper complex were characteristic of rhombic co-ordination,showing g, 2: g, > g, and A, > A, ,N A,. Both nickel and copper complexes consequently possess a distortedoctahedral configuration of M-N402 type around the central metal atoms. The characteristic features of X-raydiffraction patterns for the four metal complexes were consistent with these structural assignments.FROM our structural investigations on various divalentmetal chelates of substituted dipyrromethenes (I) ,1-3cobalt@) was found to co-ordinate tetrahedrally todipyrromethene molecules, the dihedral angle betweentwo ligand planes being maintained at nearly go”, re-gardless of the nature and bulkiness of the 5,5’-sub-stituents. Such configuration seems to minimize thesteric hindrance between such substituents in a molecule.On the other hand, copper(I1) tends to co-ordinate with11)ligands in a square-planar manner as far as the circum-stances allow. The 5,5’-substituents of dipyrromethenestake part in distorting the co-ordination geometry fromsquare-planar configuration towards tetrahedral depend-ing upon their bulkiness.This trend was also verified bya single-crystal X-ray diffraction s t ~ d y . ~ A similartrend was also suggested for the nickel(I1) complexes inour previous work2 and the distorted geometry wasillustrated by X-ray diffraction s t ~ d y .~3,3’ ,4,4’-Tetrachloro-5,5’-diet hoxycarbonyldipyrro-methene was adopted as the ligand in this work to formthe corresponding metal chelates with Corr, NP, CuII,and ZnII. Different from the previous dipyrrometheneligands, the ethoxycarbonyl groups, which would exhibitco-ordination ability under certain configurational con-ditions, are placed a t the 5,5’-positions in the presentligand. Therefore, the metal-specificity would be ex-pected for the formation of six-co-ordinated metalcomplexes at a 2 : 1 molar ratio of ligand to metal withparticipation of the ethoxycarbonyl group as a donor.t Part V, ref. 3.Y. Murakami and K.Sakata, Inovg. Chim. Ada, 1968, 2,2 Y. Murakami, Y . Matsuda, and K. Sakata, Inorg. Chem.,Y. Murakami, Y . Matsuda, and K. Sakata, Inorg. Chem.,273.1971, 10, 1728.1971, 10, 1734.Although Motekaitis and Martell reported the synthesesof CaII, CuII, NiII, ZnII, and MnTI chelates with 3,3’,4,4’-tetrachloro- and 3,3’,4,4’-tetrabrorno-5,5’-diethoxycar-bonyldipyrromethene ligands as well as their structuralinvestigations by electronic, i.r. , and n.m.r. spectro-scopy, the co-ordination behaviour of the former ligandwith particular attention to the ethoxycarbonyl groupand the structures of the resulting metal chelates wereinvestigated in more detail in this work through themeasurements of their ligand-field bands, e.s.r., and i.r.spectra, and X-ray diffraction patterns in powderedsample state.EXPERIMENTALMetal CheZates.-All the metal chelates were prepared bymetal-metal exchange reactions performed on the CaIIchelate.Syntheses of bis( 3,3’,4,4’-tetrachloro-5,5’-diethoxy-carbonyldipyrromethenato) calcium (11) , -nickel( XI), -copper-(11), and -zinc(II) were carried out by the methods describedpreviously (Found: C, 39.55; H, 2.55; N, 6.2. Calc. forC,,H,,N,O,Cl,Ni: C, 39.65; H, 2.45; N, 6-15. Found:C, 39.4; H, 2.6; N, 6.05. Calc. for C,,H,,N,O,Cl,Cu: C,39.45; H, 2.45; N, 6-15. Found: C, 39.6; H, 2.6; N, 6.2.Calc. for C,,H,,N,O,Cl,Zn: C, 39.35; H, 2.4; N, 6.1%).Bis (3,3’, 4,4’-tetrachloro-5,5’-diethoxycarbonyldipyrrome-thenato)cobalt(II) was prepared in a similar manner.Amixture of bis(3,3’,4,4’-tetrachloro-5,5’-diethoxycarbonyl-dipyrromethenato)calcium(II) (0.32 g) and cobalt(I1) acetatetetrahydrate (0.1 1 g) was refluxed in absolute ethanol (750ml) for 4 h. After the reaction mixture being allowed t ostand overnight at room temperature, the solvent was re-moved under vacuum. The residue was extracted into hotbenzene and again the solvent was removed under reducedpressure. The remaining solid material was extracted intohot n-pentane. Bright green prism-like crystals were ob-tained; yield 0.23 g (70%) (Found: C, 39.8; H, 2-6; N,6.15. Calc. for C,,H,,N,O,Cl,Co: C, 39.65; H, 2.45; K,6.15%).Spectra.-Electronic spectra in cliloroforin were re-corded on a Hitachi EPS 2 spectrophotometer at roomtemperature.1.r. spectra were measured with a JASCOM. Elder and B. R. Penfold, J . Chem. SOG. ( A ) , 1969, 2666.F. A. Cotton, B. G. DeBoer, and J. R. Pipal, Inovg. Chem.,* R. J . Motekaitis and A. E. Martell, I m v g . Chem., 1970, 9,1970, 9, 783.18321730 J.C.S. DaltonDG 403 G spectrophotometer at room temperature in chloro-form as well as by a Nujol mull technique. E.s.r. spectraof the copper chelate were recorded on a JEOL JES ME 3spectrometer equipped with a 100 kHz field modulationunit, and either with X-band or K-band microwave unit.The sample was measured in xylene-benzene (6 : 4) at- 135" and room temperature. The powdered solid samplewas also provided for measurements a t room temperature.MgO-Mn(I1) was used to establish the standard referencesignals for e.s.r.spectra.X-Ray DifjCaction Patterns.-These patterns of the pow-dered solid samples were measured using a Rigaku DenkiSD X-ray diffractometer.*RESULTSElectyonic Spectra-The electronic spectra of the CoII,NiII, and CuII chelates are shown in Figure 1. The absorp-tion bands appearing above 18 000 cm-l are attributed tocharge-transfer transitions and n ---t x* transitions withina ligand molecule. Thus, these bands bear a close resem-blance among above three metal chelates. The ligand-fieldbands are observed in a region lying below 18 000 cm-l.These data and the corresponding assignments are listed inTable 1 along with the data for some other dipyrromethenechelates from our previous work for comparison.Generalfeatures of the ligand-field bands for the present Corr chelateare similar to those for previously studied CoII chelates.These bands for the former chelate bear the closest resem-blance in their intensities to the corresponding bands for the5,5'-diphenyldipyrromethene chelate. The spectral be-haviour of the present Nil1 chelate is most analogous tothat of the 5,5'-diphenyldipyrromethene chelate. How-ever, both bands appearing in 6000-13 000 cm-l shiftedtoward higher energy region and their relative intensity issomewhat changed for the present chelate. All the ligand-field bands of the present CuII chelate shifted toward lowerenergy relative to those of the other dipyrromethenechelates previously studied by us. General features of theshow a single sharp band due to G O stretching vibration,while the CuII and NiU chelate spectra have two bands.All these chelates show a sharp single absorption attributableA (nm)2000 1000 500 LOO 300 2505LJ0 3 -210I I l l5 10 15 20 25 30 35 LOI) (cm-lFIGURE 1 Electronic absorption spectra of the 3,3',4,4'-tetra-chloro-5,5'-diethoxycarbonyldipyrromethene chelates in chloro-form a t room temperature: (A), CoII; (B), NiII; (C), CuIIto the skeletal stretching mode of the pyrrole rings ca.1600cm-1.E.s.r. Spectra.-These spectra for the Curl chelate undervarious conditions are shown in Figure 3. The solutionTABLE 1Ligand-field bands for dipyrromethene chelates and their assignments a,b620Osh847010 20osh13 30014 50016 50OshNil1 8120 (13)11 200 (82)12 930 (143)15 600sh (583)Ligand oL(11) d (111) d670Osh (24) 78OOsh (13)8200sh (53) 880Osh (17)10 000 (26)12 300 (639)13 300 (499)16 700sh (20 400)10 000 (67)13 200 (336)14 400 (304)16 900sh (1885)6300 (26) 6100 (17)11 OOOsh (48)12 700 (574)13 890 1474)11 800 (759)13 300sh 1500115 OOOsh (225) 15 9OOsh (40 500)60OOsh (3.9)8300sh (13.2)10 500 (26.3112 goo (530)'14 000 (426)15 900sh (4840)9260 (14.6)13 900 (44.8)14 900sh (55.9)CuII 12 760sh (132) 10 900 (278) 8860 (456) 7450 (45) B,,Ba f- B,14 OOOsh 1165) 12 300 (131)16 400sh (1320) 16 5OOsh (1550) 14 700 (2600) 15 900sh (1270) AJ' + B115 600 (2490)a Band positions are expressed in cm-' and molar extinction coefficients are given in parentheses after the band positions. b Measured a t room temperature in chloroform.c (I), 3,3',4,4'-tetramethyldipyrromethenc; (TI), 3,3',5,5'-tetramethyidipyrromethene; (111), 5,6'-diphenyldipyrromethene; (IV), 3,3',4,4'-tetrachloro-5,5'-diethoxycarbon-yldipyrromethene. d From ref.2.spectrum are also somewhat modified from the others andthe absorption intensities are significantly lowered.Vibrational S$ectra.-The i.r. spectra of the CoTr, NiII,CuII, and ZnI1 chelates are shown in Figure 2 only for thecarbonyl frequency region. The Corl and ZnII chelatesspectrum at room temperature shows only a single resonancepeak, while the e.s.r. spectra for polycrystalline sample andsamples in frozen homogeneous solution provide g-values ofanisotropic nature.A powdered polycrystalline samplefurnished the X-band e.s.r. spectrum of rhombic characterwhich was further verified by the aid of the correspondingK-band spectrum upon Of three g-values* The * Measurements of X-ray diffraction patterns were carriedout at the Research Institute of Yoshitomi Pharmaceutical Co..Ltd., whose courtesy is greatly acknowledged.' solution spectrum measured at - 135" clearly indicates th1973 1731relation, g, II g, > g,, under the measuring condition. Inthe g, position, there consists of nearly equally spaced fourFIGURE 2 1.r.carbon yldipytemperaturein cm-l)I-1800 1600Wavenum ber(cm-’ I1800 1620Wavenumber(cm-’ 1spectra of the 3,3’,4,4’-tetrachloro-5,5’-diethoxy-,rromethene chelates in chloroform at room(number refers to the carbonyl stretching bandH -A‘ i i i II \ g =2.000IFIGURE 3 E.s.r.spectra of bis(3,3’,4,4’-tetrachloro-5,li’-di-ethoxycarbonyldipyrromethenato) copper(I1) : A, powderedsample at room temperature (X-band) ; B, in xylene-benzene(6 : 4) at room temperature (X-band) ; C, in xylene-benzene(6 : 4) at -135” (X-band); D, powdered sample at roomtemperature (K-band)resonance peaks, which may be attributed to the hyperfineinteraction with the copper atom ( I = 3/53). In addition,7 I. M. Procter, B. J. Hathaway, D. E. Billing, R. Dudley,and P. Nicholls, J . Chem. SOC. ( A ) , 1969, 1192.one of these peaks in lower field has a super-hyperfine struc-ture due to four equivalent nitrogen donor atoms.Thesecharacteristic features of e.s.r. spectra for the CulI chelateseem to predict the compressed-tetragonal stereochemistryaround the copper a t ~ m . ~ , ~ All the e.s.r. parameters aresummarized in Table 2.X-Ruy Difimction Data.-These pat terns for the NiII,CuII, and ZnII chelates are shown in Figure 4. Theseindicate a close resemblance in the nature of molecular1 1 I I I I I1 I I I Ix111 c a,c.cI .-YcI I 1 1I ---LIP-!I5 10 15 20 25 30 35 1 0 4529 ( “ IFIGURE 4 X-Ray powder diffraction patterns of the 3,3’4,4’-tetrachloro-5,6’-diethoxycarbonyldipyrromethene chelates.The relative diffraction intensity is shown against a Braggangle 8packing between the Niu and CuII chelates in the solidstate, and consequently a similarity in their co-ordinationgeometry.On the other hand, the diffraction pattern forthe ZnII chelate is certainly different from those for theabove two chelates. Although the CoII chelate did notprovide a well refined pattern due to some crystalline nature,it is certainly not analogous to the patterns for the NiII andCuI1 chelates.8 R. J. Dosser and A. E. Underhill, J . Chem. SOC. ( A ) , 1970,881732 J.C.S. DaltonTABLE 2E .s.r. pa-ameters for bis(3,3',4,4'-tetrachloro-5,5'-diethoxycarbonyldipyrrornethenato)copper(11) aTemp.Sample ( "C)Xylene-benzene 22Powdered 22Powdered 22(6 : 4 )solution(6 : 4) solutiona The errors in g-values are withinXylene-benzene - 1351 0 4 x 104 xMicrowave IA3'"f 1A3"1source g1 g2 g1' s3 cm-1 cm-1X-band 2.280 2.201K-band 2.285 2.204 2.204X-band 2.166 bX-band 2.256 2.01 1 145 11.2+0.005 and those in A-values are less than +0.1. hveraged g-value,DISCUSSIONCobaZt(11) and Z~.YZC(II) CheZates.-The i.r. spectrum forthe present cobalt chelate indicates that all the ethoxy-carbonyl groups in a chelate molecule are placed inspace in an equivalent manner. The general feature ofthe ligand-field spectrum also shows that the cobalt ionis situated approximately in a tetrahedral ligand-field,so that the 5,5'-substituents do not generate any notice-able steric disturbance in a molecule. As a result, thecobalt ion bound to four N-donor atoms has a nonde-generate A ground state in D, symmetry upon some minordistortion from a regular tetrahedron.Since the ZnII ion has no d-electrons in its valence-shell, only i.r.spectrum and X-ray diffraction patternof the chelate provide useful data in the present work forprediction of co-ordination geometry. The zinc chelatehas a single carbonyl stretching mode as is the case for thecorresponding cobalt chelate. In addition, the X-raydiffraction pattern is significantly different from thosefor the CuII and Nil1 chelates as can be seen fromFigure 4. Thus, we believe that the zinc chelate assumesa nearly tetrahedral structure around the metal atom.Copper( 11) and N~c~EZ(II) Che2ates.-The ligand-fieldbands of the present copper chelate are shifted to lowerenergy relative to those of the dipyrromethene-CuT1chelates previously studied by us l y 2 and this shift isaccompanied by the decrease of absorption intensity.For the dipyrromet hene chelates, in which alkyl orphenyl substituents are placed at the 5,5'-positions of aligand, the dihedral angle between two ligand planeswas predicted to increase as the bulkiness of the 53'-substituents increases.Consequently, d + d bandsshift to lower energy concomitant with the increase ofabsorption intensity. Therefore, if the distorted tetra-hedral co-ordination is still retained for the presentcopper chelate, the d + d band shift to lower energymust be accompanied with the increase of absorptionintensity. The result is contrary to what would beexpected for such a case. This suggests that the co-ordination geometry does not belong to D, symmetrywith Cu-N, bond type and some other co-ordinationconfiguration comes into play.The e.s.r.spectrum for the frozen solution gave threeg-values as g, 21 g, > g3. If the co-ordination symmetryis in D,, these values are expected to be g, > g, = g3.3Furthermore, the i.r. spectrum of the present copperchelate shows the presence of two different types ofcarbonyl group. On the basis of these facts, the co-ordination geometry around the copper atom may bepredicted to be the distorted octahedron with Cu-N,O,bonding (11). For models A and B listed in Table 3 (CZvsymmetry), the ground state function #A is shown as+A = d,t. Since a g,-value is somewhat larger than2-0023, these models cannot be strictly applied to thepresent system.In addition, the degeneracy of the A ,z tFIGURE 5 Schematic representation of the co-ordination geo-metry for the copper and nickel chelates (model C) with C,symmetry; refer to Table 3 for polar co-ordinates assignedto these point charges. Structure (11) represents the ligandconfiguration in the copper chelateTABLE 3Assignments of constant values to the point chargemodelsPolar co-ordinate for a pointDonor charge a Pointatom li or di charge bN1 a 0 Zea - XI2 Zea x ZeK4 a x Ze0 1 a' 8 0 0 Z'e0 2 a' - e, xp Z'eN2 4 2N3 4 2o a = a' and 8, = x/2 for model A; a # a' and 8, = x / 2for model B; a # a' and 8 - ~ 1 2 + A8 for model C.Z e > Z'e. See Appendix for s&ficance1973 1733and B, levels does not provide an explanation for thepresence of three ligand-field bands.For model C of C,symmetry (Figure 5 and Table 3), the ground statefunction +A is represented as:*A = ad,? + Pdze - p* 4- y/d2(d.r, + dgz)The Agi (= go - gi) values are given as follows:chelate is identical enough with that for the correspond-ing copper chelate as is obvious from Figure 4, The i.r.spectra for both nickel and copper chelates are very\ *+-_---A -* -A2A2gITd D4h Oh c2v c2(d3xy - ‘d3aw -‘ - ’’)’ FIGURE 7 Energy levels of the nickel(I1) ion in the sis-co-AE-4, 1 orclinated complex under various co-ordination symmetries 3-The above equations indicate the relation, g, = g, > g3,which gives a reasonable explanation for the observedg-values.In addition, three d --+ d bands observedfor the present copper complex may be ascribed to A +-A , B .t- A , and A A transitions as seen fromFigure 6. The hyperfine coupling constants obtainedh‘ B 7 4”.much alike, particularly in the carbonyl frequencyregion. Consequently, the distorted octahedral con-figuration around the central metal atom (C, sym-metry) can be assigned to the nickel chelate. Theobserved ligand-field bands may be attributed to A , B,A (TW) * A , B, A , B (TI@)) + A , and B, A , B(TW(P)) + A transitions in an increasing order ofenergy.APPENDIXCalculation of Ligand-Field Sp12‘2tings.2-The point-charge models are established for co-ordination of sixdonor atoms to a metal as listed in Table 3 to evaluate theenergy levels as the molecular site symmetry around thecentral metal atom is varied.Models A and B belong toC,, symmetry, while model C to C,.The ligand-field potential, which arises from the arrange-ment of six negative charges in space around the centralmetal ion may be represented by the following equation.nSince terms for wz $5 2k do not become zero for 8, # 4 2 , FIGURE 6 Energy levels of the copper(I1) ion in the six-co-ordinated complex under various co-ordination symmetries the followi% modification can be adopted.from e.s.r. study furnished a relation, A , 5 A , < A,,which is consistent with the assignments of g-values.In conclusion, the co-ordination configuration of thecopper chelate is most plausibly represented by model C(Figure 5 ) .Although the energy level correlations for variousligand-field symmetries can be shown in Figure 7, theco-ordination stereochemistry of the nickel chelate can-not be predicted on the basis of d ---t d band assign-ments alone. The X-ray powder pattern for the nickelA nmynYnm + A n -mvnyn-m = UnmynQnmwhere Unm-values are represented as follows.u,, = (2v’n/2/5)ea-3{Z + ( 3 C O S ~ 8, - qzy3)U,, = - ( 1 / 6 ~ / 2 1 / 5 ) e ~ - ~ sin 8, cos ~,,Z’P-~U,, = (d7r/6)ea-5(11Z + (35 c0s4 8, - 30 cos2 6, + 3)Z’p-6)Uql = - ( 2/5x/3)eaL5( 7 C O S ~ 8, - 3 COS, O,)Z’p-5U,, = (2/35n/3)eO{sin3 8, C O S ~ 8 , , ~ ’ ~ - 5 }U,, = ( 4 3 5 ~ / 6 2 / 2 ) e a - ~ { Z + sin4 8, Z’P-~}with p = a‘la1734 J.C.S. DaltonThe basis functions areFor models A and €3, the following eigenvectors are derived.For model C with C, symmetry (Figure 5 ) , the correspondingeigenvectors are somewhat modified as follows.The coefficient of the first term in the right hand side ofeach equation is considered to be largest among others sincethe &,-value does not seem to depart significantly fromxj2. The numbering suffixed to A’s and B’s simply indi-cates the relative sequence of energy levels. The energylevel splittings and the correlation diagram under variousco-ordination site symmetry for the copper(11) chelate areshown in Figure 6 .[2/1845 Received, 4th August, 1972
ISSN:1477-9226
DOI:10.1039/DT9730001729
出版商:RSC
年代:1973
数据来源: RSC