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Transition metal chloride complexes with phenazine 5-oxide[1]
J inor°~,nucl. ('hem., 1977,~ol 39, pp. 1137-1142. PergamonPress. Printedin GreatBritain
TRANSITION METAL CHLORIDE COMPLEXES WITH PHENAZINE 5-OXIDE[I] DAVID E. CHASAN, LOUIS L. PYTLEWSK1, CLIFFORD OWENSt and NICHOLAS M. KARAYANNIS~: Department of Chemistry, Drexel University, Philadelphia. PA 19104, U.S.A. (Received 21 September 1976)
Abstract--Complex compounds of the types (CrCI3)sL2'I8H20, (MnCI2)3L2'H20, FeCI3L.2H20, CoCI2L3.6H20. (CuCI2)3L2, (CuCID2L3"2H20 and ZnC%L2.H20 with phenazine 5-oxide(L) as ligand were prepared by interaction of predried solutions of L and metal chloride. The new metal complexes were characterized by means of their IR and electronic spectra and magnetic susceptibility measurements. The Cr(III), Mn(II), Fe(IIl) and Cu(II) complexes appear to be polynuclear, comprising bridging L(O- or O,N-bonded) or CI ligands. Both Cu(II) complexes are characterized by subnormal magnetic moments, which were attributed to spin-spin coupling, occurring by a superexchange mechanism, operating through the orbitals of the bridging oxygen atoms (CuO2Cu bridges, involving O-bonded bridging L groups). The Co(II) and Zn(II) complexes are apparently monomeric, involving both N- and O-bonded L ligands.
INTRODUCTION
Synthetic and characterization studies of transition metal chloride [2], perchlorate [3] and nitrate [4] complexes with the mono-N-oxide of pyrazine (N-pyzO) were reported in recent years by these laboratories. This ligand can act either as unidentate, coordinating through the aza-group nitrogen or through the N - O oxygen, or as bidentate, bridging, coordinating through both these sites [2-4]. A number of lanthanide(III)[5], Ru(lI)[6] and Ag(I)[7] complexes with N-pyzO and derivatives have been also reported in the literature. Quite recently, we extended our work to include 3d metal complexes with quinoxaline-loxide(N-qxO) and phenazine-5-oxide (N-phzO)[8]. NqxO complexes with 3d metal chlorides and perchlorates have been reported elsewhere by these[9,10] and o t h e r [ l l ] laboratories. The present paper deals with 3d metal chloride complexes with N-phzO, while the corresponding metal perchlorate complexes are the subject of another publication [ 12]. EXPERIMENTAL N-phzO was prepared by the WOHL-AUE reaction[13], as modified by Soule[14], i.e. by refluxing nitrobenzene, aniline and potassium hydroxide in benzene. Its authenticity was confirmed by elemental analysis and its m.p. (224-225°C)[14]. Reagent grade transition metal chlorides and organic solvents were used throughout this work. Zeolite molecular sieve 4A, grade 515(Davison), was utilized for pre-drying the ligand and salt solutions [8]. As already reported in a preliminary communication [8], use of conventional organic dehydrating agents, such as triethyl orthoformate [15] or 2,2-dimethoxypropane [16], does not facilitate the precipitation of transition metal complexes with N-qxO or N-phzO. This is due to the fact that metal complexes with these ligands dissociate in the presence of several organic solvents, and especially alcohols[I,10], which are produced during the hydrolysis of the above dehydrating agents[15, 16]. It was found that molecular sieve 4A as a drying agent of ligand and salt solutions prior to their interaction, although not as effective as triethyl orthoformate or 2,2-dimethoxypropane, facilitates the tDepartment of Chemistry, Rutgers University, Camden, NJ 08102 U.S.A. :]:Amoco Chemicals Corporation, Naperville, IL 60540, U.S.A.
precipitation of metal complexes containing usually limited amounts of water [8]. If, on the other hand, no drying agent of any kind is used during the preparation of N-qxO or N-phzO complexes, the precipitates obtained are generally very heavily hydrated[8]. The preparation of the new metal complexes was effected as follows: All operations were performed in the dry-box (N2 atmosphere), because of the hygroscopic character of some of the new complexes. 3.5 rumple N-phzO were dissolved in 25 ml chloroform, while l mmole of hydrated metal chloride was separately dissolved in 20°°75mill0] acetone. The ligand and salt solutions were treated separately with molecular sieve 4A and then were allowed to interact, as previously described [8-10]. Precipitation was immediate in the cases of Cr(IIIL Mn(II), Fe(IlI), Co(IlL Cu(II) and Zn(II) chlorides, but Fe(II) and Ni(II) chlorides failed to produce solid complexes by the above or different synthetic procedures. In the case of CuCl~, in addition to the brown (CuCG)3(N-phzO)2 complex obtained by the above method, an olive-green complex of the type (CuCI2)dNphzO)3-2H20 was isolated when ligand and salt solutions were allowed to interact at a I : 1 molar ratio. Variations in the ligand to metal salt ratios in the cases of the rest of the metal chlorides studied, did not lead to the formation of complexes with different stoichiometries than those obtained at the 3.5 : 1 ratio. The new solid complexes were quickly filtered, thoroughly washed with hexane and stored in an evacuated desiccator over phosphorus pentoxide. The Cr(III), Mn(II) and Co(II) complexes are very hygroscopic, while the rest of the new complexes are stable in the atmosphere. All the new complexes dissolve easily in water and several organic solvents (nitromethane, nitrobenzene, dimethyl sulfoxide, N.N-dimethylformamide, acetone, alcohols, etc.). However, their solutions in these media apparently contain dissociation products, as manifested by the fact that they are characterized by the deep yellow color of the free ligand rather than that of the complex; dissociation seems to occur immediately upon contact of the complexes with organic solvents; in fact, as soon as the complex comes in contact with the solvent, the color of the solid changes rapidly to deep yellow. Analytical data (C, H, N determinations by Schwarzkopf Microanalytical Laboratory, Woodside, New York; metal analyses by emission spectroscopy) for the new complexes are given in Table 1. The characterization of the complexes was based on IR (Table 2) and electronic (Table 3) spectra and magnetic susceptibility measurements (Tables 3, 4). Spectral and room temperature magnetic measurements were obtained by methods described elsewhere[3]. Studies of the variation of the magnetic susceptibility of the brown Cu(ll) complex with temperature (80-297°K)
1137
D . E . CHASAN et al.
1138
Table 1. Analytical data for metal chloride complexes with N-phzO(L)
Complex
Color
C(%) Calc. Found
(CrCI~)3L2.18H20 (MnCI2)3L2.H20 FeCI3L'2H20 CoCI2L3'6H20 (CuCI2)3L2 (CuCI2)2L3'2H20 ZnC12L2.H~O
Yellow-gold Yellow-green Orange Olive-green Brown Olive-green Olive-green
24.19 36.58 36.54 52.31 36.22 48.39 52.72
24.42 36.46 36.39 52.61 36.40 47.98 53.23
Analysis H(%) N(%) Calc. Found Calc. Found
Metal(%) Calc. Found
4.41 2.31 3.07 4.40 2.03 3.16 3.33
13.1 20.9 14.2 7.1 24.0 14.2 12.0
4.62 2.59 2.73 4.18 2.27 2.95 3.61
4.70 7.11 7.10 10.17 7.04 9.41 10.25
4.61 7.12 7.17 10.14 7.24 9.12 9.99
13.5 20.7 14.4 6.8 23.7 14.2 12.0
Table 2. Pertinent IR data for N-phzO complexes with 3d metal chlorides (cm-I) Compound
1400-1200 cm-' (~N~ region)
N-phzO=L
1369 w, 1349 s, 1257 m, 1240 w, sh
(CrC13)3L2.18H20
1385 m, sh, 1375 s, 1329 w, sh, 1312w, sh, 1275 m, 1244m 1388 w, 1368 w, 1326 s, 1297 w, 1272m, 1231w 1386 m, 1373 s, 1349 w, 1326 w, 1319w, 1308w, 1275 m, 1242m 1390 m, 1371 w, 1351 w, 1323 s, 1296 w, 1278 w, sh, 1270 m, 1259 w, 1233 w 1384w, 1356 w, 1325 s, 1260 m, 1227 w 1390 w, 1362 s,b, 1341 s, sh, 1302 w, 1289 w, 1266 m, 1240 m, sh 1389 m, 1371 m, 1321 s, 1292 m, 1270 m, 1260 m, sh, 1236 m, 1201 w
(MnC12)3L2'H20 FeC13L.2H20 CoCI2L3"6H20
(CuCI2)3L2 (CuClz)2L3.2H20 ZnCI~L2.H20
900-800 cm-~ (8~_o region) 889w, 870m, 856m, 827 w, sh 883w 870w 881 w, 870 w, 862 w 868 m, 856w, sh
888w, 865 m 888m, 856w 862m
525-33cm-1 (~M~, VM-N,~M~CJ,U,~a,d)t 402m, 360m, 311 m, 247 re,b, 178w, l17w, b 499 w, 493 w, 398 w, 361 w, 331 w, 326 w, 320w, 297 w,b, 226w, 202w, 180w, b 404w, 348m, 318m, 268m, 240m, 226m, 184s, l17m, 111 m,b 396 s, 385 s, 362 s, 328 m, 311 w, 304 w, 245 w,b, 180w, b, 148m 403 m, 360 m, 353 m, 345 m, 262 m, 248 m-w, 225 m, 197 w, 178 w, 143 w, 118 w 490 vw, 404m, 351 w-m, 347 w-m, 306m, 263 m, 249 m-w, 148 m, b 368w, 350w, 277w, sh, 267w, 206 w,b, 133w 478 w, 451 w, 412 w, 406 w, 361 m, sh, 344 s, b, 304 m, 287 m, 249 m-s, 168 m, 156 w, sh, l13m, 101 m, sh
Abbreviations: s, strong; m, medium; w, weak; b, broad; v, very; sh, shoulder. tFor tentative metal-ligand stretching mode assignments see text. Table 3. Electronic spectra (Nujol mulls) and magnetic properties (297°K) of N-phzO complexes with 3d metal chlorides Compound N-phzO=L (CrC13)3L2-18H20 (MnC12)3L2.H~O FeCI3L.2H20 CoCIzL3"6H20
(CuC12)3L~ (CuCI2)2L3'2H20 ZnC12L2'H20
A.... nm
106XMc°r, cgsu
/~en,/~B
229 sh, 264 sh, 273 vs, 365 w, 382 m, 401 m, 420 sh, 424 m 230 sh, 274 vs, 362 sh, 381 s, 401 s, 420 sh, 424 s, 459 m, 500 m, 602 w, 643 w, sh, 680 w, sh 230 s, 262 s, 272 vs, 344 w, 363 sh, 380 s, 401 s, 420 sh, 424 s, 458 w 262 sh, 272 vs, 362 w, 381 m, 401 m, 424 m, 525 b, sh 230 m, 272 vs, 344 w, 364 sh, 381 s, 401 s, 420 sh, 424 s, 451 sh, 482 s, 597 m, 608 m, 624 m, 670 m, b, 690 m, sh, 940 w, sh, 1005 w, sh, 1100 w, sh, 1325 w, sh, 1470 w, sh 262 sh, 272 vs, 361 sh, 381 m, 401 m, 420 sh, 424 m, 470 m, b, sh, 545 m-w, sh, 785 w, b, 1060 w, sh 263 vs, 275 vs, 362 w, 381 m, 401 s, 420 s, sh, 425 s, 475 m, b, 555 m, b, 600 w, sh, 700 w, sh, 835 w, 1150 w, sh 230 s, 264 sh, 274 vs, 363 sh, 380 s, 401 s, 420 sh, 424 s
-5,789
-3.72
14,692 15,770 9,090
5.93 6.15 4.69
845
1.42
678
1.27
Diamagnetic
Abbreviations: s, strong; m, medium; w, weak; b, broad; v, very; sh, shoulder. were performed by Prof. A. B. P. Lever's laboratory (York University, Toronto, Ontario, Canada), by using apparatus and technique described in the literature[17]. Similar studies, covering a narrower temperature range (143-297°K), on the olive-green Cu(II) complex were performed at these laboratories, by using a Cahn Magnetic Susceptibility System No. 7600 (Table 4). Solution electronic spectral and electrolytic conductance studies were not attempted, in view of the instability of all the new complexes in the presence of suitable solvents, RESULTS AND DISCUSSION
Stoicheiometries o1: the new metal complexes. As was also the case with N-pyzO[3] and N-qxO[10] 3d metal
chloride complexes, the new N-phzO complexes show a wide variability of stoichiometries, with variation of metal ion (Table 1). It appears that with N-pyzO and derivatives there is no definite preference for coordination through the N - O oxygen or the aza-nitrogen, when these compounds function as unidentate ligands towards 3d metal ions[2--4, 10]. If electronic factors alone were determining the bonding site of unidentate ligands of this type, it might be anticipated that coordination would occur through the aza-nitrogen, which is the stronger donor site[18]. However, steric factors are also important in the case of interaction of these ligands with large
Transition metal chloride complexes with phenazine 5-oxide[I] Table4. Variations of the magnetic susceptibilitiesof CuCI2-NphzO complexes with temperature Complext
T, °K
(CuCL)~I.,
297.2 278.9 259.9 241.8 223.2 204.7 187.6 169.4 151.7 134.2 116.9 99.7 80.9 297.0 203.0 177.11 159.0 143.0
(CuCI,Ld~.2H20
106XM c'r, cgsu ~o,,~B 845 895 944 1011 1076 1160 1261 1378 1511 1660 1841 2072 2365 678 913 1002 1104 1185
1.42 1.41 1.41 1.40 1.39 1.38 1.38 1.37 1.36 1.34 1.32 1.29 1.24 1.27 1.22 1.20 1.19 1.17
+L = N-phzO. acceptor molecules, such as iodine[19], or sterically crowded metalions, as in the present case, which involves the presence of additional potentialligands (chloride ions and water molecules). Under these conditions, the oxygen site of N-phzO(I) might become more accessible for coordination than the aza-nitrogen site, whose coordination would be hindered by steric repulsions between the CH groups at the 1- and 9-ring positions and the ~
,
~
O (r) crowded acceptor atom[10, 19]. In view of the above considerations, the tendency of 1,4-diazines[20-22] and their N-oxides[2--4, 10] to function either as terminal unidentate or as bridging bidentate ligands (complexes comprising both terminal and bridging diazines or diazine N-oxides have been postulated on several occasions[2,3, 10,20]) and the fact that the molecular sieve, used during the preparative work, is not as effective a dehydrating agent as triethyl orthoformate or 2,2dimethoxy* propane, it is not surprising that metal complexes showing differing stoichiometries and ligand bonding sites (vide infra) were isolated during this work. I R spectra. N-phzO exhibits the following IR spectrum (4000-33cm-~)[12]: 3167w, 3092w, 1971w, 1924w, 1840w, 1815w, 1726w, 1620w, 1554w, 1532w, 1505m, 1463m, 1422m, 1406s, 1369w, 1349s, 1257m, 1240w, sh, l171w, 1156m, ll19s, l102s, sh, 1007m, 961m, 938w, 889w, 870m, 856m, 827w, sh, 780s, sh, 759s, b, 647 s, 634 s, 615 s, 572 m, 549 m, 402 m, 360 m, 311 m, 247 m, b, 178 w, 117 w, b. Comparisons of this spectrum with those of phenazine (phz) and phenazine 5,10-dioxide (N,N-phzO0123] have been used, in order to make uN~ and 6N_,, assignments for N-phzO. The bands at 1349 and 1257cm ' have UN_o characteristics (this mode was assigned at 1257 cm ' in the spectrum of N,N-phzO2123]), while 8N o is probably associated with the absorptions at JIN( VOI ~9 NO : - (
1139
870 and 856cm-'. The IR spectra of the new metal complexes are generally characterized by splittings of both the 1349 and 1257cm 1 bands into'several components, located at both higher and lower wavenumbers relative to the above free ligand absorptions (Table 2). This evidence suggests the presence of both N- and O-bonded N-phzO in all of the new complexes [2--4,9, 10]. Small changes are observed in the 8N o region, upon metal complex formation. In the uo. region, the Cr(llI) and Zn(II) complexes exhibit relatively sharp maxima at ca. 3400 cm t, indicative of the presence of aquo ligands [24]. The spectrum of the Cr(III) Complex is also characterized by a weaker very broad absorption, suggestive of several maxima at 3500-3200 cm '; the rest of the hydrated metal complexes, with the exception of the Zn(II) compound, are also characterized by similar very broad Vo. bands, which are most probably due to water of crystallization (lattice water)[25]. Treatment of the hydrated new complexes under reduced pressure (60 mm Hg) at 65°C for 24hr, leads to the disappearance of the broad vo. absorption at 3500-3200cm-'; thus, the Mn(II), Fe(IlI), Co(II) and olive-green Cu(II) complexes are completely dehydrated by this treatment. However, the coordinated water remains unaffected, under these conditions, as shown by the fact that the sharper vo, band at ca. 3400cm-' does not disappear from the spectra of the Cr(III) or Zn(II) complexes, after such treatment. Unfortunately the products of dehydration of the new complexes are viscous oily materials, unsuitable for meaningful characterization work. Tentative metal-ligand band assignments in the lower frequency IR region (Table 2) were based on previous assignments for 3d metal complexes with N-pyzO and N-qxO[ 2--4, 10, 11], as well as far-IR spectral assignments for transition metal complexes with aromatic amine N-oxides and related ligands [26-30], aromatic diazines[21, 22] and various 3d metal chloride[21,22, 2835] and aquo[25] complexes. The following assignments were made (cm-~): vcr_o(aquo)499,493, vcr_o(N-phzO)398, /dCr_CI 331,326,320, VCr_N297; VM.~(N-phzO) 348,318, VMn-Cl 226,184, VU°_~268,240; VF~-O (N-phzO) 396,385,362, v,:~cJ 328,245, V~-N 311,304; uc~_o(N-phzO) 403,353, v,:,, ~, 345, Vco_N262,225; brown Cu(II) complex: uc,_o(N-phzO) 404, vco_c~351,347, UCu-N306,263: olive-green Cu(II) complex: Vc,_o(N-phzO) 368,350, vc. c~ 267, vc,_, 277; uz,,_o (aquo) 478,451, Vz,_o (N-phzO) 344, Vz,_(:, 304,287, Vz° N 249. These assignments point to hexacoordinated configurations for the Cr(IlI) and Fe(lll) complexes [25, 27, 29, 32-34]. The M(II) chloride complexes appear to involve, in most cases, coordination numbers lower than six[21, 22, 25-28, 30-35]. Thus, for instance, with the exception of the Mn(II) complex, the vM(,~_o(N-phzO) modes occur at wavenumbers significantly higher than those reported for this vibration in hexacoordinated divalent 3d metal complexes with aromatic amine N-oxides[26,27]. The Vu(u~_×(X=C1 or N) vibrations also appear at higher wavenumbers than those corresponding to octahedral 3d metal chloride complexes with amine ligands[21, 22, 30-35]. Onthe basis of the overall metal-ligand stretching mode assignments, the Co(II) and the brown Cu(II) complexes seem to be tetracoordinated[27, 28, 32-35] and the Zn(II) and olive-green Cu(II) complexes pentacoordinated[25, 27, 31, 35]. In the spectrum of the Mn(lI) complex, the vx~...... vM,_c,and VM, N modes appear as doublets; the lower frequency component of each of these doublets is in the region corresponding to hexacoordinated Mn(II)[21,26],
1140
D.E. CHASAN et al.
whilst the higher frequency components point to pentacoordinated Mn(II)[2, 3, 27, 31, 35]. In view of the obviously polynuclear nature of this complex (2:3 ligand-metal ratio), it is not inconceivable that it might comprise both penta- and hexa-coordinated Mn(II). The vM_s assignments for the new complexes, in combination with their likely coordination numbers, suggest the presence of bridging ligand groups for the complexes exhibiting this mode at relatively high wavenumbers (Cr(III), Mn(II), Fe(III), Cu(II) complexes), and terminal N-bonded N-phzO for the Co(II) and Zn(II) compounds, which show vu_s at relatively low frequencies[21]. The Fe(III) complex seems to contain both terminal and bridging chloro ligands, as evidenced by the presence of Fe-C1 stretching modes at two widely differing frequency regions (the terminal chloro ligands correspond to higher frequency vM-obands than those of the bridging chloro ligands[28, 32, 33, 35], in contrast to the frequencies of vu_s corresponding to terminal and bridging diazine-type ligands, for which the reverse is true[21]). The Mn(II) complex seems to involve exclusively bridging chloro ligands and the rest of the new complexes ordyterminal Clgroups[21, 22, 28]. Finally, the ligand bands at 313 and 247, and at 178cm-j are apparently metal-sensitive (Table 2). These absorptions are most probably due to the/3s-o and 3,s_o[10,36] modes of N-phzO, respectively. Electronic spectra and magnetic properties. The Cr(III), Mn(II), Fe(III) and Co(II) complexes are magnetically normal high-spin compounds of these metal ions [37] (Table 3), but the two Cu(II) complexes are magnetically subnormal (Tables 3, 4). Bi- or poly-nuclear CuC12 complexes with aromatic amine N-oxides, characterized cu/O\cu by the presence of \O / bridges, are almost invariably magnetically subnormal, owing to spin-spin coupling, occurring by a magnetic superexchange mechanism, operating through the orbitals of the bridging oxygen atoms[38-40]. Cu(II) halide complexes of this type with pyridine- and quinoline-N-oxides show relatively large /zen decrease (by 0.5-1.0/zB), when the temperature is lowered from ambient to 80-150°K[39]. However, in the case of CuLBr2 (L=2,2'-bipyridine N,N'-dioxide; N,N-bipyO2), which involves a bidentate aromatic amine oxide ligand, p,on decreases by only 0.26/~B in the 309-102°K temperature range[40]. The new Cu(II) complexes, which also involve the potentially bidentate N-phzO ligand, behave in a similar manner as Cu(N,N-bipyO~)Br2, during temperature-variation magnetic studies, as shown in Table 4, (i.e./~on decreases as follows: brown complex, 0.18/zB from ambient ternperature to 81°K; olive-green complex, 0.10/zB from ambient temperature to 143°K). These data are clearly suggestive of the presence of CuO2Cu bridges in the new Cu(II) complexes. It should be noted that during the/zen calculations (Tables 3, 4), Pascal's constants were used for making diamagnetic corrections, whilst the temperature independent paramagnetic contribution for Cu(II) was assumed to be 60 x 10-6 cgs units, The UV-visible spectrum of N-phzO shows several maxima ( I r ~ r * and n--}~r* transitions) in the 200425nm region[41,42] (Table 3). The ligand bands at 200-382 nm undergo shifts and splittings in the spectra of the new metal complexes, but those at 401-424 nm appear to be insensitive to metal complex formation. Metalligand charge-transfer bands, which are common in 3d
metal complexes with aromatic diazines[20] and aromatic amine-and diazine-N-oxides[2-4, 43], are also present in the spectra of the new complexes. Some of the higher energy (d-d) transitions (e.g. the 4A2~(F)~4T~(F) transition of the Cr(III) compound) are masked by the visible ligand and charge-transfer bands. The Cr(III) complex shows a split 4A28(F)~4T2~(F) transition (602, 643, 680 nm), suggestive of a low-symmetry hexacoordinatedconfiguration[44].TheCo(II)complexgives a (d-d) band spectrum, which may be interpreted in terms of a pseudotetrahedral configuration[45]; the tze~ of this complex (4.69/zB) is also within the "tetrahedral" region for Co2+[37]. The (d-d) transition spectra of the two Cu(II) complexes show significant differences. Thus, the spectrum of the brown complex is much simpler than that of the olive-green compound. These spectra are consistent with a square-planar ligand environment for the former complex and a pentacoordinated configuration for the latter[46], as is also suggested by the metal-ligand IR band assignments. Likely structures for the new metal complexes. Each new complex contains N-phzO coordinated in one or more of the following manners, as suggested by the evidence discussedintheprecedingsections: (i) unidentate, N-bonded, terminal (designated as LN); (ii) unidentate, O-bonded, terminal (~); (iii) O-bonded, bridging (Lo(b)); and (iv) bidentate, bridging, O,N-bonded (sLo). Although the evidence presented is by no means sufficient to lead to unambiguous structural assignments, a tentative discussion of likely structures is considered to be in order. The types [Co(Ls)o(L0)3_nCI]CI and [Zn(L~)(Lo)C!2(OH2)], involving tetrahedral Co2+ and pentacoordinated Zn2+ seem to be the most compatible with the overall evidence. Although CoL3X2 (X =C1, Br) complexes with pyridine N-oxides are usually of the type [CoL6][CoCL][47], the electronic spectrum of the new Co(II) complex rules out the presence of the [CoC14]2anion[45,48]; furthermore, the spectrum of the new complex shows the (d-d) transition bands in the same regions as several [CoL3X]+ or [CoL2X2] (X=CI, Br, I, NCS; L = N- or P-oxide) pseudotetrahedral complexes reported[30, 49]. Elucidation of the rest of the new complexes is more difficult; in fact, these compounds appear to be bior poly-nuclear, involving bridging N-phzO and]or C1 ligands. A likely structure for the Cr(III) complex is [CI3(OH2)2CrNLo(C13)Cr(OH2)NLoCr(OH2)ECI3].13H20. For the Fe(III) and Mn(II) complexes, which also seem to comprise exclusively bridging, N,O-bonded N-phzO, structures (II) and (III) below (respectively) are consistent with the evidence presented. It should be mentioned that only single bridges (M--sLo-M) are considered as likely, since the presence of double bridges (M-(NLo)2-M) would result in severe steric interactions between the two bridging ligand groups [2--4, 10]. Finally, the two Cu(II) complexes undoubtedly contain Cu(Lo(b))2Cu bridges, in view of their magnetic behavior. Moreover, at least part of the N-phzO ligands in these complexes are also coordinated through nitrogen. Hence, structures (IV) and (V) seem most likely for the olive-green and brown Cu(II) complexes, respectively. As a final comment, it should be stressed that the isolation of some apparently monomeric and some polynuclear complexes of N-phzO with first row transition metal chlorides, is not unusual in metal complexes with p-diazines and derivatives[2, 3, 9, 10, 20-22]. For
Transition metal chloride complexes with phenazine 5-oxide[I]
l
l
NLo
NLo
c,~ I / c ~
~mn mn / I ~ C I ~ I ~C[ / NLo NLo
NLo NLO CI I C[\ l .CI ~Fe / ~.Fe /
CI/ I ~CI/
~Cu Cu I C I / I ~Lo(b) / [ ~ CI[ NL 0 NL0
I /C[~ ~ Mn I ~ C I / I MnX C I /
.2nil20
nHzO
CI~.I /Lo(b)~l /CI[ .Cu
NLo
NLo
CI/
I~I /C'~In/Ci~ L/'v'n~cl / ~CI / n/2
[ ~CI n/4
(IZ)
~Lo(b) /
(ZZZ) I
/
L
/
Cl
Cu
4H20 I
~C~
(ZV)
Cl Cl \ / a/ /Cu~ J /Cu~ L C~ + N L o (b)o(b)LN--CU--NLo(b)-o(b) N-- UJl--
I
CI \
/CI~
/ko(b)~
Cl~
I~ [ / C l ~
I /c~
CI/ Fe I ~ C I / #e~c
1141
";Cu/
/ CI
\
CI
.ct
I
a
~',Cu/
/ CI
\
CI
II
c~/ J
IV) instance, earlier work with pyrazines, established that, even with halides of the same metal ion (e.g. Co s÷ or Ni2+), complexes with a wide variety of ligand to metal
ratios (from 5:1 to 1:1) can be produced; in addition, the structural types of these complexes include monomers and
ligand-
and
halo-bridged
dimers
and
polymers [20, 22]. Similar trends have been observed by these and other laboratories, in 3d metal complexes with the N-oxides of pyrazine and quinoxaline[2-5, 7, 9--11]. REFERENCES 1. D. E. Chasan, L. L. Pytlewski, C, Owens and N . M . Karayannis, Abstracts, the 170th National Meeting, Am. Chem. Soc., Chicago, Illinois, August 24-29, 1975; No. INOR 185: taken in part from the Ph.D. Thesis of D. E. Chasan, Department of Chemistry, Drexel University (1974). 2. A. N. Speca, L. L. Pytlewski and N. M. Karayannis, J. Inorg. Nuel. Chem. 35, 4029 (1973). 3. A. N. Speca, N. M. Karayannis and L L. Pytlewski, J. Inorg. Nucl. Chem. 35, 3113 (19731. 4. A. N. Speca, N. M. Karayannis, L. L. Pytlewski and C. Owens, J. Inorg. Nucl. Chem. 38, 91 (1976). 5. G. Vicentini and L. B. Zinner, lnorg. Nuel. Chem. Lett., 1O, 629 (1974); L. B. Zinner and G. Vicentini, J. Inorg. Nuel. Chem. 37, 1999 (1975). 6. M. A. Blesa and H. Taube, lnorg. Chem., 15, 1454 (1976). 7. P. J. Huffman and J. E. House, Jr., J. Inorg. Nuel. Chem. 36, 2618 (19741. 8. D. E. Chasan, L. L. Pytlewski, R. O. Hutchins, N . M . Karayannis and C. Owens, Inorg. Nucl. Chem. Lett. 11, 41 (1975). 9. D. E. Chasan, C. Owens, N. M. Karayannis and L . L . Pytlewski, J. lnorg. Nucl. Chem. 39, 585 (19771. 10. D. E. Chasan, L. L. Pytlewski, C. Owens and N . M . Karayannis, J. lnorg. NucL Chem. 38, 1799 (19761. 11. Y. Kidani, K. Ohira and H. Koike, Nippon Kagaku Kaishi 690 (1974). 12. D. E. Chasan, L. L. Pytlewski, C. Owens and N . M . Karayannis, Ann. Chim. (Paris) 1, 241 (1976). 13. A. Wohl and W. Aue, Ber. Deutsch. Chem. Ges. 34, 2442 (1901). 14. E. C. Soule, U.S. Patent, 2,332,179, Oct. 19 (19431. 15. P. W. N. M. van Leeuwen and W. L. Groeneveld, 1norg. Nucl. Chem. Lett. 3, 145 (19671. 16. K. Starke, J. lnorg. Nuel. Chem. 11, 77 (1959). 17. J. C. Donini, B. R. Hollebone, R. A. Koehler and A. B.P. Lever, J. Phys., E, 5, 385 (1972). 18. A. R. Katritzky and F. J. Swinbourne, J. Chem. Soc. 6707 (1965).
19. N. Kulevsky and R. G. Severson, Jr., Jr.Phys. Chem. 75, 2504 (19711. 20. A. B. P. Lever, J. Lewis and R. S. Nyholm, Nature 189, 58 (19611; J. Chem. Soc. 1235 (19621; 3156, 5042 (1%31: 1187,
4761 (1%41. 21. M. Goldstein, F. B. Taylor and W. D. Unsworth, J. Chem. Soc. (Dalton Trans.) 418 (1972); M. Goldstein. J. lnorg. Nucl. Chem. 37, 567 (19751.
22. J. R. Ferraro, J. Zipper and W. Wozniak, Appl. Spectroscopy 23, 160 (1%9). 23. T. J. Durnick and S. C. Wait, Jr., J. Mol. Spectroscopy 42, 211 (19721. 24. I. Gamo, Bull. Chem. Sot:. Japan 34, 7611 (1%1): 1. Nakagawa and T. Shimanouchi, Spectrochim. Acta 20, 429 (1964); A. N. Speca, L. S. Gelfand, L. L. Pytlewski, C. Owens and N. M. Karayannis, Inorg. Chem. 15, 1493 11976). 25. M. Hass and G. B. B. M Sutherland, Proc. Roy. Soc. 236A, 427 (19561; M. Atoji and R. E. Rundle, J. Chem. Phys. 29, 1306 (1958). 26. A. D. van Ingen Schenau, W. L. Groeneveld and J. Reedijk, Spectrochim. Acta 30A, 213 (1974). 27. N. M. Karayannis, C. M. Mikulski, M. J. Strocko. L. L. Pytlewski and M. M. Labes, J. lnorg. NucL Chem. 33. 2691, 3185 (19711; lnorg. Chim. Acta 8, 91 (19741. 28. R. Whyman and W. E. Hatfield, Inorg. Chem. 6, 1859 11967). 29. A. Vinciguerra, P. G. Simpson, Y. Kakiuti and J. V. Quagliano, lnorg. Chem. 2, 286 (1963); S. A. Cotton and J. F. Gibson, J. Chem. Soc. (A), 2105 (1970). 30. A. N. Speca, L. L. Pytlewski and N. M. Karayannis, Z. Anorg. Allg. Chem. 422, 182 (1976); A. N. Speca, N. M. Karayannis and L. L. Pytlewski, lnorg. Chim. Acta 17. 29 (1976). 31. D. Bryson and R. H. Nuttall, Spectrochim. Acta 26A, 2275 (1970); P. Bamfield, R. Price and R. G. J. Miller, J. Chem. Soc. (A), 1447 (1969). 32. R. J. H. Clark and C. S. Williams, lnorg. Chem. 4. 350 (1%51; Spectrochim. Acta 23A, 1055 (19671; R. J. H. Clark, ibid. 21, 955 (1965). 33. J. R. Allkins and P. J. Hendra, J. Chem. Soc. (A), 1325 (1%7); D . M . L . Goodgame, M. Goodgame, P. J. Hayward and G. W. Rayner-Canham, lnorg. Chem. 7, 2447 (1968). 34. C. Postmus, J. R. Ferraro and W. Wozniak, Inorg. Chem. 6, 2030 (19671. 35. R. H. Nuttall, Talanta 15, 157 (1968). 36. S. Ghersetti, S. Giorgianni, M. Minari and G. Spunta, Spectrochim. Acta 31A, 445 (19751. 37. B. N. Figgis and J. Lewis, Prog. Inorg. Chem. 6, 37 (1%4). 38. N. M. Karayannis, L. L. Pytlewski and C. M. Mikulski, Coord. Chem. Rev. 11, 93 (1973); N. M. Karayannis, A. N. Speca, D. E. Chasan and L. L. Pytlewski, ibid. 20, 37 (19761. 39. W. H. Watson, lnorg. Chem. 8, 1879 (19691; S. J. Gruber, C.
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M. Harris, E. Kokot, S. L. Lenzer, T. N. Lockyer and E. Sinn, Aust. J. Chem. 20, 2403 (1%7). E. J. Halbert, C. M. Harris, E. Sinn and G. J. Sutton, Aust. J. Chem. 26, 951 (1973). T. Kubota and H. Miyazaki, Chem. Pharm. Bull. 9, 948 (1%1); Nippon Kagaku Zasshi 79, 924, 930 (1958). R. Kr~issig, D. Bergmann, N. Fliegen, R. Kummer, W, Seiffert and H. Zimmermann, Ber. Bunsenges. Phys. Chem, 74, 617 (1970). W. Byers, B. Fa-Chun Chou, A. B. P. Lever and R.V. Parish, J. Am. Chem. Soc. 91, 1329 (1%9). W. Byers, A. B. P. Lever and R. V. Parish, Inorg. Chem. 7, 1835 (1968).
45. A. B. P. Lever, Inorganic Electronic Spectroscopy, Elsevier, Amsterdam, Netherlands (1%8); B. N. Figgis, Introduction to Ligand Fields, Interscience, New York, U.S.A. (1966), 46. I. M. Procter, B. J. Hathaway and P. Nicholls, J. Chem. Soc. (A), 1678 (1%8); A. A. G. Tomlinson and B. J. Hathaway, Ibid. (A), 1685 (1%8). 47. J. A. Bertrand and D. L. Plymale, Inorg. Chem. 3, 775 (1964). 48. F. A. Cotton, D. M. L. Goodgame and M. Goodgame, J. Am. Chem. Soc. 83, 4690 (1%1). 49. D. W. Herlocker, Inorg. Chim. Acta 6, 211 (1972); M. Goodgame, D. M. L. Goodgame and F. A. Cotton, lnorg. Chem. 1,239 (1%2).
TRANSITION METAL CHLORIDE COMPLEXES WITH PHENAZINE 5-OXIDE[I] DAVID E. CHASAN, LOUIS L. PYTLEWSK1, CLIFFORD OWENSt and NICHOLAS M. KARAYANNIS~: Department of Chemistry, Drexel University, Philadelphia. PA 19104, U.S.A. (Received 21 September 1976)
Abstract--Complex compounds of the types (CrCI3)sL2'I8H20, (MnCI2)3L2'H20, FeCI3L.2H20, CoCI2L3.6H20. (CuCI2)3L2, (CuCID2L3"2H20 and ZnC%L2.H20 with phenazine 5-oxide(L) as ligand were prepared by interaction of predried solutions of L and metal chloride. The new metal complexes were characterized by means of their IR and electronic spectra and magnetic susceptibility measurements. The Cr(III), Mn(II), Fe(IIl) and Cu(II) complexes appear to be polynuclear, comprising bridging L(O- or O,N-bonded) or CI ligands. Both Cu(II) complexes are characterized by subnormal magnetic moments, which were attributed to spin-spin coupling, occurring by a superexchange mechanism, operating through the orbitals of the bridging oxygen atoms (CuO2Cu bridges, involving O-bonded bridging L groups). The Co(II) and Zn(II) complexes are apparently monomeric, involving both N- and O-bonded L ligands.
INTRODUCTION
Synthetic and characterization studies of transition metal chloride [2], perchlorate [3] and nitrate [4] complexes with the mono-N-oxide of pyrazine (N-pyzO) were reported in recent years by these laboratories. This ligand can act either as unidentate, coordinating through the aza-group nitrogen or through the N - O oxygen, or as bidentate, bridging, coordinating through both these sites [2-4]. A number of lanthanide(III)[5], Ru(lI)[6] and Ag(I)[7] complexes with N-pyzO and derivatives have been also reported in the literature. Quite recently, we extended our work to include 3d metal complexes with quinoxaline-loxide(N-qxO) and phenazine-5-oxide (N-phzO)[8]. NqxO complexes with 3d metal chlorides and perchlorates have been reported elsewhere by these[9,10] and o t h e r [ l l ] laboratories. The present paper deals with 3d metal chloride complexes with N-phzO, while the corresponding metal perchlorate complexes are the subject of another publication [ 12]. EXPERIMENTAL N-phzO was prepared by the WOHL-AUE reaction[13], as modified by Soule[14], i.e. by refluxing nitrobenzene, aniline and potassium hydroxide in benzene. Its authenticity was confirmed by elemental analysis and its m.p. (224-225°C)[14]. Reagent grade transition metal chlorides and organic solvents were used throughout this work. Zeolite molecular sieve 4A, grade 515(Davison), was utilized for pre-drying the ligand and salt solutions [8]. As already reported in a preliminary communication [8], use of conventional organic dehydrating agents, such as triethyl orthoformate [15] or 2,2-dimethoxypropane [16], does not facilitate the precipitation of transition metal complexes with N-qxO or N-phzO. This is due to the fact that metal complexes with these ligands dissociate in the presence of several organic solvents, and especially alcohols[I,10], which are produced during the hydrolysis of the above dehydrating agents[15, 16]. It was found that molecular sieve 4A as a drying agent of ligand and salt solutions prior to their interaction, although not as effective as triethyl orthoformate or 2,2-dimethoxypropane, facilitates the tDepartment of Chemistry, Rutgers University, Camden, NJ 08102 U.S.A. :]:Amoco Chemicals Corporation, Naperville, IL 60540, U.S.A.
precipitation of metal complexes containing usually limited amounts of water [8]. If, on the other hand, no drying agent of any kind is used during the preparation of N-qxO or N-phzO complexes, the precipitates obtained are generally very heavily hydrated[8]. The preparation of the new metal complexes was effected as follows: All operations were performed in the dry-box (N2 atmosphere), because of the hygroscopic character of some of the new complexes. 3.5 rumple N-phzO were dissolved in 25 ml chloroform, while l mmole of hydrated metal chloride was separately dissolved in 20°°75mill0] acetone. The ligand and salt solutions were treated separately with molecular sieve 4A and then were allowed to interact, as previously described [8-10]. Precipitation was immediate in the cases of Cr(IIIL Mn(II), Fe(IlI), Co(IlL Cu(II) and Zn(II) chlorides, but Fe(II) and Ni(II) chlorides failed to produce solid complexes by the above or different synthetic procedures. In the case of CuCl~, in addition to the brown (CuCG)3(N-phzO)2 complex obtained by the above method, an olive-green complex of the type (CuCI2)dNphzO)3-2H20 was isolated when ligand and salt solutions were allowed to interact at a I : 1 molar ratio. Variations in the ligand to metal salt ratios in the cases of the rest of the metal chlorides studied, did not lead to the formation of complexes with different stoichiometries than those obtained at the 3.5 : 1 ratio. The new solid complexes were quickly filtered, thoroughly washed with hexane and stored in an evacuated desiccator over phosphorus pentoxide. The Cr(III), Mn(II) and Co(II) complexes are very hygroscopic, while the rest of the new complexes are stable in the atmosphere. All the new complexes dissolve easily in water and several organic solvents (nitromethane, nitrobenzene, dimethyl sulfoxide, N.N-dimethylformamide, acetone, alcohols, etc.). However, their solutions in these media apparently contain dissociation products, as manifested by the fact that they are characterized by the deep yellow color of the free ligand rather than that of the complex; dissociation seems to occur immediately upon contact of the complexes with organic solvents; in fact, as soon as the complex comes in contact with the solvent, the color of the solid changes rapidly to deep yellow. Analytical data (C, H, N determinations by Schwarzkopf Microanalytical Laboratory, Woodside, New York; metal analyses by emission spectroscopy) for the new complexes are given in Table 1. The characterization of the complexes was based on IR (Table 2) and electronic (Table 3) spectra and magnetic susceptibility measurements (Tables 3, 4). Spectral and room temperature magnetic measurements were obtained by methods described elsewhere[3]. Studies of the variation of the magnetic susceptibility of the brown Cu(ll) complex with temperature (80-297°K)
1137
D . E . CHASAN et al.
1138
Table 1. Analytical data for metal chloride complexes with N-phzO(L)
Complex
Color
C(%) Calc. Found
(CrCI~)3L2.18H20 (MnCI2)3L2.H20 FeCI3L'2H20 CoCI2L3'6H20 (CuCI2)3L2 (CuCI2)2L3'2H20 ZnC12L2.H~O
Yellow-gold Yellow-green Orange Olive-green Brown Olive-green Olive-green
24.19 36.58 36.54 52.31 36.22 48.39 52.72
24.42 36.46 36.39 52.61 36.40 47.98 53.23
Analysis H(%) N(%) Calc. Found Calc. Found
Metal(%) Calc. Found
4.41 2.31 3.07 4.40 2.03 3.16 3.33
13.1 20.9 14.2 7.1 24.0 14.2 12.0
4.62 2.59 2.73 4.18 2.27 2.95 3.61
4.70 7.11 7.10 10.17 7.04 9.41 10.25
4.61 7.12 7.17 10.14 7.24 9.12 9.99
13.5 20.7 14.4 6.8 23.7 14.2 12.0
Table 2. Pertinent IR data for N-phzO complexes with 3d metal chlorides (cm-I) Compound
1400-1200 cm-' (~N~ region)
N-phzO=L
1369 w, 1349 s, 1257 m, 1240 w, sh
(CrC13)3L2.18H20
1385 m, sh, 1375 s, 1329 w, sh, 1312w, sh, 1275 m, 1244m 1388 w, 1368 w, 1326 s, 1297 w, 1272m, 1231w 1386 m, 1373 s, 1349 w, 1326 w, 1319w, 1308w, 1275 m, 1242m 1390 m, 1371 w, 1351 w, 1323 s, 1296 w, 1278 w, sh, 1270 m, 1259 w, 1233 w 1384w, 1356 w, 1325 s, 1260 m, 1227 w 1390 w, 1362 s,b, 1341 s, sh, 1302 w, 1289 w, 1266 m, 1240 m, sh 1389 m, 1371 m, 1321 s, 1292 m, 1270 m, 1260 m, sh, 1236 m, 1201 w
(MnC12)3L2'H20 FeC13L.2H20 CoCI2L3"6H20
(CuCI2)3L2 (CuClz)2L3.2H20 ZnCI~L2.H20
900-800 cm-~ (8~_o region) 889w, 870m, 856m, 827 w, sh 883w 870w 881 w, 870 w, 862 w 868 m, 856w, sh
888w, 865 m 888m, 856w 862m
525-33cm-1 (~M~, VM-N,~M~CJ,U,~a,d)t 402m, 360m, 311 m, 247 re,b, 178w, l17w, b 499 w, 493 w, 398 w, 361 w, 331 w, 326 w, 320w, 297 w,b, 226w, 202w, 180w, b 404w, 348m, 318m, 268m, 240m, 226m, 184s, l17m, 111 m,b 396 s, 385 s, 362 s, 328 m, 311 w, 304 w, 245 w,b, 180w, b, 148m 403 m, 360 m, 353 m, 345 m, 262 m, 248 m-w, 225 m, 197 w, 178 w, 143 w, 118 w 490 vw, 404m, 351 w-m, 347 w-m, 306m, 263 m, 249 m-w, 148 m, b 368w, 350w, 277w, sh, 267w, 206 w,b, 133w 478 w, 451 w, 412 w, 406 w, 361 m, sh, 344 s, b, 304 m, 287 m, 249 m-s, 168 m, 156 w, sh, l13m, 101 m, sh
Abbreviations: s, strong; m, medium; w, weak; b, broad; v, very; sh, shoulder. tFor tentative metal-ligand stretching mode assignments see text. Table 3. Electronic spectra (Nujol mulls) and magnetic properties (297°K) of N-phzO complexes with 3d metal chlorides Compound N-phzO=L (CrC13)3L2-18H20 (MnC12)3L2.H~O FeCI3L.2H20 CoCIzL3"6H20
(CuC12)3L~ (CuCI2)2L3'2H20 ZnC12L2'H20
A.... nm
106XMc°r, cgsu
/~en,/~B
229 sh, 264 sh, 273 vs, 365 w, 382 m, 401 m, 420 sh, 424 m 230 sh, 274 vs, 362 sh, 381 s, 401 s, 420 sh, 424 s, 459 m, 500 m, 602 w, 643 w, sh, 680 w, sh 230 s, 262 s, 272 vs, 344 w, 363 sh, 380 s, 401 s, 420 sh, 424 s, 458 w 262 sh, 272 vs, 362 w, 381 m, 401 m, 424 m, 525 b, sh 230 m, 272 vs, 344 w, 364 sh, 381 s, 401 s, 420 sh, 424 s, 451 sh, 482 s, 597 m, 608 m, 624 m, 670 m, b, 690 m, sh, 940 w, sh, 1005 w, sh, 1100 w, sh, 1325 w, sh, 1470 w, sh 262 sh, 272 vs, 361 sh, 381 m, 401 m, 420 sh, 424 m, 470 m, b, sh, 545 m-w, sh, 785 w, b, 1060 w, sh 263 vs, 275 vs, 362 w, 381 m, 401 s, 420 s, sh, 425 s, 475 m, b, 555 m, b, 600 w, sh, 700 w, sh, 835 w, 1150 w, sh 230 s, 264 sh, 274 vs, 363 sh, 380 s, 401 s, 420 sh, 424 s
-5,789
-3.72
14,692 15,770 9,090
5.93 6.15 4.69
845
1.42
678
1.27
Diamagnetic
Abbreviations: s, strong; m, medium; w, weak; b, broad; v, very; sh, shoulder. were performed by Prof. A. B. P. Lever's laboratory (York University, Toronto, Ontario, Canada), by using apparatus and technique described in the literature[17]. Similar studies, covering a narrower temperature range (143-297°K), on the olive-green Cu(II) complex were performed at these laboratories, by using a Cahn Magnetic Susceptibility System No. 7600 (Table 4). Solution electronic spectral and electrolytic conductance studies were not attempted, in view of the instability of all the new complexes in the presence of suitable solvents, RESULTS AND DISCUSSION
Stoicheiometries o1: the new metal complexes. As was also the case with N-pyzO[3] and N-qxO[10] 3d metal
chloride complexes, the new N-phzO complexes show a wide variability of stoichiometries, with variation of metal ion (Table 1). It appears that with N-pyzO and derivatives there is no definite preference for coordination through the N - O oxygen or the aza-nitrogen, when these compounds function as unidentate ligands towards 3d metal ions[2--4, 10]. If electronic factors alone were determining the bonding site of unidentate ligands of this type, it might be anticipated that coordination would occur through the aza-nitrogen, which is the stronger donor site[18]. However, steric factors are also important in the case of interaction of these ligands with large
Transition metal chloride complexes with phenazine 5-oxide[I] Table4. Variations of the magnetic susceptibilitiesof CuCI2-NphzO complexes with temperature Complext
T, °K
(CuCL)~I.,
297.2 278.9 259.9 241.8 223.2 204.7 187.6 169.4 151.7 134.2 116.9 99.7 80.9 297.0 203.0 177.11 159.0 143.0
(CuCI,Ld~.2H20
106XM c'r, cgsu ~o,,~B 845 895 944 1011 1076 1160 1261 1378 1511 1660 1841 2072 2365 678 913 1002 1104 1185
1.42 1.41 1.41 1.40 1.39 1.38 1.38 1.37 1.36 1.34 1.32 1.29 1.24 1.27 1.22 1.20 1.19 1.17
+L = N-phzO. acceptor molecules, such as iodine[19], or sterically crowded metalions, as in the present case, which involves the presence of additional potentialligands (chloride ions and water molecules). Under these conditions, the oxygen site of N-phzO(I) might become more accessible for coordination than the aza-nitrogen site, whose coordination would be hindered by steric repulsions between the CH groups at the 1- and 9-ring positions and the ~
,
~
O (r) crowded acceptor atom[10, 19]. In view of the above considerations, the tendency of 1,4-diazines[20-22] and their N-oxides[2--4, 10] to function either as terminal unidentate or as bridging bidentate ligands (complexes comprising both terminal and bridging diazines or diazine N-oxides have been postulated on several occasions[2,3, 10,20]) and the fact that the molecular sieve, used during the preparative work, is not as effective a dehydrating agent as triethyl orthoformate or 2,2dimethoxy* propane, it is not surprising that metal complexes showing differing stoichiometries and ligand bonding sites (vide infra) were isolated during this work. I R spectra. N-phzO exhibits the following IR spectrum (4000-33cm-~)[12]: 3167w, 3092w, 1971w, 1924w, 1840w, 1815w, 1726w, 1620w, 1554w, 1532w, 1505m, 1463m, 1422m, 1406s, 1369w, 1349s, 1257m, 1240w, sh, l171w, 1156m, ll19s, l102s, sh, 1007m, 961m, 938w, 889w, 870m, 856m, 827w, sh, 780s, sh, 759s, b, 647 s, 634 s, 615 s, 572 m, 549 m, 402 m, 360 m, 311 m, 247 m, b, 178 w, 117 w, b. Comparisons of this spectrum with those of phenazine (phz) and phenazine 5,10-dioxide (N,N-phzO0123] have been used, in order to make uN~ and 6N_,, assignments for N-phzO. The bands at 1349 and 1257cm ' have UN_o characteristics (this mode was assigned at 1257 cm ' in the spectrum of N,N-phzO2123]), while 8N o is probably associated with the absorptions at JIN( VOI ~9 NO : - (
1139
870 and 856cm-'. The IR spectra of the new metal complexes are generally characterized by splittings of both the 1349 and 1257cm 1 bands into'several components, located at both higher and lower wavenumbers relative to the above free ligand absorptions (Table 2). This evidence suggests the presence of both N- and O-bonded N-phzO in all of the new complexes [2--4,9, 10]. Small changes are observed in the 8N o region, upon metal complex formation. In the uo. region, the Cr(llI) and Zn(II) complexes exhibit relatively sharp maxima at ca. 3400 cm t, indicative of the presence of aquo ligands [24]. The spectrum of the Cr(III) Complex is also characterized by a weaker very broad absorption, suggestive of several maxima at 3500-3200 cm '; the rest of the hydrated metal complexes, with the exception of the Zn(II) compound, are also characterized by similar very broad Vo. bands, which are most probably due to water of crystallization (lattice water)[25]. Treatment of the hydrated new complexes under reduced pressure (60 mm Hg) at 65°C for 24hr, leads to the disappearance of the broad vo. absorption at 3500-3200cm-'; thus, the Mn(II), Fe(IlI), Co(II) and olive-green Cu(II) complexes are completely dehydrated by this treatment. However, the coordinated water remains unaffected, under these conditions, as shown by the fact that the sharper vo, band at ca. 3400cm-' does not disappear from the spectra of the Cr(III) or Zn(II) complexes, after such treatment. Unfortunately the products of dehydration of the new complexes are viscous oily materials, unsuitable for meaningful characterization work. Tentative metal-ligand band assignments in the lower frequency IR region (Table 2) were based on previous assignments for 3d metal complexes with N-pyzO and N-qxO[ 2--4, 10, 11], as well as far-IR spectral assignments for transition metal complexes with aromatic amine N-oxides and related ligands [26-30], aromatic diazines[21, 22] and various 3d metal chloride[21,22, 2835] and aquo[25] complexes. The following assignments were made (cm-~): vcr_o(aquo)499,493, vcr_o(N-phzO)398, /dCr_CI 331,326,320, VCr_N297; VM.~(N-phzO) 348,318, VMn-Cl 226,184, VU°_~268,240; VF~-O (N-phzO) 396,385,362, v,:~cJ 328,245, V~-N 311,304; uc~_o(N-phzO) 403,353, v,:,, ~, 345, Vco_N262,225; brown Cu(II) complex: uc,_o(N-phzO) 404, vco_c~351,347, UCu-N306,263: olive-green Cu(II) complex: Vc,_o(N-phzO) 368,350, vc. c~ 267, vc,_, 277; uz,,_o (aquo) 478,451, Vz,_o (N-phzO) 344, Vz,_(:, 304,287, Vz° N 249. These assignments point to hexacoordinated configurations for the Cr(IlI) and Fe(lll) complexes [25, 27, 29, 32-34]. The M(II) chloride complexes appear to involve, in most cases, coordination numbers lower than six[21, 22, 25-28, 30-35]. Thus, for instance, with the exception of the Mn(II) complex, the vM(,~_o(N-phzO) modes occur at wavenumbers significantly higher than those reported for this vibration in hexacoordinated divalent 3d metal complexes with aromatic amine N-oxides[26,27]. The Vu(u~_×(X=C1 or N) vibrations also appear at higher wavenumbers than those corresponding to octahedral 3d metal chloride complexes with amine ligands[21, 22, 30-35]. Onthe basis of the overall metal-ligand stretching mode assignments, the Co(II) and the brown Cu(II) complexes seem to be tetracoordinated[27, 28, 32-35] and the Zn(II) and olive-green Cu(II) complexes pentacoordinated[25, 27, 31, 35]. In the spectrum of the Mn(lI) complex, the vx~...... vM,_c,and VM, N modes appear as doublets; the lower frequency component of each of these doublets is in the region corresponding to hexacoordinated Mn(II)[21,26],
1140
D.E. CHASAN et al.
whilst the higher frequency components point to pentacoordinated Mn(II)[2, 3, 27, 31, 35]. In view of the obviously polynuclear nature of this complex (2:3 ligand-metal ratio), it is not inconceivable that it might comprise both penta- and hexa-coordinated Mn(II). The vM_s assignments for the new complexes, in combination with their likely coordination numbers, suggest the presence of bridging ligand groups for the complexes exhibiting this mode at relatively high wavenumbers (Cr(III), Mn(II), Fe(III), Cu(II) complexes), and terminal N-bonded N-phzO for the Co(II) and Zn(II) compounds, which show vu_s at relatively low frequencies[21]. The Fe(III) complex seems to contain both terminal and bridging chloro ligands, as evidenced by the presence of Fe-C1 stretching modes at two widely differing frequency regions (the terminal chloro ligands correspond to higher frequency vM-obands than those of the bridging chloro ligands[28, 32, 33, 35], in contrast to the frequencies of vu_s corresponding to terminal and bridging diazine-type ligands, for which the reverse is true[21]). The Mn(II) complex seems to involve exclusively bridging chloro ligands and the rest of the new complexes ordyterminal Clgroups[21, 22, 28]. Finally, the ligand bands at 313 and 247, and at 178cm-j are apparently metal-sensitive (Table 2). These absorptions are most probably due to the/3s-o and 3,s_o[10,36] modes of N-phzO, respectively. Electronic spectra and magnetic properties. The Cr(III), Mn(II), Fe(III) and Co(II) complexes are magnetically normal high-spin compounds of these metal ions [37] (Table 3), but the two Cu(II) complexes are magnetically subnormal (Tables 3, 4). Bi- or poly-nuclear CuC12 complexes with aromatic amine N-oxides, characterized cu/O\cu by the presence of \O / bridges, are almost invariably magnetically subnormal, owing to spin-spin coupling, occurring by a magnetic superexchange mechanism, operating through the orbitals of the bridging oxygen atoms[38-40]. Cu(II) halide complexes of this type with pyridine- and quinoline-N-oxides show relatively large /zen decrease (by 0.5-1.0/zB), when the temperature is lowered from ambient to 80-150°K[39]. However, in the case of CuLBr2 (L=2,2'-bipyridine N,N'-dioxide; N,N-bipyO2), which involves a bidentate aromatic amine oxide ligand, p,on decreases by only 0.26/~B in the 309-102°K temperature range[40]. The new Cu(II) complexes, which also involve the potentially bidentate N-phzO ligand, behave in a similar manner as Cu(N,N-bipyO~)Br2, during temperature-variation magnetic studies, as shown in Table 4, (i.e./~on decreases as follows: brown complex, 0.18/zB from ambient ternperature to 81°K; olive-green complex, 0.10/zB from ambient temperature to 143°K). These data are clearly suggestive of the presence of CuO2Cu bridges in the new Cu(II) complexes. It should be noted that during the/zen calculations (Tables 3, 4), Pascal's constants were used for making diamagnetic corrections, whilst the temperature independent paramagnetic contribution for Cu(II) was assumed to be 60 x 10-6 cgs units, The UV-visible spectrum of N-phzO shows several maxima ( I r ~ r * and n--}~r* transitions) in the 200425nm region[41,42] (Table 3). The ligand bands at 200-382 nm undergo shifts and splittings in the spectra of the new metal complexes, but those at 401-424 nm appear to be insensitive to metal complex formation. Metalligand charge-transfer bands, which are common in 3d
metal complexes with aromatic diazines[20] and aromatic amine-and diazine-N-oxides[2-4, 43], are also present in the spectra of the new complexes. Some of the higher energy (d-d) transitions (e.g. the 4A2~(F)~4T~(F) transition of the Cr(III) compound) are masked by the visible ligand and charge-transfer bands. The Cr(III) complex shows a split 4A28(F)~4T2~(F) transition (602, 643, 680 nm), suggestive of a low-symmetry hexacoordinatedconfiguration[44].TheCo(II)complexgives a (d-d) band spectrum, which may be interpreted in terms of a pseudotetrahedral configuration[45]; the tze~ of this complex (4.69/zB) is also within the "tetrahedral" region for Co2+[37]. The (d-d) transition spectra of the two Cu(II) complexes show significant differences. Thus, the spectrum of the brown complex is much simpler than that of the olive-green compound. These spectra are consistent with a square-planar ligand environment for the former complex and a pentacoordinated configuration for the latter[46], as is also suggested by the metal-ligand IR band assignments. Likely structures for the new metal complexes. Each new complex contains N-phzO coordinated in one or more of the following manners, as suggested by the evidence discussedintheprecedingsections: (i) unidentate, N-bonded, terminal (designated as LN); (ii) unidentate, O-bonded, terminal (~); (iii) O-bonded, bridging (Lo(b)); and (iv) bidentate, bridging, O,N-bonded (sLo). Although the evidence presented is by no means sufficient to lead to unambiguous structural assignments, a tentative discussion of likely structures is considered to be in order. The types [Co(Ls)o(L0)3_nCI]CI and [Zn(L~)(Lo)C!2(OH2)], involving tetrahedral Co2+ and pentacoordinated Zn2+ seem to be the most compatible with the overall evidence. Although CoL3X2 (X =C1, Br) complexes with pyridine N-oxides are usually of the type [CoL6][CoCL][47], the electronic spectrum of the new Co(II) complex rules out the presence of the [CoC14]2anion[45,48]; furthermore, the spectrum of the new complex shows the (d-d) transition bands in the same regions as several [CoL3X]+ or [CoL2X2] (X=CI, Br, I, NCS; L = N- or P-oxide) pseudotetrahedral complexes reported[30, 49]. Elucidation of the rest of the new complexes is more difficult; in fact, these compounds appear to be bior poly-nuclear, involving bridging N-phzO and]or C1 ligands. A likely structure for the Cr(III) complex is [CI3(OH2)2CrNLo(C13)Cr(OH2)NLoCr(OH2)ECI3].13H20. For the Fe(III) and Mn(II) complexes, which also seem to comprise exclusively bridging, N,O-bonded N-phzO, structures (II) and (III) below (respectively) are consistent with the evidence presented. It should be mentioned that only single bridges (M--sLo-M) are considered as likely, since the presence of double bridges (M-(NLo)2-M) would result in severe steric interactions between the two bridging ligand groups [2--4, 10]. Finally, the two Cu(II) complexes undoubtedly contain Cu(Lo(b))2Cu bridges, in view of their magnetic behavior. Moreover, at least part of the N-phzO ligands in these complexes are also coordinated through nitrogen. Hence, structures (IV) and (V) seem most likely for the olive-green and brown Cu(II) complexes, respectively. As a final comment, it should be stressed that the isolation of some apparently monomeric and some polynuclear complexes of N-phzO with first row transition metal chlorides, is not unusual in metal complexes with p-diazines and derivatives[2, 3, 9, 10, 20-22]. For
Transition metal chloride complexes with phenazine 5-oxide[I]
l
l
NLo
NLo
c,~ I / c ~
~mn mn / I ~ C I ~ I ~C[ / NLo NLo
NLo NLO CI I C[\ l .CI ~Fe / ~.Fe /
CI/ I ~CI/
~Cu Cu I C I / I ~Lo(b) / [ ~ CI[ NL 0 NL0
I /C[~ ~ Mn I ~ C I / I MnX C I /
.2nil20
nHzO
CI~.I /Lo(b)~l /CI[ .Cu
NLo
NLo
CI/
I~I /C'~In/Ci~ L/'v'n~cl / ~CI / n/2
[ ~CI n/4
(IZ)
~Lo(b) /
(ZZZ) I
/
L
/
Cl
Cu
4H20 I
~C~
(ZV)
Cl Cl \ / a/ /Cu~ J /Cu~ L C~ + N L o (b)o(b)LN--CU--NLo(b)-o(b) N-- UJl--
I
CI \
/CI~
/ko(b)~
Cl~
I~ [ / C l ~
I /c~
CI/ Fe I ~ C I / #e~c
1141
";Cu/
/ CI
\
CI
.ct
I
a
~',Cu/
/ CI
\
CI
II
c~/ J
IV) instance, earlier work with pyrazines, established that, even with halides of the same metal ion (e.g. Co s÷ or Ni2+), complexes with a wide variety of ligand to metal
ratios (from 5:1 to 1:1) can be produced; in addition, the structural types of these complexes include monomers and
ligand-
and
halo-bridged
dimers
and
polymers [20, 22]. Similar trends have been observed by these and other laboratories, in 3d metal complexes with the N-oxides of pyrazine and quinoxaline[2-5, 7, 9--11]. REFERENCES 1. D. E. Chasan, L. L. Pytlewski, C, Owens and N . M . Karayannis, Abstracts, the 170th National Meeting, Am. Chem. Soc., Chicago, Illinois, August 24-29, 1975; No. INOR 185: taken in part from the Ph.D. Thesis of D. E. Chasan, Department of Chemistry, Drexel University (1974). 2. A. N. Speca, L. L. Pytlewski and N. M. Karayannis, J. Inorg. Nuel. Chem. 35, 4029 (1973). 3. A. N. Speca, N. M. Karayannis and L L. Pytlewski, J. Inorg. Nucl. Chem. 35, 3113 (19731. 4. A. N. Speca, N. M. Karayannis, L. L. Pytlewski and C. Owens, J. Inorg. Nucl. Chem. 38, 91 (1976). 5. G. Vicentini and L. B. Zinner, lnorg. Nuel. Chem. Lett., 1O, 629 (1974); L. B. Zinner and G. Vicentini, J. Inorg. Nuel. Chem. 37, 1999 (1975). 6. M. A. Blesa and H. Taube, lnorg. Chem., 15, 1454 (1976). 7. P. J. Huffman and J. E. House, Jr., J. Inorg. Nuel. Chem. 36, 2618 (19741. 8. D. E. Chasan, L. L. Pytlewski, R. O. Hutchins, N . M . Karayannis and C. Owens, Inorg. Nucl. Chem. Lett. 11, 41 (1975). 9. D. E. Chasan, C. Owens, N. M. Karayannis and L . L . Pytlewski, J. lnorg. Nucl. Chem. 39, 585 (19771. 10. D. E. Chasan, L. L. Pytlewski, C. Owens and N . M . Karayannis, J. lnorg. NucL Chem. 38, 1799 (19761. 11. Y. Kidani, K. Ohira and H. Koike, Nippon Kagaku Kaishi 690 (1974). 12. D. E. Chasan, L. L. Pytlewski, C. Owens and N . M . Karayannis, Ann. Chim. (Paris) 1, 241 (1976). 13. A. Wohl and W. Aue, Ber. Deutsch. Chem. Ges. 34, 2442 (1901). 14. E. C. Soule, U.S. Patent, 2,332,179, Oct. 19 (19431. 15. P. W. N. M. van Leeuwen and W. L. Groeneveld, 1norg. Nucl. Chem. Lett. 3, 145 (19671. 16. K. Starke, J. lnorg. Nuel. Chem. 11, 77 (1959). 17. J. C. Donini, B. R. Hollebone, R. A. Koehler and A. B.P. Lever, J. Phys., E, 5, 385 (1972). 18. A. R. Katritzky and F. J. Swinbourne, J. Chem. Soc. 6707 (1965).
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