Inorg. Chem. 1983, 22, 879-884
879
Contribution from the Institut fur Anorganische Chemie, Technische Hochschule Darmstadt, D-6 100 Darmstadt, FRG, and Abteilung Physiologische Chemie, Rheinisch-Westftilische Technische Hochschule Aachen, D-5 100 Aachen, FRG
Metal Complexes with Tetrapyrrole Ligands. 29.' Synthesis and Electron Spin Resonance Spectra and Electron Nuclear Double Resonance Investigations of Nitridochromium(V) Porphyrins JOHANN W. BUCHLER,*2aCHRISTINE DREHER,2aKIONG-LAM LAY,ZaADRIAAN RAAP,Zb and KLAUS GERSONDE*2b Received May 13, I982
Mononuclear pentacoordinated nitridochromium(V) porphyrins, nitrido(tetra-p-tolylporphinato)chromium(V), CrN(TTP), and nitrido(octaethylporphinato)chromium(V), CrN(OEP), are prepared by hypochlorite oxidation of the corresponding chromium(II1) porphyrins, CrOH(TTP).2Hz0 and CrOH(OEP).'/2H20, in the presence of ammonia. These remarkably stable species are identified by UV/vis, IR, and mass spectra. An investigation of these paramagnetic compounds by ESR and ENDOR spectroscopy has furnished evidence for the Crv(d'/d,) state of the central metal and the coordination of a single axial nitrogen. The X-and Q-band ESR as well as the 14NENDOR spectra are identical for both CrN(TTP) hyperfine splitting and CrN(0EP): At room temperature we find an isotropic signal at go= 1.9825 and an isotropic ao(53Cr)= 2.83 mT. A superhyperfine splitting a(I4N) = 0.27 mT due to five apparently equivalent I4N nuclei is observed. At 77 K an anisotropic ESR signal with g, = 1.9945 and gll = 1.9583 and anisotropic hyperfine values of U , ( ~ ~ C=~ ) 2.24 mT and = 4.01 mT have been determined. 14N ENDOR spectra measured at 3.6 K serve to discern the axial and equatorial superhyperfinesplitting constants: For Npyrrolo all = 0.36, aL2= 0.14, and all = 0.31 mT, and for Naxial,all = 0.37, a12 = 0.34, and all = 0.13 mT. The ESR and ENDOR parameters are characteristic for a d' system with strong spin localization in the d, orbital and nearly no spin localization in dz2,which may be the reason for the high stability of these complexes.
Introduction Since their first description by Tsutsui in 1966,3chromium porphyrins have been frequently investigated. Topics of interest were novel synthetic procedures and the identification of axial ligand^,"^ substitutionally labile c h r ~ m i u m ( I I I ) , ~ electrochemical studies of the redox states and of the axial ligand optical emission,12 electron spin resonance (ESR) l 3 and the thermodynamics of axial ligand binding,13 synthesis and reaction of Cr" porphyrins with dioxygen,14 and use of Cr"' porphyrins as catalysts for biomimetic hydrocarbon oxidations. 5-18 Part 28: Buchler, J. W.; Dreher, C.; Lay, K. L.Z . Naturforsch., E Anorg. Chem., Org. Chem. 1982,378, 1155-1162. (a) Technische Hochschule Darmstadt. (b) Technische Hochschule Aachen. (a) Tsutsui, M.; Ichakawa, M.; Vohwinkel, F.; Suzuki, K. J. Am. Chem. Soc. 1966,88,854-855.(b) Tsutsui, M.; Velapoldi, R. A.; Suzuki, K.; Vohwinkel, F.; Ichakawa, M.; Koyano, T. Ibid. 1969,91,6262-6266. Adler, A. D.; Longo, F. R.; Kampas, F.; Kim, J. J. Inorg. Nucl. Chem. 1970,32,2443-2445. Fleischer, E. B.; Srivastava, T. S. Inorg. Chim. Acta 1971,5,151-154. Buchler, J. W.; Eikelmann, G.; Puppe, L.; Rohbock, K.; Schneehage, H. H.; Weck, D. Liebigs Ann. Chem. 1971,745, 135-151. Buchler,' J. W.; Rohbock, K. Inorg. Nucl. Chem. Lett. 1972, 8, 1073-1076. Buchler, J. W.; Puppe, L.; Rohbock, K.; Schneehage, H. H. Chem. Ber. 1973, 106,2710-2732. (a) Fleischer, E. B.; Krishnamurthy, M. J . Am. Chem. SOC.1971,93, 3784-3786. (b) Fleischer, E. B.; Krishnamurthy, M. J . Coord. Chem. 1972,2,89-100. (a) Kadish, K. M.: Davis, D. G.: Fuhrhoo. J. H. Anpew. Chem. 1972. 84,1072-1073. (b) Fuhrhop, J.-H.; Kadiih, K. M.; D h , D. G. J. Am: Chem. SOC.1973,95,5140-5147. Bottomley, L. A.;Kadish, K. M. J . Chem. SOC.,Chem. Commun. 1981, 1212-1 214. Gouterman, M.; Hanson, L. K.; Khalil, G.-E.; Leenstra, W. R.; Buchler, J. W. J. Chem. Phys. 1975,62,2343-2353. Summerville, D. A.; Jones, R. D.; Hoffmann, B. M.; Basolo, F. J . Am. Chem. SOC.1977,99, 8195-8202. (a) Cheung, S. K.; Grimes, C. J.; Wong, J.; Reed, C. A. J . Am. Chem. SOC.1976,98,5028-5030. (b) Reed, C. A.; Kouba, J. K.; Grimes, C. J.; Cheung, S. K. Inorg. Chem. 1978,17,2666-2670. Groves, J. T.; Kruper, W. J., Jr. J . Am. Chem. SOC.1979, 101, 7613-761 5. Groves, J. T.; Kruper, W. J., Jr.; Nemo, T. E.; Myers, R. S. J . Mol. Catal. 1980. 7. 169-177. Groves, J. T . ;Kruper, W. J., Jr.; Haushalter, R. C.; Butler, W. M. Inorg. Chem. 1982,21, 1363-1368. Groves, J. T.; Haushalter, R. C. J . Chem. Soc., Chem. Commun. 1981, 1165-1166.
0020-166918311322-0879%01SO10
Under aerobic conditions, the oxidation state of chromium in porphyrins is 111. Zinc amalgam19 or chromous acetylacetonate reductionI4 of Cr(TTP)Cl (1A) or Cr(OEP)Cl(3A) (Table I) yield Cr" porphyrins; these are also observed as primary products of the metal insertion with chromium hexa ~ a r b o n y l .CrIV ~ porphyrins have been first postulated from cyclic voltammograms.I0 Recently, three groups independently succeeded in isolating oxochromium(1V) porphyrins: CrO(TPP) (lB),17-19CrO(TTP) (2B),17*20 and CrO(0EP) (3B).20 (3B).20 Whereas we prepared the latter two complexes by oxidation of hydroxochromium(II1) complexes, CrOH(TTP)-2H20 (2C, in analogy to lC5) and CrOH(OEP).'/,H20 (3C21)with hypochlorite or iodosylbenzene, Groves obtained the first CrV porphyrin, CrO(TPP)Cl (lD), from a chlorochromium(II1) porphyrin, CrCl(TPP) (lA), by oxidation with iodosylben~ene;'~ CrO(TTP)Cl (lD), however, is easily reduced to CrO(TTP) (lB), e.g. by CH2C12.18As a strong oxidant, 1D even attacks hydrocarbons. ESR measurements of 1D furnished evidence for a Crv(d') oxidation state.18 Another CrV tetrapyrrole, i.e. oxo(2,3,17,18-tetramethyl-7,8,12,13-tetraethylcorrolato)chromium(V), has been also identified by ESR.22 The ESR solution spectra of both oxochromium(V) complexes were run at 293 K and hence gave only the isotropic g value and hyperfine splitting constants.'8.22 Although the related oxomanganese(V) porphyrins are even more reactive than the oxochromium(V) porphyrin^,^^ we have succeeded in the preparation of very stable, diamagnetic, red nitridomanganese(V) porphyrins, i.e. MnN(TTP) (2E) and MnN(0EP) (3E), from qanganese(II1) porphyrins by hypochlorite oxidation in the presence of ammonia.' We have subjected the chromium(II1) porphyrins 2C and 3C to the same "oxidizing nitridation" and have obtained likewise the surprisingly stable, red nitridochromium(V) porphyrins CrN(19) Budge, J. R.; Gatehouse, B. M. K.; Nesbit, M. C.; We;, B. 0. J. Chem. SOC.,Chem. Commun. 1981, 370-371. (20) Buchler, J. W.; Lay, K. L.;Castle, L.; Ullrich, V. Inorg. Chem. 1982, 21, 842-845. (21) Rohbock, K. Ph.D. Thesis, Technische Hochschule Aachen, 1972. (22) (a) Matsuda, Y.; Yamada, S.; Murakami, Y. Inorg. Chim. Acta 1980, 44, L309-L311. (b) Murakami, Y.; Matsuda, Y.; Yamada, S. J. Chem. SOC.,Dalton Trans. 1981,855-861. (23) Groves, J. T.; Kruper, W. J.; Haushalter, R. C. J. Am. Chem. Soc. 1980, 102,6375-6377.
0 1983 American Chemical Society
Buchler et al.
880 Inorganic Chemistry, Vol. 22, No. 6, 1983 Table I. Specification of Porphyrins and Coordination Groups" R
R
3, M(0EP)LL' I
R
1, M(TPP)LL', R = H 2, M(TTP)LL', R = CH,
coord groups M
L
A B
Cr
c1
C
Cr
Cr
0
D E
Cr Mn
N
OH 0
coord groups L'
OH2
c1
M
L
L'
F G
Cr
NH, OMe
I J
Ti
N NH, N 0 0
H
os os V
a Abbreviations used: (TPP)'-, (TTP)'-, (OEP)'-, and (sa1en)'- = dianions of tetraphenylporphyrin, tetra-ptolylporphyrin, octaethylporphyrin, and N,N'-ethylenebis(salicylidenamine),respectively; Me, methyl; Et, ethyl; py, pyridine,
(TTP) (2F)and C r N ( 0 E P ) (3F). This paper describes the synthesis and the spectroscopic characterization of 2F and 3F. Whereas infrared and electronic absorption spectra did not allow a doubtless identification of the chromium(V) oxidation state, ESR and ENDOR (electron nuclear double resonance) measurements in a wide range of temperature led to a characterization of the oxidation state Crv(dl/d,). T h e electronic g tensor and, in addition, the hyperfine and quadrupole tensor components of the five nitrogen atoms provide direct information about the spin distribution in these compounds. T h e substitution in the porphyrin ring system is without any effect on the hyperfine coupling constants of both the pyrrole nitrogen atoms and the axial nitrogen atom, indicating a strong axial nitrogen-chromium interaction.
Experimental Section Materials. Anhydrous chromium trichloride (Riedel de Haen), benzonitrile (Merck-Schuchardt,synthesisgrade), sodium hypochlorite (aqueous solution, 13%active chlorine, BASF), and octaethylporphine [H2(OEP),Strem Chemicals] were used as purchased. meso-Tetra-p-tolylporphine [H2(TTP)] was synthesized and purified according to previously described procedure^.^^*^^ Alumina (A1203,type I, neutral) and silica gel @io2, type I, neutral) were obtained from Woelm Pharmaceuticals and deactivated with water to the required grades. Apparatus. Mass spectra were obtained with a Varian MAT 3 11 A instrument [electron impact (E1 MS), source temperatures 2CC)-250 OC; field ion desorption (FID MS)], infrared spectra with Perkin-Elmer 325 or 397 instruments, electronic absorption spectra (ES) with a Unicam S P 800 B spectrophotometer or an Aminco DW-2 doublewavelength spectrophotometer (Figure 1; in toluene, bathochromic shifts of 2-3 nm vs. CH2C12are observed). X- and Q-band ESR and ENDOR spectra were measured in the temperature range 3.5-295 K with ER 420 and EN 200 spectrometers, respectively,from Bruker Analytische Messtechnik (Karlsruhe). The ESR and ENDOR spectra ~~
(24) Adler, A. D.; Longo, F. R.;Finarelli, J. D.; Goldmacher, J.; Assour, J.; Korsakoff, L. J . Org. Chem. 1967, 32, 476. (25) Barnett, G. H.; Hudson, M. F.; Smith, K. M. J . Chem. Soc., Perkin Trons. I 1975, 1401-1403.
of 2F and 3F were measured in normal and perdeuterated toluene. The radiofrequency sweep range was 1-100 MHz. Low-temperature measurements were performed with an Oxford Instruments ESR 9 helium cryostat. Elementary analyses were performed by the Alfred Bernhardt Analytische Laboratorien, D-525 1 Elbach, West Germany. The samples were dried at 50 OC torr). Aquohydroxo(tetra-p-tolylporphinato)chromium(III) Hydrate, sample of H2(TTP) CrOH(TTP)H20.H20 (ZC). A 670-mg (1-"01) (freed from ~ h l o r i n ~ and ~ )792 mg (5 mmol) of anhydrous CrC1, are boiled in 350 mL of benzonitrilefor 24 h under reflux in a slow stream of nitrogen, which carries off the HC1 formed during the reaction. After cooling and filtration from excess CrC13,the solvent is distilled off [75-80 OC torr)]. The residue is dissolved in the minimum volume of CHzC12and chromatographed on neutral alumina (grade 111; column 40 X 3 cm) with CH2C12. Unreacted H2(TTP) is eluted with CH2C12 and afterward the green Cr"' porphyrin with CH2C12/MeOH(9:1), 1 mL of aqueous 2 N NaOH added, and the solution concentrated to beginning crystallization. The yield is 658 mg of violet crystals of CrOH(TTP)H20.H20 (89%). Anal. Calcd for CaH4,N40,Cr (mol wt 773.9): C, 74.50; H, 5.34; N, 7.24; 0, 6.20; Cr, 6.72. Found: C, 74.76; H, 5.13; N, 7.10; 0, 5.85; Cr, 7.15 (difference). ES (CH2C12),A, (log e): 600 nm (4.02), 561 (4.14), 523 (3.39, 436 (5.47). Hydroxo(octaethylporphinato)chromium(III) Hemihydrate, CrOH(OEP).1/2H20(3C).21A 534-mg (1-mmol) quantity of H2(OEP) and 960 mg (6 mmol) of CrC13 are boiled in 200 mL of benzonitrile for 6 h under reflux in a slow stream of nitrogen as mentioned above. After cooling and removal of the solvent in vacuo, the residue is dissolved in CH2C12 and the solution filtered and chromatographed on neutral alumina (grade 111; column 40 X 3 cm). The small amounts of unreacted H2(OEP) (first fraction) are discarded, and then the red main fraction eluted with CH2C12/MeOH (9:l) is collected and taken to dryness in vacuo. The residue is recrystallized from CH2C12/MeOH (1:l) and 1 mL of 10% aqueous NaOH. The yield is 548 mg of violet crystals of CrOH(OEP).1/2H20 (90%). Anal. Calcd for C36HaN401,5Cr(mol wt 610.8): C, 70.79; H, 7.59; N, 9.17; 0, 3.93; Cr, 8.52. Found: C, 70.45; H, 7.40; N, 9.26; 0, 4.21; Cr, 8.68 (difference). ES (CH2C12),A, (log e): 646 nm (2.67), 572 (3.77), 540 (3.89), 421 (5.06), 382 (4.40), 371 (4.40), 347 (4.46). IR (KBr): 3610 (sharp, m; OH coordinated),26 3420
Inorganic Chemistry, Vol. 22, No. 6, I983 881
Nitridcchromium(V) Porphyrins cm-l (broad; H20). E1 MS: -1200 [Cr20(0EP)2+,
