Organometallics 1987, 6 , 1703-1712
1703
Syntheses, Reactivities, Molecular Structures, and Physical Properties of Paramagnetic Bis(tetraphenylcyclopentadieny1) Complexes of Vanadium, Chromium, Cobalt, and Nickel Michael P. Castellani,'a Steven J. Geib,lb Arnold L. Rheingold,* I b and William C. Trogler*Ia Department of Chemistry, D-006, University of California at San Diego, La Jolla, California, 92093, and Department of Chemistry, University of Delaware, Newark, Delaware 19716 Received December 10, 1986
The reactions between I, K(CJ-€Ph&O.5"F, and metal halides of the first transition series yield complexes of the type (C5HPh4)2M(M = V, Cr, Co, and Ni, compounds 11,111, V, and VII, respectively). Crystals of all four complexes belong to the space group P1,Z = 1, and possess rigorous molecular inversion symmetry. The unit-cell parameters for I1 are a = 8.431 (2) A, b = 10.893 (3) A, c = 13.012 (3) A, a! = 66.30 ( 2 ) O , /3 = 75.56 (2)O, y = 85.54 (2)O, aqd V = 1059.4 (5) A3 with final values of RF and 5.56% and Rwp = 6.09%. Complex I11 crystallizes with a = 8.300 (4) A, b = 10.900 (3) A, c = 12.930 (5) A, a! = 66.53 (3)O, p = 75.02 (3)O, y = 85.18 (3), and V = 1036.2 (7) A3 with final values O f RF = 5.71% and RwF = 6.36%. The unit-cell parameters for V are a = 8.297 (2) A, b = 10.938 (4) A, c = 12.936 (4) A, a! = 66.74 (2)O, /3 = 74.78 (4)O, y = 84.99 f2)O, and = 1040.5 (6) A3 with final values of RF = 5.67% and RwF = 5.66%. Complex VI1 crystallizes with a = 8.237 (6) A, b = 10.874 (8) A, c = 12.946 (11) A, a = 66.91 (6)O, /3 = 75.78 (6)O,y = 86.02 (6)O, and V = 1033 (1) A3 with final values of RF = 9.86% and RwF = 10.6%. The difference in metal-carbon bond lengths between (C5H5I2Mand (C5HPh4)2M complexes decreases on going from Fe (0.05 A) to V (0.02 A), which suggests decreasing interaction between phenyl groups on opposing C5rings. Redox potentials of (C5HPh4)2Mcomplexes resemble those of (C5H5)2Mand [ (C5HPh4)zCr]PF6, [ (C5HPh4)&o]PF6,and [ (C5HPh4)2Ni]PF6 were prepared by oxidation of the neutral metallocenes with AgPFB. EPR and solid-state magnetic moment measurements show that (C5HPh4)zM complexes occupy the same ground-state electronic configurations as corresponding (C5H5)2Mand (C5Me5IzMderivatives. suggest that the low molecular symmetry The EPR measurements on [ (C5HPh4)2Cr]PF6and (C5HPh4)2Co (Ci) of these complexes perturbs the metallocene energy levels more than Jahn-Teller distortions in the complexes show much reduced reactivity when compared unsubstituted complexes (Dw),The (C5HPh4)2M with (C5H5)2Mcomplexes.
v
Introduction Many substituted bis(cyclopentadienyl)iron,2 cobalt: and nickel) complexes have been prepared; however, few such complexes of other first-row transition metals are Except for ferrocene,216few metallocene derivatives exclusively incorporate phenyl substituent^.^-^ While physical properties have been measured for many substituted neutral metallocenes of the first-row transition metals,2-5J1studies of phenyl-substituted metallocenes have been limited primarily to 'H NMRg and 13CNMRlO spectral characterization. Crystal structures have been reported for one substituted vanadocene12and nicke10cene.l~ No structural data (1)(a) University of California at San Diego. (b) University of Dela-
ware.
(2)Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds. Comprehensive Organometallic Chemistry; Pergamon: Oxford, 1982;Vol. 4,p 475. (3)(a) Sheata, J. E. J. Organomet. Chem. Libr. 1979, 7 , 461. (b) Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds. Comprehensive Organometaltic Chemistry; Pergamon: Oxford, 1982;Vol. 5,p 244. (4)(a) Jolly, P.W.; Wilke, G. The Organic Chemistry of Nickel; Academic: New York, 1974. (b) Wilkmson, G., Stone, F. G. A., Abel, E. W., Eds. Comprehensive Organometallic Chemistry; Pergamon: Oxford, 1982;Vol. 6,p 189. (5) (a) Wilkinson, G., Stone, F. G. A,, Abel, E. W., Eds. Comprehensive Organometallic Chemistry; Pergamon: Oxford, 1982;Vol. 3,p 970. (b) Zbid. Vol. 3,p 672. (c) Ibid. Vol. 4,p 113. (6) (a) Slocum, D. W.; Duraj, S.; Matusz, M.; Cmarik, J. L.; Simpson, K. M.; Owen, D. A. In Metal Containing Polymeric Systems; Sheats, J. E., Carraher, C. E., Jr., Pittman, C. U., Jr., Eds.; Plenum: New York, 1985;pp 59-68. (b) McVey, S.; Pauson, P. L. J. Chem. SOC. 1965,4312. (7) Schott, A,; Schott, H.; Wilke, G.; Brandt, J.; Hoberg, H.; Hoffmann, E. G. Justus Liebigs Ann. Chem. 1973,508. (8)K l h i , W.; Ramacher, L. Angew. Chem., Int. Ed. Engl. 1986,25, 96. (9)Kbhler, F.H.;Mataubayashi, G. Chem. Ber. 1976,109,329. (10)(a) Kohler, F.H. J.Organomet. Chem. 1976,91,57. (b) Kohler, F. H.; Mataubayashi, G. 2.Naturforsch., E Anorg. Chem., Org. Chem. 1976,31B, 1153. (11)Robbins, J. L.;Edelstein, N.; Spencer, B.; Smart, J. C. J. Am. Chem. SOC.1982,104, 1882.
is available for substituted chromocenes or c~baltocenes.'~ Structural studies of bis(pentamethylcyclopentadieny1)metal complexes have been limited to (C5Me5)2M(M = V,12Mn,15Fe15),and the vanadium structure suffers from disorder. This lack of structural information for substituted metallocenes, and our interest16 in the physical properties of phenyl-substituted metallocenes, led us to prepare complexes of the type (C5HPh4),M (M = V, Cr, Mn, Co, Ni). Given the T symmetry (anti rotamer) observed16 for (C5HPh4)2Fein the solid state, we wondered whether a similar rotamer would be observed for other octaphenylmetallocenes. Structural studies of these sterically congested complexes lay the foundation for a conformational analysis of sterically crowded organometallic complexes, a topic of current interest in organic17 and organometallic1*chemistry. Complexes incorporating the pentamethylcyclopentadienyl ligand exhibit significant (12)Gambarotta, S.;Floriani, C.; Chiesi-Villa, A.; Guastini, C. Znorg. Chem. 1984,23,1739. (13)Scroggins, W. T.;Rettig, M. F.; Wing, R. M. Inorg. Chem. 1976, 15, 1381. (14)Crystal structures of two cobaltocene-carborane zwitterions have been reported. (a) Churchill, M. R.; DeBoer, B. G. J. Am. Chem. SOC. 1974,96,6310.(b) Grimes, R.N.; Pipal, J. R.; Sinn, E. J.Am. Chem. SOC. 1979,101,4172. (15)Freyberg, D. P.; Robbins, J. L.; Raymond, K. N.; Smart, J. C. J. Am. Chem. SOC.1979,101, 892. (16)Castellani, M. P.; Wright, J. M.; Geib, S. J.; Rheingold, A. L.; Trogler, W. C. Organometallics 1986,5,1116. (17)(a) Siegel, J.; Mislow, K. J. Am. Chem. SOC.1983,105,7763. (b) Taber, D. F.; Ruckle, R. E., Jr. Zbid. 1986,108, 7686. (c) Oki, M. Top. Stereochem. 1983,14,1. (d) March, J. Aduanced Organic Chemistry; Wiley: New York, 1985. (e) Ruchardt, C.; Beckhaus, H.-D. Angew. Chem., Int. Ed. Engl. 1985,24,529. (18)(a) Hunter, G.; Mislow, K. J. Chem. SOC.,Chem. Commun. 1984, 172. (b) Williamson, R. L.; Hall, M. B. Organometallics 1986,5,2142. ( c ) Blount, J. F.; Hunter, G.; Mislow, K. J. Chem. SOC.,Chem. Commun. 1984,170.(d) Gallucci, J. C.; Gautheron, B.; Gugelchuck, M.; Meunier, P.; Paquette, L. A. Organometallics 1987,6,15.(e) Bosnich, B.;Fryzuk, M. D. Top. Stereochem. 1981,12,119.(0 Tolman, C. A. Chem. Rev. 1977, 77,313.
0276-7333/S7/2306-1703$01.50/0 0 1987 American Chemical Society
1704 Organometallics, Vol. 6, No. 8, 1987
changes in reactivity from the corresponding cyclopentadienyl complexes because of steric and electronic difference^.'^ The tetraphenylcyclopentadienyl ligand may be prepared easily and yields complexes that often crystallize. A delineation of tetraphenylcyclopentadienyl metallocene chemistry is needed before it finds general use as a ligand. This work examines how the steric bulk of the phenyl rings affects the reactivities, molecular structures, EPR spectra, and magnetic and redox properties of (C,HPh,),M (M = V, Cr, Co, Ni). Experimental Section Except where noted, reactions of materials used standard Schlenk techniques. Solids were manipulated under nitrogen in a Vacuum Atmospheres glovebox equipped with a HE-493 dritrain. Benzene, tetrahydrofuran (THF), toluene, diethyl ether, and pentane were refluxed over sodium-benzophenone ketyl and distilled under nitrogen. Dichloromethane was refluxed over CaH, and distilled under nitrogen. Lithium tetraphenylcyclopentadienide was prepared as described previous1y,l6 except that tetraphenylcyclopentadienonewas prepared by a literature synthesis.20 The [Ni(NH3)6]C121and Cr2(02CCH3)4nreagents were prepared by literature methods. The Mn(CF3S03), reagent was prepared by the reaction between MnCO, and CF3S03Hin water, followed by dehydration under vacuum at 135 "C for 2 h. Anhydrous CrCl, (Aesar), VCl,, CoBrz (Strem), NiClZ-6Hz0(Mallinkrodt), AgPF6, and CF3C02H (Aldrich) were purchased and used without purification. The K H reagent (Aldrich) was separated from the accompanying mineral oil by Soxhlet extraction with pentane under a nitrogen atmosphere. Magnetic susceptibilities were measured with a BTi Model VTS-905 SQUID (Super Quantum Interference Device) Susceptometer on samples (ca. 50 mg) wrapped in Parafilm (ca. 0.1 g) and suspended from a cotton thread. The samples were transferred rapidly from a nitrogen-filled Schlenk tube into the instrument and placed under a helium atmosphere. Samples were corrected for wax diamagnetism and for ligand diamagnetism with a bis(tetraphenylcyclopentadienyl)iron(I1)blank. Measurements were made a t 20-22 temperatures on each sample in the temperature range 7-300 K a t a constant field strength of 10.00 kG. Cyclic voltammograms were recorded with a BAS-100 Electrochemical Analyzer and a Houston Instruments DMP-40 digital plotter. A conventional three-electrode cell [Pt button working electrode, Pt wire auxiliary electrode, and a Ag/Agf (0.1 M AgNO, in CH,CN) reference electrode] contained 2 mM solutions of the complexes in electrolyte (0.25 M) solution. The supporting electrolyte (tetra-n-butylammonium perchlorate, Baker Polarographic Grade) was recrystallized twice from a mixture of ethyl acetate and isooctane. EPR spectra were recorded with a Varian E-3 spectrometer with t h e use of diphenylpicrylhydrazyl as the field marker. Samples were cooled to 77 K by immersion in an Nz filled Dewar or by placing them in a stream of Nz gas cooled to 78-80 K. Proton NMR spectra were recorded on a GE QE-300 NMR spectrometer a t 300.152 MHz. Elemental analyses were performed by Schwartzkopf Microanalytical Laboratories.
Synthesis of Potassium Tetraphenylcyclopentadienide 0.5-Tetrahydrofuran,I. Addition of dry T H F (100 mL) to a solid mixture of tetraphenylcyclopentadiene (9.55 g, 25.8 mmol) and potassium hydride (1.47 g, 36.6 mmol) produced an orange-red solution with concurrent Hz gas evolution. After gas evolution ceased (3 h), the reaction mixture was filtered through a frit. The filtrate was evaporated to dryness under vacuum, and the resulting (19) (a) King, R. B.; Bisnette, M. E. J.Organomet. Chem. 1967,8,287. (b) Bercaw, J. E.; Marvich, R. H.; Bell, L. G.; Brintzinger, H. H. J. Am. Chem. SOC.1972, 94, 1219. (c) Maitlis, P. M. Acc. Chem. Res. 1978, 2 1 , 301. (20) Johnson, J. R.; Grummitt, 0 . Organic Syntheses; Wiley: New York, 1955; Collect. Vol. 111, p 806. (21) Cordes, J. F. Chem. Ber. 1962, 95, 3084. (22) Jolly, W. L. The Synthesis and Characterization of Inorganic Compounds; Prentice-Hall: Englewood Cliffs, NJ, 1970; p 442. (23) (a) KBhler, F. H.; Prhsdorf, W. Z. Z. Naturforsch., E : Anorg. Chem., Org. Chem. '1977,32E, 1026. (b) Bouma, R. J.; Teuben, J. H.; Beukema, W. R.; Bansemer, R. L.; Huffman, J. C.; Caulton, K. G. Inorg. Chem. 1984, 23, 2715.
Castellani e t al. solid was vacuum dried overnight. T h e solid was ground in a mortar and pestle and heated to 50 OC for 2 h under vacuum to remove residual THF. The beige powder was obtained in 96% yield (11.0 g, 24.7 mmol). Anal. Calcd for C6,H5&0: C, 83.74; H, 5.67. Found: C, 83.91; H, 5.90.
Synthesis of Bis(tetraphenylcyclopentadieny1)vanadium(II), 11. A T H F solution (20 mL) of VCl, (0.47 g, 2.8 mmol) and 2-3 mg of NaH was refluxed overnight, followed by addition of Zn dust (105 mg, 1.6 mmol) and a continued 12 h reflux of the solution. The mixture was cooled to room temperature and transferred via cannula (without filtering) into a solution of K(C5HPh4)(2.23 g, 5.9 mmol) in THF (30 mL). The solution was refluxed overnight followed by solvent removal in vacuo. The green solid was purified by extraction with boiling benzene. The benzene extract was evaporated to dryness under vacuum, and the resulting solid was dissolved in a minimum of boiling toluene (ca. 50 mL). The hot solution was filtered rapidly followed by cooling the solution to -15 "C. After several days green, microcrystalline I1 precipitated in 50% yield (1.17 g, 1.5 mmol). Anal. Calcd for C58H42V C, 88.19; H , 5.36. Found: C, 87.82; H, 5.36.
Synthesis of Bis(tetraphenylcyclopentadieny1)chromium(II), 111. Dry T H F (30 mL) was added to a solid mixture of CrClz (0.20 g, 1.6 mmol) and K(C5HPh4) (1.52 g, 3.4 mmol) and refluxed overnight. Removal of solvent in vacuo yielded a magenta residue, which was extracted with boiling benzene. The extract was dried under vacuum, and the resulting solid was dissolved in a minimum (40 mL) of boiling toluene, filtered, and cooled to -15 "C overnight. Microcrystah of 111were obtained in 47% yield (0.61 g, 0.77 mmol). Anal. Calcd for C58H42Cr:C, 88.07, H, 5.35. Found: C, 87.50; H, 5.47.
Synthesis of Bis(tetraphenylcyclopentadieny1)chromium(II1) Heduorophosph.5-Dichloromethane, IV. Dry CHzClz(15 mL) was added to a solid mixture of I11 (0.20 g, 0.25 mmol) and AgPF6 (0.071 g, 0.28 mmol). After being stirred for several hours, the red-brown solution was filtered into a Schlenk tube. The volume was reduced under vacuum to saturation before layering an equal volume of pentane on top. After several days, filtering the solution yielded IV (0.18 g, 0.18 mmol) as black crystals in 72% yield. Anal. Calcd for C1l,H~C1zCrzFlzP,: C, 71.82; H, 4.43. Found: C, 72.29; H, 4.45. Synthesis of Bis(tetraphenylcyclopentadienyl)cobalt(II), V. A mixture of anhydrous CoBrz (0.50 g, 2.3 mmol) and K(C5HPh4)(2.13 g, 4.8 mmol) reacted in T H F (25 mL) to form a purple solution. After the solution was stirred for 1 day, the T H F was removed in vacuo and the resulting solid was purified by extraction with boiling benzene. The volume of the benzene extract was reduced in vacuo, and the resulting solution was heated to reflux. The solution volume was then adjusted until all solid dissolved (110 mL) before it was cooled slowly to room temperature. After several days, dark purple, crystalline V was isolated in 76% yield (1.39 g, 1.7 mmol). Anal. Calcd for C58H42C~: C, 87.31; H, 5.30. Found: C, 88.15; H, 5.67.
Synthesis of Bis(tetraphenylcyclopentadienyl)cobalt(III) Hexafluorophosphate, VI. T o a mixture of V (0.60 g, 0.75 mmol) and AgPF6 (0.19 g, 0.75 mmol) was added 15 mL of THF. After the solution was stirred overnight, the T H F was removed in vacuo and the residue was extracted with a minimum of CHzCl, (in air) to yield a red solution! Hexanes were layered on this solution to yield red crystals of air-stable VI (0.58 g, 0.62 mmol) in 82% yield after it was left standing for several days. Anal. Calcd for C58H4&~F6P:C, 73.88; H, 4.49. Found: C, 74.72; H,
4.57.
Synthesis of Bis(tetraphenylcyclopentadienyl)nickel(II), VII. A mixture of [Ni(NH3)6]C12(0.52 g, 2.2 mmol) and K(C5HPh4) (2.09 g, 4.7 mmol) in T H F (50 mL) was refluxed for 70 h and then cooled to room temperature. After solvent removal in vacuo, the residue was extracted with boiling benzene. The extract was evaporated to dryness under v a c u w , and the residue was dissolved in a minimum of boiling toluene and filtered. Cooling the filtrate to -15 "C for several days produced brown, microcystalline VI1 (1.24 g, 1.6 mmol) in 69% yield. Anal. Calcd for C58H42Ni: C, 87.33; H, 5.31. Found: C, 87.52; H, 5.52. Synthesis of Bis(btraphenylcyclopentadienyl)nickel(III) Hexafluorophosphate-O.5-Dichloromethane, VIII. Dry CHzClz(20 mL) was added to a solid mixture of VI1 (0.63 g, 0.79 mmol) and AgPF6 (0.20 g, 0.79 mmol). After being stirred ov-
(CJZPh,), Complexes of V , Cr, Co, and Ni
Organometallics, Vol. 6, No. 8, 1987 1705
Table I. Crystal and Refinement Data for OctaDhenslmetallocenes cryst system space group a,
A
b, A C, 8, a,deg 0,deg 79 deg
v, A3
z
cryst dimens, mm abs coeff, cm-' 29 scan range, deg scan technique weighting factor, p unique data unique data obsd datalparameter std rflns GOF" RF" &Fa
triclinic
triclinic
triclinic
triclinic
triclinic
Pi
pi
Pi
Pi
Pi
8.431 (2) 10.893 (3) 13.012 (3) 66.30 (2) 75.56 (2) 85.45 (2) 1059.4 (5) 1 0.23 X 0.24 X 0.36 2.9 4-45 8/29 0.0008 2777 (2924 read) 2145 (> 5a(F0)) 9.58 3 stds/197 rflns 1.866 5.56 6.09
8.300 (4) 10.900 (3) 12.930 (5) 66.53 (3) 75.02 (3) 85.18 (3) 1036.2 (7) 1 0.23 X 0.28 X 0.30 3.1 4-45 9/29 0.0025 2725 (2870 read) 1943 (> 547,)) 8.67
8.339 (4) 10.867 (5) 12.830 (7) 66.40 (4) 73.47 (4) 83.72 (4) 1021.3 (9) 1 0.31 X 0.31 X 0.31 4.2 4-52 omega 0.0008 4019 (4209 read) 3498 (> 3a(F0)) 15.62
8.297 (2) 10.938 (4) 12.936 (4) 66.74 (2) 74.78 (2) 84.99 (2) 1040.5 (6) 1 0.20 X 0.20 X 0.40 4.5 4-48 9/29 0.0010 3287 (3614 read) 2363 (> 4a(F0)) 10.55
8.237 (6) 10.874 (8) 12.946 (11) 66.91 (6) 75.78 (6) 86.02 (6) 1033 (1) 1 0.18 X 0.23 X 0.42 5.1 4-42 9/29 0.0075 2204 (2924 read) 1722 (> 5u(F0)) 7.69
1.223 5.71 6.36
1.432 4.52 5.09
1.274 5.67 5.66
1.541 9.86 10.60
16. ernight, the solution was cannula filtered into a Schlenk tube and the solid residue was extracted with CH2C12to remove all the green-brown product. An equal volume of pentane was layered on this solution. After several days green-brown crystals of VI11 (0.47 g, 64%) were collected by filtration, washed with benzene (to remove residual VII), and dried in vacuo. Anal. Calcd for Cll7H,&l2Fl2Ni2P2: C, 71.33; H, 4.40. F o u n d C, 71.21; H, 4.56. X-ray Structural Determination. Crystal data and parameters used during the collection of intensity data for C58H42V, C58H42Cr,CS8H42Co,and CMH4,Niare given in Table I. Crystals of V, Cr, and Ni were grown by layer diffusion of pentane into saturated dichloromethane solutions of the particular compound. The Co compound was crystallized similarly from T H F solution. Crystals of V (green), Cr (magenta), Co (purple), and Ni (orange-brown) were attached to fiie glass fibers with epoxy cement. All four crystallized in the triclinic space group PI and are isomorphous with the previously reported structure of octaphenylferrocene.16 Unit-cell dimensions were derived from the least-squares fit of the angular settings of 25 reflections with 14 < 28 < 26O for each crystal. A profiie fitting procedure was applied to all intensity data to improve the precision of the measurement of weak reflections. Reflections for the Ni complex were corrected for absorption effects by using the program XAES (H. Hope), which is based on deviations in F, and F, values. An absorption correction was not needed for V, Cr, and Co because of uniform crystal dimensions and low absorption coefficients (V, 2.9 cm-'; Cr, 3.1 cm-'; Co, 4.5 cm-'; Ni, 5.1 cm-'). Including a n absorption correction for Co had no significant effect on the refinement. A hemisphere (hh, hk, +l) of data were collected on a Nicolet R3m/p automated diffractometer using graphite-monochromated Mo K a radiation (A = 0.71053 A) at ambient temperatures (22-24 OC) and a variable scan speed (5-20 deg/min). Three standard reflections were monitored for each 197-reflection block. For all complexes decay of the standard reflections was 61 Imposing a C,, distortion on a D M molecule increases the distortion parameter, A, which breaks the orbital degeneracy. A second quenching effect arises from a smaller than expected orbital reduction parameter, k'. This parameter reflects electron delocalization from the metal d orbitals onto the ligand.53 Measurements of the magnetic moment of Cp2Cras a function of temperature yielded two differeot values (2.9757and 3.20 pBBs6l). While there is disagreement over the value of the moment, each follows Curie-Weiss behavior over wide temperature ranges. Both Gordon and Warren56 and Konig et al.57conclude the ground state for chromocene is 93 and both claim to treat their data satisfactorily with ligan2 field theory. This assignment, which agrees with UV-photoelectron spectroscopic studies,58arises from the observed moment being much greater than the spin-only value (2.83 pug). Octaphenylchromocenepossesses low symmetry (Ci) that precludes orbital degeneracy. If the energy difference between the levels were much smaller than the Jahn-Teller splittings in the higher symmetry analogues, a second-order Jahn-Teller distortion could occur in (C5HPh4)2Cr.If site splitting of the ground-state degeneracy is sufficiently large, the susceptibility will obey the Curie law. We find that (C5HPh4)2Crfollows Curie-Weiss behavior between 7 and 180 K with peff= 2.90 pB and 0 = -1 K (Table XII). Above 180 K, the moment increases at a faster rate and the points curve below the Curie-Weiss line as predicted above. The degree of curvature, which is small, suggests that the Ci site symmetry in (C5HPhJ2Crmimics the effect of the Jahn-Teller distortion in Cp2Cr. As our measured moment is not much larger than the spin-only value, a conclusive assignment of the ground state (3E2gor 3A2g) cannot be made; however, in light of the results for C P , C P ~and ' ~ (C5Med2Crl1a 3Ea derived state seems more No EPR spectrum was observed for probable. (C5HPh4),Crin toluene at 77 K or 300 K, which resembles the behavior of Cp2Cr1land (C5Me5)2Cr.11 As discussed earlier for Cp2V and (C5HPh4)2V, [ (C5HPh4),Cr]PF6,another 15-electron complex, should (54) (a) Prins, R.; Biloen, P.; van Voorst, J. D. W. J. Chern. Phys. 1967, 46, 1216. (b) Prins, R.; van Voorst, J. D. W. Ibid. 1968, 49, 4665. (55) Ammeter, J. H. J. Magn. Reson. 1978, 30, 299. (56) (a) Gordon, K. R.; Warren, K. D. J.Organornet. Chem. 1976,117, (227. (b) Gordon, K. R.; Warren, K. D. Inorg. Chem. 1978, 17, 987. (57) Konig, E.; Schnakig, R.; Kremer, S.; Kanellakopulos, B.; Klenze, R. Chem. Phys. 1978,27, 331. (58) Evans, S.; Green, M. L. H.; Jewitt, B.; King, G. H.; Orchard, A. F. J. Chem. SOC., Faraday Trans. 2 1974, 70, 356. (59) Nussbaum, M.; Voitlbder, J. Z. Naturforsch.,A: Phys., Phys. Chem., Kosmophy. 1965,20A, 1417. (60) Prins, R.; van Voorst, J. D. W.; Schinkel, C. Chem. Phys. Lett. 1967, 1, 54. (61)Engelmann, F. Z. Naturforsch., B: Anorg. Chem., Org. Chem. 1953, 8, 775.
( C a P h , ) , Complexes of V, Cr, Co, and Ni
Organometallics, Vol. 6, No. 8, 1987 1711
Table XIII. EPR Data for First-Row Metallocenes temp, K , gz Or g, gy g, i04A,, cm-' 77 3.98012 2.002 21.5 (A,) 4 3.976412 2.0014 20.9
complex
host CPZV methylcyclohexane CP& (C5Me6)zV toluene (c~HPh4)zV THF CpzCr+ CPzMg [(CSMe6)zCrlPF6 (C5Me6)zMg [(C6HPh4)zCr]PF6n toluene/CHzClz (1:2) CPzCO 2-MeTHF (C6Me6)&o toluene (CsMe6)zFe (C6HPh4)&On toluene [Cp2ColPF6 Cp2Ni+ [(C5Me6)~NilPF6 [(C5Me5)2C~lPFB [(C5HPh4)zNi]PF6n toluene/CHzClz (1:2)
19 77 4 17 77 4 14 9 77 4 8 77
3.97312 4.000/2 3.954/2 4.01/2 3.96812 1.81 2.0 @bo) 1.693 1.999 1.972 1.973 2.018
4.050/2 1.733 2.095 2.016 2.014 2.072
2.001 1.996 2.002 1.99 2.005 1.69
16.0 17.1 b b b
1.754 1.884 1.801 1.831 1.884
