96
Organometallics 1983, 2, 96-100
Asymmetrical Sandwich Compounds. The Preparation and Characterization of ($-Benzene) (7'- 1,2,3,4,5-pentafluoro-6-(diphenylphosphino)benzene)chromium(0) and Its Reaction with [Rh(CO),CI], Romolo Faggiani,la Nguyen Hao,lb Colin J. L. Lock,*la Brian G. Sayer,lband Michael J. McGlinchey*lb Department of Chemistry and the Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada L8S 4M1 Received June 28, 1982
Metal atom synthesis of (C6H6)Cr(C6FSH), followed by lithiation and treatment with chlorodiphenyl2. Crystals phosphine, gave (~6-benzene)(~6-1,2,3,4,5-pentafluor~6-(diphenylphosphino)be~ene)c~omi~(O), of 2 were monoclinic of space group B 1 / c with cell dimensions a = 8.341 (1) A, b = 12.472 (2) A, c = 21.033 (2) A, and p = 115.13 (9)O and had four formula units in the unit cell. The crystal structure was determined by standard methods and refined to R 1 = 0.0595 and R2= 0.0694 on the basis of 2126 reflections. The data were collected with use of Mo KLYradiation and a Syntex P21 diffractometer. The benzene and pentafluorophenyl rings sandwich the chromium atom, which lies closer to the pentafluorophenyl ring (Cr-C(F) range = 2.083 (6)-2.104 (6) 8, vs. Cr-C(H) range = 2.142 (81-2.164 (6) 8,). The bound phosphorus atom causes distortion of the pentafluorophenyl ring so that the carbon atom bound to phosphorus is 2.149 (2) 8, from the chromium atom; the internal ring angle at the carbon atom bound to phosphorus is reduced to 114.3 (5)', and adjacent internal ring angles are increased (122.4 (5), 123.3 (5)'). Other bond lengths and angles are normal. The 235-MHz 19FNMR spectrum of 2 showed enormous increases in the fluorine-fluorine coupling constants relative to those in the free arene. 2 reacted with [Rh(CO)&l], to give 3. the trimetallic complex [(C6H6)Cr(C6FSPPh2)]*Rh(co)cl,
Introduction Two questions stimulated this work. One concerned the relative lengths of metal-carbon bonds in markedly asymmetric sandwich compounds. The second was whether one could use the availability of functionalized chromium-arene sandwich complexes (chromarenes9 to synthesize molecules containing both a chromarene moiety and another catalytic centre such as a 16-electron square-planar rhodium atom. The ability of a chromarene system to catalyze polymerization2 or hydrogenation processes3 is well-known. It appeared t h a t the metal-vapor cocondensation procedure might yield compounds suitable for both ~ t u d i e s . ~ An attempt was made to study the first problem by the s y n t h e ~ i s and ~ ~ , ~characterization of ($-benzene)($hexafluorobenzene)chromium(O), (C6F6)Cr(C6H6).A detailed vibrational spectroscopic study has already been reported6 which showed the asymmetry of the compound along the sixfold axis. Crystallographic studies were un(1) (a) Institute for Materials Research. (b) Department of Chemistry. (c) Agarwal, A.; McGlinchey, M. J.; Tan,T.-S.J. Organomet. Chem. 1977, 141, 85-97. (2) Tsutsui, M.; Koyano, T. J . Polym. Scz., Part A 1967,5, 683-684. (3) Sneeden, R. P. A. "Organochromium Compounds"; Academic Press: New York, 1975; pp 169-171. (4) (a) Skell, P. S.; Williams-Smith,D. L.; McGlinchey, M. J. J . Am. Chem. SOC.1973,95,3337-3340. (b)Middleton, R.; Hull, J. F.; Simpson, S. R.; Tomlinson, C. H.; Timms, P. L. J. Chem. Soc., Dalton Trans. 1973, 120-124. (c) McGlinchey, M. J.; Tan, T.-S. Can. J. Chem. 1974, 52, 2439-2443. (d) Klabunde, K. J.; Efner, H. F. Inorg. Chem. 1975, 14, 789-791. (e) Graves, V.; Lagowski, J. J. Ibid. 1976, 15, 577-586. (0 Nesmeyanov, A. N.; Yur'eva, L. P.; Zaitseva, N. N.; Vasynkova, N. I. J. Organomet. Chem. 1978, 153,341-344. (g) Moeckel, R.; Elschenbroich, C. Angew. Chem., Int. Ed. Engl. 1977, 16, 870-871. (h) Kundig, E. P.; Timms, P. L. J. Chem. SOC.,Dalton Trans. 1980, 991-995. (i) Nguyen, Hao; McGlinchey, M. J. J . Organomet. Chem. 1979, 165, 225-231. fi) Gastinger, R. G.; Klabunde, K. J. Transition Met. Chem. 1979, 4, 1-13. (5) McGlinchey, M. J.; Tan, T.-S. J. Am. Chem. SOC. 1976, 98, 2271-2275. ( 6 ) Laposa, J. D.; Nguyen Hao; Sayer, B. G.; McGlinchey, M. J. J . Organomet. Chem. 1980,195, 193-201.
successful, however, in determining the differences in the metal-carbon bond lengths to the fluorinated and nonfluorinated rings. The compound crystallizes in a hexagonal space group, and the structure is markedly disordered. The sandwich compound is stacked up the hexagonal axis, but a translationally equivalent stacks may be inverted. Thus a t z = 0 and ll2,one has averages of benzene and hexafluorobenzene rings, and a t z = 1/4 and 3 / 4 one has half chromium atoms. This problem arises because both the inter- and intramolecule distances between the sandwich rings are roughly 3.4 A. In order to study this problem further, it was necessary to introduce some asymmetry into one of the rings. Fortunately, from our attempts to study the second problem, a compound was available, namely, the (dipheny1phosphino)pentafluorochromarene 2.
Experimental Section 'H and 31PNMR spectra were obtained at 2.114 T on a Bruker WH90 at 90 and 36.43 MHz, respectively; tetramethylsilane and 85% H3P04were used as external references. 19FNMR spectra were obtained at 5.872 T on a Bruker WM 250 at 235.38 MHz; C6D6was used as the solvent and CFCl, as the external reference. Spectral simulation was achieved with Bruker's "PANIC" iterative software and an ASPECT 2000 computer. Mass spectrometry was performed on a VG micromass 7070 spectrometer equipped with a VG2035 data system. Infrared spectra were recorded on a Perkin-Elmer 337 grating spectrometer. Melting points were uncorrected. Microanalysis results were from Guelph Chemical Laboratories Ltd., Guelph, Ontario. Preparation of 6-(Diphenylphosphino)-1,2,3,4,5-pentafluorochromarene, 2. To a solution of (C6H6)Cr(C6F5Li) (1 mmol) in ether at -78 'C was added a very slight excess of chlorodiphenylphosphine. The solution was stirred under an atmosphere of nitrogen for 2 h by which time the starting redbrown solution had turned orange. The solution was allowed to warm to room temperature, stirred a further 3 h, and filtered and the ether removed in vacuo. The residue was taken up in benzene and chromatographed on a silica gel column. Elution of a red band with 50% benzene, 40% hexane, and 10% ether gave 2 (145
0276-733318312302-0096$01.50/0 0 1983 American Chemical Society
Asymmetrical Sandwich Compounds
Organometallics, Vol. 2, No. I , 1983 97
Table I. Crystal Data compd fw cryst size, mm systematic absences space group unit cell parameters a
b C
P
vol, ' 4 3 radiation, '4 ; temp, "C
z
Pcalcd, g qobsd, g
linear abs coeff, cmT3 2e (max);reflctns collctd std reflctns (esd, %) no. of independent reflctns no. with I > 3o(I) 3o(I) > I > 0, Fc > Fo 3o(I) > I > 0, Fc < Fo I < 0, rejected final R , , b , R , final shift/error(max); average final difference map highest peak (e location lowest valley (e location weighting error in an observn of unit weight
C,,H,,CrF,P 482.35 cylinder, r = 0.15; 1 = 0.36 h01,1= 2n t 1; OhO, h = 2n + 1 P2,lc (No. 14)
8.341 (1) 12.473 (2) 21.033 (2) 115.13 (9) 1981.1 (5) 0.709 26; -70 (1) 4 1.617 1.6 7.43 45". h, h , trl
used in refinement 303 181
0.0595, 0.0694 0.042; 0.002 0.94; 0.50, 0.45, 0.30 -0.33; 0.45, 0.50, 0.70
w = (u' 1.778
+ (0.025F0)2)-'
Table 11. Atomic Positional Coordinates for Non-Hydrogen Atoms ( X lo4) atom X Y 2 2472 (1) 2743.7 (7) -158.6 (5) 1174 (7) 2562 ( 4 j 526 (3j 2780 ( 7 ) 3122 (4) 859 (3) 4018 (5) 3218 (8) 565 (3) 2053 (8) 4378 (5) -93 (3) 3882 (4) 440 (8) -433 (3) -141 (3) 2990 (4) 5 (8) 3992 (4) 2804 (3) 1496 (2) 4804 (4) 913 ( 2 ) 4504 (3) -366 (2) 2465 (5) 5263 (3) -747 (4) -1072 ( 2 ) 4245 (3) -1593 (4) -504 (2) 2527 (3) 2768 (8) -354 (3) 1068 (5) 4417 (8) 109 (3) 1482 (5) 5072 (9) -76 (3) 2396 (5) 4104 (9) -713 (3) 2897 (5) 2429 (9) -1175 (3) 2507 (5) -991 (3) 1768 (8) 1579 (5) -353 (7) 2129 (4) 1466 (3) -223 (8) 3217 (5) 1582 (3) -953 (9) 3703 (5) 1994 (3) -1803 (9) 3091 (6) 2297 (4) -1918 (9) 2201 (4) 2011 (6) -1225 (8) 1511 (5) 1779 (3) 2392 (8) 734 (5) 1485 (3) 3343 (8) 1028 (5) 2183 (3) 4863 (9) 451 (6) 2607 (4) 5387 (10) -400 (6) 2323 (4) 4421 (10) -708 (6) 1636 (4) 2908 (9) -152 (5) 1213 (3) 384 (2) 875.2 (8) 1426 (1) '
absorption: this will introduce a maximum error in F, of < 1%. Solution of the Structure. The coordinates of the chromium atom were found from a three-dimensional Patterson synthesis, a Reflection 002 was too strong to measure. R , = 2: IIFol- I F c l I / Z I F o l ; R , = { Z W ( I F ~ I -I F c 1 ) 2 / ~ ~ F o 2 } " Z . and a series of full-matrix least-squares refinements followed by electron density difference syntheses revealed all the atoms. The Non-hydrogen atoms. temperature factors of the chromium and phosphorus atoms were made anisotropic, and further refinement (not refining hydrogen mg, 0.301 mol; 30%). After recrystallization from benzene, dark atoms) minimizing w(F,- FJ2 was terminated when the maximum cherry-red crystals were obtained: mp 185 OC (with decomposhift/error fell below 0.05. These results are reported here. One sition); Anal. Calcd for C24H16CrF5P; C, 59.75; H, 3.32. Found: further cycle, the refinement of x, y , z of the hydrogen atoms, C, 59.9; H,3.5. mass spectrum, m/z (%) 482 (CUHl6CrF5P+,351, was performed to give a rough estimate of the errors on the 464 (C2,H1,CrF4P+, 45), 404 (C18HloCrF5P+, 45), 386 hydrogen atom positions. No correction was made for secondary (C18H11CrF4P+, 30), 352 (C18HlP5P+,15),334 (C18H11F4P+, 171, extinction. Scattering curves were taken from ref 9, and anom275 (Cl2H5F5P+,14), 219 (CsF&r+, lo), 201 (C6HF4Crf,35), 185 alous dispersion corrections from ref 10 were applied to the curves (C12H1$+, 60),168 (C~HFS',25), 149 (CsHF4+,501,130 (C6&,Cr+, for Cr and P. Atom parameters for non-hydrogen atoms are listed 70), 78 (C&,3+, loo), (Cr', 90). Preparation of Chlorocarbonylbi~(~~-6-(diphenyl- in Table 11." phosphin0)-1,2,3,4,5-pentafluorochromarene)rhodium( I), 3. Results and Discussion [Rh(C0)2C1]2(0.04 mmol) and 2 (0.08 mmol) were stirred in benzene at room temperature for 4 h under an atmosphere of Syntheses. 1,2,3,4,5-Pentafluorochromarene, 1, prenitrogen. Removal of the solvent in vacuo gave 3, mp 212 "C, pared by cocondensing benzene, pentafluorobenzene and as brown microcrystals in 90% yield. Anal. Calcd for chromium vapor a t -196 "C, is known to possess a relaC4&32C1Cr2FloOP2RhC, 52.01; H, 2.83. Found C, 51.8; H, 3.1. tively acidic proton in the fluorinated ring.'J2 Lithiation The spectroscopic data are collected in Table IV. Collection of the X-ray Data. Precession photographs showed the crystal was monoclinic and unit cell parameters were obtained (9) Cromer, D. T.; Waber, J. T. "International Table for X-ray from a fit of x, 4, and 20 for 15 reflections (18.2 C 28 C 30.2) Crystallography"; Ibers, J. A., Hamilton, W. C., Eds.; Kynoch Press: recorded on a Syntex P21 diffractometer with use of graphiteBirmingham, England, 1974; Vol. IV, Table 2.2A, p 72 ff. (10) Cromer, D. T., ref 9, Table 2.3.1, pp 149-150. monochromated Mo K a l radiation (0.70926 A at -70 "C). (11)All calculations were carried out on a CYBER 170/730 computer. Measurements were made at low temperature because insuffiInitial data treatment used programs from the XRAY 76 package ciently precise structure solution was obtained at room temper(Stewart, J. M. Technical Report TR-446, Computer Science Center, ature. Crystal data and other numbers related to data collection University of Maryland College Park, MD, 1976). The structure was are summarized in Table I. The density was obtained by flotation solved with use of SHELX (Sheldrick, G. M. "A Programme for Crystal in aqueous zinc bromide solution. Intensities were measured by Structure Solution &d Refinement"; University of Cambridge: Cambridge, England, 1976). Final refinement and difference maps used the using a coupled B(crystal)-28(~0unter)scan. The methods of scan full-matrix least-squares program CUDLS and Fourier program SYMFOU, rates and initial data treatment have been described.'~~ Corwritten internally by J. S. Stephens and J. S. Rutherford, respectively. rections were made for Lorentz-polarization effects but not for Planes and interplanar angles were calculated with use of NRC-22 (Pippy, (7) Lippert, B.; Lock, C. J. L.; Rosenberg, B.; Zvagulis, M. Inorg. Chem. 1977,16, 1525-1529. (8) Hughes, R. P.; Krishnamachari, N.; Lock, C. J. L.; Powell, J.; Turner, G. Znorg. Chem. 1977, 16, 314-319.
M. E.; Ahmed, F. R. "NRC-22"; National Research Council of Canada: Ottawa, Ontario (1978). Diagrams were prepared by using ORTEP-11 (Johnson, C. K. Report ORNL-5138; Oak Ridge National Laboratory: Oak Ridge, TN, 1976). (12) Tan, T.-S.; McGlinchey, M. J. J. Chem. Soc., Chem. Commun. 1976, 155-156.
98 Organometallics, Vol. 2, No. I , 1983
C(l)-C(2) C(4)-C(5) C( 11)-C(12) C(14)-C(15)
Faggiani et al.
Table 111. Interatomic Distances ( A ) and Angles (Deg) Bond Distances 1.406 ( 8 ) 1.373( 8 ) 1.403 ( 8 ) 1.404 (ioj 1.407( 8 ) Cf 2)-F12) 1.350 16) Cf 3bFf31 C(5 j-Fi5 j 1.365(6j CiGj-FiSj 1.355( 8 ) P-C(31) 1.828(7) 1.842(6) P-C(Z1) Cr-C(3) 2.098(6) 2.149 (7) Cr-C(2) Cr-C(6) 2.083 (6) Cr-C(5) 2.095 (6) Cr-C(l3) 2.164 (6) Cr-Cf12) 2.157( 7 ) 2.143 (9) 2.142 ( 8 ) cr-c(i6j c~-c( 15) ~~~
C(4)-F(4) P-C(l) Cr-C(l) Cr-C(4) Cr-C(11) Cr-C(14)
~
~
1.353 16) 1.352 (sj 1.836 (5) 2.104 (6) 2.096(7) 2.144 ( 8 ) 2.156(6j
Bond Angles
F(4)-C(4)-C(3) F( 5)-C( 5)-C(6) C(1)-Cr-C(11) C(4)-Cr-C( 14) C(l)-Cr-C(14) C(4)-Cr-C(11) C(l)-P-C(Zl)
123.2(5) 120.8(5) 119.6(6) 119.1(5) 118.0(4) 116.6 (5) 119.4(5) 119.0(5) 99.0(3) 96.4 (3) 172.0(3) 173.5(2) 100.5 (3)
C( 2)-C( 3)-C( 4) C( 5)-C(6)-C(1) C(12)-C(13)-C(14)
119.8(5) 122.4(5) 120.3 (6)
C(3)-C(4)-C(5) C(6)-C(l)-C(2) C(13)-C(14)-C(15)
119.4(6) 114.3 (5) 120.8(7)
F(4)-C(4)-C( 5) F(6)-C(6)-C(5) C(Z)-Cr-C(lZ) C( 5)-Cr-C( 15)
121.0(5) 118.1 (4) 98.4(2) 98.6 (2)
C(5)-Cr-C(12) C(l)-P-C(31)
105.4(3)
F(5)-C(5)-C(4) F(6)-C(6)-C(l) C(3)-Cr-C(13) Cf6)-Cr-C(16) c(3j-cr-cji~j C(6)-Cr-C(13) C(21)-P-C(31)
120.3 (6) 119.5 (5) 96.7(3) 100.5 (2) 172.6(zj 173.9 (3) 102.8(3)
c(zj-cr-c(i5 j
172.5 (zj 175.8(2)
and reaction with chlorodiphenylphosphine gave a 30% yield of 1,2,3,4,5-pentafluoro-6-(diphenylpho~aphino)chromarene, 2, as cherry-red, air-stable crystals which are readily soluble in benzene but somewhat unstable when left in chloroform or methylene chloride for extended periods. Treatment of a benzene solution of [Rh(CO),CI], with 2 a t room temperature gave a 90% yield of trans-
chlorocarbonylbis((pentafluorochromareny1)diphenyl~ phosphine)rhodium(I), 3, as brown, air-stable microcrystals. Figure 1. The molecule 2 showing the atom numbering.
2. Crystallography. The molecule is shown in Figure 1, and selected bond angles and distances are given in Table 111. The chromium atom is sandwiched between
the benzene ring and the pentatluorophenyl ring which are nearly parallel (dihedral angle = 2.7 (5)"). The rings nearly eclipse one another; torsional angles, C(i)-ring center(+ring center(1i)-C(li), are about loo. The chromium atom is significantly closer to the pentatluorophenyl ring (Cr, 1.573 (1) A, out of ring plane and CrC(F) range = 2.083 (6)-2.104 (6) 8, vs. Cr, 1.635 (1) A, out of ring plane and Cr-C(H) range = 2.142 (8)-2.164 (6) A). We assume the strongly electronegative fluorine atoms caused electron density to he drawn from the chromium atom into the antibonding ?r* orbitals of the phenyl ring, giving stronger CrC(F) bonds. This does not cause any detectable differences in the C-C distances in the ring, but the phenyl ring is distorted because of the presence of the phosphorus atom bond to C(1). There is an apparent decrease in C-C bond lengths in the phenyl ring as one moves away from C(1). The errors are too large to say with certainty although C(l)-C(6) (1.428 (7)A) is significantly longer than
C(3)
