508 (6)I. D. Brown and J. D. Dunitz, Acta Crystalbgr., 13, 28 (1960). (7)D. M. Lemal in "Nitrenes," W. Lwowski, Ed., Interscience. New York, N.Y., 1970,p 345. (8)(a) G. A. Heath, R. Mason, and K. M. Thomas, J. Amer. Chem. SOC., 96, 259 (1974);(b) R. Mason, K. M. Thomas, J. A. Zubieta, P. G. Douglas, A. R. Galbraith, and B. L. Shaw, !bid., 96, 260 (1974). (9)F. A. Cotton and C. M. Lukehart, Progr. lnorg. Chem., 16,487 (1972);D. J. Cardin. B. Cetinkaya, and M. F. Lappert, Chem. Rev., 72, 545 (1972). (10)W. R. McBride and H. W. Kruse, J. Amer. Chem. SOC.,79,572(1957). (11) D. M. Lemal, F. Menger, and E. Coats, J. Amer. Chem. Soc.,86, 2395 ( 1964). (12)An aqueous solution of sodium hydroxide may also be used to increase the pH in these steps.
(13)J. G. Atkinson, D. W. Cillis, and R. S. Stuart, Can. J. Chem., 47, 477 (1969). (14)A. D. Mighell. A. Santoro, and J. D. H. Donnay. "International Tables for X-Ray Crystallography." Vol. 1, 3rd ed, The Kynoch Press, Birmingham, England, 1969,p 530. (15)P. W. R. Corfield, R . J. Doedens, and J. A. Ibers, lnorg. Chem., 6, 197 (1967). (16)J. H. Enemark, M. S. Quinby, L. L. Reed, M. J. Steuck, and K. K. Walthers, lnorg. Chem., 9, 2397 (1970). (17)Other programs used in the solution and refinement included Zalkin's FORDAP Fourier summation program. Woolfson's MULTAN package of direct methods programs, Iber's NUCLS group least-squares refinement program based on Busing and Levy's ORFLS. Busing and Levy's ORFFE, Johnson's ORTEP plotting program, Corfields RANGER weighting analysis program, and the general absorption program AGNOST.'' All computations were performed on a CDC 6400 computer. (18)P. Coppens, L. Leiserowitz, and D. Rabinovich, Acta Crystallogr., 18,
1035 (1965). (19)J. A. Ibers, D. H. Templeton, B. K. Vainshtein, G. E. Bacon, and K. Lonsdale, ref 14,Vol. 3, 1962,p 202. (20)D. T. Cromer and J. T. Waber, Acta Crystallogr., 18, 104 (1965). (21)W. C. Hamilton, Acta Crystallogr., 16, 502 (1965).
(22)J. A. lbers and W. C. Hamiltan, Acta Crystallogr., 17, 781 (1964). (23)D. T. Cromer, Acta Crystallogr.,18, 17 (1965). (24)See paragraph at end of paper regarding supplementary material. (25)H. Wieland and H. Fressel, Justus Liebigs Ann. Chem.. 392, 133 (1912). (26) S.F. Nelson, R. 8. Metzler, and M. Iwamura, J. Amer. Chem. SOC.,91, 5103 (1969). (27)G. S.Hammond and R. C. Neuman, Jr., J. Phys. Chem., 67, 1655, 1659 ( 1963). (28) C. R6mming and K. Waerstand, Chem. Commun., 299 (1965). (29)H. Ondik and D. Smith, ref 14,2nd ed, Vol. 3. 1968,p 260. (30)M. Massaux, M. J. Bernard, and M. Le-Bihan, Acta Crystallogr., Sect. B, 27, 2419 (1971). (31)R. Graziani, G. Bombieri, and E. Forsellini, J. Chem. SOC. A, 2331 (1971). (32)C. H. Chang, R. F. Porter, and S. H. Bauer, J. Amer. Chem. SOC., 92, 5313 (1970). (33)W. H. Beamer. J. Amer. Cbem. SOC.,70, 2979 (1948). (34)R. M. Curtis and R. A. Pasternak, Acta Crystallogr., 8, 675 (1955). (35)R. J. Kurland and E. B. Wilson, Jr., J. Chem. Phys., 27, 585 (1957). (36)B. Bak, D. Christensen, L. Hansen, and J. Rastrup-Anderson. J. Chem. Phys.. 24, 720 (1956). (37)L. Pauling, "The Nature of the Chemical Bond," 3rd ed, Cornell University Press, ithaca, N.Y., 1960,p 260. (38)N. V. Sutton, Anal. Chem., 36, 2120 (1964);R. Preussmann, H. Hengy, and A. von Hodenberg, Anal. Chim. Acta, 42, 95 (1968). (39)W. M. Tolles, W. R. McBride, and W.E. Thun, J. Amer. Chem. Soc., 91, 2443 (1969). (40)F. Klages, G. Nober, F. Kircher. and M. Bock, Justus Liebigs Ann. Cbem., 547, l(1941). (41)W. H. Urry, 2. L. F. Gaibel, J. C. Duggan, and S. S. Tseng., J. Amer. Chem. SOC.,95, 4338 (1973). (42)A. W. Nineham, Chem. Rev., 55, 355 (1955). (43)W. D. Hooper, Rev. Pure Appl. Chem., 19, 221 (1969). (44) W. G. Nigh in "Oxidation in Organic Chemistry," W. S.Trahanosky. Ed., Academic Press, New York, N.Y., 1973,p 1.
Synthesis, Crystal Structure, and Magnetic Properties of a Dimeric Quinoline Adduct of Copper( 11) Trifluoroacetate James A. Moreland and Robert J. Doedens* Contribution f r o m the Department of Chemistry, University of California, Irvine, California 92664. Received September 19, 1974
Abstract: Further synthetic investigations of the copper(I1) trifluoroacetate-quinoline system have led to the isolation and characterization of two new products, in addition to the two previously reported. A hygroscopic green crystalline material This material has been shown by a crystal structure analysis to be the dimeric quinoline adduct [Cu(OzCCF3)2(quinoline)]2. hydrolyzes readily to monomeric blue Cu(O2CCF3)2(quinoline)(H20). The dimeric complex crystallizes in space group C 2/c with a = 14.886 (24) A, b = 16.707 (29) A, c = 13.694 (23) A, and 6 = 1 1 1.26 (5) '. Observed and calculated densities are 1.74 (2) and 1.76 g/cm3, respectively. The structure determination was based upon 1555 independent counter data; anisotropic full-matrix least-squares refinement converged to a conventional R factor of 0.062. The centrosymmetric diquinolinetetra-p-trifluoroacetato(U,O)-dicopper(I1) molecule has the familiar bridged dimeric copper(I1) acetate structure with an unusually long C u - C u distance of 2.886 (4) A. Magnetic susceptibility data (85-340'K) conform to the usual dimer equation, with a singlet-triplet energy separation of 2 J = -310 cm-l. The electron paramagnetic resonance spectrum of a polycrystalline sample of the dimer shows a triplet pattern much like that of copper(I1) acetate hydrate. The unexpectedly close similarity of the magnetic properties of the acetate and trifluoroacetate adducts forces a reexamination of the hypothesis that the magnitude of metal-metal interaction in these dimers is determined by the strength of the parent carboxylic acid.
A vast number of dimeric copper(1I) carboxylate monoadducts, [ C U ( O ~ C R ) ~ Lhave ] ~ , been investigated in an effort to determine t h e factors influencing t h e magnitude of the intramolecular magnetic exchange interaction which occurs between t h e two C u 2 + ions in these compounds.' O n e frequently advanced relationship is that between t h e basicity of the bridging carboxylate anion, a s measured by the p K , of its parent acid, and t h e magnitude of the exchange coupling constant 25. Although there is some experimental support for such a correlation, there also exist exceptionsIO to the postulated dependence of 2J upon pK,, and t h e entire situation must still be regarded as ill-defined. Journal of the American Chemical Society
/
97:3
/
T h e situation is further complicated by t h e general disinclination toward formation of t h e bridged dimeric structure by copper(1I) complexes of t h e stronger carboxylic acids. Thus, t h e anhydrous copper(I1) carboxylates C u ( 0 2 C R ) 2 with R = CHC12, CC13, and CF3 a r e probably not dimeri c l l - 1 3 and these carboxylates tend to form monomeric, magnetically dilute adducts, C U ( O ~ C R ) ~ Lwith ~ , most bases.l4-I6 For this reason dimeric copper(I1) trichloroacetates or trifluoroacetates, which could potentially be important in clarifying t h e relationship between p K and 2J, have not been available until very recently. W e have recently shown that the copper(I1) trifluoroace-
February 5, I975
509 age of 30% by the end of the data collection. The decay was linear with time and equivalent for all four standards. The observed intensities were scaled to compensate for the change in intensity of the standards. Previously described methods were employed in processing the data.20 The p factor in the expression for the standard deviation of the observed intensities was given the value of 0.05. Of the 1975 independent reflections collected, 1555 were above background by three or more standard deviations. Solution and Refinement of the Crystal Structure. The coordinates of the single copper atom in the asymmetric unit of space group C 2 / c were determined from a three-dimensional Patterson map. The positions of the remaining nonhydrogen atoms were determined from Fourier difference maps. Initial refinement of all nonhydrogen atoms with individual isotropic temperature factors converged to discrepancy factors
t a t e adduct initially formulated a s Cu(02CCF3)2(quin)IS (where quin = quinoline) is in fact t h e tetranuclear basic carboxylate [C~2OH(O2CCF3)3(quin)2]2.~’ However, in t h e course of our synthetic investigations of t h e copper(I1) trifluoroacetate-quinoline system, three new products in addition to t h e tetranuclear carboxylate and t h e well-known bis adduct C ~ ( 0 2 C C F 3 ) 2 ( q u i n ) 2 ~were ~ . ~ ~isolated. O n e of these products proves to be t h e dimeric adduct [ C u (02CCF3)2(quin)]2; in this paper we report the details of its preparation, crystal structure, and magnetic behavior. Portions of these results have previously been communicated in preliminary form.’*
Experimental Section Preparation of the Complex. The violet bisquinoline adduct of Cu(I1) trifluoroacetate was heated in an evaporating dish at 80’. The complex eventually became light green in color. Crystals suitable for X-ray study were obtained from the green powder by Soxhlet extraction and recrystallization from hot benzene. The resulting light green crystals were extremely hygroscopic, turning to a light blue powder on exposure to air. C, H , and N analyses of both the green product and the blue decomposition product were performed by Chemalytics, Inc., of Tempe, Ariz. Anal. Calcd for (green) C U C ~ ~ H ~ NC, O 37.28; ~ F ~ :H , 1.68; N , 3.34. Found: C, 39.05: H, 1.68; N , 3.44. Calcd for (blue) CuC13H9N05F6: C, 35.91; H, 1.62; N , 3.22. Found: C, 35.63; H, 1.68; N, 2.94. The instability of the green product led to difficulty in obtaining reproducible analytical results and presumably accounts for the poor agreement between observed and calculated analyses for this material. Collection and Reduction of the X-Ray Data. Precession photographs ( h 01, h 1 I , Okl, l k l ) displayed monoclinic symmetry with k # 2n: h01, I # 2n; OkO, k # systematic absences (hkl, h 2 n ) consistent with either space group Cc or C2/c. Satisfactory solution and refinement of the structure were achieved in the latter, centrosymmetric space group, which was also indicated by the distribution statistics for normalized structure factors.I9 Lattice parameters were obtained by least-sqgares refinement of the setting angles of 13 reflections which had been accurately centered on a Picker four-circle X-ray diffractometer. The unit cell constants (21’, X (Mo K a ) ) 0.70926 A) obtained in this manner are a = 14.866 (24) A, b = 16.707 (29) A, c = 13.694 (23) A, and ,!i= ’ 1 1 1.26 ( 5 ) ’ . The numbers in parentheses are the standard deviations obtained from least-squares refinement of the setting angles. The density of 1.76 g/cm3 calculated on the basis of eight formula units (four dimeric molecules) per unit cell agrees well with a density of 1.74 (2) g/cm3 obtained by flotation in a CHZBr2-CHZCIZ solution. Intensity data were collected from a green, nearly octahedral crystal of dimensions 0.37 X 0.47 X 0.40 mm. The bounding planes of the crystal were of the {I1 1 j, 11 I O ) , { 1 I f ) , and 1170)forms. The crystal was mounted under nitrogen on a glass fiber approximately along the crystallographic c axis. It was then sprayed with an acrylic coating because of its instability in air. This proved to be a more effective means of preserving the crystal than mounting in a capillary, though decomposition still occurred over a period of weeks. Narrow-source open-counter w scans through several reflections displayed an average full width at half-maximum of 0.14’, indicative of an acceptably low mosaic spread. The data were collected by the use of procedures described previously.20 A takeoff angle of 1.5’ was employed. The diffracted beam was filtered through 3.0 mil N b foil. The counter aperture was 5 X 5 mm and was positioned 30.0 mm from the crystal. The pulse height analyzer was set to admit -95% of the Mo K a peak. Data were collected by the 0-20 scan method. A symmetric scan range of &0.80° Crom the calculated scattering angle was used. The intensities of all independent reflections with 20 I44’ were collected. The scan rate was I’/min, and stationary background counts of 20 sec were taken at each end of the scan range. Copper foil attenuators were automatically inserted whenever the count rate exceeded -I 0,000 counts/sec; only 1 1 reflections required attenuation. Four standard reflections, chosen to lie in widely separated regions of reciprocal space, were monitored after every 100 reflections throughout the data collection. The intensity of these standards decreased an aver-
+
Moreland, Doedens
based on the 1 5 5 5 reflections with F, 2 3a(F0). At this point it was noted on a difference Fourier map that there was a great deal of thermal motion and/or disorder of the CF3 groups. Further refinement employed anisotropic thermal parameters for all nonhydrogen atoms. Because of the large number of parameters involved, the anisotropic refinement was carried out in blocks. The first block included the scale factor, the metal atom, and the trifluoroacetate ligands. The second block was comprised of the scale factor, the Cu atom, and the quinoline ligand. Hydrogen atoms of the quinoline were included as fixed contributions in the refinement. New hydrogen positions were calculated after each pair of cycles. An absorption correction was applied to the observed intensities. Based upon a linear absorption coefficient of 14.52 cm-I, the calculated transmission factors ranged from 0.57 to 0.70. Final anisotropic refinement converged to R I = 0.062 and Rl = 0.087. A final difference map had no peaks greater than 1 e/A3; the largest of these residual peaks were in the vicinity of the fluorine atoms. The largest parameter shift in the last cycle was
