Sekutowski, Jungst, and Stucky
1848 Inorganic Chemistry, Vol. 17, No. 7, 1978
at g = 2.088 and 1.83 1. There was no very low-field signal at g = 2.088 seen in the Q-band spectrum. In several spectra, however, a signal at g = 1.922 was observed in the Q-band spectrum. Acknowledgment. The support of the National Science Foundation under Grants NSF-DMR-76-01058 and CHE77-24964 is gratefully acknowleged by G.D.S. and B.F.F. D.N.H. is grateful for support from National Institutes of Health Grant HL 13652. Registry No. 1, 66172-45-0; 2, 66172-46-1; 3, 66172-47-2; 4, 66 172-48-3.
References and Notes School of Chemical Sciences and the Materials Research Laboratory. School of Chemical Sciences;Camille and Henry Dreyfus Teacher-Scholar Fellow, 1972-1977; A. P. Sloan Foundation Fellow, 1976-1978. B. N. Figgis and G. Robertson, Nature (London), 205, 694 (1965). A. Earnshaw, B. pi. Figgis, and J. Lewis, J . Chem. SOC.A , 1659 (1966). A. P. Ginsberg, R. L. Martin, and R. C. Sherwood, Inorg. Chem., 7, 932 (1968). R. Beckett, R. Colton, B. F. Hoskins, R. L. Martin, and D. G. Vince, Aust. J . Chem., 22, 2527 (1969). A. Hasegawa, J. Chem. Phys., 55, 3101 (1971). (a) G. Kothe, E. Ohmes, J. Brickmann, and H. Zimmermann, Angew. Chem., Inr. Ed. Engl., 10, 938 (1971); (b) J. Brickmann and G. Kothe, J . Chem. Phys., 59, 2807 (1973). (a) A. Hudson and G. R. Luckhurst, Mol. Phys., 13, 409 (1967); (b) G. Kothe, A. Naujok, and E. Ohmes. ibid., 32, 1215 (1976). G. Kothe, F. A. Neugebauer, and H. Zimmermann, Angew. Chem., Int. Ed. Engl., 11, 830 (1972). B. F. Fieselmann, A. M. McPherson, G. L. McPherson, D. L. Lichtenberger, and G. D. Stucky, for publication in J . A m . Chem. Sot. “Beilsteins Handbuch der Organischen Chemie”, Vol. 26, p 239. P. C. Wailes, R. S. P. Coutts, and H. Weigold, “Organometallic Chemistry of Titanium, Zirconium, and Hafnium”, Academic Press, New York, N.Y., 1974, pp 68, 211.
M. L. H. Green and C. R. Lucas, J. Chem. SOC.,Dalton Trans., 1000 (1972). R. Juigst, D. Sekutowski,J. Davis, M. Luly, and G Stucky,Inorg. Chem., 16, 1645 (1977). (a) R. Jungst, D Sekutowski, and G. Stucky, J . A m Chem. SOC.,96, 8108 (1974); (b) D. G. Sekutowski and G. D. Stucky, Inorg. Chem., 14, 2192 (1975). D. G.Sekutowski, Ph.D. Thesis, University of Illinois, 1975. L. T. Reynold and G. Wilkinson, J. Inorg. Nucl. Chem., 9, 88 (1959). J. P. Chandler, Program 66, Quantum Chemistry Program Exchange, Indiana University, Bloomington, Ind., 1973. D. M. Duggan, E. K. Barefield, and D. N. Hendrickson, Inorg. Chem., 12, 985 (1973). F. E. Mabbs and D. J. Machin, “Magnetism and Transition Metal Complexes”, Chapman and Hall, London, 1973, pp 5 , 170. B. F. Fieselmann, Ph.D. Thesis, University of Illinois, 1977. E. I. Lerner and S. J. Lippard, Inorg. Chem., 16, 1537 (1977). S. Emori, M. Inoue, M. Kishita, M. Kubo, S. Mizukami, and M. Kono, Inorg. Chem., 7 , 2418 (1968). W. E. Hatfield and F. L. Bunger, Inorg. Chem., 8, 1194 (1969). B. Bleaney and K. D. Bowers, Proc. R. SOC.London, Ser. A , 214,451 (1952). M. F. Lappert and A. R. Sanger, J . Chem. SOC.A , 874 (1971). K. Issleib and H. Hackert, 2. Nuturforsch., E , 21, 519 (1966). M.F. Lappert and A. R. Sanger, J. Chem. Soc. A , 1314 (1971). J. L. Petersen and L. F. Dahl, J . A m . Chem. Soc., 96, 2248 (1974); 97, 6422 (1975); J. L. Petersen, D. L. Lichtenberger, R. F. Fenske, and L. F. Dahl, ibid., 97, 6433 (1975). (a) E. Wasserman, L. C. Synder, and W. A. Yager, J . Chem. Phys., 41, 1763 (1964); (b) J. Reedijk and B. Nieuwenhuijse, Red. Trau. Chim. Pays-Bas, 91, 533 (1972). W. A. Yager, E. Wasserman, and R. M. Cramer, J . Chem. Phys., 37, 1148 (1962). T. R. Felthouse and D. N. Hendrickson, submitted for publication in Inorg. Chem. B. F. Fieselmann, D. N. Hendrickson, and G.D. Stucky, Inorg. Chem., in press. N. D. Chasteen and R. L. Belford, Inorg. Chem., 9, 169 (1970). A. J. McAlees, R. McCrindle, and A. R. Woon-Fat, Inorg. Chem., 15, 1065 (1976).
Contribution from the School of Chemical Sciences and the Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801
Magnetic Exchange between Titanium(II1) Centers in a Series of Linear Trimetallic Compounds and the Structural Properties of Bis[p-dichloro-bis( cyclopentadienyl)titanium(III)]manganese(II)-Bis( tetrahydrofuran), [(q5-C5H5)2TiC1]2MnC12*20C4H8 DENNIS S E K U T O W S K I , R U D O L P H JUNGST, and G A L E N D. STUCKY* Received July 27, 1977 The magnetic properties of a series of d i titanium(II1) complexes of general formula [ ($-C5H5)2TiX]2MX2 (X = halide, M = Zn, Be, Mn) have been determined. From variable-temperature magnetic susceptibility measurements, an intramolecular antiferromagnetic interaction between the d’ centers of those compounds containing a diamagnetic (do or d”) central metal atom has been observed. The triplet state has been found to be between 31.4 and 13.8 cm-’ above the singlet ground state. Although the magnitude of the exchange coupling constant is larger than one would expect for an intermolecular exchange interaction, it is much lower than what has previously been observed in titanium(II1) halide dimers of general formula [ (q5-C5H5)2TiX]2. Single-crystal X-ray diffraction methods have been employed to determine the molecular structure of [($-C5H5)2TiCl] 2MnC12.23C4H8. This material crystallizes in the monoclinic space group P2,/c ( C2,5)with two dimers in a unit cell of dimensions a = 8.167 ( 5 ) A, b = 11.453 (8) A, c = 16.249 (12) A, and /3 = 91.64 (3)”. Least-squares refinement of 2768 independent reflections has led to a final weighted R factor of 0.057. The structure consists of a linear trimetallic molecule with chlorine atoms bridging the metal atoms. T h e geometry around the central manganese atom is tetragonal as opposed to the pseudotetrahedral geometry of the central atom in the other members of the series. The tetrahydrofuran molecules are coordinated in a trans geometry to the manganese atom and the cyclopentadienyl rings on each titanium atom are eclipsed. Attempts have been made to simulate the magnetic susceptibility of this compound with theoretical equations including both terminal interactions Ti(dl)-Ti(dl) and nearest-neighbor interactions Ti(d1)-Mn(d5). T h e fit was only sensitive to Jilz,5,2and this was found to be -8 cm-l.
Introduction Interest in magnetic interactions has greatly expanded over the last few years. A number of recent reviews have indicated the success that workers in this field have had in correlating the magnitude of the magnetic coupling constant to both structural parameters and molecular orbital calculations for 0020-1669178113 17- 1848$01 .OO/O
dimeric metal The results have been particularly useful in the understanding of exchange mechanisms. However, very few studies have been undertaken to examine the magnetic properties of trimetallic systems. Three metals can be geometrically arranged in a triangular or linear configuration. Magnetic exchange in homonuclear
0 1978 American Chemical Society
Magnetic Exchange in Linear Trimetallic Compounds compounds where all the metal atoms are located on the corners of an equilateral triangle around an oxygen atom have been determined for [Cr30(0a~)6(H20)3]C1.6H20 (d3-d3-d3) and [Fe30(0ac)6(H20)3]C1.6H20 (d5-dS-d5).4-7 The compounds were found to have an antiferromagnetic interaction with J = -10.4 cm-' and J = -30 cm-', respectively. Variable-temperature magnetic susceptibility measurements on trimeric iron(II1) alkoxides have also indicated an antiferromagnetic interaction between the metal centers, and the results are consistent with the metal atoms being in an equilateral triangle; however structural data are lacking.8 Sinn has reported the magnetic properties of a number of trimetallic complexes where the metal atoms are in an isosceles triangle arrangement.g Two copper atoms (d9) were bridged by a variety of paramagnetic and diamagnetic metal centers; however a measurable value for exchange interactions between the terminal metals was not found. Since the magnetic data were only collected down to liquid nitrogen temperatures, the possibility of such an interaction cannot be excluded for these compounds. The only example of 1,3 magnetic exchange within a linear triad of metal atoms has been found by Ginsberg for Ni3(acac),. Variable-temperature magnetic susceptibility studies have shown that an antiferromagnetic exchange between the terminal nickel atoms via the paramagnetic nickel(I1) central atom does yield an improved fit to the experimental data.lOJ1 Studies have not been undertaken for linear trimetallic complexes where the central metal is diamagnetic. The limited number of magnetic studies of trimetallic systems is probably a result of the synthetic difficulties involved in preparing a series of such complexes in which one can introduce a systematic variation in geometry in order to observe its influence on the magnetic coupling constant. With the exception of the compounds reported in this paper, all linear trimetallic organometallic complexes that have been structurally characterized to date have been diamagnetic. We have previously communicated our discovery of antiferromagnetic exchange between Ti(II1) centers via a diamagnetic metal center in a series of nearly linear trimetallic complexes.12 We wish now to report the details and interpretation of our magnetic data for these systems and the results of exchange through a paramagnetic center in [($C5Hs)2TiCl]2MnC12.20C4H,.The physical properties of this latter compound indicated that it was not isostructural with the other members of the series, and a three-dimensional X-ray analysis of the material was undertaken to ascertain its molecular structure.
Experimental Section Synthesis. The compounds were all prepared and characterized as given in ref 13. X-ray Data. Preliminary precession photographs of [($C S H ~ ) ~ T ~ C ~ ] ~ M ~(Mo C ~K~a .radiation) ~ O C ~ revealed H~ that the crystals were monoclinic. The observed systematic absences hOl, I = 2n 1, and OM), k = 2n 1, are compatible with space group n 1 / c (C2,'; No. 14). A triangular prism with edges which varied from 0.07 to 0.13 mm was used for data collection. Lattice parameters were obtained by a least-squares refinement of 14 reflections, which were carefully hand centered on a Picker four-circlediffractometer (T = 23 'C, h 0.71069 A). The final values obtained were a = 8.167 ( 5 ) A, b = 11.453 (8) A, c = 16.249 (12) A, and fi = 91.64 (3)'. The density calculated on the basis of two molecules per unit cell is 1.523 g cmw3,while the observed value of 1.53 A 0.03 g cm-3 was obtained by flotation in a bromobenzene and m-bromoaniline mixture. Several w scans showed a typical peak width at half-height to be 0.125O indicating that the mosaicity was acceptable for data collection. Intensity data were measured on a fully automated Picker four-circle diffractometer using Mo Ka radiation monochromated by a higly oriented graphite crystal. A 8-28 scan technique was used with a scan width of 1.5', a scan rate of 2'/min, and a takeoff angle of 1.6'.
+
+
Inorganic Chemistry, Vol. 17, No. 7, I978 1849 Table I. Positional Parameters for the Nonhydrogen Atoms in [( q 5C ,H,),TiCl] ,MnC1,~2OC4H, Atoms
Y
X
0.000
-0.25715 (11) -0.27867 (14) 0.2594 (15) -0.3391 (9) -0.4810 (9) -0.5085 (8) -0.3874 (10) -0.2832 (8) -0.1284 (8) -0.2966 (IO) -0.3612 (8) -0.2366 (12) -0.0935 (8) 0.1124 (4) 0.2610 (7) 0.2823 (9) 0.1495 (9) 0.0451 (7)
0.000
0.18938 (8) 0.09708 (11) 0.8991 (11) 0.00961 (5) 0.0630 (7) 0.1608 (7) 0.1699 (6) 0.0780 (7) 0.3434 (5) 0.3593 ( 5 ) 0.3843 (6) 0.3837 (6) 0.3577 (5) 0.3390 (3) 0.2855 (5) 0.1789 (6) 0.1702 (7) 0.2741 (5)
Z
0.0000
0.14336 (5) -0.00081 (11) 0.1428 (7) 0.1986 (5) 0.1669 (4) 0.2123 (5) 0.2719 (4) 0.2650 (4) 0.0769 (4) 0.0630 (4) 0.1383 (6) 0.1967 (4) 0.1602 (4) 0.4495 (2) 0.4797 (3) 0.4325 (4) 0.3721 (5) 0.3807 (3)
Background counts, each of 10-s duration, were taken at both ends of the scan. Copper foil attenuators were automatically inserted in front of the counter whenever the counting rate exceeded 10000 counts/s. Three standards were measured every 50 reflections in order to check for crystal and counter stability. Whenever these standards showed any significant fluctuationsduring data collection, the crystal was recentered and that particular section of data was recollected. One quadrant of intensity data (hkl and hkl) was measured to 50" in 28. A total of 2768 unique reflections were measured, 1510 of which were considered observed by the criteria Zobsd> 3u,(I). Here u, = [T, + o.25(t,/t,)2(Bl + B2)]1/2where T, is the total counts, tc/tF is the ratio of the time counting peak intensity to that spent counting backgrounds, and B1 and B2 are the background counts. Initial structure solution was accomplished using just the observed reflections. Final refinement using all of the data was carried out with weights assigned on the basis of counting statistics. No significant systematic variation of w(Fo- Fc)2was observed with respect to (sin @)/A or the magnitude of the structure factors. The nonhydrogen scattering factors were taken from the tabulation of Cromer and WaberI4 and the hydrogen scattering factors from Stewart, et al.I5 Anomalous dispersion corrections for the titanium, manganese and chlorine atoms were those of Cromer and Liberman.I6 Lorentz and polarization corrections and the calculation of the observed structure factor amplitudes from the raw data were carried out using the program VANDY. Absorption corrections were made (p = 13.3 cm-') with the program ORABS. Structure Determination and Refinement. The structure was solved in a straightforward manner by application of direct-methods (FAME and MULTAN) and Fourier techniques. All computer programs employed have been previously referen~ed.~'From the generated E map the titanium and manganese atom positions were found, and they coincided with the positions obtained from a Patterson map. From density measurements, only half of the molecule could be in an asymmetric unit of the cell, indicating that the central manganese atom was on the crystallographic center of inversion. This was consistent with the metal atom positions, and subsequent application of Fourier calculations and least-squares refinement led to the discovery of all nonhydrogen atoms. Final anisotropic refinement of all parameters with the exception of the hydrogen atom temperature factors, which were set equal to the isotropic temperature factor of the carbon atom to which they were bonded, gave an error of fit equal to 1.4275 and R1 = CIFol - IFcl/CIFol= 0.095 and R2 = [Cw(lFoI- IF,I)2/CwF2]1/2 = 0.057. Final positional parameters, anisotropic thermal parameters, interatomic distances, and bond angles are given in Tables I-IV, respectively. Physical Measurements. Variable-temperature (4.2-295 K) magnetic susceptibility measurements were made with a Princeton Applied Research Model 150A vibrating-sample magnetometer calibrated with CuS04.5H20. A calibrated gallium arsenide diode was used in the temperature-controlling and -sensing device. All experimental data were corrected for diamagnetism using Pascal's constants and computer fit to theoretical expressions with STEPT by
1850 Inorganic Chemistry, Vol. 17, No. 7, I978
Sekutowski, Jungst, and Stucky
Table 11. Anisotropic Thermal Parameters for the Nonhydrogen Atoms in [(C ,H,),TiCl] ,MnC1;20C4H, Atom Mn Ti CK1)
cm C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) 0 C(11) C(12) C(13) C(14) a
U,la 0.0391 (6) 0.0420 (5) 0.0377 (7) 0.0428 (7) 0.097 (5) 0.074 (5) 0.050 (4) 0.096 (5) 0.065 (4) 0.091 (5) 0.107 (6) 0.069 (5) 0.155 (8) 0.077 (5) 0.048 (2) 0.053 (3) 0.096 (5) 0.097 (1) 0.078 (4)
u 2 2
u33
u 12
u,3
' 2 3
0.04087 (6) 0.0467 (6) 0.0542 (8) 0.0593 (9) 0.051 (4) 0.116 (6) 0.105 (6) 0.088 (5) 0.107 (6) 0.049 (3) 0.051 (4) 0.058 (4) 0.05 2 (4) 0.058 (4) 0.058 (2) 0.062 (4) 0.097 (5) 0.112 (6) 0.069 (4)
0.041 3 (5) 0.0456 (5) 0.0485 (8) 0.0425 (7) 0.100 (5) 0.063 (4) 0.102 (5) 0.057 (4) 0.063 (4) 0.063 (4) 0.083 (5) 0.138 (7) 0.078 (5) 0.083 (5) 0.049 (3) 0.069 (4) 0.107 (5) 0.1 20 (7) 0.043 (3)
0.0007 (5) 0.0020 (5) 0.0025 (6) 0.0012 (7) 0.010 (4) 0.046 (5) 0.006 (4) 0.028 (4) 0.011 (4) 0.004 (3) 0.004 (4) 0.016 (4) 0.004 (5) 0.017 (3) 0.009 (2) 0.013 (3) 0.038 (5) 0.019 (5) -0.002 (3)
-0.0007 (5) 0.0062 (4) -0.0056 (5) -0.0030 (5) 0.050 (5) 0.002 (3) 0.028 (4) 0.028 (4) 0.006 (3) 0.028 (3) 0.036 (5) 0.034 (5) 0.025 (5) 0.017 (4) 0.007 (1) 0.007 (3) 0.01 3 (5) -0.013 (5) -0.005 (3)
0.0006 (5) -0.0046 (5) -0.0058 (7) 0.0041 (7) 0.008 (4) 0.013 (5) 0.020 (5) 0.019 (4) 0.029 (4) 0.002 (3) 0.005 (4) 0.004 (5) -0.015 (4) -0.010 (4) -0.01 1 (2) -0.011 (3) -0.041 (5) -0.064 (6) -0.008 (3)
The form of the anisotropic ellipsoid is e ~ p [ - 2 n ~ ( h ~ U , ,ta *k2U2,b** ~ t IzU,,c*2
+ 2hkU,,a*b* + 2hlU,,a*c* + 2klU2,b*c*)].
Table 111. Interatomic Distances (A) for the Nonhydrogen Atoms in [(C,H,),TiCl] 2MnC1,~20C,H,a MnCl(1) Mn-Cl( 2) Mn-O Mn-Ti TiCl(1) TiCl(2) C1( 1)-C1(2) Cl(l)-C1(2)' Ti-C(l)
2.533 (2) 2.531 (2) 2.227 (3) 3.850 (2) 2.572 (2) 2.578 (2) 3.355 (3) 3.793 (3) 2.351 (6)
C(l)C(2) C(2)4(3) C(3)C(4)
1.396 (9) 1.363 (9) 1.369 (9)
C(6)-C(7) CU)-C@) C(8)-C(9)
1.397 (9) 1.377 (9) 1.371 (10)
Ti-C(2) Ti-C(3) Ti-C(4) Ti-C(5) TiC(6) Ti-C(7) TiC(8) Ti-C(9) TiC(10)
2.367 2.389 2.382 2.367 2.334 2.360 2.390 2.392 2.357
(6) (6) (6) (6) (6) (6) (6) (7) (6)
C(4)-C(5) C(5)-C(1)
1.360 (9) 1.400 (9)
C(9)-C(10) C(lO)-C(6)
1.359 (9) 1.386 (8)
c:2V
C!&
CP 1
CP 2
A
THF O-C(l1) C(ll)C(12) C(12)-C(13)
1.434 (6) 1.455 (8) 1.446 (9)
Figure 1. Molecular structure of [(C5H5)2TiC1]2MnC12.20C4H~, Thermal ellipsoids are shown at the 42% probability level.
C(13)-C(14) C(14)-0
1.472 (9) 1.438 (6)
a Errors in the lattice parameters are included in the estimated standard deviations.
Table IV. Bond Angles (deg) for the Nonhydrogen Atoms in [(C,H,),TiCl] ,MnC1,~20C,H8 C1(2)-Mn-C1(1) C1(2)-MnC1(1)' C1( l)-Ti-C1(2) Mn-CI(l)-Ti Mn-C1(2)-Ti
82.99 97.01 81.31 97.91 97.78
(5) 0-Mn-Cl(1) (5) 0-Mn-Cl(2) (6) 0-MnCl(1)' (5) 0-Mn-Cl(2)' (5)
90.8 (1) 88.6 (1) 89.2 (1) 91.4 (1)
C(ll)-O-C(14) OC(ll)-C(12) C(ll)-C(l2)-C(13)
THF 110.2 (4) C(12)-C(13)
