48
Organometallics 1983, 2, 48-52
Bent Metallocenes Containing Potentially Bidentate Ligands. The Crystal and Molecular Structure of Bis( 7-cyclopentadienyl)bis( benzoato)titanium(I V ) David M. Hoffman, Nicholas D. Chester, and Robert C. Fay' Department of Chemistry, Cornel1 University, Ithaca, New York 14853 Received June 29, 7982
The crystal and molecular structure of bis(ll-cyclopentadienyl)bis(benzoato)titanium(IV),( 8 C5H5)2Ti(02CC6H5)2, has been determined by X-ray diffraction and has been refined anisotropically by least-squares methods to R , = 0.086 and R2 = 0.077 using 2373 independent diffractometer data having 5 50.0' and lFol > 2 . 0 ~ The ~ . compound crystallizes in the monoclinic space group P2,/c with four 2OMOK, molecules in a cell having dimensions a = 16.078 (3) A, b = 12.853 (3) A, c = 16.076 (2) A, fl = 142.685 (7)' (Pobd = 1.395 and Pealed = 1.386 g ~ m - ~The ) . molecules have a distorted tetrahedral structure in which the Ti atom is attached to two 0-C H5 groups and two monodentate benzoate ligands (Ti-C = 2.337-2.393 A; Ti-0 = 1.922 (7) and 1.930 ( 5 ) (centroid C5H5)-Ti-(centroid C5H5)= 131.7 (5)'; and 0-Ti-0 = 91.4 (3)'). The relatively short Ti-0 bond lengths and large Ti-0-C bond angles (148.6 (4) and 147.9 (7)') suggest that the Ti atom achieves an effective 18-electron configuration via Ti-0 T bonding. Extended Huckel molecular orbital (EHMO) calculations confirm the existence of a strong a-type interaction involving T ~ * + and in-plane p orbitals of the coordinated benzoate oxygen the la, orbital of the ( V - C ~ H ~ ) ~fragment atoms. EHMO calculations and geometrical considerations indicate that the alternate coordination geometry having one monodentate and one bidentate carboxylate ligand is precluded by 0 - C steric interactions.
1;
nitrobenzoate derivative by X-ray diffraction5 Introduction In order to further delineate the structure of (7Many Ti(1V) complexes of the type (7-C5H5)2TiX2 have C,H5)2Ti(02CR)2complexes, we have synthesized and been reported where X is a potentially bidentate ligand.' determined by X-ray crystallography the structure of (7The structures of some of these complexes have not been C5H5)*Ti(0&C6H5)2. definitively determined. I n the present study, we are concerned with the complexes where X is a carboxylate,* Experimental Section compounds whose structures are a matter of some conReagents and General Techniques. Triethylamine was troversy. refluxed for 18 h over calcium hydride and then distilled from On the basis of IR data Chandra et al. assigned structure hydride. It was stored under nitrogen until needed. 1 t o the compounds ( T ~ C H ~ C ~ H ~ ) ~ Tfor ~ ( RO ~= C R )calcium ~ Benzoic acid was dried under vacuum over phosphorus(V) oxide CHC12 or CH2C1. For R = CH3, C2H5,n-C3H7,or C6H5 for 6 days at room temperature and then stored under nitrogen. Bis(8-cyclopentadieny1)titaniumdichloride was purchased from Alfa Products and used without further purification. Solvents were dried by refluxing for at least 24 h over sodium/benzophenone (tetrahydrofuran)or potassium/benzophenone (hexanes). The synthesis and handling of ( T ~ C ~ H ~ ) ~ T ~ (was O ~carried CC~H~)~ II out under anhydrous conditions in a dry nitrogen atmosphere. Bis(tl-cyclopentadienyl)bis(benzoato)titanium(IV). Triethylamine (1.6 mL, 11.5 mmol) was added by syringe to a mixture of (q-C5Hs),TiCl,(1.4 g, 5.6 mmol) and benzoic acid (1.37 g, 11.2 mmol) in 100 mL of tetrahydrofuran at room temperature. The I clear blood-red reaction mixture became cloudy and bright orange a different structure was proposed having one $-CH3C5H4 was removed by filafter being stirred for 4 h. [(C2H5)3NH]C1 ligand, one q1-CH3C5H,ligand, and two bidentate cartration, and the solvent was removed by pumping. Recrystalliboxylate ligand^.^ Interestingly, in a n early IR study by zation of the resulting orange solid from tetrahydrofuran/hexanes mp 198-201 afforded orange crystals of (8-CSH5)2Ti(02CC6H5)2: Vyshinskii e t al., (.rl-C5H5)2Ti(02CC6H,)2 a n d ( 7 "C dec (lit.2a188-192 "C dec); 'H NMR (ppm, CDCI3 solution) C5H5)2Ti(02CC6H4-p-N02)2 were both assigned structure -6.62 (C6H5),multiplets at -7.5 and -8.1 (C6H5);IR (cm-', Kujol l., This formulation was later confirmed for the p mull) v,,~(COO) 1642 ( s ) , v,,(COO) 1350 (s), 1320 (m),1298 (s), other bands 3090 (w), 3069 (w), 1590 (w), 1287 (s), 1170 (a), 1130 (m), 1063 (w), 1015 (w), 1022 (w), 870 (w), 829 (m), 713 (m), 671 (1) See for instance: (a) Klein, H.-P.; Thewalt, U. J . Organomet. (w),591 (w), 568 (m), 450 (vw), 419 (m). Chem. 1981, 206, 69-75. (b) Thewalt, U.; Klein, H.-P. 2. Kristallogr. 1980, 153, 307-315. (c) Bhushan, B.; Mittal, I. P.; Chhatwal, G. R.; Nuclear Magnetic Resonance Spectra. Proton chemical Kaushik, N. K. J. Inorg. Nucl. Chem. 1979,41,159-160. (d) Sharan, R.; shifts were measured at ambient probe temperature (-34 'C) Gupta, G.; Kapoor, R. N. Transition Met. Chem. (Weinheim,Ger.) 1978, relative to an internal reference of tetramethylsilane with a Varian 3, 282-285. (e) Sharma, R. K.; Singh, R. V.; Tandon, J. P. J. Inorg. Nucl.
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Chem. 1980, 42, 1382-1384. (2) (a) Razuvaev, G. A.; Latyaeva, V. N.; Vyshinskaya, L. I. Dokl. Akad. Nauk SSSR, Ser. Khim.1961,138,1126-1129; Dokl. Chem. (Engi. Transl.) 1961,138,592-594. (b) Razuvaev, G. A.; Latyaeva, V. N.; Lineva, A. N. Dokl. Akad. N a u k SSSR, Ser. Khim. 1969, 187, 340-342; Dokl. Chem. (Engl. Transl.) 1969, 187, 545-547. Razuvaev, G. A,; Latyaeva, V. N.; Lineva, A. N. Zh. Obshch. Khzm. 1971, 41, 1556-1560; J . Gen. Chem. USSR (Engl. Transl.) 1971, 41, 1560-1564. (3) Chandra, K.; Sharma, R. K.; Garg, B. S.; Singh, R. P. J . Inorg. Nucl. Chem. 1980, 42, 187-193.
0276-7333/83/2302-0048$01.50/0
(4) Vyshinskii, N. N.; Ermolaeva, T. I.; Latyaeva, V. N.; Lineva, A. N.; Lukhton, N. E. Dokl. Akad. Nauk SSSR, Ser. Khim.1971, 198, 10811084; Dokl. Chem. (Engl. Transl.) 1971, 198, 487-490. (5) (a) Gladkikh, E. A.; Kuntsevich, T. S. Zh. Strukt. Khim.1973,14, 949-950; J . Struct. Chem. (Engl. Transl.) 1973, 14, 898-899. ib) Kuntsevich, T. S.; Gladkikh, E. A,; Lebedev, V. A,; Lineva, A. N.; Belov, N. V. Kristallografiya 1976, 21, 80-88; Soc. Phys.-Crystallogr. (Engl. Trans/.) 1976, 21, 40-44.
LC1983 American Chemical Society
Bent Metallocenes Containing Potentially Bidentate Ligands EM-390 9 0 - e spectrometer. The sweep width was calibrated
with a sample of chloroform-d, 99.8 atom % deuterium, and tetrametbylsilane. Infrared Spectra. The infrared spectrum was recorded in the region 400&400 em-' with a Perkin-Elmer 337 grating spectrophotometer. The estimated uncertainty in reported frequencies is i 4 em-'. Crystallography. Several orange crystals of (v--C5H5),Ti(0&C6H5), were sealed in 0.5-mm diameter Lindemann glass capillaries under an atmosphere of dry nitrogen. Axial photographs indicated the crystal system to he monoclinic, and the systematically absent reflections (h01for h # 2n and OkO for k # 2n) identified the space group as PZl/a. The data were reindexed to give the standard space group P2,lc. The lattice constants of a = 16.078 (3) A, b = 12.853 (3) A, c = 16.076 (2) A, and B = 142.685 ( 7 ) O were determined by least-squares refinement of the diffraction geometry for 15 reflections (28 > Z O O ) centered on a computer-controlled four-circle Syntex P2, diffractometer using graphite-monochromated Mo Ka radiation (A = 0.71069 A). The calculated density based upon four molecules of (n-C5H6)zTi(OZCC6H5)z per unit cell is 1.386 g The ob. served density, measured by flotation using a solution of carbon tetrachloride and hexanes, was 1.395 g An irregularly shaped crystal of approximate dimensions 0.32 X 0.26 X 0.16 mm was chosen for collection of intensity data The data were collected on the Syntex P2, diffractometer using the 8-20 scan technique with graphite-monochromated Mo Ka radiation at a takeoff angle of 6.3O and a glancing angle of 2.5O. A variable scan rate ranging from ZO/minfor reflections of intemie 5150 counts/s to 29.3'/min for reflections of intensity 21500 counts/s was employed. The range of each scan consisted of a base width of 2.0° at 20 = Oo and an increment of A(20) = (0.692 tan 8)" to allow for spectral dispersion; background counts of duration equal to half the total scan time were taken at both limits of the scan. The intensities of three standard reflections, measured at 63-reflection intervals, indicated no crystal decomposition or misalignment. A total of 3741 unique reflections having 28 5 50.0' were scanned. The linear absorption coefficientwas calculated to be 4.72 em-'. The maximum error resulting from neglect of absorption corrections was estimated to be
