AMIDO COMPLEXES OF (CYCLOPENTADIENYL)DICHLOROTITANIUM(IV) - TI-N MULTIPLE-BOND CHARACTER

Reaction of (RC5H4)TiCl3 (1a, R = H; 1b, R = CH3) with Li{NH(t-Bu)}in THF affords (RC5H4)TiCl2{NH(t-Bu)} (2a,R = H;2b,R = CH3) in 80-90% isolated yields. The moisture-sensitive red-orange compounds can be crystallized from CH2Cl2/hexane mixtures. The X-ray structures for the two compounds were determined and found to be similar. Multiple-bond character in the Ti-N bond is suggested by short Ti-N distances, 1.879 (3) angstrom (2a) and 1.871 (5) angstrom (2b). Data were collected on an Enraf-Nonius CAD-4 diffractometer (lambda(Mo K-alpha) = 0.710 73 angstrom) in the omega-2-theta mode to a maximum 2-theta of 52-degrees. Crystal data for 2a: C9Hl5Cl2NTi, M(r) = 256.03, monoclinic, P2(1)/m, a = 6.149 (1) angstrom, b = 10.888 (3) angstrom, c = 9.004 (3) angstrom, beta = 100.44 (2)-degrees, V = 593 angstrom3, D(calcd) = 1.43 g cm-3, Z = 2. A total of 1352 reflections were collected, of which 1239 were unique, and 836 reflections with F(o)2 > 3.0-sigma(F(o))2 were used in the refinement, which gave R = 0.036 and R(w) = 0.045. Crystal data for 2b: C10H17Cl2NTi, M(r) = 270.06, monoclinic, P2(1)/c, a = 6.198 (2) angstrom, b = 11.660 (2) angstrom, c = 17.748 (4) angstrom, beta = 98.73 (2)-degrees, V = 1268 angstrom3, D(cald) = 1.41 g cm-3, Z = 4. A total of 2865 reflections were collected, of which 2620 were unique, and 990 reflections with F(o)2 > 3.0-sigma(F(o))2 were used in the refinement, which gave R = 0.048 and R(w) = 0.051. A variable-temperature NMR study was conducted to further explore the pi-character of the Ti-N bond.