VANADIUM(III) CARBON AND TITANIUM(III) CARBON FUNCTIONALITIES SUPPORTED BY A TETRADENTATE SCHIFF-BASE LIGAND

Alkylation of the titanium(III)- and vanadium(III)-Schiff base complexes [(THF)M(acacen)(Cl)] [M = Ti (1), V (2); acacen = N,/N′-ethylenebis(acetylacetone iminato) dianion] by using Grignard reagents led to the corresponding organometallic derivatives [M(acacen)R] [M = Ti, R = CH2Ph (3), Ph (4), Mes (5); M = V, R = Me (6), CH2Ph (7), Ph (8), Mes (9)]. The alkylation occurred exclusively at the metal, and the simultaneous loss of the axial solvent was observed. The organometallic derivatives 3-9 occur either in the monomeric form, complexes 4, 5, 8, and 9, or in the dimeric form, complexes 3, 6, and 7, as suggested by the X-ray analysis and the magnetic moment. Dimerization is achieved by a sharing of an oxygen of the Schiff base between two [M(acacen)] moieties. Complexes 3–9 are quite soluble in organic solvents and relatively thermally stable compared to the corresponding cyclopentadienyl derivatives. The solid-state structure determination revealed a significant intramolecular hydrogen bonding between the alkyl or aryl groups and the oxygens from the Schiff base ligand. M−C bond lengths (Å) [Ti−C = 2.216 (20), 5; V−C = 2.156 (9), 7; V−C = 2.064 (5), 8] are in agreement with the presence of a σ bond. Crystallographic details for X-ray structures of 5, 7, and 8 are as follows. Complex 5: space group P21/n,a = 11.295 (2) Å, b = 12.561 (2) Å, c = 15.377 (2) Å, β = 104.72 (1)°, V= 2110.0 (6) Å3, Z = 4, Dcalcd= 1.226 g cm−3. The final R factor was 0.105 for 1146 independent reflections. Complex 7: space group P2Jc, α = 1 1.856 (3) Å, b = 18.016 (5) Å, c = 8.775 (3) Å, β = 95.54 (2)°, V= 1865.6 (9) Å3, Z = 2, DaM= 1.297 g cm−3. The final R factor was 0.053 for 1248 independent reflections. Complex 8: space group P21/c, a = 7.886 (2) Å, b = 15.180 (4) Å, c = 15.150 (4) Å, β = 104.45 (1)°, V= 1756.2 (8) Å3, Z = 4, Dcalcd= 1.325 g P21/c, The final R factor was 0.068 for 2700 independent reflections. © 1990, American Chemical Society. All rights reserved.