The synthesis of [Ti(O-i-Pr)Cl-2(PhCHO)(mu-Cl)](2) and its reactions with oxygen-containing ligands L (L = DMF, DMSO, i-PrOH). The crystal structure of Ti(O-i-Pr)Cl-3(PhCHO)(i-PrOH) and the H-1 variable-temperature NMR studies of solution structures

摘要

Ti(O-i-Pr)Cl-3 reacted with 1 molar equiv. of benzaldehyde to give the dimeric complex [Ti(O-i-Pr)Cl-2(PhCHO)(mu-Cl)](2) (2) which reacted further with 2 molar equiv. of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO). or 2-propanol (i-PrOH) to give the six-coordinate monomeric complexes Ti(O-i-Pr)Cl-3(PhCHO)L (L = DMF (3), DMSO (4), or i-PrOH (5)). In the reaction of 2 with i-PrOH, the formation of the simple adduct 5 demonstrates the preferred nature of the monomeric six-coordinate species to the chloride-bridged or the alkoxide-bridged dimeric complex. The complexes 2-5 are highly dynamic in solution and the H-1 variable-temperature NMR studies show 17 observable -CHO signals for the chloride-bridged dimeric complex 2, indicating the presence of more than 10 isomeric species in solution. For the monomeric complexes 3 and 4, all four geometric isomers are observed. For the complex 5, however, the observation of 11 benzaldehyde -CHO signals indicates the presence of hydrogen-bonded dimeric species in solution in addition to the four expected monomeric isomers. The solution structures of complexes 2-5 are discussed. For the complex 5, the dynamic process for the exchange of the hydroxy hydrogen between the O-i-Pr and the i-PrOH ligands is observed. Despite the presence of several isomeric speices in solution, the lowest-enegy species 5-A crystallizes in the triclinic P (1) over bar space group with a = 8.976(2), b = 10.412(2), c = 11.744(2) Angstrom, alpha = 67.49(1), beta = 69.18(1), gamma = 71.68(1)degrees, z = 2, R = 0.043, R-w = 0.064, and Gof = 1.57. The solid state structure of 5-A exhibits the trans, position of the benzaldehyde ligand relative to the 2-propoxide ligand, suggesting a relative bonding order of O--i-Pr > Cl- > i-PrOH > PhCHO. (C) 2000 Elsevier Science S.A. All rights reserved. [References: 25]