Synthesis, Characterization, and One-Electron Reduction of Mixed-Cyclopentadienyl/Aryloxide Titanium Dichlorides

Abstract

The synthesis and characterization of a series of titanium dichloride derivatives containing both cyclopentadienyl and various substituted aryloxide ligands, [CpTi(OAr)Cl2] 10−18 and [Cp*Ti(OAr)Cl2] 19, 20, have been investigated. Compounds 10−18 are formed from the reaction of [CpTiCl3] with either 1 equiv of the substituted parent phenol in the presence of excess pyridine or with 1 equiv of the corresponding lithium salt of the substituted parent phenoxide in hydrocarbon solvents. Compounds 13, 14, 16, and 17 are chiral molecules (a nonresolved racemic pair) as a result of the presence of either ortho-(1-naphthyl) or ortho-(1-tetrahydronaphthyl) substituents on the phenoxide ligands. Titanium dichloride compounds 19 and 20 are formed in the reaction of [Cp*TiCl3] with the corresponding lithium salts of the substituted parent phenoxides in hydrocarbon solvents. The compounds 11, 13, 14, 15, 16, 18, 19, and 20 have been subjected to single-crystal X-ray diffraction analysis, and each was shown to possess a pseudo-tetrahedral geometry. The compound [CpTi(OC6H2Np-2-But2-4,6)Cl2] (16) (Np = 1-naphthyl) reacts with 1 equiv of sodium (mercury amalgam) per titanium to produce the chlorine-bridged titanium dimer [(OC6H2Np-2-But2-4,6)CpTi{μ-Cl}2TiCp(OC6H2Np-2-But2-4,6)] (21). The solid-state structure of 21 shows that the cyclopentadienyl rings are arranged in a transoid fashion about the [Ti{μ-Cl}2Ti] core with a Ti−Ti distance [3.336(1) Å] and Cl−Ti−Cl bond angles [92.07(4)°] intermediate between those found in paramagnetic [Cp2Ti{μ-Cl}2TiCp2] and diamagnetic [(ArO)2Ti{μ-Cl}2Ti(OAr)2].