Synthesis, characterization, and one-electron reduction of mixed-cyclopentadienyl/aryloxide titanium dichlorides

The synthesis and characterization of a series of titanium dichloride deriv atives containing both cyclopentadienyl and various substituted aryloxide l igands, [CpTi(OAr)Cl-2] 10-18 and [Cp*Ti(OAr)Cl-2] 19, 20, have been invest igated. Compounds 10-18 are formed from the reaction of [CpTiCl3] with eith er 1 equiv of the substituted parent phenol in the presence of excess pyrid ine or with 1 equiv of the corresponding lithium salt of the substituted pa rent phenoxide in hydrocarbon solvents. Compounds 13, 14, 16, and 17 are ch iral molecules (a nonresolved racemic pair) as a result of the presence of either ortho-(l-naphthyl) or ortho(1-tetrahydronaphthyl) substituents on th e phenoxide ligands. Titanium dichloride compounds 19 and 20 are formed in the reaction of [Cp*TiCl3] with the corresponding lithium salts of the subs tituted parent phenoxides in hydrocarbon solvents. The compounds 11, 13, 14 , 15, 16, 18, 19, and 20 have been subjected to single-crystal X-ray diffra ction analysis, and each was shown to possess a pseudo-tetrahedral geometry . The compound [CpTi(OC6H2Np-2-Bu-2(t)-4,6)Cl-2] (16) (Np = l-naphthyl) rea cts with 1 equiv of sodium (mercury amalgam) per titanium to pro duce the c hlorine-bridged titanium dimer [(OC6H2Np-2-Bu-2(t)-4,6)CpTi{mu -Cl}(2)TiCp( OC6H2Np-2-Bu-2(t)-4,6)] (21). The solid-state structure of 21 shows that th e cyclopentadienyl rings are arranged in a transoid fashion about the [Ti{m u -Cl}(2)Ti] core with a Ti-Ti distance [3.336(1) Angstrom] and Cl-Ti-Cl bo nd angles [92.07(4)degrees] intermediate between those found in paramagneti c [Cp2Ti{mu -Cl}(2)TiCp2] and diamagnetic [(ArO)(2)Ti{mu -Cl}(2)Ti(OAr)(2)] .