Half-Sandwich Titanium(IV) Complexes with Klauis Tripod Ligand

Treatment of [Ti(O-i-Pr)2Cl2] with NaLOEt (LOEt- = [CpCo{P(O)(OEt)2}3]-, Cp = eta^5-C5H5) afforded [LOEt Ti(O-iPr)2CI] that reacted with HCI in ether to give [LOEtTiCI3] (1). The average Ti-O and Ti-CI distances in 1 are 1.975 and 2.293 A, respectively. Reaction of titanyl sulfate with NaLoEt in water followed by addition of HBF4 afforded [LOEt TiF3] (2), the Ti-O and Ti-F distances of which are 2.020(2) and 1.792(2) A, respectively. The Zr(IV) analogue [LOEtZrF3] (3) was prepared similarly from zirconyl nitrate, NaLoet, and HBF4 in water. The Zr-O and average Zr-F distances in 3 are 2.139(2) and 1.938(2) A, respectively. Treatment of 1 with tetrachlorocatechol (H2Cl4cat) afforded [LOEt Ti(Cl4cat)CI] (4). The average Ti-O(P), Ti-O(C), and Ti-CI distances in 4 are 1.972, 1.926, and 2.334 A, respectively. Hydrolysis of 4 in the presence of EtsN yielded the mu-oxo dimer [(LOEt)2 Ti2(Cl4cat)2(mu-O)] (5). The average Ti-O(P), Ti-O(C), and Ti-O(Ti) distances in 5 are 2.027, 1.926, and 1.7977(9) A. Treatment of 1 with 1.1-binaphthol (BINOLH2) in the presence of Et3N afforded [(LoEt)2Ti2(mu-O)2(mu-BINOL)].2BINOLH2 (6.2BINOLH2). Complex 1 is capable of catalyzing ring opening of epoxides with MesSiNs under solvent-free conditions presumably via a Ti-azide intermediate.