Half-sandwich titanium(IV) complexes with Klaui's tripod ligand

Treatment of [Ti(O-i-Pr)(2)Cl-2] with NaLOEt (L-OEt-= [CpCo{P(O)(OEt)(2)}(3)](-) Cp = eta(5)-C5H5) afforded [LOEtTi(O-i-Pr)(2)Cl] that reacted with HCl in ether to give [LOETTiCl3] (1). The average Ti-O and Ti-Cl distances in 1 are 1.975 and 2.293 Angstrom, respectively. Reaction of titanyl sulfate with NaLOEt in water followed by addition of HBF4 afforded [LOEtTiF3] (2), the Ti-O and Ti-F distances of which are 2.020(2) and 1.792(2) Angstrom, 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) Angstrom, respectively. Treatment of 1 with tetrachlorocatechol (H(2)Cl(4)cat) afforded [LOEtTi(Cl(4)cat)Cl] (4). The average Ti-O(P), Ti-O(C), and Ti-Cl distances in 4 are 1.972, 1.926, and 2.334 Angstrom, respectively. Hydrolysis of 4 in the presence of Et3N yielded the mu-oxo dimer [(L-OEt)(2)Ti-2(Cl(4)cat)(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) Angstrom. Treatment of 1 with 1,1'-binaphthol (BINOLH2) in the presence of Et3N afforded [(L-OEt)(2)Ti-2(mu-O)(2)(mu-BINOL)].2BINOLH(2) (6.2BINOLH(2)). Complex 1 is capable of catalyzing ring opening of epoxides with Me3SiN3 under solvent-free conditions presumably via a Ti-azide intermediate.