NOVEL ARYLTITANIUM(IV) COMPLEXES CONTAINING ETA(3)-NCN-PSEUDOFACIAL-BONDED AND ETA(3)-NCN-MERIDIONAL-BONDED [C6H3(CH2NME2)(2)-2,6](-) (ABBREVIATED AS NCN) LIGANDS - THE CRYSTAL-STRUCTURES OF [TICL2(ETA(3)-FAC-NCN)(O-I-PR)], [TICL(ETA(3)-MER-NCN)(O-I-PR)(OTF)] CONTAINING AN ETA(1)-O-BONDED TRIFLATE ANION, AND THE 7-COORDINATED [TI(ETA(3)-MER-NCN)(O-I-PR)(OTF)(2)] CONTAINING ETA(1)-O-BONDED AND ETA(2)-O,O'-BONDED

Titanium(IV) derivatives of the chelating monoanionic aryldiamine liga nd [C6H3(CH2NMe2)(2)-2,6](-) (abbreviated as NCN) are prepared by trea ting [TiCl3(OR)] (R = i-Pr, C6H4OMe-4) with [Li(NCN)](2). [TiCl2(NCN)( O-i-Pr)] is smoothly methylated by methyllithium in toluene to give [T iClMe(NCN)(O-i-Pr)] and [TiMe2(NCN)(O-i-Pr)]. Enhancement of the Lewis acidity of the titanium center has been studied by substituting chlor o ligands for triflato ligands to give [TiCl(NCN)(O-i-Pr)(OTf)] and [T i(NCN)(O-i-Pr)(OTf)(2)]. X-ray studies of the dichloride and triflate complexes feature eta(3)-pseudofacial and eta(3)-meridional bonding mo des for the NCN ligand, respectively. These different NCN bonding mode s are explained in terms of the trans influence of the alkoxy and trif lato ligands. A rare example of an organo titanium(IV) complex with a seven-coordinate titanium center is observed in the bis(triflate) comp lex as a result of bidentate O,O'-bonding mode of the triflato anion t o one titanium center that is unprecedented in early transition metal chemistry. The triflato ligands exhibit a strong covalent bonding to t itanium both in the solid state and in solution; the latter is demonst rated by the observation that cationic species are not formed upon add ition of Lewis bases like THF, acetonitrile, and 1,2-bis(dimethylamino )ethane.