Aryltitanium(IV) complexes with the η3-C,N,N′-pseudofacially coordinating ligand [C6H4(CH2N(Me)CH2CH2NMe2)-2]-.: The X-ray crystal structure of [TiCl2(CNN)(O-i-Pr)]

Reaction of [TiCl3(O-i-Pr)] with [Li(CNN)](2) (CNN = monoanionic C6H4(CH2N(Me)CH2CH2NMe2)-2) in 2:1 molar ratio in toluene at -78 degrees C afforded [TiCl2(CNN)(O-i-Pr)] as a 3:2 molar mixture of two stereoisomers. The stereoisomers differ by the mutual position of the chloro and alkoxy ligands. Molecular modelling calculations and an X-ray analysis of one of the stereoisomers indicated that the alkoxy ligand exhibits a strong trans preference to the weakest rr-donating ligated atom, i.e., the N(Me-2) atom of the CNN ligand. The molecular structure of this stereoisomer, as determined by X-ray analysis, involves an octahedral titanium center with an eta(3)-fac-C,N,N'-bonded CNN ligand. A strong M-O(alkoxy) interaction is illustrated by an almost linear M-O-C bond angle of 172.4(2)degrees. As a result of the pseudofacially bonded CNN ligand, the titanium center as well as the central N-donor center are stereogenic resulting in the formation of two enantiomers. A (CNN)titanium(IV) dimethyl complex is accessible via reaction of 1 with two equivalents of MeLi and contains likewise an eta(3)-fac-C,N,N'-bonded CNN ligand. (C) 1997 Elsevier Science S.A.