Stoichiometric olefin insertion into the Ti-C bond of four-coordinate cationic bis(phenolate) titanium aryl and benzyl complexes

A series of five-coordinate bis(phenolate) titanium hydrocarbyl complexes (MBP)Ti(eta(2)-R)R' was prepared, with MBP = 2,2'-methylenebis(4-methyl-6-tert-butylphenolate), R = C6H4(o-CH2NMe2); R' = Cl, OSO2CF3, Me, CH2CMe3 or R = CH2C6H4(o-NMe2); R' = Cl, Me. A structure determination of (MBP)Ti[eta(2)-C6H4(o-CH2NMe2)]OSO2CF3 showed the metal to have a distorted trigonal bipyramidal coordination geometry. Cationic four-coordinate derivatives [(MBP)Ti(eta(2)-R)](+) were generated by reacting the R' = Me derivatives with the Lewis acid B(C6F5)(3). These cations were found to undergo stoichiometric insertions of ethene and propene into the Ti-C bond, as seen by 1D and 2D-NMR spectroscopy and quenching reactions with CD3OD. (C) 1999 Elsevier Science S.A. All rights reserved.