Synthesis of titanium, zirconium, and hafnium complexes that contain diamido donor ligands of the type [(t-BuN-o-C6H4)(2)O](2-) and an evaluation of activated versions for the polymerization of 1-hexene

Titanium, zirconium, and hafnium dialkyl complexes that contain the [(t-Bu- d(6)-N-o-C6H4)(2)O](2-) ([t-BuNON](2-)) ligand have been prepared. Only [t- BuNON]TiMe2 could be isolated, but [t-BuNON]ZrR2 and [t-BuNON]HfR2 complexe s could be isolated in which (for example) R = Me, Ee, or i-Bu. X-ray studi es showed [t-BuNON]MMe2 structures (M = Ti or Zr) to be of the "twisted fac " variety in which two amido nitrogens occupy equatorial positions in a dis torted trigonal bipyramid. However, in solution all such species show equiv alent alkyl groups on the NMR time scale as a consequence of formation of a n intermediate mer structure that contains a planar oxygen donor. In analog ous complexes that contain the {[Me(CD3)(2)CNC6H4][Me(CD3)(2)CN-2,4-Me2C6H2 ]O}(2-) or {[Me(CD3)(2)CNC6H4][Me(CD3)(2)N-2- EtC6H3]O}(2-) ligand the two metal alkyl groups are inequivalent on the NPIIIR time scale. Addition of t rimethylphosphine to [t-BuNON]Zr(CH2CH3)(2) yields structurally characteriz ed, pseudooctahedral [trBuNON]Zr(eta(2)-C2H4)(PMe3)(2). Addition of B(C6F5) (3) to [t-BuNON]ZrMe2 yields structurally characterized {[t-BuNON]ZrMe}[MeB (C6F5)(3)], while addition of [PhNMe2H[B(C6F5)(4)] to [t-BuNON]ZrMe2 in bro mobenzene-d(5) generates "{[t-BuNON]ZrMe(PhNMe2)][B(C6F5)(4)]", which is an active catalyst for the polymerization of up to 500 equiv of 1-hexene in a living manner at 0 degrees C. The analogous hafnium systems are not as wel l behaved, since the dimethylaniline is insufficiently labile. No polymeriz ation activity is observed for activated titanium dialkyl complexes. Polyme rization activity is quenched upon addition of THF or dimethoxyethane to th e cationic complexes. An X-ray structure of {[t-BuNON]ZrMe(THF)(2)][B(C6F5) (4)] shows it to be a pseudooctahedral species in which the [t-BuNON](2-) l igand adopts a "twisted mer" geometry, while the X-ray structure of {[t-BuN ON]ZrMe(MeOCH2CH2OMe)][B(C6F5)(4)] was found to be of the "twisted fac" var iety. In the case of hafnium, pseudooctahedral cationic bis-THF or DME comp lexes can be isolated even when the anion is [B(C6H5)(4)](-); like all comp lexes that contain THF or DME they are essentially inactive for polymerizat ion of 1-hexene.