Synthesis, structures, dynamics, and olefin polymerization behavior of group 4 metal (pyCAr(2)O)(2)M(NR2)(2) complexes containing bidentate pyridine alkoxide ancillary ligands

The reaction of 2-lithiopyridine and the appropriate diarylketone followed by hydrolysis yields pyCAr(2)OH pyridine-alcohols (1a, Ar = 4-Bu-t-C6H4; 1b, pyCAr(2)OH = 2-pyridyl-9-fluorenol; 1c, Ar = 3-CF3-C6H4; 1d, Ar = 4-Ph-C6H4; 1e, Ar = 4-NEt2-C6H4; 1f, pyCAr(2)-OH = 1-(2-pyridyl)-1-dibenzosuberol; 1g, Ar = 3,5-(CF3)(2)-C6H3). The reaction of Ti(NMe2)(4) with 2 equiv of la-g yields (pyCAr(2)O)(2)Ti(NMe2)(2) (2a-g) and NMe2H. The reaction of Zr(NMe2)(4) with 2 equiv of 1a,b,e yields (pyCAr(2)O)(2)Zr(NMe2)(2) (3a,b,e), while similar reactions with 1c,d yield mixtures of (pyCAr(2)O)(x)Zr(NMe2)(4-x) (x = 1-3) species. {pyC(3-CF3-C6H4)(2)O}(3)-Zr(NMe2) (4c) and {pyC(4-NEt2-C6H4)(2)O}(4)Zr (5e) are prepared from Zr(NMe2)(4) and 3 equiv of 1c or 4 equiv of 1e, respectively. The reaction of Hf(NMe2)(4) with 2 equiv of 1a,e yields (pyCAr(2)O)(2)Hf(NMe2)(2) (6a,e), while reaction with 3 equiv of 1b,c yields (pyCAr(2)O)(3)Hf(NMe2) (7b,c). X-ray crystallographic analyses establish that 2b, 2e, and 3a adopt distorted octahedral structures with a trans-O, cis-py, cis-amide arrangement of ligands. NMR data show that (pyCAr(2)O)(2)M(NMe2)(2) complexes adopt the same structure in solution but undergo inversion of configuration at the metal with racemization barriers (Delta G double dagger (racemization)) in the range of 12-14 kcal/mol. Treatment of (pyCAr(2)O)(2)M(NMe2)(2) complexes With Al(Bu-1)(3) and methylalumoxane (MAO) yields active, multisite ethylene polymerization catalysts.