Zirconium Complexes of Fluorinated Aryl Diamides

The reaction of excess Ar F NHLi with (ICH 2 CH 2 OCH 2 ) 2 affords the new diamines (Ar F NHCH 2 CH 2 OCH 2 ) 2 ( 1, Ar F = C 6 F 5; 2, Ar F = 3,5-C 6 H 3 (CF 3 ) 2 ) in moderate yield. Direct protonolysis of Zr(CH 2 Ph) n Cl 4 - n ( n = 2−4) or Zr[N(SiMe 3 ) 2 ] n Cl 4 - n ( n = 2, 3) with 1 or 2 (1 equiv) affords the zirconium complexes Zr(Ar F NCH 2 CH 2 OCH 2 ) 2 (X)(Y) (Ar F = C 6 F 5: 3, X = Y = Cl; 4, X = N(SiMe 3 ) 2, Y = Cl; 5, X = Cl, Y = CH 2 Ph; 6, X = Y = CH 2 Ph. Ar F = 3,5-C 6 H 3 (CF 3 ) 2: 7, X = Y = Cl; 8, X = Y = CH 2 Ph). The structures of 1, 4, 5, and 7 were established by X-ray crystallography with the zirconium complexes 4, 5, and 7 all adopting a monocapped trigonal bipyramidal geometry in the solid state. However, in solution, these complexes display higher symmetry due to rapid ligand rearrangement. The silylamido complex 4 shows restricted rotation of the C 6 F 5 rings in solution (Δ G ⧧ = 49 ± 3 kJ mol - 1 ). Abstraction of a benzyl group from 6 by B(C 6 F 5 ) 3 affords {Zr[CH 2 OCH 2 CH 2 N(C 6 F 5 )] 2 (CH 2 Ph)} + {(PhCH 2 )B(C 6 F 5 ) 3 } - ( 9 ). This complex shows evidence for η 2 -benzyl coordination and does not polymerize ethylene at room temperature. Treatment of 3 with excess MAO (500 equiv) and ethylene (1 atm, 50 °C) affords polyethylene at a modest rate (3.2 kg mol - 1 Zr h - 1 ).