Zirconium complexes of fluorinated aryl diamides

The reaction of excess ArFNHLi with (ICH2CH2OCH2)2 affords the new diamines (ArFNHCH2CH2OCH2)2 (1, ArF = C6F5; 2, ArF = 3,5-C6H3(CF3)2) in moderate yield. Direct protonolysis of Zr(CH2Ph)nCl4-n (n = 2−4) or Zr[N(SiMe3)2]nCl4-n (n = 2, 3) with 1 or 2 (1 equiv) affords the zirconium complexes Zr(ArFNCH2CH2OCH2)2(X)(Y) (ArF = C6F5:  3, X = Y = Cl; 4, X = N(SiMe3)2, Y = Cl; 5, X = Cl, Y = CH2Ph; 6, X = Y = CH2Ph. ArF = 3,5-C6H3(CF3)2:  7, X = Y = Cl; 8, X = Y = CH2Ph). 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 C6F5 rings in solution (ΔG⧧ = 49 ± 3 kJ mol-1). Abstraction of a benzyl group from 6 by B(C6F5)3 affords {Zr[CH2OCH2CH2N(C6F5)]2(CH2Ph)}+{(PhCH2)B(C6F5)3}- (9). This complex shows evidence for η2-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).