Synthesis and Structural Diversity of Group 4 Metal Complexes with Multidentate Tethered Phenoxy-Amidine and Phenoxy-Amidinate Ligands

The coordination chemistry of the multidentate tethered amidine-phenol {4,6-tBu(2)C(6)H(2)O (2-C(NR)=NR}H-2 ({LONR}H-2, R = iPr, 2,6-iPr(2)C(6)H(3) (Ar)) and new guanidine-phenol {4,6-tBu(2)C(6)H(2)ON(C6H3)(2-C(NR)=NR}H-2 ({LON(Ph)N-iPr}H-2) pro-ligands with group 4 metals has been studied. sigma-Bond and salt metathesis reactions were explored to coordinate these (pro)ligands onto zirconium and hafnium. Alkane elimination reactions between {LONR}H-2 and Zr(CH2Ph)(4) afforded mixed-ligand monobenzyl {(LONR)-N-H}{LONR}Zr(CH2Ph) (R = iPr; 1) and monoligand tribenzyl {(LONAr)-N-H}Zr(CH2Ph)(3) (R = Ar; 2) complexes, respectively. Alkane and amine elimination reactions between {LON(Ph)N-iPr}H-2 and Zr(CH2Ph)(4) or Hf(NMe2)(4) unexpectedly resulted in cleavage of the ligand backbone and eventual isolation of {(Ph)NC6H2(tBu)(2)O}Zr{(iPrN)(2)CCH2Ph}(2) (3) and {(Ph)NC6H2(tBu)(2)O}Hf{(iPrN)(2)CNMe2}(2) (4), respectively. Salt metathesis reactions between {LONR}Li-2 and ZrCl4(THF)(n) (n = 0, 2), conducted in 1:1 ratios, led upon crystallization to diverse chloro complexes: [{LONiPr}ZrCl](3)(mu(3)-O)(mu(3)-Cl) (5), {{LONAr}(2)ZrCl(mu(2)-Cl)](2)[{(LONAr)-O-H}ZrCl(mu(2)-Cl)](mu(3)-OH) (6), and {(LONAr)-N-H}ZrCl3(THF) (7). Similar salt metathesis reactions between the monolithium salts {(LONR)-O-H}Li and ZrCl4, conducted in 2:1 ratios, allowed the selective preparation of bis(phenoxy-amidine) complexes with pendant amino groups {(LONR)-N-H}(2)ZrCl2 (R = iPr, 8; R = Ar, 9). All complexes were authenticated by elemental analysis, X-ray crystallography, and NMR spectroscopy. Complexes 5, 6, 8, and 9, upon activation with MAO, showed poor to moderate productivities (4-172 (kg of PE) mol(-1) h(-1)) in the polymerization of ethylene, giving linear polymers with large polydispersities.