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

Abstract

International audienceThe coordination chemistry of the multidentate tethered amidine-phenol {4,6-tBu2C6H2O(2-C(NR)═NR}H2 ({LONR}H2, R = iPr, 2,6-iPr2C6H3 (Ar)) and new guanidine-phenol {4,6-tBu2C6H2ON(C6H5)(2-C(NR)═NR}H2 ({LON(Ph)NiPr}H2) pro-ligands with group 4 metals has been studied. σ-Bond and salt metathesis reactions were explored to coordinate these (pro)ligands onto zirconium and hafnium. Alkane elimination reactions between {LONR}H2 and Zr(CH2Ph)4 afforded mixed-ligand monobenzyl {LOHNR}{LONR}Zr(CH2Ph) (R = iPr; 1) and monoligand tribenzyl {LOHNAr}Zr(CH2Ph)3 (R = Ar; 2) complexes, respectively. Alkane and amine elimination reactions between {LON(Ph)NiPr}H2 and Zr(CH2Ph)4 or Hf(NMe2)4 unexpectedly resulted in cleavage of the ligand backbone and eventual isolation of {(Ph)NC6H2(tBu)2O}Zr{(iPrN)2CCH2Ph}2 (3) and {(Ph)NC6H2(tBu)2O}Hf{(iPrN)2CNMe2}2 (4), respectively. Salt metathesis reactions between {LONR}Li2 and ZrCl4(THF)n (n = 0, 2), conducted in 1:1 ratios, led upon crystallization to diverse chloro complexes: [{LONiPr}ZrCl]3(μ3-O)(μ3-Cl) (5), [{LONAr}2ZrCl(μ2-Cl)]2[{LHONAr}ZrCl(μ2-Cl)](μ3-OH) (6), and {LOHNAr}ZrCl3(THF) (7). Similar salt metathesis reactions between the monolithium salts {LHONR}Li and ZrCl4, conducted in 2:1 ratios, allowed the selective preparation of bis(phenoxy-amidine) complexes with pendant amino groups {LOHNR}2ZrCl2 (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

Chiral and achiral (imino)phenoxy-based cationic group 4 non-metallocene complexes as catalysts for polymerization of renewable α-methylene-γ-butyrolactones

“…Other chemical shifts matched well with the analogous (amidine)phenoxy zirconium tribenzyl complex. 60 1 H and 13 C NMR chemical shifts of the zirconium dibenzyl complex 3 also closely matched with the analogous salalen titanium compound. 43 Generation and characterization of cationic benzyl complexes The solid-state structure of 4 (Fig.…”

Trinuclear Zirconium Polyhydride ({Cp*Zr(BH3CH3)}(μ-H)2{Cp*Zr(BH3CH3)}(μ-H){Cp*Zr(BH3CH3)})(μ-κ2C,H:κ1C:κ2C,H-CHBH3) and Its Derivatives: Compounds Containing a Pentacoordinated Carbon Atom

“…The μ 3 -bridging Zr–O bond distances fall into the range 2.220(6)–2.317(6) Å, and the corresponding Zr–O–Zr bond angles fall into the range 88.2(2)–113.8(2)°. The μ 3 -bridging Zr–O bond distances have been reported to fall into the range 2.05(1)–2.375(4) Å . All three terminal [CH 3 BH 3 ] − ligands in 5 bond to the Zr atoms through a bidentate bonding mode, and their Zr–B distances fall into the range 2.563(11)–2.585(8) Å …”

Zirconium Permethylpentalene Amidinate Complexes: Characterization, Bonding, and Olefin Polymerization Catalysis

“…Group 4 complexes with multiple amidinate ligands have been previously reported including a small number of tris , and tetrakis amidinate complexes, although these are limited to small N -alkyl groups. , Bis­(amidinate) complexes are more common, including those whereby the ligating groups are tethered by a bridge, , although the choice of N , N ′-substituents is relatively limited (SiMe 3 , − i Pr, − Cy, − C­(Me)­Ph, C 6 F 5 , Dipp, and Xyl) . Depending on the nature of the amidinate ligand, the N , N ′ groups can also be C–H-activated; Hessen and co-workers reported that Zr­{N­(2,6- i Pr-C 6 H 3 ) 2 CH}­Me 2 can be thermolyzed at 50 °C, resulting in double C–H bond activation of the isopropyl methyl groups and cyclometallation to afford Zr­{N­(2- i Pr-6-CMe 2 -C 6 H 3 ) 2 CH} 2 .…”