Ethylenebis(salicylideneiminato)zirconium Dichloride:  Crystal Structure and Use as a Heterogeneous Catalyst in the Polymerization of Ethylene

Abstract

In the solid-state structure of the Schiff base salen [salen ) N, N′-ethylenebis(salicylideneiminato)] zirconium dichloride complex Zr(salen)Cl2(THF), C20H22Cl2N2O3Zr, a quadridentate ligand, occupies four sites in the pseudopentagonal bipyramidal coordination. The coordination sphere is completed by one THF molecule, and two chloride ions are forced into the trans-position. Removal of THF, while Zr(salen)Cl2(THF) is heated in toluene, leads to a six-coordinated complex with the two chloride ligands assuming the cis-position. This property was successfully utilized in the preparation of a homogeneous Zr(salen)Cl2 catalyst precursor. Heating of Zr(salen)Cl2(THF) in toluene in the presence of SiO2 causes deposition of Zr(salen)Cl2 on to the silica support, producing a heterogeneous catalyst, which shows an acceptable activity in ethylene polymerization at 80 °C and at low ethylene pressures in the presence of the cocatalyst methylaluminoxane.

Coordination polyhedra of eight-coordinate zirconium complexes and a network built up by crisscross Cl...Cl contacts

“…Although apparent changes were observed in the coordination polyhedron of (1) relative to that of Zr(dsp) 2 and Zr(trans-dsd) 2 [5,6], the Zr-N and Zr-O bond lengths obtained for (1) are all comparable to those in the analogous bis(salen)zirconium complexes derived from either aromatic diamines or 1,2-diaminocyclohexane. The five-membered chelate ring of each 5-Cldse ligand in (1) is in a typical gauche conformation with the two ethene carbon atoms, one above the N 2 O 2 mean plane and one below it, as were the cases in previously reported molecular structures of Zr(3,5-di-tert-Budse)-Cl 2 AE sol (sol ¼ THF, H 2 O) complexes [30,31]. (1) and (2) Complex (1) Complex (2) Table 2.…”

A Binaphthyl‐Bridged Salen Zirconium Catalyst Affording Atactic Poly(propylene) and Isotactic Poly(α‐olefins)

“…An early study by Repo et al [1] explored the performances of simple salen Zr complexes, in which the tetradentate Schiff-base ligand coordinates the metal in a substantially planar fashion, to result in poor catalytic activity in the polymerization of ethylene and in a lack of activity in the polymerization of propene. Related acen (N,N 0 -ethylenebis(acetylacetoneiminate)) and hexafluoroacen Zr alkyl complexes, displaying non-planar Schiff-base ligands, have been investigated by Jordan and co-workers, [2] who reported low to moderate ethylene polymerization activities after activation with [HNMe 2 Ph][B(C 6 F 5 ) 4 ] and Al i Bu 3 .…”

Salicylidene-imine-zirconium(IV) complexes in combination with methylalumoxane as catalysts for the conversion of hexa-1,5-diene: adjusting of the catalytic activity

“…Whereas titanium complexes have a distorted octahedral structure in the compounds (acen)TiCl 2 and (salen)TiX 2 [28, 29, 35 -38, 41], the structures of the Zr and Hf analogues are variable: Adducts with THF show a pentagonal-bipyramidal structure with both chloro ligands in axial positions and THF together with the N 2 -O 2 donor set of the chelate ligand in the equatorial plane; in the octahedral THF-free complexes, however, the chlorides are cis to each other [27,39,40]. In a complex of the type (acen)ZrR 2 (L: quadridentate Schiff base with diamino-biphenyl bridge) the metal center has a trigonal-prismatic environment with an C-Zr-C angle of 130° [26].…”

“…): 96 (M + , 30), 81 (100), 79 (20), 70 (27), 67 (24), 55 (38), 39 (62). -GC-IR: ν/cm -1 = 3 074 (=CH); 2 958 and 2 888 (CH 2 /CH 3 ); 1656 (C=C); δ/cm -1 = 1 449 (CH 2 ); 1 366 (CH 3 ); 879 (=CH 2 ).…”