Group 4 Metal Olefin Polymerization Catalysts Stabilized by Bidentate O,P Ligands

Abstract

A series of bis(phosphanylphenoxide) group 4 metal dichloride complexes has been synthesized via treatment of MCl4(THF)2 (M = Ti, Zr, Hf) with sodium salts of the phosphanylphenols. The complexes bearing diphenylphosphine donors adopt C 1-symmetric, all-cis ground-state structures as determined by X-ray crystallography. In solution an O,P ligand exchange process is observed. Eyring analyses indicate a nondissociative process proposed to proceed via a 120° rotation of the P,P,Cl or the O,P,Cl trigonal faces. A zirconium complex containing diisopropylphosphine donors adopts a configurationally rigid trans-P2 geometry. In ethylene polymerization studies (methylaluminoxane (MAO) activation), bis(6-tert-butyl-2-diphenylphosphanylphenoxide) zirconium and hafnium catalysts gave activities up to 49 000 and 2000 g/mmol·h·bar, respectively. Both of these catalysts also afforded efficient catalyzed chain growth using ZnEt2. The zirconium derivative afforded activities up to 13 300 g/mmol·h for propylene polymerization using “dried”-MAO (DMAO) as the cocatalyst. The polymer had a slight syndiotactic bias and is formed by a chain-end control mechanism. A dibenzyl analogue of the highly active zirconium catalyst revealed an all-cis structure by crystallography, but a mixture of isomers in solution by NMR spectroscopy. Cationic monoalkyl complexes were synthesized using either [CPh3][B(C6F5)4] or DMAO and suggest a highly fluxional structure for the catalytically active species.

Mastering the Third Dimension of Salicylaldimine‐Type Ligand Systems: Development of a Convenient Route to Bis(“ferrocene–saliminato”)zirconium Chemistry

“…The system is C 2 -symmetric and gives rise to a single set of NMR signals for its pair of symmetry-equivalent chelate ligands [e.g., . [14] The equilibrium ratio is 1:1.1 in CD 2 Cl 2 at 298 K.…”

Well-defined vanadium complexes as the catalysts for olefin polymerization

“…A remarkable decrease in catalytic activity of 6a-d (at 30 min more than 70% of activity was reduced in contrast with that at 5 min) was observed, whereas catalysts 6e-f, 7 and 8 bearing softer second-row donors (S, P) showed a smaller decrease (ca. 30%), indicating the latter four catalysts possess higher thermal stability [63][64][65][66][67][68]71,72].…”

Methyl–oxygen bond cleavage in hemilabile phosphine–ether ligand of ruthenium(II) complexes

“…For example, C-O bond cleavage of strained cyclic ethers by transition-metals has been applied to catalysis of isomerization to carbonyl compounds, coupling to form esters, and carbonylation to lactones [2,6]. On the other hand, transition-metal complexes contain monoanionic oxygen donor ligands, especially phosphanylphenoxides, are currently receiving considerable attention largely because of their potential use as homogeneous catalyst precursors for polymerization of terminal olefins and ring-opening polymerization of heterocyclic molecules [10][11][12][13][14][15].…”