Diverse Structure−Activity Trends in Amine Bis(phenolate) Titanium Polymerization Catalysts

Abstract

The activity of amine bis(phenolate) Ti dibenzyl complexes in 1-hexene polymerization catalysis as a function of the phenolate substituents was investigated. Two series of Ti complexes carrying either a dimethylamino or a methoxy sidearm donor were prepared and characterized. In each series, the substituents on the phenolate rings were either alkyl groups of varying bulk or electron-withdrawing chloro groups. When activated with a suitable Lewis acid, all precatalysts have shown reactivity toward 1-hexene. Different structure−activity trends were observed in the two series: The activity of the catalysts of the “OMe” series was low to moderate and was almost independent of the phenolate substituents. In contrast, the activity of the “NMe2” catalysts had a strong dependence on both the steric and electronic character of the phenolate substituents, ranging from mild to highly active. The difference in polymerization activity trends between the two series may be traced back to their different tendency toward misinsertions. A “NMe2”-Ti complex having Cl groups in the ortho, para positions of the phenolate rings led to the most active catalyst and to a remarkably high-M w polymer (>4 000 000) obtained within 1 h of polymerization at RT. The characterization of this ultrahigh-M w atactic poly(1-hexene) by means of oscillatory rheometry and stress relaxation experiments indicated typical elastomeric behavior at RT.

Synthesis, Structure, and C–C Cross‐Coupling Activity of (Amine)bis(phenolato)iron(acac) Complexes

“…Moreover, all of these paramagnetic complexes have been analytically verified by elemental analysis and MALDI-TOF mass spectrometry. Magnetic moment measurements indicate high-spin d 5 iron centers. Electronic absorption spectra in the UV/Vis range exhibit strong charge-transfer bands, which are slightly solvent dependant.…”

“…[L5]Fe(acac) (5), and [L6]Fe(acac) (6). In all of these complexes, the phenolato oxygen atoms are cis-oriented.…”

Synthesis, characterization and catalytic properties for olefin polymerization of two new dimeric zirconium(IV) complexes having diamine-bis(phenolate) and chloride ligands

“…They inter alia comprise a family of complexes of tetradentate dianionic diamine bis(phenolate) ligands (introduced by Kol and co-workers) in which one donor is located on the pendant arm [1][2][3][4][5][6][7][8][9][10]. The presence of an extra donor on the pendant arm in these complexes leads to the catalysts which are extremely reactive in 1-olefin polymerization, while tridentate complexes with the same [ONO] ligand cores are rapidly deactivated and they give only traces of oligomers [3].…”

“…The presence of an extra donor on the pendant arm in these complexes leads to the catalysts which are extremely reactive in 1-olefin polymerization, while tridentate complexes with the same [ONO] ligand cores are rapidly deactivated and they give only traces of oligomers [3]. All complexes of that type investigated in the olefin polymerization reactions were monomeric and mostly apart from the dianionic diamine bis(phenolate) ligand they contained two benzyl groups as labile monoanionic groups [1][2][3][4][5]8,9,[11][12][13][14][15]. The reports on the synthesis of chloro-derivatives and their use in olefin (co)polymerization are very rare up to now [10,15].…”

“…Moreover, taking into account that (i) investigated until now zirconium and titanium complexes having diamino-bis(phenolate) ligands with various structures display in majority a very high activity in 1-olefin polymerization but they all produce sterreoireegular poly(1-olefins) [5,15] and that (ii) the most important strategy for tacticity control is ligand design, we undertook the preparation of zirconium complex with new unsymmetrically substituted ligand which could have beneficial effect on catalyst stereoselectivity. For that reason apart from the standard diamine bis(phenolate) ligands with dimethylamino donor on the sidearm and with two t-Bu groups on both aromatic rings we used the new one, in which only one aromatic ring is substituted by t-Bu groups.…”