Syntheses, Reactions, and Ethylene Polymerization of Titanium Complexes with [N, O, S] Ligands

Abstract

Tridentate dianionic arylsulfide ligands [2-(2-SC 6 H 4 )NdCHC 6 H 4 O] 2-(La), [6-Me-2-(2-SC 6 H 4 )Nd CHC 6 H 3 O] 2-(Lb), and [4-Me-6-Bu t -2-(2-SC 6 H 4 )NdCHC 6 H 2 O] 2-(Lc) have been synthesized. Reactions of Ti(OPr i ) 4 and TiCl 4 with the tridentate dianionic arylsulfide ligands (La-Lc) afford monomeric and dimeric titanium complexes {Tirespectively. Hydrolysis of 4c in THF solution containing a small amount of water produces the tetranuclear complex {TiComplexes 2a-5c are characterized by 1 H NMR spectra and elemental analysis. The molecular structures of 2a, 2b, 2c, 3b, and 5c have been characterized by single-crystal X-ray diffraction analyses. The effect of steric hindrance on the structure of products has been investigated. When activated by excess methylaluminoxane (MAO), 2a-2c, 4a-4c, and 5c can be used as catalysts for ethylene polymerization and exhibit moderate to good activities.

TiIV Complexes of Redox‐Active Schiff Bases

“…These shorter Ti-O distances and wider Ti-O-C angles at the equatorial positions indicate stronger π bonding trans to the long Ti-O1 bridging bonds. The same was true of (IЈ)-Ti(OiPr) 2 [20] with essentially the same distances and angles, considering the variability within the crystal of (IVЈ)Ti-(OiPr) 2 .…”

“…Moreover, (IЈ)Ti(OtBu) 2 showed torsional distortion, with an angle of about 26°be-tween the rings. This distortion seems to be a general phenomenon with ONS ligands Ϫ L 2 Ti species also showed this [20] Ϫ but is apparently much reduced or absent in ONO analogues. [19,21] Its origin is likely to be the significantly longer Ti-S bond [2.40 Å in CpTi(IЈ)Cl vs. 1.89 Å for the equivalent bond in the ONO analogue], [19] as well as perhaps the greater steric demand of the sulfur atom and its poorer π-overlap with the imino portion.…”

“…[20] However, this crystal displayed four distinct molecules (labelled A-D) within the same unit cell (Figure 3), which occupy the centre (A), four edges (B), two faces (C) and eight corners (D). Each molecule was dinuclear and locally symmetrical and showed a distorted octahedral environment around the Ti atoms and meridional coordination of the tridentate.…”

“…Indeed, monomeric structures similar to (IЈ)Ti-(OtBu) 2 have previously been reported for CpTi(IЈ)Cl [19] and for CpTi(L)Cl and LTi(OiPr) 2 obtained from the 3-tertbutyl-5-methylsalicylaldehyde analogue of H 2 I (H 2 L). [20] These displayed similarly distorted square pyramidal geometries where three of the four basal positions were occu- pied by the ONS ligand, and the OR groups were nonequivalent. As only one set of tBu signals was detected by 1 H and 13 C NMR spectroscopy of (IЈ)Ti(OtBu) 2 , the two nonequivalent OtBu groups must undergo rapid exchange in solution.…”

Effect of the Bridging Unit in Bis-( Benzoxazolyl ) Titanium , Zirconium and Vanadium Complexes on Catalytic Ethylene Polymerization Reactions

“…In this context, the application of transition metal complexes with organic ligands containing hetero atoms like N, O, S, P a. o. that can act as multi dentate ligands is an attractive approach. [1][2][3][4][5] Chelating benzimidazole type ligands have been studied by several research groups [6][7][8][9][10] and 1,2-bis-benzimidazoles and 2,6-bis(benzimidazolyl)pyridine are well known ligand precursors for late transition metal complexes. [11][12][13][14][15][16][17][18][19][20][21] In all cases, benzothiazoles behave as nitrogen donors, except in a few cases when bridging benzothiazole acts as a bidentate ligand involving both N and S donation.…”