Principles of Mononucleating and Binucleating Ligand Design

Dinuclear dialkoxo-bridged cyclopentadienylsiloxo titanium complexes

“…Similar behaviour was described for a titanium-aluminium dinuclear compound. 43 Activation of e-CL with complexes 4 and E proceeded in both cases by cleavage of the acyl-oxygen bond, confirmed by 1 The reactivity of the chloro derivatives 1a and 1b toward Al(C 6 F 5 ) 3 depends on the type of bridging dialkoxo ligand, the ethyleneglycolate bridge is totally transferred to aluminium whereas substitution of one chloro ligand is preferred for the catecholate-bridged compound 1b. This difference is attributed to the lesser accessibility of the p electrons of the oxygen atoms in this last type of bridging group, due to higher arene ring acidity, which should hinder the interaction with the Lewis acid.…”

“…The isolated solid consisted mainly of 1c, but it contained some irremovable decomposition products, which prevented us from obtaining a correct elemental analysis, though satisfactory spectroscopy data were obtained. Data for 1c: 1 64 mmol) and one equivalent of (HO) 2 SiPh 2 (0.08 g, 0.32 mmol). The mixture was stirred for three days at ambient temperature.…”

“…The isolated solid consisted mainly of 1d, but it contained some irremovable decomposition products, which prevent us from obtaining correct elemental analysis, though satisfactory spectroscopy data were obtained. Data for 1d: 1 BzMgCl (2 M, 1.66 mL, 3.32 mmol) was injected to a solution of 1a (1.00 g, 1.66 mmol) in diethyl ether (50 mL) at -78 • C. The reaction mixture was warmed to room temperature and stirred overnight. 10 mL of hexane were added and the solution was filtered.…”

“…The volatiles were removed under vacuum leaving an oil that was washed with hexane (2 ¥ 2 mL) to give 8B as an orange solid (0.146 g, 85%). Data for 8B: 1 Polymerization of e-caprolactone with dinuclear complex 4. e-Caprolactone (1 g) was added via syringe to a stirred solution of complex 4 (0.04 mmol) in toluene (5 mL), in a glove box. The polymerization mixture was stirred at the desired temperature.…”

“…1 In this regard, olefin polymerization and copolymerization processes with group 4 dinuclear complexes have provided modified final products with respect to those obtained using mononuclear derivatives. 2- 14 Alkoxo, aryloxo and related ligands stabilize high oxidation metal complexes and chelating diol derivatives are adequate ligands for generating bimetallic systems.…”