Dinuclear Titanium(IV) Complexes Bearing Phenoxide‐Tethered N‐Heterocyclic Carbene Ligands with cisoid Conformation through Control of Hydrolysis

In situ generated N‐heterocyclic carbene salt derivative Na 2 (L) of 1,3‐bis(4,6‐di‐ tert ‐butyl‐2‐hydroxybenzyl)imidazolium bromide, [H 3 (L)]Br, reacted with 1 equiv. of TiBr 4 at –78 °C to give a titanium complex of the composition [(L)TiBr 2 (thf)] ( 1 ), while the reaction in a 2:1 ratio under the same conditions afforded bisligand titanium complex [(L) 2 Ti] ( 2 ). Two oxygen‐bridged titanium dimers, {[(L)TiBr] 2 (μ‐O)} ( 4 ) and {[(L)Ti(μ‐O)] 2 } ( 5 ), were obtained by control of hydrolysis of 1 and [(L)Ti(CH 2 Ph) 2 ] ( 3 ) in tetrahydrofuran and diethyl ether. The molecular structures of 2 , 4 , and 5 have been confirmed by X‐ray single‐crystal analysis. The phenoxide‐functionalized NHC ligand adopts transoid conformation in mononuclear complex 2 but rare cisoid conformation in dinuclear complexes 4 and 5 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)