Synthesis and Characterization of Ti Complexes Using 4‐ tert ‐Butyl‐2,6‐bis(hydroxymethyl)phenol: X‐ray Structures of a Confacial Bioctahedron with Terminal Nucleophilic Phenylmethoxide Ligands, and a Ti 4 O 16 Core Protected by Two Hydrophobic Binding Pockets

Treatment of 4‐ tert ‐butyl‐2,6‐bis(hydroxymethyl)phenol (H 3 L) with [TiO(acac) 2 ] in protic solvents at elevated temperatures leads to the formation of the dinuclear complex (Et 4 N)[L 3 Ti 2 ] 1 , whereas carrying out the reaction at room temperature or in aprotic solvents leads to the formation of the tetranuclear complex (Et 4 N) 2 [L 2 (HL) 4 Ti 4 O 2 ] 2 . Heating 2 in protic solvents leads to the formation of 1 , but 2 is stable in non‐protic solvents such as THF even upon heating. Dissolving 1 in an aprotic solvent leads to the formation of 2 . The anion of 1 consists of a confacial bioctahedron with a [(BzO) 3 Ti IV (μ 2 ‐OPh) 3 Ti IV (OBz) 3 ] − core. The phenylmethoxide ligands (BzO − ), and the phenolato ligands are bound to the strong Lewis acid Ti IV . The bond lengths are for Ti−OBz ca. 1.83 Å and for Ti−μ 2 ‐OPh ca. 2.11 Å. Despite the highly covalent Ti−OBz bond, the phenylmethoxide ligands exhibit nucleophilic character, and a tendency to bridge two Ti IV ions as demonstrated by the synthesis of the tetranuclear complex 2 . The dianion in 2 consists of a Ti 4 O 16 core with two hydrophobic half‐bowl shaped pockets built from three tert ‐butylbenzene units each. The hydrophobic pockets allow access to the Lewis basic μ 3 ‐O 2− ligands of the Ti 4 O 16 core. In the crystal structure of 2· 2CH 3 CN, two Et 4 N + cations occupy these two binding pockets. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)