Synthesis of di-, tri- and penta-nuclear titanium(iv) species from reactions of titanium(iv) alkoxides with 2,2′-biphenol (H₂L¹) and 1,1′-binaphthol (H₂L²); crystal structures of [Ti₃(μ₂-OPrⁱ)₂(OPrⁱ)₈L¹], [Ti₃(OPrⁱ)₆L¹₃], [Ti₅(μ₃-O)₂(μ₂-OR)₂(OR)₆L¹₄] (R = OPrⁱ, OBuⁿ) and [Ti₂(OPrⁱ)₄L²₂]

Abstract

Reaction of titanium(iv) alkoxides [Ti(OR)(4)](R = OPr(i), OBu(n)) with 2,2[prime or minute]-biphenol [C(12)H(8)(OH)(2), H(2)L(1)] affords two trinuclear species [Ti(3)(OPr(i))(10)L(1)] and [Ti(3)(OPr(i))(6)L(1)(3)] each possessing an open-chain V-shaped arrangement of three titanium atoms with the former having both bridging alkoxide and biphenylate groups and the latter having only biphenylate as bridging groups. Variations in reaction conditions yield the pentanuclear species [Ti(5)([micro sign](3)-O)(2)(OR)(8)L(1)(4)](R = OPr(i), OBu(n)) which have two central bridging oxygen atoms in the Ti(5) framework and bridging alkoxide and biphenylate groups. In contrast 1,1[prime or minute]-binaphthol [C(24)H(12)(OH)(2), H(2)L(2)] yields the dinuclear [Ti(2)(OPr(i))(4)L(2)(2)] where only the binaphthylate ligands act as bridging groups. Some of the compounds show catalytic activity in esterification reactions.