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 = OPrⁱ, OBuⁿ) with 2,2′-biphenol [C₁₂H₈(OH)₂, H₂L¹] affords two trinuclear species [Ti₃(OPrⁱ)₁₀L¹] and [Ti₃(OPrⁱ)₆L¹₃] 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 [Ti₅(μ₃-O)₂(OR)₈L¹₄] (R = OPrⁱ, OBuⁿ) which have two central bridging oxygen atoms in the Ti₅ framework and bridging alkoxide and biphenylate groups. In contrast 1,1′-binaphthol [C₂₄H₁₂(OH)₂, H₂L²] yields the dinuclear [Ti₂(OPrⁱ)₄L²₂] where only the binaphthylate ligands act as bridging groups. Some of the compounds show catalytic activity in esterification reactions.