Crown ether complexes of titanium(iv) chloride and bromide and the structures of the hydrolysis products [Ti2Cl6(μ-O)(18-crown-6)2] and [Ti4Cl8(μ-O)4(15-crown-5)4]

Abstract

The titanium(IV) complexes of 12-crown-4, 15-crown-5 and 18-crown-6 and of 1,4-dithia-7,10,13-trioxacyclopentadecane (L′) of type [TiX₄(η²-L)] (X = Cl or Br, L = 15-crown-5 or 18-crown-6; X = Br, L = 12-crown-4) and [TiCl₄(L′)] have been prepared from TiX₄ and the ligands in anhydrous toluene, and characterised by analysis, IR, UV-visible and ¹H NMR spectroscopy. Complexes with TiI₄ do not form under similar conditions. The [TiCl₄(L′)] complex contains the thia-oxa-crown coordinated via sulfur to the titanium. The complexes are extremely readily hydrolysed and examples of the first two stages of the hydrolysis have been characterised by X-ray crystallography. These are the dimer [(18-crown-6)Cl₃Ti(μ-O)TiCl₃(18-crown-6)] which contains a single non-linear oxo-bridge linking two six-coordinate titanium centres also coordinated η² to 18-crown-6 and to three (mer) chlorines. The second product is the tetrameric [{TiOCl₂(15-crown-5)}₄] in which there is an eight-membered ring composed of alternating Ti and O, each titanium also coordinated η² to 15-crown-5 and two terminal (cis) chlorines.