Crown ether complexation of titanium: synthesis and structural characterisation of a cationic oxygen-bridged titanium(IV) dimer

Abstract

1,4,7,10-Tetraoxacyclododecane (12-crown-4) reacts with [TiCl₃(MeCN)₃][SbCl₆] in MeCN to form a complex which provides the crown ether titanoxane [{TiCl(µ-O)(12-crown-4)}₂][SbCl₆]₂·2CH₂Cl₂1 following inadvertent hydrolysis. The structure of 1 contains a discrete di-µ-oxo-dititanium cation placed on a crystallographic centre of inversion, two regular (O_h) SbCl₆^– anions and two molecules of CH₂Cl₂ as lattice solvate. The complex crystallises in the space group P2₁/n with cell dimensions a= 8.337(4), b= 21.307(10), c= 13.626(8)Å, β= 107.13(4)°, with Z= 2; R= 0.038 for 3271 observed reflections [l/σ(l) 2.0]. The core Ti₂O₂ ring is planar with dimensions Ti–O 1.823(4) and 1.811(3)Å and O–Ti–O 79.7(2) and Ti–O–Ti 100.3(2)°. In addition to the two bridging oxygen atoms each titanium atom is bonded to one chlorine [Ti–Cl 2.277(2)Å] and all four oxygen atoms of a crown macrocycle [Ti–O 2.121(4)–2.237(4), mean 2.242 Å].