Mono- and dinuclear complexes of sulfones with the tetrachlorides of group 4

Abstract

The reactions of dialkyl sulfones [R₂SO₂: R = Me (a), Et (b), Ph (c), R₂ = –(CH₂)₄– (d)] with the metal tetrachlorides of Group 4 [MCl₄: M = Ti (1), Zr(2), Hf (3)] give different products mainly depending on the sulfone/M molar ratio. Compounds of formula [M₂Cl₈(R₂SO₂)₂] [M = Ti, R₂ = –(CH₂)₄– (1d); M = Zr, R = Et (2b), R = Ph (2c)] and [MCl₄(R₂SO₂)₂] (sulfone/M = 2) [M = Ti, R = Me (1aa); M = Zr, R = Me (2aa), R = Ph (2cc), R₂ = –(CH₂)₄– (2dd); M = Hf, R = Me (3aa), R₂ = –(CH₂)₄– (3dd)] have been obtained. By X-ray diffraction methods the dinuclear titanium and zirconium adducts, [Ti₂Cl₈(μ-sulfolane-O,O′)₂] (1d) and [Zr₂Cl₈(μ-Ph₂SO₂-O,O′)₂] (2c) have been established to contain bridging sulfone and hexacoordinated metal centres, while the mononuclear zirconium complex [ZrCl₄(Me₂SO₂)₂] (2aa) has cis-monodentate sulfones in a slightly distorted octahedral geometry. The reaction between TiCl₄ and sulfolane (tetrahydrothiophene 1,1-dioxide) in SOCl₂ affords the 1 ∶ 1 adduct independent of the sulfone/Ti molar ratio. Ligand-exchange and inter-conversion between mononuclear and dinuclear species have been observed by NMR, while the spectral features of the SO₂ moiety have been assigned by IR- and Raman spectroscopies.