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

The reactions of dialkyl sulfones[R2SO2: R = Me (a), Et (b), Ph (c), R-2 = -(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, R-2 = -(CH2)(4-) (1d); M = Zr, R = Et (2b), R = Ph ( c)] and [MCl4(R2SO2)(2)] (sulfone/M = 2) [M = Ti, R = Me (1aa); M = Zr, R = Me (2aa), R = Ph (2cc), R-2 = -(CH2)(4-) (2dd); M = Hf, R = Me (3aa), R-2 = -(CH2)(4-) (3dd)] have been obtained. By X-ray diffraction methods the dinuclear titanium and zirconium adducts, [Ti2Cl8(mu-sulfolane-O,O')(2)] (1d) and [Zr2Cl8(mu-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.