Synthesis and characterisation of derivatives of monocyclopentadienylbis(arene-1,2-dithiolato)titanium(IV); crystal structures of M[Ti(η5-C5Me5)(1,2-S2C6H4)2] [M = Tl or N(PPh3)2]

Abstract

Thallium(I) derivatives of monocyclopentadienylbis(arene-1,2-dithiolato)titanium, Tl[Ti(η⁵-C₅H_nMe_5 – n)(S₂C₆H₃R)₂ (1–6; n = 0, 4 or 5; R = H or Me), have been synthesised and isolated in yields of 31–65% from reactions of the corresponding trichloromonocyclopentadienyltitanium reagents, Ti(η⁵-C₅H_nMe_5 – n)Cl₃ and thallium salts of the benzene-1,2-dithiol or toluene-3,4-dithiol in tetrahydrofuran. Reaction between Tl[Ti(η⁵-C₅Me₅)(1,2-S₂C₆H₄)₂] and bis(triphenylphosphine)iminium chloride, [N(PPh₃)₂]Cl, has also afforded the derivative [N(PPh₃)₂][Ti(η⁵-C₅Me₅)(1,2-S₂C₆H₄)₂] 7. Products have been characterised by elemental analysis, NMR, IR and mass spectroscopy, and by X-ray diffraction. The structure of 7, in the crystalline state as a tris(dichloromethane) solvate, comprises an ionic lattice containing discrete [Ti(η⁵-C₅Me₅)(1,2-S₂C₆H₄)₂]^– anions of four-legged piano stool geometry with two chelating benzene-1,2-dithiolate ligands folded along the S· · ·S axis in exo and endo conformations, respectively, relative to the cyclopentadienyl ring. The crystal structure of Tl[Ti(η⁵-C₅Me₅)(S₂C₆H₄)₂] 1 contains two forms of the anion [Ti(η⁵-C₅Me₅)(S₂C₆H₄)₂]^– in endo/endo and endo/exo conformations, respectively, which are unsymmetrically co-ordinated to the Tl^I cations. A Tl^I ion is connected by two Tl–S bonds to endo dithiolate ligands of each anion and there is also one Tl–S interaction between pairs of endo/endo and endo/exo forms. Additional weaker Tl· · ·S interactions to the Tl^I ions generate a linked chain of dimeric units. In solution, NMR spectra suggest a more symmetrical structure for all derivatives but shifts in resonances support the retention of co-ordinate links between the cyclopentadienylbis(arene-1,2-dithiolato)titanium anion and Tl^I.