Synthesis and reactivity of silylated tetrathiafulvalenes

Abstract

Novel organosilylated tetrathiafulvalenes (TTFs) possessing Si–H or Si–Si bonds have been synthesised. The crystal structures of several derivatives have been determined by X-ray diffraction, including that of dimeric (Si₂Me₄)(TTF)₂ (11) incorporating a diatomic SiMe₂–SiMe₂ linker. Cyclic voltammetry measurements in all cases show two oxidation waves. DFT calculations were performed to rationalize the absence of an electronic communication between the two TTF moieties of 11 through the disilanyl spacer. The reactivity of the Si–H bond has been exploited to prepare the dinuclear complex [{Ru(CO)₄}₂{μ-(Me₂Si)₄TTF}] (14), starting from Ru₃(CO)₁₂ and TTF(SiMe₂H)₄ (1). Treatment of 14 with 2 equiv. of PPh₃ or dppm results in selective substitution of a CO ligand trans to a SiMe₂ group to afford mer-[{Ru(PPh₃)(CO)₃}₂{μ-(Me₂Si)₄TTF}] (13) and mer-[{Ru(CO)₃}₂(η¹-dppm){μ-(Me₂Si)₄TTF}] (16). Attempts to transform the Si–H bonds of some TTF(SiMe₂H)_n (n = 1, 2) into Si–O functions using stoichiometric amounts of water in the presence of tris(dibenzylideneacetone)dipalladium(0) were unsuccessful. Quantitative cleavage of the C_TTF–Si bond was observed instead of formation of TTF-based-siloxanes. Essays of catalytic bis-silylation of phenylacetylene with 11 and TTF(SiMe₂-SiMe₃) (9) in the presence of Pd(OAc)₂/1,1,3,3-tetramethylbutylisocyanide failed. Again, cleavage of the C_TTF–Si bond was noticed.