Abstract
The syntheses and single-crystal X-ray structures of several well-defined hexaphenyltrisiloxanediolates of sodium, titanium, and iron are reported. All these compounds contain eight-membered MSi3O4 rings (M = Na, Ti, Fe). Treatment of 1,1,3,3-tetraphenyldisiloxane-1,3-diol, (HO)SiPh2OSiPh2(OH) (1), with excess metallic Na in THF afforded the sodium-hexaphenyltrisiloxandiolate reagent [Ph2Si(OSiPh2O)2]2Na4(THF)4 (3a) in 68% yield. Single crystals suitable for X-ray diffraction were obtained for the diglyme solvate [Ph2Si(OSiPh2O)2]2Na4(diglyme)2 (3b) which was prepared in 76% yield by recrystallization of 3a from diglyme (=ethylene-bis(2-methoxyethyl)ether). Readily accessible 3a has been demonstrated to be a highly useful precursor for new transition metal hexaphenyltrisiloxanediolates (=metallacyclotetrasiloxanes). Reaction of 3a with an excess of TiCl4 in THF provided the titanacyclotetrasiloxane derivative [Ph2Si(OSiPh2O)2]TiCl2(THF)2 (4) with octahedral coordination around titanium. Similar reaction of 3a with FeCl3 in THF afforded the anionic spirocyclic iron(III) complex [Na(DME)3][{Ph2Si(OSiPh2O)2}2Fe] (5) as yellow-brown crystals in 71% yield. An iron(III) analog of 4, the anionic ferracyclotetrasiloxane complex [Li(DME)3][Ph2Si(OSiPh2O)2FeCl2] (6) was prepared in moderate yield (53%) by deprotonation of 1,1,3,3,5,5-hexaphenyl-1,3,5-trisiloxanediol, Ph2Si(OSiPh2OH)2 (2), with n-butyllithium followed by reaction with FeCl3 in DME. The molecular and crystal structures of 3b, 4, 5, and 6 have been determined by X-ray diffraction.
Published Version
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