f-element disiloxanediolates: Novel Si-O-based inorganic heterocycles

The preparation and structural characterization of scandium and f-element c omplexes derived from the disiloxanediolate dianion. [(Ph2SiO)(2)O](2), are reported. Reactions of in situ prepared Ln[N(SiMe3)(2)](3) (Ln=Eu, Sm. Gd) with (Ph2SiOH)(2)O in different stoichiometries afforded the lanthanide di siloxanediolates [Eu([(Ph2SiO)(2)O]Li(Et2O)}(3)] (1), [{{(Ph2SiO)(2)O}Li(dm e)}(2)- SmCl(dme)] (2), and [{{(Ph2SiO)(2)O}Li(thf)(2)}(2)GdN(SiMe3)(2)] (3 ). In situ formed (Ph2SiOLi)(2)O reacted with anhydrous NdBr3 (molar ratio 3:1) to give polymeric [{Nd((Ph2SiO)(2)O}3{mu -Li(thf)}(2){mu (2)-LiBrLi(th f)(Et2O)}}(n)] (4). Treatment of 3 with Ph2Si(OH)(2) in the presence of ace tonitrile yielded the dilithium trisiloxanediolate derivative [(Ph2Si(OSiPh 2-O)(2)}{Li(MeCN)}(2)](2) (5), which according to an X-ray analysis display s an Li4O4 heterocubane structure. The trinuclear scandium complex [{{(Ph2S iO)(2)O}Sc(acac)(2)}(2)Sc(acac)] (6) was obtained by reaction of [(C5Me5)Sc (acac)(2)] (C-5-Me-5 = eta (5)-pentamethylcyclopentadienyl) with (Ph2SiOH)( 2)O in a 3:2 molar ratio. Selective formation of the colorless uranium(VI) derivative [U{Ph2Si(OSiPh2O)(2)}(2){(Ph2SiO)(2)O}] (7) was observed when ur anocene, U(eta (8)-C8H8)(2), was allowed to react with (Ph2SiOH)(2)O. An X- ray diffraction study of the solvated derivative [U(Ph2Si(OSiPh2O)(2)}(2)(P h-2-SiO)(2)O}]. Et2O TMEDA (TMEDA = N,N.N',N'-tetramethyl-ethylenediamine) (7a) revealed the presence of both the original [(Ph2SiO)(2)O](2-) dianion as well as the ring-enlarged [Ph2Si(OSiPh2O)(2)](2-) ligand in the same mol ecule.