Reactions of alkali metal and yttrium alkyls with a sterically demanding bis(aryloxysilyl)methane: Formation of aryloxide complexes by Si-O bond cleavage

Reaction of bis(bromodimethylsilyl)methane (BrSiMe2)(2)CH2 (1) with two equivalents of 2,6-diisopropylphenol ((ArOH)-O-i) in the presence of the auxiliary base NEt3 affords the bis(aryloxysilyl)methane ((ArOSiMe2)-O-i)(2)CH2 (2) as a colourless oil following work-up The reaction of 2 with [Li(Bu-n)] in the presence of [K(OBut)] promoted Si-O bond cleavage and the sole isolable product from this reaction was found to be the colourless, crystalline heterobimetallic complex [(Li(OAr)}(2)(K((OAri)}(2)(THF)(4)] (3) The in situ reaction of 2 with one equivalent of (Li(Bu-n)I in the presence of one equivalent of [K(OBut)] and subsequent addition to one equivalent of (Y(I)(3)(THF)(3) (5)] afforded colourless, crystalline [Y(OAri)(I)(2)(THF)(3)] (4) as the only isolable product No reaction was observed between IY(Bn)(3)(THF)(3)] (Bn = CH2C6H5) and one equivalent of 2 in toluene at loom temperature, heating solutions led to decomposition and recovery of 2 In THF, the reaction between 2 and one equivalent of [Y(Bn)(3)(THF)(3)] resulted in Si-C bond cleavage with concomitant Si-C bond formation to give (BnSiMe2)(2)CH2 (5) as a colourless oil and the colourless, crystalline compounds (Y(OAri)(2)(Bn)(THF)] (7), and [Y(OAri)(3)(THF)(2)] (8) which were separated by fractional crystallisation. In an attempt to prepare 7 by a rational route, [Y(OAri)(2)(1)(THF)(2)] (6) was prepared from the reaction of [Y(I)(3)(THF)(35)] with two equivalents of [K(OAri)]. However, although 6 could be prepared by a rational salt elimination route, attempts to convert it to 7 resulted instead in 8 being recovered as the only isolable product This is proposed to be the result of Schlenk-type equilibria, which is supported by the observation that dissolution of pure 6 in benzene results in the additional presence of 8 in the H-1 NMR spectrum over 12h Compound 7 was prepared rationally from the reaction between [Y(Bn)(3)(THF)(3)] and two equivalents of HOAr' However, although crystalline 7 could be isolated in sufficient quantities for analysis, NMR spectra were consistent with the formation of 8 in solution from Schlenk-type equilibria. Compounds 2-8 have been variously characterised by X-ray diffraction, NMR and FUR spectroscopy, and CHN microanalyses. (C) 2010 Academic des sciences Published by Elsevier Masson SAS All rights reserved.