196716-83-3Relevant articles and documents
Organometallic reactivity on a calix[4]arene oxo surface. Synthesis and rearrangement of Zr-C functionalities anchored to a calix[4]arene moiety
Giannini, Luca,Caselli, Alessandro,Solari, Euro,Floriani, Carlo,Chiesi-Villa, Angiola,Rizzoli, Corrado,Re, Nazzareno,Sgamellotti, Antonio
, p. 9198 - 9210 (2007/10/03)
This report concerns the formation and the main properties of Zr-C functionalities supported by the O4 matrix of either the monoalkylated (trianionic) or dialkylated (dianionic) forms of [p-Bu(t)-calix[4]arene] (1). The synthesis of the starting materials [p-Bu(t)-calix[4]-(OMe)2(O)2ZrCl2] (4) and [{μ-p-Bu(t)-calix[4]-(OMe)(O)3}2 Zr2Cl2] (10) has been performed via the lithiation of the corresponding protic forms, [p-Bu(t)-calix[4]-(OMe)2(OH)2]] (2) and [p-Bu(t)-calix[4]-(OMe)(OH)3] (8), followed by reaction with ZrCl4·(thf)2. Complex 4 undergoes a facile base-induced (base = Et3N, Py) demethylation, leading to the monomethoxy derivative [p-Bu(t)-calix[4]-(OMe)(O)3ZrCl2]-[MeNEt3]+ (5) and ionization of the Zr-Cl bond to give [p-Bu(t)-calix[4]-(OMe)2(O)2Zr(OTf)2] (6). The alkylation of 4 led to the corresponding dialkylaryl derivatives [p-Bu(t)-calix[4]-(OMe)2(O)2ZrR2] (R = Me, 12; R = CH2Ph, 13; R = CH2-SiMe3, 14 R = p-MeC6H4, 15]. They undergo a base-induced demethylation and dealkylation illustrated by the obtention of [p-Bu(t)-calix[4]]-(OMe)(O)3Zr(CH2Ph)(Py)] (18), while the thermal decomposition gave a particularly interesting result in the case of 15, with the formation of the corresponding η2-benzyne, [p-Bu(t)-calix[4]-(OMe)2(O)2-Zr(η2-MeC6H3) (16). Cationic alkyl derivatives of zirconium have been obtained, in the case of 13, using the monoelectronic oxidizing agent [Cp2Fe]+ or a strong Lewis acid such as [B(C6F5)3], [p-Bu(t)-calix [4]-(OMe)2(O)2-Zr(CH2Ph)]+BPh4- (19); [p-Bu(t)-calix[4]-(OMe)2(O)2Zr(CH2Ph)(thf)]+BPh4- (20); and [p-Bu(t)-calix[4]-(OMe)2(O)2-Zr(CH2Ph)]+ [B(C6F5)3(CH2Ph)]- (21). The cationic alkyl derivatives undergo easy demethylation by pyridine to give 18. The alkylation of 10 with LiPh led to a dimeric dimetallic aryl compound, [{μ-p-Bu(t)-calix[4]-(OMe)(O)3}2-Zr2Ph2] (22), where the calix[4]arene unit bridges two metal atoms and the methoxy groups are only weakly bound to the metal. The spectator methoxy group binds strongly to the metal in the monomeric η2-iminoacyl [p-Bu(t)-calix[4]-(OMe) (O)3Zr(Bu(t)N=CPh)] (23), formed from the migratory insertion of Bu(t)NC into the Zr-Ph in 22. The proposed structures have been supported by X-ray analyses carried out on 4, 6, 13, 16, 22, and 23.