Solubilizing functionalized molecular aluminosilicates

Abstract

Molecular aluminosilicate LAl(SH)(μ-O)Si(OH)(O^tBu)₂1 (L = [HC{C(Me)N(Ar)}₂]⁻, Ar = 2,6-ⁱPr₂C₆H₃) has been prepared from LAl(SH)₂2 and (^tBuO)₂Si(OH)₂ in high yield. When reacted with one equiv. of water, the unique aluminosilicate containing two terminal hydroxy groups LAl(OH·THF)(μ-O)Si(OH)(O^tBu)₂3 can be isolated. However, when 2 is reacted with the bulkier silanol (^tBuO)₃SiOH, no reaction is observed. The desired LAl(SH)(μ-O)Si(O^tBu)₃6 can be prepared in a two-step synthesis between LAlH₂4 and (^tBuO)₃SiOH giving first LAl(H)(μ-O)Si(O^tBu)₃5, which reacts further with elemental sulfur to give 6 as the only product. Direct hydrolysis of 6 was conducted to obtain LAl(OH)(μ-O)Si(O^tBu)₃7, however, such hydrolysis always resulted in a complete decomposition of the starting material. Therefore we used boric acid, which condenses in non-polar solvents and slowly evolve water, to hydrolyze 6 to 7 under mild conditions. Compounds 1, 3 and 5–7 have been characterized by single-crystal X-ray diffraction.