P[N(iBu)CH2CH2]3N: A versatile non-ionic base for the synthesis of higher coordinate silicates

A room temperature reaction of tetramethyl-orthosilicate with catechol or substituted catechol derivatives, or hydroxy carboxylic acids in the presence of the proazaphosphatrane P(iBuNCH2CH2)3N, readily affords the first examples of phosphonium salt stabilized higher coordinate silicates of the type [HP(iBuNCH2CH2)3N]2[Si(L)3] in high yields. A single crystal X-ray structural investigation of [HP(iBuNCH2CH2)3N]2[Si(O2C6H4)3] revealed a hexacoordinate silicate framework with two independent phosphatranium cations, possessing strong transannular Nax→P bonds.