Synthesis and characterisation of a new mixed [Si(IV), Al(III)] μ-oxo-isopropoxide and its acid complexes

Reaction of dimethyldiacetoxysilane with aluminium isopropoxide was carried out in 1 : 2 molar ratio in refluxing cyclohexane and a mixed [Si(IV), Al(III)] μ-oxo-isopropoxide of the composition Me₂SiO₂Al₂(OPrⁱ)₄ was isolated. This compound was characterised by elemental analysis and IR and NMR spectral studies. The tertiary butanol derivative, Me₂SiO₂Al₂(OBu^t)₄, was prepared by alcoholysis. Reactions of this mixed [Si(IV), Al(III)] μ-oxo-isopropoxide with monobasic bidentate carboxylic acids, such as trans-cinnamic acid (HCA) and dihydrocinnamic acid (HDCA) and with dibasic tridentate carboxylic acids such as salicylic acid (H₂SA) and benzilic acid (H₂BA) were also studied. Products of the type Me₂SiO₂Al₂(OPrⁱ)_4-n(L)_n [where HL = trans-cinnamic acid (HCA), dihydrocinnamic acid (HDCA) and n = 1,2,3 or 4] and Me₂SiO₂Al₂(OPrⁱ)_4-2n(L)_n [where H₂L = salicylic acid (H₂SA), benzilic acid (H₂BA) and n = 1 or 2] were isolated and characterised by elemental and spectral studies.