Synthesis and characterization of tris(catecholato) silicates, [(C6H4O2)(3)Si](2-) with different counter cations-first pyrolysis study and X-ray structure of [{(CH3)(2)CH}(2)NH2](2)[(C6H4O2)(3)Si]center dot 2CH(3)CN center dot H2O

The synthesis of hypervalent iris(catecholato)silicate ion, [(C6H4O2)(3)Si] (2-) with six different counter cations: (i) diethylammonium (I), (ii) trie thylammonium (II), (iii) diisopropylammonium (III), (iv) morpholinium (IV), (v) piperazinium (V) and (vi) N-methylpiperazinium (VI) has been achieved (yield: ca.95%) by the reaction of catt catechol and tetraethoxysilane in p resence of the corresponding amine. Single crystal X-ray structure of compo und (III) has been determined. It crystallizes in orthorhombic system [spac e group P2(1)2(1)2(1); a = 11.735(2), b = 13.708(3), c=23.283(5) Angstrom; alpha = 90 degrees beta= 90 degrees, gamma = 90 degrees; Volume=3745.4(11) Angstrom (3); Density = 1.165 gcm(-3); Z = 4; R = 0.0585; wR2(I) = 0.1610 a nd 3677 reflections] and the structure shows slightly distorted octahedral geometry around silicon. Results of TG, DT and EG analysis of compounds (I) -(VI) reveal the influence of the counter cation on thermal stability. Benc h scale pyrolysis of (I) and (II) convert them to [(C6H4O2)(2)Si](n) by the quantitative expulsion of ammonium catecholate salt, (M+)(2)[(C6H4O2)](2-) Cr-MAS Si-29-nmr spectral data suggests that [(C6H4O2)(2)Si](n) is a simpl e mixture.