The synthesis of hypervalent tris(catecholato)silicate ion, [(C6H4)2)3Si]2− with six different counter cations: (i) diethylammonium (I), (ii) triethylammonium (II), (iii) diisopropylam-monium (III), (iv) morpholinium (IV), (v) piperazinium (V) and (vi) N-methylpiperazinium (VI) has been achieved (yield: ca.95%) by the reaction of catechol and tetraethoxysilane in presence of the corresponding amine. Single crystal X-ray structure of compound (III) has been determined. It crystallizes in orthorhombic system [space group P212121; a = 11.735(2), b = 13.708(3), c = 23.283(5) Å; α = 90°, β = 90°, γ = 90°; Volume = 3745.4(11) Å3; Density = 1.165 gem-3; Z = 4; R = 0.0585; wR2(I) = 0.1610 and 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. Bench scale pyrolysis of (I) and (II) convert them to [C6H4O2)2Si], by the quantitative expulsion of ammonium catecholate salt, (M+)2[(C6H4O2)]2−. CP-MAS 29Si -nmr spectral data suggests that [(C6H4O2)2Si]1, is a simple mixture. © 1999 OPA (Overseas Publishers Association) N.V.