Synthesis and Characterization of Tris(catecholato)Silicates, [(C₆H₄O₂)₃Si]²⁻ with Different Counter Cations – First Pyrolysis Study and X-ray Structure of [{(CH₃)₂CH}₂NH₂]₂[(C₆H₄O₂)₃Si] · 2CH₃CN · H₂O

Article type: Research Article

Authors: Kingston, J.V. | Vargheese, Babu | Sudheendra Rao, M.N.

Affiliations: Department of chemistry, | Regional sophisticated Instrumentation Centre, Indian Institute of Technology Madras, Chennai-600036, India

Note: [] Corresponding author.

Abstract: The synthesis of hypervalent tris(catecholato)silicate ion, [(C6H4O2)3Si]2− with six different counter cations: (i) diethylammonium (I), (ii) triethylammonium (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 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 gcm−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]n by the quantitative expulsion of ammonium catecholate salt, (M+)2[(C6H4O2)]2−. CP-MAS 29Si-nmr spectral data suggests that [(C6H4O2)2Si]n is a simple mixture.

DOI: 10.1080/13583140012331339039

Journal: Main Group Chemistry, vol. 3, no. 2, pp. 79-90, 2000