Catalytic transformation of silicon tetraisocyanate Si(NCO)4 to a polymeric silylcarbodiimide

Abstract

A new way for the preparation of inorganic polymeric carbodiimide‐based networks is presented which resembles the transformation of molecular isocyanates using 1‐phenyl‐3‐methyl‐2‐phospholene‐1‐oxide as a catalyst. The respective reaction sequence, well established in preparative organic chemistry, has been applied for the synthesis of carbodiimide‐based SiNC(O) materials. Starting from Si(NCO)4 (silicon tetraisocyanate), a transformation to an insoluble extended inorganic array was achieved in boiling dodecan (T = 216 °C). Analysis of the polymer using X‐ray diffraction, FT‐IR, density measurement, matrix‐assisted laser desorption/ionization time of flight and TGA revealed that this highly moisture‐sensitive amorphous network consists of oligomers of high molar mass and exhibits a high density of around 1.5 g cm−3, which corresponds quite well to the calculated density of crystalline Si(NCN)2 reported in the literature. Degradation of this 'SiNC(O) phase' with the release of N2 and (CN)2 finally provided SiC as the only crystalline product. No indication of the formation of crystalline Si3N4 or intermediate crystalline 'SiC2N4', silicon carbodiimide (= Si(NCN)2), was noticed. Copyright © 2013 John Wiley & Sons, Ltd.