During the formation of organic-inorganic hybrid materials by the sol-gel process, the observation of multiphase systems at different stages of the reaction is not uncommon. An assessment of the chemical species formed before and after gelation is not an easy task because complex mixtures are generally found in these systems. In this study, the identification of intermediates developed during the formation of a hybrid obtained from tetraethoxysitane (TEOS) and 4-[(5-dichloromethylsilyl)pentyloxy]cyanobenzene monomer has been undertaken. Solution and solid-state Si-29- and C-13-NMR spectra, recorded at different degrees of conversion, allow the elucidation of the mechanism of hybrid formation. 4-[(5-dichloromethylsilyl)pentyloxy]cyanobenzene, (DCN), DCN-TEOS cyclosiloxanes and low-molecular-weight linear copolysiloxanes are formed in the early stages of the process and before gelation occur. Before the gel is formed, cyclic species undergo an acid-catalyzed ring-opening copolymerization with silica to produce a random copolymer. Other intermediates of the Q(ij) type (where Q indicates a four-functional silicon, the first subscript indicates the number of siloxane bridges connected to the silicon site, and the second subscript indicates the number of silanol groups) that develop before the gel is formed have also been identified. Spectral peak patterns of the final hybrid, observed in solid-state Si-29 and C-13-NMR spectra, are also discussed. (c) 2005 Wiley Periodicals, Inc.