Chemistry of gas phase association reactions in 13-15 CVD has been reviewed. Results of the extensive quantum chemical modeling of group 13-15 CVD show high thermodynamic favorability of the association reactions even at elevated (700-1000 K) temperatures. Formation of a variety of ring, cage and cluster species is viable in vapors; among them the needle-shaped oligomers and polymers are predicted to have an exceptional stability. Thus, generation of 13-15 nanowires and nanoparticles via association route emerges as a viable alternative to the traditional surface-based CVD techniques. Competitiveness of the metal - pnictogen and metal - carbon bonds results in carbon inclusion into the cluster core with formation of the 13-15-carbon cages, which are expected to be kinetically stable. This may limit the practical use of the association reactions starting from the metallorganic precursors. Formation of the nitrogen-rich adamantine-like cages is viable in the excess of ammonia at temperatures below 700K.