Thermodynamic properties of the group 13-15 pnictidometallanes [HMYH]_n, (M = Al, Ga, In; Y = N, P, As; n = 1-16) have been predicted at the B3LYP/LANL2DZ(d,p) level of theory. Process of the gas phase generation of [HMYH]_n clusters is favorable thermodynamically at low temperatures. Al and N-containing clusters are predicted to be exceptionally stable. Spontaneous generation of [RMYH]_n oligomers with n = 12-14 is expected during chemical vapor deposition processes at low temperature-high pressure conditions.