The thermochemistry of association reactions of organogallium precursors for the GaN chemical vapor deposition (CVD) is studied. Geometries, relative energies, and vibrational frequencies of ring and cluster compounds [RGaNR '](n), [R2GaNR ' (2)](m), (n = 2-4, 6; m = 2-3; R, R ' = H, CH3) are obtained at the hybrid Hartree-Fock/density functional level of theory (B3LYP/pVDZ). Formation of the [RGaNR '](4) tetramer and [RGaNR '](6) hexamer species is thermodynamically favorable in the gas phase at temperatures up to 720 K (R = H, R ' = CH3) and 920-940 K (R = H, CH3, R ' = H). The thermodynamic analysis of the major gas-phase reactions indicates that association processes might play a key role in the GaN CVD under low-temperature-high-pressure conditions.