MOCVD growth of tungsten nitride (WNx) and tungsten carbonitride (WNxCy) thin films has been reported from the complexes Cl-4(CH3CN)W(NR) (1: R = Ph; 2: R = Pr-i; 3: R = C3H5). To evaluate the role of the imido substituent in film growth, gas-phase homogeneous decomposition of precursor molecules was investigated using density functional theory (DFT) calculations. Computational results and NMR kinetics of acetonitrile exchange by 2 in solution verified that dissociation of the acetonitrile ligand should be facile for 1-3 in the temperature range used for film growth (> 450 degrees C). A computational search for transition states for cleavage of W-Cl bonds in the presence of H-2 carrier gas was consistent with a similar to-bond metathesis pathway. Natural bonding orbital (NBO) analysis and bond energy calculations indicated that 1 has a stronger N-C(imido) bond and a slightly weaker W-bond than 2 and 3, suggesting a greater role for W-N bond cleavage in depositions from 1. These results are consistent with mass spectrometric fragmentation patterns from 1-3 and low nitrogen content in films deposited from 1 as compared to those from 2 and 3.