Threshold photoelectron photoion coincidence spectroscopy was used to study a series of cobalt–organic complexes with phosphine and phosphine analogue ligands: PMe3Co(CO)2NO, PEt3Co(CO)2NO, AsMe3Co(CO)2NO, and SbMe3Co(CO)2NO. The two lowest energy dissociative photoionization channels were sequential carbonyl losses in all four cases. Nitrosyl loss was also observed as a minor channel from the molecular ion and as a major competitive dissociation from the first (carbonyl loss) daughter ion. Further sequential CO and NO losses lead to the LCo+ (L = PMe3, PEt3, AsMe3, SbMe3) ions, which, similarly to an earlier threshold collision-induced dissociation (TCID) mass spectrometry study on the phosphine complexes,(1) exhibited parallel ethene loss and methane loss dissociation reactions, although the bare metal ion was not observed. Unimolecular statistical rate theory (RRKM) calculations were performed to model the first two carbonyl loss channels and relate cobalt–carbonyl bond energy trends to the electron donor and acceptor properties of the phosphine analogue ligands. Co–CO bond energies of 0.90 ± 0.09, 0.84 ± 0.08, 1.13 ± 0.08, and 1.15 ± 0.09 eV were obtained in LCo(CO)2NO+ (L = PMe3, PEt3, AsMe3, SbMe3, respectively) and 0.82 ± 0.11, 0.74 ± 0.11, 0.95 ± 0.10, and 0.94 ± 0.09 in the first daughter ions, respectively.