The Ru(II) amido complex (PCP)Ru(CO)(PMe3)(NHPh) (1) (PCP = 2,6-((CH2PBu2)-Bu-i)(2)C6H3) reacts with compounds that possess polar C = N, C = N, or C = O bonds (e.g., nitriles, carbodiimides, or isocyanates) to produce four-membered heterometallacycles that result from nucleophilic addition of the amido nitrogen to an unsaturated carbon of the organic substrate. Based on studies of the reaction of complex 1 with acetonitrile, the transformations are suggested to proceed by dissociation of trimethylphosphine, followed by coordination of the organic substrate and then intramolecular N-C bond formation. In the presence of ROH (R = H or Me), the fluorinated amidinate complex (PCP)Ru(CO)(N(Ph)C(C6F5)NH) (6) reacts with excess pentafluorobenzonitrile to produce (PCP)Ru(CO)(F)(N(H)C(C6F5)NHPh) (7). The reaction with MeOH also produces o-MeOC6F4CN (> 90%) and p-MeOC6F4CN (< 10%). Details of the solid-state structures of (PCP)Ru(CO)(F)(N(HPC6F5)NHPh) (7), (PCP)Ru(CO)[PhNC{NH(hx)}N(hx)] (8), (PCP)Ru(CO){N(Ph)C(NHPh)O} (9), and (PCP)Ru(CO){OC(Ph)N(Ph)} (10) are reported.