Nitric Oxide Disproportionation Mediated by a Rh Complex with an Asymmetric Pincer Ligand: Spectroscopic Detection of a Dinitrosyl Intermediate

The disproportionation of nitric oxide was studied by FTIR with two different Rh(I)PCN complexes as mediators (PCN 1‐((diethylamino)methyl)‐3‐((di‐tertbutylphosphino)methyl)‐benzene). As had already been reported for a PCP analogue, reaction yielded a Rh(PCN)(NO)(NO2) complex along with gaseous N2O in both cases. However, when [Rh(PCN)(NO)]⋅ was used as a reactant, FTIR monitoring allowed for the detection of signals of a reaction intermediate, coherent with the expected but seldom reported dinitrosyl species Rh(PCN)(NO)(NO). DFT studies on this species revealed that pincer hemilability of the amino arm is involved in its stabilization, therefore accounting for the differences observed in reactivity between PCN and PCP. Disproportionation of nitric oxide mediated by a rhodium complex with an asymmetric pincer ligand PCN was studied. A dinitrosyl intermediate was detected by FTIR monitoring. Its structure was determined by DFT calculations, which showed that hemilability of the amino arm in the PCN ligand is involved in the reaction, thus stabilizing an otherwise elusive intermediate species.