Ligand Reactivity in Diarylamido/Bis(Phosphine) PNP Complexes of Mn(CO)3 and Re(CO)3

The syntheses of meridionally ligated tricarbonyl complexes (PNP)Mn(CO)3 and (PNP)Re(CO)3 are described (PNP = [2-P(CHMe2)2-4-MeC6H3]2N−). Cyclic voltammograms show reversible one-electron redox couples for both parent compounds (−0.34 V vs Cp2Fe0/+ for (PNP)Mn(CO)3, −0.25 V vs Cp2Fe0/+ for (PNP)Re(CO)3), and chemical oxidation with AgOTf results in formation of the corresponding paramagnetic triflate salts [(PNP)Mn(CO)3]OTf and [(PNP)Re(CO)3]OTf. Electron paramagnetic resonance spectra and computational results indicate that this event is primarily ligand centered; allylation of the organic ligand moiety of [(PNP)Mn(CO)3]OTf with allyltributylstannane is consistent with this assignment. The oxidation (PNP)Mn(CO)3 to [(PNP)Mn(CO)3]OTf results in a shift in average CO stretching frequency of 30 cm−1; protonation of (PNP)Mn(CO)3 with TfOH to form [(PNHP)Mn(CO)3]OTf results in a similar magnitude shift.