Radical (NO) and nonradical (N₂O) reagents convert a ruthenium(IV) nitride to the same nitrosyl complex

The ruthenium(IV) nitride complex (PNP)RuN (PNP = (Bu₂PCH ₂-SiMe₂)₂N^-) reacts rapidly with 2NO to form (PNP)Ru(NO) and N₂O, via no detectable intermediate. The linear nitrosyl complex has a planar structure. In a slower reaction, (PNP)RuN reacts with N₂O by O-atom transfer (established by ¹⁵N labeling) to give the same nitrosyl complex and N₂. Density functional theory (B3LYP) calculations show both reactions to be very thermodynamically favorable. Analysis of possible intermediates in each reaction shows that radical (PNP)RuN(NO) has much spin density on nitride N (hence, N^2-), while one 2 + 3 metallacycle, (PNP)RuN₃O, has the wrong connectivity to form a product. Instead, an intermediate with a doubly bent N₂O (hence, a two-electron reduced N-nitrosoimide form) brings the O atom in proximity to the nitride N on the path to a product.