Metal-catalyzed CÀNb ond formation reactions via acylnitrene transfer have recently attracted muchattention, but direct detection of the proposed acylnitrenoid/acylimido M-(NCOR) (R = aryl or alkyl) species in these reactions poses af ormidable challenge.H erein, we report on Ru(NCOR) intermediates in CÀNb ond formation catalyzed by [Ru IV -(Por)Cl 2 ]/N 3 COR, ac atalytic method applicable to aziridine/ oxazoline formation from alkenes,a mination of substituted indoles, a-amino ketone formation from silyl enol ethers, amination of C(sp 3 ) À Hbonds,and functionalization of natural products and carbohydrate derivatives (up to 99 %y ield). Experimental studies,i ncluding HR-ESI-MS and EPR measurements,coupled with DFT calculations,lend evidence for the formulation of the Ru(NCOR) acylnitrenoids as aR u V -imido species.

DFT calculations are performed on [Ru(II)(bpy)2(tmen)](2+) (M1, tmen = 2,3-dimethyl-2,3-butanediamine) and [Ru(II)(bpy)2(heda)](2+) (M2, head = 2,5-dimethyl-2,5-hexanediamine), and on the oxidation reactions of M1 to give the C-C bond cleavage product [Ru(II)(bpy)2(NH=CMe2)2](2+) (M3) and the N-O bond formation product [Ru(II)(bpy)2(ONCMe2CMe2NO)](2+) (M4). The calculated geometrical parameters and oxidation potentials are in good agreement with the experimental data. As revealed by the DFT calculations, [Ru(II)(bpy)2(tmen)](2+) (M1) can undergo oxidative deprotonation to generate Ru-bis(imide) [Ru(bpy)2(tmen-4 H)](+) (A) or Ru-imide/amide [Ru(bpy)2(tmen-3 H)](2+) (A') intermediates. Both A and A' are prone to C-C bond cleavage, with low reaction barriers (ΔG(≠)) of 6.8 and 2.9 kcal mol(-1) for their doublet spin states (2)A and (2)A', respectively. The calculated reaction barrier for the nucleophilic attack of water molecules on (2)A' is relatively high (14.2 kcal mol(-1)). These calculation results are in agreement with the formation of the Ru(II)-bis(imine) complex M3 from the electrochemical oxidation of M1 in aqueous solution. The oxidation of M1 with Ce(IV) in aqueous solution to afford the Ru(II)-dinitrosoalkane complex M4 is proposed to proceed by attack of the cerium oxidant on the ruthenium imide intermediate. The findings of ESI-MS experiments are consistent with the generation of a ruthenium imide intermediate in the course of the oxidation.

Metal-catalyzed … …a cylnitrene transfer reactions are widely proposed to proceed via M(NCOR) intermediates.I nt heir Research Article on page 18619, Chi-Ming Che and co-workers report [Ru(Por)Cl 2 ]-catalyzed highly selective acylnitrene transfers to alkenes,i ndoles, silyl enol ethers,a nd C(sp 3 )ÀHb onds to afford aziridines/oxazolines,3 -aminoindoles, a-aminoketones,a nd N-acyl amines,r espectively,a nd also experimental and computational evidence that porphyrin-supported Ru(NCOR) intermediates,w hich belong to Ru V -imido species,a re involved in these reactions.