Analysis of these complexes using the natural bond orbital method evinces NHC ligands possessing trans influence.ii

Several conclusions of interest have emerged from a computational study of copper-catalyzed phenylisocyanate synthesis from nitrobenzene and carbon monoxide. Nitrobenzene complexes coordinate in a κ 1 -O fashion, while nitrosobenzene complexes generally coordinate in a κ 1 -N fashion. With regard to thermodynamics, differences were observed for neutral (amidate, amidinate, -diketiminate) versus cationic (diimine, NHC) complexes, although discernible trends were less evident for calculated kinetic barriers. The deoxygenation of the nitroso oxygen of the nitrosobenzene complex to form a coppernitrene intermediate is postulated to be the rate-determining step. For the mechanism assumed in eqs 2 through 5, each step is exothermic. These individual steps are also calculated to possess reasonable kinetic barriers. Hence, copper-based complexes deserve consideration as potential catalysts for the phosgenefree synthesis of arylisocyanates from nitroaromatics.