Bent CNN bond of diazo compounds, RR′(CN+N−)

► A compound bearing bent diazo group (R1(CNN)R2) was found. ► Diazo compounds with bent bonds tend to increase their R1CN angles. ► Bending of the diazo CNN bond is principally ascribable to steric congestion. ► The α-carbonyl group exerts attractive interaction to bend the CNN bond. ► The potential surface for bending the CNN bond is significantly shallow.