In the solid-state structure, the CCN and CCO linkages are both linear with angles of approx. 178°. The C-O and C-N bond lengths are in the range of double bonds (cf. 1.17 Å in Ar2CC=O) or slightly shorter (approx. 1.27 for C=N) , whereas the two C-C bonds are still shorter than single bonds. The IR spectrum of solid 2 (as well as in DCM and THF solution, Fig. and Fig. ) features three signals in the region of the fundamental asymmetric and symmetric stretching vibration of the NCCCO linkage (2121-2250 cm 1 ) as suggested by computational studies on a bent structure of 2 (see the SI). The third vibration can presumably be ascribed to a combination of lower-energy vibrations, as has been reported for other ketene-like species (Figure ). 39