Difluorovinylidene, F 2 CC:

An alkyne–vinylidene isomerization is also possible with the difluoro compounds 1 and 2! Irradiation of 2 (λ = 193 nm) in an Ar matrix yields 1 exclusively. The IR spectrum agrees with results of novel abinitio calculations, which also suggest that 1 —in sharp contrast to the vinylidenes RHCC—is protected against isomerization into 2 by a kinetic barrier. Irradiation with light with λ > 230nm converts 1 back into 2 . Already at 35–42 K 1 adds CO and N 2 to yields F 2 CCCO and F 2 CCNN, respectively.