Bond-shift isomers: the co-existence of allenic and propargylic phenylnitrile imines.

We discovered a 1,3-dipolar species co-existing in two different structures. Photolysis of matrix-isolated 5-phenyltetrazole generates two forms of phenylnitrile imine: propargylic and allenic. They are not resonance structures but correspond to different energy minima, representing bond-shift isomers. These distinct species were characterized spectroscopically and confirmed by calculations up to the CASSCF(14,12) theory level.