Structure Analysis of a Transient Triplet Carbene Trapped in a Crystal

A light-induced transient bis(2,4,6-trichlorophenyl)carbene trapped in a yield of ca. 20% in the crystal of the precursor diazomethane was characterized by X-ray crystallography at low temperatures. The most interesting geometrical parameters are the carbenic angle θ and the bond distances between the carbenic carbon and the phenyl carbons. The obtained θ is 142(2)°, while the distances are 1.437(15) and 1.423(16) Å, respectively. These values are significantly different from the corresponding values for the precursor diazomethane (127.1(1)° and 1.477(1) and 1.480(1) Å, respectively). On the basis of IR spectroscopy and theoretical calculations, the carbene is judged to be in the triplet ground state.