The current use of the term carbenoid is
discussed, particularly in the context of carbene transfer
reactions from diazo compounds, where intermediates of
type LnM=CR1R2, or one of its resonance forms, are tagged
which such name. We herein discuss this issue, on the
basis of the data evidencing the metal-carbene nature of
those intermediates, as well as the existence of carbenoids
of type (N2)(M)C R1R2 en route to the formation to LnM=C
R1R2’ from diazo reagents. We propose the exclusive use of
the carbenoid term to species of type (X)(M)C R1R2 with a
tetrasubstituted carbon center that upon loss of X afford an
effective carbene transfer process.