Although carbenes have long held the interest of chemists. they have remained
confined to the category of highly reactive. transient species for many
years. Increasing interest in the use of iransition metals to trap such short-lived
intermediates led in 1964 to the first successful isolation by Fischer and Maasbiil
(1 86) of a well-characterized complexed carbene (1).
Since then the field of transition metal carbene complexes has experienced explosive
growth and continues to expand at a rapid rate. Recently attention has
been focused on the reactions of isolable complexes as mechanistic models for
metal-catalyzed organic reactions such as olefin cyclopropanation, the
Fischer-Tropsch synthesis, and olefin metathesis.