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Sir:The chemical and physical properties of carbenes continue to provoke widespread interest. Physical techniques, such as lowtemperature absorptionZ and EPR3 spectroscopy, and CIDNP4 studies have shown the electronic ground state of most carbenes to be the triplet. Product studies, however, have shown that chemical reactions can originate from either the singlet or the triplet state of the ~a r b e n e .~ This reactive duality complicates the mechanistic interpretation of the chemistry of carbenes since, most commonly, the product mixture obtained is the result of an unknown combination of reaction from the singlet and the triplet. In this report, we describe the results of our pulsed-laser spectrophotometric investigation of the chemistry of both singlet ('FI) and triplet (3Fl) fluorenylidene. These carbenes are conveniently

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