Prototypical Transition-Metal Carbenes, (CO)Cr═CH, (CO)Fe═CH, (CO)Ni═CH, (CO)Mo═CH, (CO)Ru═CH, (CO)Pd═CH, (CO)W═CH, (CO)Os═CH, and (CO)Pt═CH: Challenge to Experiment.

Transition-metal carbenes are useful in organometallic chemistry due to their demonstrated use as catalysts in carbon-carbon bond-forming reactions. Yet the prototypical transition-metal carbenes, consisting of a single metal center doubly bonded to a methylene ligand and surrounded by carbonyls, have been elusive to experimental synthesis. This theoretical work examines the structures and properties of nine prototypical transition-metal carbenes. Optimized values for M═CH bond lengths, dissociation energies, and vibrational frequencies are reported. The M═CH bond distances range from 1.81 (Ni) to 2.05 Å (Pd). The M═CH dissociation energies fall in the range of 16.4 (Pd) to 92.3 kcal mol (Os). The spectroscopic observation of several of these molecules should be possible.