Journal of Physical Chemistry A, Vol.122, No.32, 6570-6577, 2018
Prototypical Transition-Metal Carbenes, (CO)(5)Cr=CH2, (CO)(4)Fe=CH2, (CO)(3)Ni=CH2, (CO)(5)Mo=CH2, (CO)(4)Ru=CH2, (CO)(3)Pd=CH2, (CO)(5)W=CH2, (CO)(4)Os=CH2, and (CO)(3)Pt=CH2: 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=CH2 bond lengths, dissociation energies, and vibrational frequencies are reported. The M=CH2 bond distances range from 1.81 (Ni) to 2.05 A (Pd). The M=CH2 dissociation energies fall in the range of 16.4 (Pd) to 92.3 kcal mol(-1) (Os). The spectroscopic observation of several of these molecules should be possible.