Bis(1,3,4,5-tetramethylimidazol-2-ylidene)
bis(1,2,3,4,5-pentamethylcyclopentadienyl)samarium
Arduengo, A. J., III; Tamm, M.; McLain, S. J.; Calabrese, J. C.; Davidson, F.; Marshall, W. J. J. Am. Chem. Soc., 1994, 116, 7927. 
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