What caught my eye was a paper that just came out in Early View in ACIE by the Diaconescu group at UCLA, in which examined the reaction of a dibenzyl uranium complex with multiple equivalents of methylimidazole. They found that instead of merely coordinating, as one would expect such a heterocycle to do with a transition metal, the metal center inserted itself into the C2 position's C-H bond on two separate methylimidazole molecules; a third equivalent coordinates via the lone pair. By using deuterated benzene as the solvent, they were able to observe that two equivalents of toluene are also formed, confirming the C-H insertion steps. Mechanistically, uranium doesn't proceed through oxidative addition or reductive elimination steps like the transition metals; rather, it goes through a sigma-bond metathesis type 4-center transition state. The C-H insertion positions are highlighted in red.
The intermediates in brackets were not able to be isolated in this case, but when 1-methylbenzimidazole was used instead of 1-methylimidazole, the reaction stopped at the first intermediate directly after the imidazole coupling, and they were able to isolate and confirm the structure of the complex. Here are the crystal structures of the reaction with 1-methylimidazole to compare with the products (with 50% and 35% ellipsoids, respectively).