We are exploring the synthesis of actinide (Th, U) aryl complexes by utilizing the chelating aryl ligand 2-lithio-N,N-dimethylbenzylamine (2-Li-C6H4NMe2).  Thus, addition of 4 equiv of 2-Li-C6H4NMe2 to ThCl4(DME)2 results in the formation of the homoleptic chelate complex, Th(2-C6H4NMe2)4 (1  ).  However, addition of 6 equiv of 2-Li-C6H4NMe2 to UCl4 results in the unprecedented formation of a uranium(IV) dibenzyne complex Li2[U(2-C6H3NMe2)2(2-C6H4NMe2)2] (2  ).  To our knowledge, 2   is the first example of an actinide benzyne complex and the first example of a metal dibenzyne complex. Complex 2 has been fully characterized, including analysis by X-ray crystallography and DFT calculations.  Interestingly, complex 2  exists as a mixture of isomers in solution, two of which have been structurally characterized.   The reactivity of 2  has been explored.  Reaction of 2  with 1 equiv of I2 gives the intramolecular C-C coupled product, Li[U(I)[(2-C6H3NMe2-3-C6H4NMe2)](2-C6H3NMe2)(2- C6H4NMe2)] (3  ), formed by aryl insertion into a benzyne unit, similar to reactivity seen in transition metal benzyne complexes.

Isolation of an actinide benzyne complex

243rd National Meeting (2012)

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