Synthetic Utility of Tetrabutylammonium Salts in Uranium Metallocene Chemistry

Tetrabutylammonium chloride and nitrate salts react with (C5Me5)2UCl2 to expand the coordination sphere of the metallocene to form the formal 9- and 10-coordinate complexes, [NBu4]­[(C5Me5)2UCl2(NO3)], 1, and [NBu4]­[(C5Me5)2UCl2(NO3)], 2, respectively. Complex 2 displays modified reactivity compared to that of (C5Me5)2UCl2 in substitution reactions with Khpp [hpp =1,3,4,6,7,8-hexahydro-2H-pyrimido­(1,2-a)­pyrimidine] and K­(NC4Me4) in the synthesis of (C5Me5)2U­(hpp)­Cl, (C5Me5)­U­(hpp)3, and (C5Me5)2U­(NC4Me4)­Cl. The U3+ complex, [NBu4]­[(C5Me5)2UCl2], can be formed by reduction of 2 with K­(Hg), as well as with KC5Me5, K2C8H8, and Li3N.