Isolation of U(ii) compounds using strong donor ligands, C 5 Me 4 H and N(SiMe 3 ) 2 , including a three-coordinate U(ii) complex

New examples of uranium in the formal +2 oxidation state have been isolated by reduction of Cptet3U (Cptet = C5Me4H) and U(NR2)3 (R = SiMe3) in the presence of 2.2.2-cryptand (crypt) to produce [K(crypt)][Cptet3U] and [K(crypt)][U(NR2)3], respectively. Both complexes have properties consistent with 5f36d1 electron configurations and demonstrate that the U(ii) ion can be isolated with electron donating ligands.