Synthesis and reactivity of the imido analogues of the uranyl ion

Addition of 1.5 equiv of I-2 to a THF solution of UI3( THF)(4), containing either 6 equiv of (BuNH2)-Bu-t or 2 equiv of RNH2(R = Ph, 3,5-(CF3)(2)C6H3, 2,6-(Pr-i) 2C6H3) and 4 equiv of NEt3, generates orange solutions containing U((NBu)-Bu-t) I-2(2)(THF)(2) (1) or U(NAr)(2)I-2(THF)(3)(Ar) Ph, 2; 3,5-(CF3)(2)C6H3, 3; 2,6-(iPr)(2)C6H3, 4), respectively, all of which can be isolated in good yields. Alternatively, 1 can be prepared by reaction of uranium metal with 3 equiv of I-2 and 6 equiv of (t)BuNH2, also in good yield. Complexes 1-4 have been characterized by X-ray crystallography, and each of these complexes exhibits linear N-U-N linkages and short U-N bonds. Using density functional theory simulations of complexes 1 and 2, two triple bonds between the metal center and the nitrogen ligands were identified. Complexes 1 and 2 readily react with neutral Lewis bases such as pyridine or Ph3PO to form U(NR)(2)I-2(L)(2)(R)Bu-t, L) py, 5; Ph3PO, 7; R) Ph, L) py, 6; Ph3PO, 8), and with PMe3 to form U(NR)(2)I-2( THF)(PMe3)(2)( R) Bu-t, 9; Ph, 10). The solid-state molecular structures of 5, 7, and 9 have been determined by X-ray crystallography, and these complexes, like their parent compounds, exhibit linear N-U-N angles and short U-N bonds. Complexes 1 and 2 also react with AgOTf in CH2Cl2, forming U(NR)(2)(OTf)(2)(THF)(3)(R) Bu-t, 11; Ph, 12) after recrystallization from THF. Crystals of 12 grown from CH2Cl2 were found to contain a dimer, [U( NPh)(2)(OTf)(2)( THF)(2)](2) , a complex possessing bridging triflate groups.