First Actinide Complexes of the Nitrogen-Containing Ligands Dinitramide (N(NO2)2−), 4,5-Dicyano-1,2,3-triazolate (C4N5−), and Dicyanamide (N(CN)2−)

Abstract

The syntheses and characterization of uranyl complexes of nitrogen-containing ligands are reported. For the first time, an actinide complex containing dinitramide ligands coordinated to the actinide center in UO(2)(N(NO(2))(2))(2)(OP(NMe(2))(3))(2) (1) has been isolated and structurally characterized. Using an excess of OP(NMe(2))(3), the dinitramide ligands were replaced by OP(NMe(2))(3) ligands resulting in the formation of the salt [UO(2)(OP(NMe(2))(3))(4)][N(NO(2))(2)](2) (2). Both complexes 1 and 2 were characterized using IR, Raman, as well as (1)H, (13)C, (14)N and (31)P{(1)H} NMR spectroscopy, in addition to C/H/N analysis. The structures of 1 and 2 were determined by single crystal X-ray diffraction. 1: monoclinic, P2(1)/n, a = 12.5389(3), b = 7.9496(2), c = 15.8172(4) A, beta = 110.842(3) degrees , V = 1473.48(6) A(3), Z = 2. 2: orthorhombic, Pbca, a = 14.5640(6), b = 15.3697(6), c = 45.7789(18) A, V = 10247.3(7) A(3), Z = 8. The related complex [UO(2)(N(CN)(2))(2)(OP(NMe(2))(3))(2)] (3) containing the dicyanamide ligand (N(CN)(2)(-)) coordinated to the U(VI) center was synthesized and characterized using IR, Raman, (1)H, (13)C and (31)P{(1)H} NMR spectroscopy. The structure of 3 was determined using single crystal X-ray diffraction and revealed a dinuclear complex containing both terminal and bridging N(CN)(2)(-) ligands. 3: monoclinic, P2(1)/c, a = 15.5873(9), b = 14.2132(6), c = 13.2006(5) A, beta = 100.029(3) degrees, V = 2879.8(2) A(3), Z = 2. Finally, in this investigation of the coordination of relatively nitrogen-rich ligands to uranium centers, the synthesis, characterization, and isolation of the first U(VI) complex showing coordination of the triazolate ligand via a ring nitrogen atom is reported in UO(2)((NC)(2)C(2)N(3))(2)(OPPh(3))(3) (4). Complex 4 was characterized using IR, Raman, (1)H, (13)C and (31)P{(1)H} NMR spectroscopy. The solid state structure of 4 was determined using single crystal X-ray diffraction. 4: monoclinic, P2(1)/n, a = 18.9970(2), b = 31.9500(3), c = 20.1133(2) A, beta = 111.4449(4) degrees, V = 11362.69(19) A(3), Z = 8. To the best of our knowledge, compounds 1 and 2 are the first structurally characterized complexes where a dinitramide ligand is coordinated to an f-block center. Complex 3 is the first structurally characterized actinide dicyanamide complex and a rare example of a dinuclear uranyl complex showing a 12 membered U-N-C ring formed by bridging dicyanamide ligands between two uranyl centers. Finally, complex 4 is the first isolated and structurally characterized uranium complex containing a triazolate ligand coordinated to the U(VI) center. Complexes 3 and 4 are examples of uranyl complexes containing ligands coordinated via nitrogen atoms to the U(VI) center. Whereas the dinitramide ligand can coordinate via N or O atoms, in complex 1, the [N(NO(2))(2)](-) ligand acts as a bidentate chelate ligand, and only coordination via the oxygen atoms to the U(VI) center was observed in the crystalline state.