Iodide, Azide, and Cyanide Complexes of (N,C), (N,N), and (N,O) Metallacycles of Tetra- and Pentavalent Uranium

In contrast to the neutral macrocycle [UN*2(N,C)] (1) [N* = N­(SiMe3)3; N,C = CH2SiMe2N­(SiMe3)] which was quite inert toward I2, the anionic bismetallacycle [NaUN*(N,C)2] (2) was readily transformed into the enlarged monometallacycle [UN*(N,N)­I] (4) [N,N = (Me3Si)NSiMe2CH2CH2SiMe2N(SiMe3)] resulting from CC coupling of the two CH2 groups, and [NaUN*(N,O)2] (3) [N,O = OC­(CH2)­SiMe2N­(SiMe3)], which is devoid of any UC bond, was oxidized into the UV bismetallacycle [Na­{UN*(N,O)2}2(μ-I)] (5). Sodium amalgam reduction of 4 gave the UIII compound [UN*(N,N)] (6). Addition of MN3 or MCN to the (N,C), (N,N), and (N,O) metallacycles 1, 4, and 5 led to the formation of the anionic azide or cyanide derivatives M­[UN*2(N,C)­(N3)] [M = Na, 7a or Na­(15-crown-5), 7b], M­[UN*2(N,C)­(CN)] [M = NEt4, 8a or Na­(15-crown-5), 8b or K­(18-crown-6), 8c], M­[UN*(N,N)­(N3)2] [M = Na, 9a or Na­(THF)4, 9b], [NEt4]­[UN*(N,N)­(CN)2] (10), M­[UN*(N,O)2(N3)] [M = Na, 11a or Na­(15-crown-5), 11b], M­[UN*(N,O)2(CN)] [M = NEt4, 12a or Na­(15-crown-5), 12b]. In the presence of excess iodine in THF, the cyanide 12a was converted back into the iodide 5, while the azide 11a was transformed into the neutral UV complex [U­(N{SiMe3}­SiMe2C­{CHI}O)2I­(THF)] (13). The X-ray crystal structures of 4, 7b, 8a–c, 9b, 10, 12b, and 13 were determined.