Treatment of the metallacycle [UN*(2)(N,C)] [N* = N(SiMe3)(2); N,C = CH2SiMe2N(SiMe3)] with [HNEt3][BPh4], [HNEt3]Cl, and [pyH][OTf] (OTf = OSO2CF3) gave the cationic compound [UN*(3)][BPh4] (1) and the neutral complexes [UN*X-3] [X = Cl (3), OTf (4)], respectively. The dinuclear complex [{UN*(mu-N,C)(mu-OTf)}(2)] (5) and its tetrahydrofuran (THF) adduct [{UN*(N,C)(THF)(mu-OTf)}(2)] (6) were obtained by thermal decomposition of 4. The successive addition of NEt4CN or KCN to 1 led to the formation of the cyanido-bridged dinuclear compound [(UN*(3))(2)(mu-CN)][BPh4] (7) and the mononuclear mono- and bis(cyanide) complexes [UN*(3)(CN)] (2) and [M][UN*(3)(CN)(2)] [M = NEt4 (8), K(THF)(4) (9)], while crystals of [K(18-crown-6)][UN*(3)(CN)(2)] (10) were obtained by the oxidation of [K(18-crown-6)][UN*(3)(CN)] with pyridine N-oxide. The THF adduct of 1, [UN*(3)(THF)][BPh4], and complexes 2-7, 9 and 10 were characterized by their X-ray crystal structure. In contrast to their U(III) analogues [NMe4][UN*(3)(CN)] and [K(18-crown-6)](2)[UN*(3)(CN)(2)] in which the CN anions are coordinated to the metal center via the C atom, complexes 2 and 9 exhibit the isocyanide U-NC coordination mode of the cyanide ligand. This U-III/U-IV differentiation has been analyzed using density functional theory calculations. The observed preferential coordinations are well explained considering the electronic structures of the different species and metal-ligand bonding energies. A comparison of the different quantum descriptors, i.e., bond orders, NPA/QTAIM data, and energy decomposition analysis, has allowed highlighting of the subtle balance between covalent, ionic, and steric factors that govern the U-CN/NC bonding.