Formation of an α‑Diimine from Isocyanide Coupling Using Thorium(IV) and Uranium(IV) Phosphido–Methyl Complexes

To probe the reactivity of two potential sites at tetravalent thorium and uranium metal centers, we examined the monophosphido methyl complexes, (C5Me5)2An­(CH3)­[P­(SiMe3)­(Mes)], An = Th, U; Mes = 2,4,6-Me3C6H2. Reaction of these mixed ligand complexes with one, two, and three (or excess) equivalents of tBuNC was explored. When (C5Me5)2An­(CH3)­[P­(SiMe3)­(Mes)] is treated with one equivalent of tBuNC, the iminoacyl products, (C5Me5)2An­[η2-tBuNCCH3]­[P­(SiMe3)­(Mes)], are formed. Using three equivalents (or excess) of tBuNC results in the formation of an α-diimine moiety, (C5Me5)2An­[κ2-(N,N)–N(tBu)­CCN­(tBu)­CN(tBu)­CH2]. When two equivalents of tBuNC are added, only the mono-insertion or α-diimine was observed in a 3:1 ratio. Density functional theory calculations were carried out to determine the lowest energy pathway in the formation of the α-diimine product via the iminoacyl complex.

为探究四价钍（thorium）与铀（uranium）金属中心两处潜在位点的反应活性，我们对单膦基甲基配合物(C₅Me₅)₂An(CH₃)[P(SiMe₃)(Mes)]展开了研究，其中An = Th、U；Mes = 2,4,6-三甲基苯基（2,4,6-Me₃C₆H₂）。我们考察了该混合配体配合物与1当量、2当量、3当量（或过量）叔丁基异氰（tBuNC）的反应。当(C₅Me₅)₂An(CH₃)[P(SiMe₃)(Mes)]与1当量tBuNC反应时，会生成亚胺酰基产物(C₅Me₅)₂An[η²-tBuN=CCH₃][P(SiMe₃)(Mes)]。当使用3当量（或过量）tBuNC时，会得到含有α-二亚胺结构单元的产物(C₅Me₅)₂An[κ²-(N,N)–N(tBu)C=CN(tBu)C=N(tBu)CH₂]。当加入2当量tBuNC时，仅以3:1的比例观测到单插入产物与α-二亚胺产物。我们通过密度泛函理论（Density Functional Theory）计算，确定了经由亚胺酰基配合物生成α-二亚胺产物的最低能量反应路径。