Photochemical Route to Actinide-Transition Metal Bonds: Synthesis, Characterization and Reactivity of a Series of Thorium and Uranium Heterobimetallic Complexes

A series of actinide–transition metal heterobimetallics has been prepared, featuring thorium, uranium, and cobalt. Complexes incorporating the binucleating ligand N­[ο-(NHCH2PiPr2)­C6H4]3 with either Th­(IV) (4) or U­(IV) (5) and a carbonyl bridged [Co­(CO)4]− unit were synthesized from the corresponding actinide chlorides (Th: 2; U: 3) and Na­[Co­(CO)4]. Irradiation of the resulting isocarbonyls with ultraviolet light resulted in the formation of new species containing actinide–metal bonds in good yields (Th: 6; U: 7); this photolysis method provides a new approach to a relatively unusual class of complexes. Characterization by single-crystal X-ray diffraction revealed that elimination of the bridging carbonyl and formation of the metal–metal bond is accompanied by coordination of a phosphine arm from the N4P3 ligand to the cobalt center. Additionally, actinide–cobalt bonds of 3.0771(5) Å and 3.0319(7) Å for the thorium and uranium complexes, respectively, were observed. The solution-state behavior of the thorium complexes was evaluated using 1H, 1H–1H COSY, 31P, and variable-temperature NMR spectroscopy. IR, UV–vis/NIR, and variable-temperature magnetic susceptibility measurements are also reported.

本研究合成了一系列锕系-过渡金属异双金属配合物（actinide–transition metal heterobimetallics），涵盖钍、铀与钴三种金属中心。以双核配体N­[ο-(NHCH2PiPr2)­C6H4]3分别与Th(IV)（化合物4）或U(IV)（化合物5）结合，并带有桥联羰基连接的[Co(CO)4]−单元的配合物，可由对应锕系氯化物（钍前驱体为2；铀前驱体为3）与四羰基合钴酸钠（Na[Co(CO)4]）反应制备得到。将所得异羰基配合物经紫外光辐照后，以较高产率得到含锕系-金属键的新型物种（钍对应产物6；铀对应产物7）；该光解策略为一类相对少见的配合物提供了全新的合成途径。单晶X射线衍射表征结果表明，在消除桥联羰基并形成金属-金属键的过程中，配体N4P3上的一条膦臂会与钴中心发生配位。此外，测得钍配合物与铀配合物的锕系-钴键长分别为3.0771(5) Å与3.0319(7) Å。本研究通过1H核磁共振谱、1H–1H COSY（氢-氢相关）核磁共振谱、31P核磁共振谱及变温核磁共振谱，对钍配合物的溶液态行为进行了表征。同时还报道了红外光谱、紫外-可见-近红外光谱与变温磁化率的测试结果。