Coordination geometries of transition metals play vital roles in the self-assembly process of supramolecular coordination complexes. Herein, seven-coordinate 3d metal ions were applied as templates and catalytically active sites for subcomponent self-assembly that resulted in a new category of covalent metallacycles. Single-crystal structures showed that the sizes, configurations, and functionalization of covalent metallacycles could be tuned by the selection of rigid dihydrazide, transition metal ions, and prefunctionalized subcomponents, respectively. Moreover, metallacycles decorated with carboxylic groups could be employed as precursors to prepare aerogels through hierarchical self-assembly, which also exhibited high catalytic activity for cycloaddition of CO 2 into cyclic carbonates.
The construction of C−S bonds is of great importance in the field of synthetic and medicinal chemistry. Herein, solvent-induced umpolung reactions from dioxygenation to interligand C−S cross-coupling in bis(cyclometalated) Ir(III) thiolate complexes are reported in good to excellent yields at room temperature. Specifically, the reaction of rac-[Ir(pq) 2 (aet)] (where pq is 2-phenylquinoline and aet is 2-aminoethanethiolate) can be selectively switched to dioxygenation in acetonitrile solution in the presence of O 2 , resulting in the formation of a sulfinato complex rac-[Ir(pq) 2 (aes)] (where aes is 2-aminoethanesulfinato). Alternatively, the reaction in trifluoroethanol solution leads to interligand C−S cross-coupling, affording a rac-[Ir(pq)(pqaet)](PF 6 ) [where pqaet is 2-((2-phenylquinolin-8-yl)thio)ethan-1amine] complex, which generates a new tetradentate ligand in situ. Mechanistically, the formation of electrophilic metal thiyl radicals is proposed as a key intermediate in the interligand C−S coupling reaction. Furthermore, the sequential oxidation of a thioether complex into a sulfoxide complex is also observed at room temperature using H 2 O 2 as an oxidant. Additionally, a new approach for the synthesis of a hexadentate ligand is developed through sequential C−S and C−N interligand coupling of metal thiolate complexes in situ under visible light irradiation in the presence of O 2 .
There is growing interest in designing electrocatalysts for highly selective electroreduction of CO2 to deeply reduced products like CH4. However, CO2-to-CH4 conversion remains a great challenge in controlling the multi-electron/proton...
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