In the past few years, redox non-innocent ligands have played a key role in the isolation of highly efficient catalysts by stabilizing low formal oxidation states of first row transition metals. Inspired by this unprecedented work, our group has developed a phosphine-substituted diimine (DI) ligand, which can coordinate to a metal center in a tetradentate fashion while accepting one or two electrons. This project began with the synthesis of a k4-DI iron dihalide complex followed by its reduction under N2 atmosphere. The reduction process yields a dinitrogen coordinated formal Fe(0) complex, which has been characterized by single crystal X-ray diffraction, multinuclear NMR and IR spectroscopy. Electronic structure investigation by DFT revealed neutral ligand character in the dihalide complex and monoradical anion character in the dinitrogen coordinated complex. Interestingly, heating the Fe(0) dinitrogen complex yields a dimer which is believed to form through an intramolecular C-H and C-P activation process. Analysis of the reaction mixture by 31P NMR spectroscopy revealed formation of both the cis- and trans-isomer of the dimer although only the cis-isomer can be isolated via recrystallization from a concentrated benzene-pentane solution at room temperature. Additionally, it is believed that the dimeric complex features monoradical DI ligands, based on the bond distances obtained from single crystal X-ray diffraction. The electronic structure investigation of these complexes and the plausible mechanism of dimer formation will be presented.

C-H and C-P activation by a redox non-innocent ligand supported iron dinitrogen complex

251st National Meeting (2016)

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