Hydride Reactivity of NiII?X?NiII Entities: Mixed‐Valent Hydrido Complexes and Reversible Metal Reduction |
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Authors: | Henrike Gehring Ramona Metzinger Christian Herwig Julia Intemann Prof?Dr Sjoerd Harder Prof?Dr Christian Limberg |
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Institution: | 1. Institut für Anorganische Chemie, Humboldt‐Universit?t zu Berlin, Brook‐Taylor‐Strasse 2, 12489 Berlin (Germany), Fax: (+49)?030‐2093‐6966;2. Stratingh Institute of Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands) |
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Abstract: | After the lithiation of PYR‐H2 (PYR2?={NC(Me)C(H)C(Me)NC6H3(iPr)2}2(C5H3N)]2?), which is the precursor of an expanded β‐diketiminato ligand system with two binding pockets, its reaction with NiBr2(dme)] led to a dinuclear nickel(II)–bromide complex, (PYR)Ni(μ‐Br)NiBr] ( 1 ). The bridging bromide ligand could be selectively exchanged for a thiolate ligand to yield (PYR)Ni(μ‐SEt)NiBr] ( 3 ). In an attempt to introduce hydride ligands, both compounds were treated with KHBEt3. This treatment afforded (PYR)Ni(μ‐H)Ni] ( 2 ), which is a mixed valent NiI? μ‐H? NiII complex, and (PYR‐H)Ni(μ‐SEt)Ni] ( 4 ), in which two tricoordinated NiI moieties are strongly antiferromagnetically coupled. Compound 4 is the product of an initial salt metathesis, followed by an intramolecular redox process that separates the original hydride ligand into two electrons, which reduce the metal centres, and a proton, which is trapped by one of the binding pockets, thereby converting it into an olefin ligand on one of the NiI centres. The addition of a mild acid to complex 4 leads to the elimination of H2 and the formation of a NiIINiII compound, (PYR)Ni(μ‐SEt)NiOTf] ( 5 ), so that the original NiII(μ‐SEt)NiIIX core of compound 3 is restored. All of these compounds were fully characterized, including by X‐ray diffraction, and their molecular structures, as well as their formation processes, are discussed. |
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Keywords: | bridging ligands hydrides mixed‐valent compounds nickel reduction |
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