Hydride Reactivity of NiIIXNiII Entities: Mixed‐Valent Hydrido Complexes and Reversible Metal Reduction. Issue 5 (4th January 2013)

• Record Type: Journal Article
• Authors: Gehring, Henrike; Metzinger, Ramona; Herwig, Christian; Intemann, Julia; Harder, Sjoerd; Limberg, Christian
• Is Part Of: Chemistry. Volume 19:Issue 5(2013)
• Page Start: 1629
• Page End: 1636
• Publication Date: 2013-01-04
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201203201
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>After the lithiation of PYR‐H<sub>2</sub> (PYR<sup>2−</sup>=[{NC(Me)C(H)C(Me)NC<sub>6</sub>H<sub>3</sub>(<italic>i</italic>Pr)<sub>2</sub>}<sub>2</sub>(C<sub>5</sub>H<sub>3</sub>N)]<sup>2−</sup>), which is the precursor of an expanded β‐diketiminato ligand system with two binding pockets, its reaction with [NiBr<sub>2</sub>(dme)] led to a dinuclear nickel(II)–bromide complex, [(PYR)Ni(μ‐Br)NiBr] (<bold>1</bold>). The bridging bromide ligand could be selectively exchanged for a thiolate ligand to yield [(PYR)Ni(μ‐SEt)NiBr] (<bold>3</bold>). In an attempt to introduce hydride ligands, both compounds were treated with KHBEt<sub>3</sub>. This treatment afforded [(PYR)Ni(μ‐H)Ni] (<bold>2</bold>), which is a mixed valent Ni<sup>I</sup>μ‐HNi<sup>II</sup> complex, and [(PYR‐H)Ni(μ‐SEt)Ni] (<bold>4</bold>), in which two tricoordinated Ni<sup>I</sup> moieties are strongly antiferromagnetically coupled. Compound <bold>4</bold> 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 Ni<sup>I</sup> centres. The addition of a mild acid to complex <bold>4</bold> leads to the elimination of H<sub>2</sub> and the formation of a Ni<sup>II</sup>Ni<sup>II</sup> compound, [(PYR)Ni(μ‐SEt)NiOTf] (<bold>5</bold>), so that the original Ni<sup>II</sup>(μ‐SEt)Ni<sup>II</sup>X core of compound <bold>3</bold> 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.</p> </abstract>