The Influence of Nucleophilic and Redox Pincer Character as well as Alkali Metals on the Capture of Oxygen Substrates: The Case of Chromium(II). Issue 43 (9th July 2020)

• Record Type: Journal Article
• Authors: Labrum, Nicholas S.; Curtin, Gregory M.; Jakubikova, Elena; Caulton, Kenneth G.
• Is Part Of: Chemistry. Volume 26:Issue 43(2020)
• Page Start: 9547
• Page End: 9555
• Publication Date: 2020-07-09
• Subjects: aggregates -- chromium -- oxo -- pincer ligands -- reduction; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202000457
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Dimeric [CrL]2, where L is the conjugate base of bis‐pyrazolyl pyridine, is evaluated for its ability to undergo inner sphere and outer sphere redox chemistry. It reacts with Cp2 Fe + to give [Cr4 (HL)4 (μ4 ‐O)] 2+, still containing divalent Cr. Reduction (KC8 ) of [CrL]2 by two electrons gives [K2 (THF)3 Cr3 L3 (μ3 ‐O)], and by four electrons gives [K4 (THF)10 Cr2 L2 (μ‐O)], each of which has scavenged (hydr)oxide from glass surface because of the electrophilicity of the underligated Cr. [K4 (THF)10 Cr2 L2 (μ‐O)], is shown by comprehensive DFT calculations and analysis of intra‐ligand bond lengths to contain a pyridyl radical L 3− and Cr II, illustrating that this pincer is proton‐responsive, redox active, and a versatile donor to associated K + ions here. The K + electrophiles interact with electron‐rich oxo, but do not significantly (>5 kcal mol −1 ) alter spin state energies. Inner sphere oxidation of [CrL]2 with a quinone gives [Cr2 L2 (semiquinone)2 ], while pre‐reduced [CrL]2 2− reacts with quinone to give [K3 (THF)3 Cr2 L2 (catecholate)2 (μ‐OH)], a product of capture of two undercoordinated LCr(catecholate) 1− by hydroxide. Abstract : Grabbing hold : Dimeric [CrL]2, where L is bis‐(pyrazolate)pyridine, is evaluated for its ability to undergo inner sphere and outer sphere redox chemistry. The remarkable [K4 (THF)10 Cr2 L2 (μ‐O)] is shown by comprehensive DFT calculations and analysis of intra‐ligand bond lengths to contain a pyridyl radical L 3− and Cr II, illustrating that this pincer is proton‐responsive, redox active, and a versatile donor to associated K + ions.