The Influence of Nucleophilic and Redox Pincer Character as well as Alkali Metals on the Capture of Oxygen Substrates: The Case of Chromium(II)

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 Cp 2 Fe + to give [Cr 4 (HL) 4 (μ 4 ‐O)] 2+ , still containing divalent Cr. Reduction (KC 8 ) of [CrL] 2 by two electrons gives [K 2 (THF) 3 Cr 3 L 3 (μ 3 ‐O)], and by four electrons gives [K 4 (THF) 10 Cr 2 L 2 (μ‐O)], each of which has scavenged (hydr)oxide from glass surface because of the electrophilicity of the underligated Cr. [K 4 (THF) 10 Cr 2 L 2 (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 [Cr 2 L 2 (semiquinone) 2 ], while pre‐reduced [CrL] 2 2− reacts with quinone to give [K 3 (THF) 3 Cr 2 L 2 (catecholate) 2 (μ‐OH)], a product of capture of two undercoordinated LCr(catecholate) 1− by hydroxide.