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The Influence of Nucleophilic and Redox Pincer Character as well as Alkali Metals on the Capture of Oxygen Substrates: The Case of Chromium(II)
Author(s) -
Labrum Nicholas S.,
Curtin Gregory M.,
Jakubikova Elena,
Caulton Kenneth G.
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202000457
Subject(s) - chemistry , semiquinone , electrophile , redox , inner sphere electron transfer , nucleophile , outer sphere electron transfer , hydroxide , pyridine , medicinal chemistry , pincer movement , chromium , oxidation state , quinone , ligand (biochemistry) , crystallography , coordination sphere , inorganic chemistry , stereochemistry , ion , metal , organic chemistry , crystal structure , catalysis , biochemistry , receptor
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.