Element–Element Bond Formation upon Oxidation and Reduction. Issue 18 (13th March 2020)

• Record Type: Journal Article
• Authors: Piesch, Martin; Graßl, Christian; Scheer, Manfred
• Is Part Of: Angewandte Chemie international edition. Volume 59:Issue 18(2020)
• Page Start: 7154
• Page End: 7160
• Publication Date: 2020-03-13
• Subjects: arsenic -- cobalt -- cyclic voltammetry -- phosphorus -- redox chemistry; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201916622
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: The redox chemistry of [(Cp′′′Co)2 (μ, η 2 :η 2 ‐E2 )2 ] (E=P (1 ), As (2 ); Cp′′′=1, 2, 4‐tri( tert ‐butyl)cyclopentadienyl) was investigated. Both compounds can be oxidized and reduced twice. That way, the monocations [(Cp′′′Co)2 (μ, η 4 :η 4 ‐E4 )][X] (E=P, X=BF4 (3 a ), [FAl] (3 b ); E=As, X=BF4 (4 a ), [FAl] (4 b )), the dications [(Cp′′′Co)2 (μ, η 4 :η 4 ‐E4 )][TEF]2 (E=P (5 ), As (6 )), and the monoanions [K(18‐c‐6)(dme)2 ][(Cp′′′Co)2 (μ, η 4 :η 4 ‐E4 )] (E=P (7 ), As (8 )) were isolated. Further reduction of 7 leads to the dianionic complex [K(18‐c‐6)(dme)2 ][K(18‐c‐6)][(Cp′′′Co)2 (μ, η 3 :η 3 ‐P4 )] (9 ), in which the cyclo‐P4 ligand has rearranged to a chain‐like P4 ligand. Further reduction of 8 can be achieved with an excess of potassium under the formation of [K(dme)4 ][(Cp′′′Co)2 (μ, η 3 :η 3 ‐As3 )] (10 ) and the elimination of an As1 unit. Compound 10 represents the first example of an allylic As3 ligand incorporated into a triple‐decker complex. Abstract : Unexpected E−E bond formation : The versatile redox chemistry of the polypnictogen cobalt complexes [(Cp′′′Co)2 (E2 )2 ] (E=P, As) was investigated. Both oxidation and reduction lead to the formation of two new E−E bonds and to the cyclization of the separated E2 ligands into E4 ligands in the coordination sphere of two {Cp′′′Co} fragments.