Single metal four-electron reduction by U(ii) and masked "U(ii)" compounds. Issue 17 (1st April 2021)

• Record Type: Journal Article
• Authors: Modder, Dieuwertje K.; Palumbo, Chad T.; Douair, Iskander; Scopelliti, Rosario; Maron, Laurent; Mazzanti, Marinella
• Is Part Of: Chemical science. Volume 12:Issue 17(2021)
• Page Start: 6153
• Page End: 6158
• Publication Date: 2021-04-01
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d1sc00668a
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : Both a masked and the actual complex [U(ii ){N(SiMe3 )2 }3 ] + effect the reduction of azobenzene to yield a U(vi ) bis-imido species providing the first example of a "clear-cut" metal centred four-electron reduction in f-element chemistry. Abstract : The redox chemistry of uranium is dominated by single electron transfer reactions while single metal four-electron transfers remain unknown in f-element chemistry. Here we show that the oxo bridged diuranium(iii ) complex [K(2.2.2-cryptand)]2 [{((Me3 Si)2 N)3 U}2 (μ-O)], 1, effects the two-electron reduction of diphenylacetylene and the four-electron reduction of azobenzene through a masked U(ii ) intermediate affording a stable metallacyclopropene complex of uranium(iv ), [K(2.2.2-cryptand)][U( η 2 -C2 Ph2 ){N(SiMe3 )2 }3 ], 3, and a bis(imido)uranium(vi ) complex [K(2.2.2-cryptand)][U(NPh)2 {N(SiMe3 )2 }3 ], 4, respectively. The same reactivity is observed for the previously reported U(ii ) complex [K(2.2.2-cryptand)][U{N(SiMe3 )2 }3 ], 2 . Computational studies indicate that the four-electron reduction of azobenzene occurs at a single U(ii ) centre via two consecutive two-electron transfers and involves the formation of a U(iv ) hydrazide intermediate. The isolation of the cis -hydrazide intermediate [K(2.2.2-cryptand)][U(N2 Ph2 ){N(SiMe3 )2 }3 ], 5, corroborated the mechanism proposed for the formation of the U(vi ) bis(imido) complex. The reduction of azobenzene by U(ii ) provided the first example of a "clear-cut" single metal four-electron transfer in f-element chemistry.