Reaction of di- and tri-valent chromium amides with O2†

Abstract

Homoleptic divalent [{Cr(NRR′)}₂(µ-NRR′)₂]·3thf (R = R′ = cyclohexyl 1a; R = 3,5-Me₂C₆H₃, R′ = adamantyl 1b) and trivalent chromium amides [Cr(NRR′)₃] (R = R′ = C₆H₁₁ 2a; R = 3,5-Me₂C₆H₃, R′ = adamantyl 2b; RR′ = 2,2,6,6-Me₄C₅H₆N 2c) were synthesized by reaction of [CrCl₂(thf)₂] or [CrCl₃(thf)₃] with the appropriate amount of the corresponding lithium amide. All of these complexes, with the exception of 2c, reacted with dioxygen to give the hexavalent chromium dioxo bis(amide) derivative, [Cr(NRR′)₂O₂] 4a and 4b. A possible intermediate [{Cr(NRR′)₂}₂(µ-O)₂]·C₆H₅Me was isolated by comproportionating 1b with 4b. A diamagnetic chromium(V) dimeric species, [{Cr(NRR′)₂O}₂(µ-O)] 5b was isolated upon treatment of 4b with P(C₆H₁₁)₃. The crystal structures of complexes 1b, 2b, 2c, 3b, 4a, 4b and 5b have been determined.