A Nucleophilic Chromium(V) Dioxo Radical Anion.
Treatment of Cr(NRAr)(3) (R = C(CD(3))(2)CH(3) or tert-butyl, Ar = 2,5-C(6)H(3)FMe) with oxygen gives the purple chromium(VI) complex O(2)Cr(NRAr)(2) in 83% purified yield. Upon one-electron reduction with cobaltocene, the d(1) dioxo cobaltocenium salt [CoCp(2)][O(2)Cr(NRAr)(2)] was isolated in 89% yield. The dioxo anion displays solid-state magnetic behavior consistent with a Curie-Weiss paramagnet with one unpaired electron. The chromium(V) dioxo [CoCp(2)][O(2)Cr(NRAr)(2)] acts as a nucleophile toward ClSiPh(3), ClC(O)Ph, and MeOTf to afford the monooxo complexes OCr(OSiPh(3))(NRAr)(2) (86% yield), OCr[OC(O)Ph](NRAr)(2) (34% yield), and OCr(OMe)(NRAr)(2) (76% yield), respectively. Two of these rare examples of monooxo chromium(V) derivatives, OCr(OSiPh(3))(NRAr)(2) and OCr[OC(O)Ph](NRAr)(2), were structurally characterized and display Cr-O(oxo) distances of 1.611(6) and 1.588(3) Å, respectively. The benzoate complex features an eta(1)-carboxylate ligand. All of the monooxo complexes show three peaks in their (2)H NMR spectra consistent with isomers arising from restricted rotation about the Cr-N bonds. Two of the complexes, O(2)Cr(NRAr)(2) and OCr(OSiPh(3))(NRAr)(2), were examined by cyclic voltammetry.
Odom
Aaron L.
AL
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139.
Mindiola
Daniel J.
DJ
Cummins
Christopher C.
CC