Rhodium‐Mediated Formation of Peroxides from Dioxygen: Isolation of Hydroperoxo, Silylperoxo, and Methylperoxo Intermediates

Abstract

Out of thin air, a rhodium complex converts molecular oxygen into hydrogen peroxide, bis(trimethylsilyl) peroxide, and methyl hydroperoxide. Intermediate η1‐hydroperoxo and η1‐silylperoxo, and η1‐methylperoxo complexes have been isolated. Another η1‐methylperoxo (see picture) and an η1‐hydroperoxo complex have been characterized by X‐ray crystallography.

Rhodium and Iridium Fluorido and Bifluorido Complexes Derived from Peroxido Precursors

“…It has been shown that the peroxido complexes trans ‐[M(4‐C 5 F 4 N)(O 2 )(CN t Bu)(PR 3 ) 2 ] (M = Rh, R = Et; M = Ir, R = i Pr) can react with the Brønsted acids HX (e.g., X = Cl, CF 3 COO) to yield hydrogen peroxide and the corresponding complexes trans ‐[M(4‐C 5 F 4 N)(X) 2 (CN t Bu)(PR 3 ) 2 ] . In a comparable conversion, treatment of the rhodium peroxido complex trans ‐[Rh(4‐C 5 F 4 N)(O 2 )(CN t Bu)(PEt 3 ) 2 ] with NEt 3 · 3HF in thf afforded the fluorido bifluorido compound trans ‐[Rh(4‐C 5 F 4 N)(F)(FHF)(CN t Bu)(PEt 3 ) 2 ] ( 1 ) and hydrogen peroxide after 2 days (Scheme ).…”

“…As mentioned above, previous studies on the reactivity of rhodium and iridium peroxido complexes revealed that the peroxido unit behaves as a nucleophile ,. [16b], [16c], [17a] Thus, the rhodium complex trans ‐[Rh(4‐C 5 F 4 N)(O 2 )(CN t Bu)(PEt 3 ) 2 ] reacts with electrophiles such as HCl, alkyl triflates, or pinacolborane (4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane) resulting initially in the cleavage of the metal–oxygen bond in the trans position with respect to the tetrafluoropyridyl ligand.…”

“…The 31 P{ 1 H} NMR spectrum of 4 shows a doublet of multiplets at δ = 28.8 ppm with a coupling constant of 1 J Rh,P = 85 Hz. [13a], For 5 , a doublet of doublets is detected at δ = 7.1 ppm. The phosphine atoms in mutually trans positions couple to two inequivalent fluorine atoms with coupling constants of 2 J P,F = 22 and 27 Hz.…”

“…NEt 3 · 3HF and HF · pyridine were purchased from Aldrich. trans ‐[Rh(4‐C 5 F 4 N)(O 2 )(CN t Bu)(PEt 3 ) 2 ] and trans ‐[Ir(4‐C 5 F 4 N)(O 2 )(CN t Bu)(P i Pr 3 ) 2 ] were prepared according to literature procedures . NMR analyses were carried out with Bruker DPX 300, Avance III 300, and Avance III 500 spectrometers.…”

Activation of small molecules by a rhodium bis(phosphinite) pincer complex

“…Thus, the rhodium hydrido chloride complex RhH(Cl) [2,6 (Bu t 2 PO) 2 C 6 H 3 ] (1) synthesized herein was used as the starting material for the preparation of complexes with labile two electron ligands, Rh(L)[2,6 (Bu t 2 PO) 2 C 6 H 3 ] (4, 5), as well as of rhodium complexes with small mol ecules, such as CO (3), H 2 (10), N 2 (11,12), and O 2 (6). Complexes 6 and 10-12, were shown to undergo inter conversions.…”