Etude du radical nitroxyde tétraméthyl-2,2,6,6 piperidine-1 oxyle-1 ou `tanane'. II. Affinement de la structure cristallographique de la forme quadratique désordonée

C−H Activation from Iron(II)‐Nitroxido Complexes

“…These complexes are observed to activate CÀHs ubstrates with concomitant NÀOr upture.M echanistic studies indicate that CÀHb ond activation is rate-determining in this transformation and we propose the iron-nitroxido species as the active oxidant, although we cannot exclude the in situ formation of an iron-oxo species.P roducts of N À Ob ond cleavage have been characterized as iron(II) and iron(III)hydroxide complexes reminiscent of species formed upon OÀOb ond cleavage in enzymatic pathways. [7,11] The 57 Fe Mçssbauer spectrum for ( Ar L)Fe-(AZADO) (3)f eatures as ingle quadrupole doublet with an isomer shift as well as aq uadrupole splitting that are significantly increased as compared to the values observed for 2 (d = 0.74 mm s À1 , j DE Q j= 0.59 mm s À1 for 2, d = 0.95 mm s À1 , j DE Q j= 1.51 mm s À1 for 3) ( Figure 2c). [10] Bond metrics and angles (NÀO1 .441 (3) ,sum of angles on nitrogen = 3328 8)a re similar to those previously reported for an oxygen bound k 1 -TEMPO ligand on iron and are consistent with the reduction of TEMPO (N À O1 .283(9) ) to [TEMPO] À .…”

“…[10] Bond metrics and angles (NÀO1 .441 (3) ,sum of angles on nitrogen = 3328 8)a re similar to those previously reported for an oxygen bound k 1 -TEMPO ligand on iron and are consistent with the reduction of TEMPO (N À O1 .283(9) ) to [TEMPO] À . [7,11] The 57 Fe Mçssbauer spectrum for ( Ar L)Fe-(AZADO) (3)f eatures as ingle quadrupole doublet with an isomer shift as well as aq uadrupole splitting that are significantly increased as compared to the values observed for 2 (d = 0.74 mm s À1 , j DE Q j= 0.59 mm s À1 for 2, d = 0.95 mm s À1 , j DE Q j= 1.51 mm s À1 for 3) ( Figure 2c). The parameters for 3 are in line with other four-coordinate highspin iron(II) dipyrrin complexes and we therefore assign 3 as af our-coordinate species with a k 2 -N,O-AZADO ligand bound to the central iron, [12] ab inding mode that has been observed previously upon treatment of an Fe I precursor with 9-azanoradamantane N-oxyl.…”

A Radical Approach to Hydroxylaminotrichlorosilanes: Synthesis, Reactivity, and Crystal Structure of TEMPO‐SiCl3 (TEMPO = 2,2,6,6‐Tetramethylpiperidine‐N‐oxyl)

“…The N-O bond lengths found in these studies are 1.269, 1.270, and 1.295 Å. [31][32][33] In the course of our investigations we have been able to obtain crystals of TEMPO by sublimation with excellent quality for X-ray diffraction. The structure could be solved and refined with an R 1 value of 3.8 % and no disordered atoms.…”

C−H Activation from Iron(II)‐Nitroxido Complexes

“…[10] Bond metrics and angles (N–O 1.441(3) Å, sum of angles on nitrogen = 332°) are similar to those previously reported for an oxygen bound κ 1 -TEMPO ligand on iron and are consistent with the reduction of TEMPO (N–O 1.283(9) Å) to [TEMPO] − . [7,11] The 57 Fe Mössbauer spectrum for ( Ar L)Fe(AZADO) ( 3 ) features a single quadrupole doublet with an isomer shift as well as a quadrupole splitting that are significantly increased as compared to the values observed for 2 (δ = 0.74 mm / s , |ΔE Q | = 0.59 mm / s for 2 , δ = 0.95 mm / s , |ΔE Q | = 1.51 mm / s for 3 ) (Figure 2c). The parameters for 3 are in line with other four-coordinate high-spin iron(II) dipyrrin complexes and we therefore assign 3 as a four-coordinate species with a κ 2 - N,O -AZADO ligand bound to the central iron, [12] a binding mode that has been observed previously upon treatment of an Fe(I) precursor with 9-azanoradamantane N -oxyl.…”