10.1021/ic991098p.s002
Andreja Bakac
Andreja
Bakac
Ilia A. Guzei
Ilia A.
Guzei
Hydrogen Atom and Hydride Transfer in the Reactions of Chromium(IV) and
Chromium(V) Complexes with Rhodium Hydrides. Crystal Structure of a
Superoxorhodium(III) Product
American Chemical Society
2000
hydride
deuterium isotope effect
rate constants
L 1
solvate water molecules
superoxo
L 2
NH
CH
CN
aneN
Cr
Chromium
aq
IV
hydrogen atom abstraction
Hydride
2000-01-28 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Hydrogen_Atom_and_Hydride_Transfer_in_the_Reactions_of_Chromium_IV_and_Chromium_V_Complexes_with_Rhodium_Hydrides_Crystal_Structure_of_a_Superoxorhodium_III_Product/3626583
The aquachromyl ion, Cr<sup>IV</sup><sub>aq</sub>O<sup>2+</sup>, reacts with the hydrides L(H<sub>2</sub>O)RhH<sup>2+</sup> (L = L<sup>1</sup> = [14]aneN<sub>4</sub> and L<sup>2</sup> = <i>meso</i>-Me<sub>6</sub>-[14]aneN<sub>4</sub>) in aqueous solutions in the presence of molecular oxygen to yield Cr<sub>aq</sub><sup>3+</sup> and the superoxo
complexes L(H<sub>2</sub>O)RhOO<sup>2+</sup>. At 25 °C, the rate constants are ∼10<sup>4</sup> M<sup>-1</sup> s<sup>-1</sup> (L = L<sup>1</sup>) and 1.12 × 10<sup>3</sup> M<sup>-1</sup> s<sup>-1</sup> (L
= L<sup>2</sup>). Both reactions exhibit a moderate deuterium isotope effect, <i>k</i><sub>RhH</sub>/<i>k</i><sub>RhD</sub> = ∼3 (L<sup>1</sup>) and 3.3 (L<sup>2</sup>), but no
solvent isotope effect, <i>k</i><sub>H</sub><sub><sub>2</sub></sub><sub>O</sub>/<i>k</i><sub>D</sub><sub><sub>2</sub></sub><sub>O</sub> = 1. The proposed mechanism involves hydrogen atom abstraction followed by
the capture of LRh(H<sub>2</sub>O)<sup>2+</sup> with molecular oxygen. There is no evidence for the formation of L(H<sub>2</sub>O)Rh<sup>2+</sup> in the
reaction between L(H<sub>2</sub>O)RhH<sup>2+</sup> and (salen)Cr<sup>V</sup>O<sup>+</sup>. The proposed hydride transfer is supported by the magnitude
of the rate constants (L = L<sup>1</sup>, <i>k</i> = 8800 M<sup>-1</sup> s<sup>-1</sup>; (NH<sub>3</sub>)<sub>4</sub>, 2500; L<sup>2</sup>, 1000) and isotope effects (L = L<sup>1</sup>, kie = 5.4;
L<sup>2</sup>, 6.2). The superoxo complex [L<sup>1</sup>(CH<sub>3</sub>CN)RhOO](CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>·H<sub>2</sub>O crystallizes with discrete anions, cations,
and solvate water molecules in the lattice. All moieties are linked by a network of hydrogen bonds of nine different
types. The complex crystallized in the triclinic space group <i>P</i>1̄ with <i>a</i> = 9.4257(5) Å, <i>b</i> = 13.4119(7) Å, <i>c</i> =
13.6140(7) Å, α = 72.842(1)°, β = 82.082(1)°, γ = 75.414(1)°, <i>V</i> = 1587.69(14) Å<sup>3</sup>, and <i>Z</i> = 2.