Title

Reduction of RuVI(N) to RuIII-NH3 by Cysteine in Aqueous Solution

Document Type

Journal Article

Publication Date

2018

DOI

10.1021/acs.inorgchem.8b00238

Abstract

The reduction of metal nitride to ammonia is a key step in biological and chemical nitrogen fixation. We report herein the facile reduction of a ruthenium(VI) nitride complex [(L)RuVI(N)(OH2)]+ (1, L = N,N′-bis(salicylidene)- o-cyclohexyldiamine dianion) to [(L)RuIII(NH3)(OH2)]+ by Lcysteine (Cys), an ubiquitous biological reductant, in aqueous solution. At pH 1.0−5.3, the reaction has the following stoichiometry: [(L)RuVI(N)(OH2)]+ + 3HSCH2CH(NH3)CO2 → [(L)RuIII(NH3)(OH2)]+ + 1.5(SCH2CH(NH3)CO2)2. Kinetic studies show that at pH 1 the reaction consists of two phases, while at pH 5 there are three distinct phases. For all phases the rate law is rate = k2[1][Cys]. Studies on the effects of acidity indicate that both HSCH2CH(NH3 +)CO2 – and −SCH2CH(NH3 +)CO2 − are kinetically active species. At pH 1, the reaction is proposed to go through [(L)- RuIV(NHSCH2CHNH3CO2H)(OH2)]2+ (2a), [(L)RuIII(NH2SCH2CHNH3CO2H)(OH2)]2+ (3), and [(L)RuIV(NH2)(OH2)]+ (4) intermediates. On the other hand, at pH around 5, the proposed intermediates are [(L)RuIV(NHSCH2CHNH3CO2)- (OH2)]+ (2b) and [(L)RuIV(NH2)(OH2)]+ (4). The intermediate ruthenium(IV) sulfilamido species, [(L)- RuIV(NHSCH2CHNH3CO2H)(OH2)]2+ (2a) and the final ruthenium(III) ammine species, [(L)RuIII(NH3)(MeOH)]+ (5) (where H2O was replaced by MeOH) have been isolated and characterized by various spectroscopic methods.

Source Publication

Inorganic Chemistry

Volume Number

57

Issue Number

10

First Page

5850

Last Page

5858

This document is currently not available here.

Share

COinS