Mechanistic Studies on Fast Ligand‐Substitution Reactions of a Very Labile Pd^II Complex in Several Ionic Liquids

Abstract

Detailed kinetic studies on the ligand-substitution reactions of the very labile [Pd(terpy)Cl] + (terpy = 2,2Ј:6Ј,2ЈЈ-terpyridine) complex have been performed for neutral and anionic nucleophiles in several imidazolium-based ionic liquids. The detailed substitution mechanisms derived from the obtained rate and activation parameters differ from those expected on the basis of data aquired in aqueous medium, since the selected ionic liquids significantly affect the nucleophilic attack

Elucidation of inorganic reaction mechanisms in ionic liquids: the important role of solvent donor and acceptor properties

“…In general, the insertion of CO 2 in Ru-H was studied under pseudo-first-order conditions as a function of the CO 2 concentration, temperature and pressure, to determine the rate constants and activation parameters ΔH ≠ , ΔS ≠ and ΔV ≠ , respectively. Although the application of ILs could be problematic in terms of their higher viscosity 15 as compared to conventional solvents, in the case of [emim][NTf 2 ] the stoppedflow kinetics were not affected by the viscosity and showed single-exponential behavior. For all solvents under investigation, the observed rate constants k obs resulted in linear concentration dependences, with no significant intercept.…”

“…In this context, we first concentrated on the significant effect of a series of ionic liquids on ligand substitution reactions of Pt II and Pd II complexes. 14, 15 We then extended our studies to complex-formation reactions involving lithium ions, 16 a topic related to supramolecular and accumulator chemistry, and to the activation of small molecules, viz. carbon dioxide 17 and nitric oxide.…”

Deactivation of the Cobalt Catalyst for the Cyclotrimerization of Acetylenes in Ionic Liquids: Solvent Effects on the Mechanism and Thermal and Pressure Activation Parameters

“…Furthermore, the use of ionic liquids as solvents for kinetico-mechanistic studies has also been tried in other simple reactions. These have been found to be both practically innocent, providing no changes in the mechanism occurring from the classical solvent systems − and producing very important changes in the mechanisms involved due to their polar (and sometimes basic) nature. − It is clear that the possibility of ionic liquids forcing important changes in the reaction mechanisms and kinetic behavior of some processes is an important challenge, − especially when considering the stabilization of charged transient species . The results obtained for the system studied in (Bmim)(NTf 2 ) solution in the absence of added PPh 3 shown in Table are surprising; the process observed with equivalent UV–vis spectral changes is much faster, with thermal and pressure activation parameters showing dramatic differences with respect to those found for the classical solvent media.…”

Understanding chemical reaction mechanisms in ionic liquids: successes and challenges

“…Intuitively longer dead times in the stopped-flow method could be anticipated using highly viscous ILs. This aspect has been thoroughly investigated and the dead times are significantly increased; 18 the technique may still be employed with that issue in mind.…”