Evidence for Associative Ligand Exchange Processes on Solvated Lithium Cations

Abstract

The ligand exchange mechanism of solvated lithium cations has been studied using DFT calculations (RB3LYP/6-311+G**). The water exchange mechanism on [Li(H(2)O)(4)](+) was found to be limiting associative (A) involving a five-coordinate intermediate, whereas ammonia exchange on [Li(NH(3))(4)](+) was found to follow an associative interchange (I(a)) mechanism. The suggested mechanisms are discussed in reference to available experimental and theoretical data.

Ligand Exchange Processes on Solvated Zinc Cations – DFT Analysis of Hydrogen Cyanide Exchange on [Zn(HCN)6]2+

“…In accordance with the expected trend, the calculated change in the Zn-N bond lengths during the exchange reaction (∆∑) were found to be positive for the limiting dissociative mechanism and negative for the associative interchange mechanism (see Table 1). In addition, ∑r 3 increases significantly on going from the transition state, The overall mechanistic findings demonstrate that as in the case of Li + , [17,18] Be 2+ , [19] and Al…”

“…Following the suggestions of Hartmann et al, [13] and for comparison with recent studies on solvent exchange at Li + , [17,18,22] Be 2+ , [19,23] and Al 3+ , [20,21] we fully optimized the structures at the B3LYP/6-311+G** level of theory [24] and characterized by computation of vibration frequencies the structures as local minima or transition states.…”

Ligand‐Exchange Processes on Solvated Lithium Cations: DMSO and Water/DMSO Mixtures

“…Whereas experimental methods investigate reactions under real conditions in a whole ensemble of molecules, quantum-chemical calculations can focus on a single molecule in the presence of a small number of solvent molecules, for example, those of the first solvation shell. [2][3][4][5][6][7] This complementary approach allows further mechanistic insight to be gained.…”

“…Solutions of alkalimetal ions, mostly Li + , in DMSO have also been investigated experimentally [46][47][48][49] and theoretically, [41,[50][51][52][53] as well as in water/ DMSO mixtures [54][55][56] and in other solvent combinations. [57][58][59] One of the first reports on the utilisation of 7 Li NMR in the investigation of LiClO 4 in various solvents (including DMSO) was published by Maciel et al [88] In DMSO, no evidence for contact ion pairing was observed [56,60] as might be expected, for instance, in THF (DN = 7.4). [61] It was also shown that Li + interacts preferentially with DMSO electrostatically through the oxygen donor of the S=O group.…”

“…While many studies have explored the behaviour of Li + in DMSO and water/DMSO mixtures, to our knowledge, no attempts have been made to investigate the ligand-exchange mechanism of solvated Li + in DMSO and in water/DMSO mixtures. Herein, we extend our combined quantum-chemical and experimental investigations of the ligand-exchange mechanism around Li + [7] and focus on DMSO and water/DMSO mixtures.…”