A cadmium hydroxide complex of a N₃S-donor ligand containing two hydrogen bond donors: synthesis, characterization, and CO₂ reactivity

Treatment of the ebnpa (N-2-(ethylthio)ethyl-N,N-bis((6-neopentylamino-2-pyridyl)methyl)amine) ligand with a molar equivalent amount of Cd(ClO₄)₂·5H₂O in CH₃CN followed by the addition of [Me₄N]OH·5H₂O yielded the cadmium hydroxide complex [(ebnpaCd)₂(µ-OH)₂](ClO₄)₂ (1). Complex 1 has a binuclear cation in the solid-state with secondary hydrogen-bonding and CH/π interactions involving the ebnpa ligand. In acetonitrile, 1 forms a binuclear/mononuclear equilibrium mixture. The formation of a mononuclear species has been confirmed by conductance measurements of 1 at low concentrations. Variable temperature studies of the binuclear/mononuclear equilibrium provided the standard enthalpy and entropy associated with the formation of the monomer as ΔH° = +31(2) kJ mol⁻¹ and ΔS° = +108(8) J mol⁻¹ K⁻¹, respectively. Enhanced secondary hydrogen-bonding interactions involving the terminal Cd–OH moiety may help to stabilize the mononuclear complex. Treatment of 1 with CO₂ in acetonitrile results in the formation of a binuclear cadmium carbonate complex, [(ebnpaCd)₂(µ-CO₃)](ClO₄)₂ (2).