Diastereomeric preference in 1,4,7-tris((S)-2-hydroxy-3-phenylpropyl)-1,4,7-triazacyclononanelithium(I) and its sodium(I) analogue

In N,N-dimethylformamide (DMF), 1,4,7-tris((S)-2-hydroxy-3-phenylpropyl)-1,4,7-triazacyclononane forms metal complexes, [M(S-thppc9)]+, for which log K (dm3 mol−1)=3.01, 2.65, 2.66, 2.65, 2.42 and 7.59 (all±0.05) where M+=Li+, Na+, K+, Rb+, Cs+ and Ag+, respectively. Variable temperature 13C{1H} NMR spectroscopy shows that the interchange between equivalent forms of a single diastereomer occurs for [Li(S-thppc9)]+ and [Na(S-thppc9)]+ characterised by: k=43±5 and 2900±100 s−1, at 298.2 K, ΔH‡=22.5±1.6 and 33.8±1.6 kJ mol−1, and ΔS‡=−133±5 and −59±6 J K−1 mol−1, respectively. Gas phase ab initio modelling shows these complexes and their K+ analogue to preferentially form distorted trigonal prismatic Λ, Δ, and Λ diastereomers, respectively.