Studies on the synthesis and electrochemistry of crown ether dithiocarbamates and the molecular dynamics of bis(aza-15-crown-5)thiuram disulphide. Crystal structure of cobalt tris[(aza-15-crown-5)dithiocarbamate]

Abstract

Reaction of aza-15-crown-5 (1,4,7,10-tetraoxa-13-azacyclopentadecane) with sodium hydroxide and carbon disulphide yields sodium (aza-15-crown-5)dithiocarbamate (sodium 1,4,7,10-tetraoxa-13-azacyclopentadecane-13-carbodithioate), (1). 4′-Aminobenzo-15-crown-5 (15-aminobenzo-1,4,7,10,13-pentaoxacyclopentadecane) forms the corresponding dithiocarbamate (2). Oxidative dimerization of compound (1) yields bis(aza-15-crown-5)thiuram disulphide [13,13′-(1,4-dithioxo-2,3-dithiabutane-1,4-diyl)di(1,4,7,10-tetraoxa-13-azacyclopentadecane)], (3), in contrast (2) decomposes under the same conditions to 4′-isothiocyanatobenzo-15-crown-5. The energy barrier to rotation about the S₂C–N bond of compound (3), ΔG^‡= 65.3 ± 0.5 kJ mol^–1, as measured by ¹³C-{¹H} and ¹H dynamic n.m.r. spectroscopy. When 2 equivalents of NaBPh₄ are present ΔG^‡ falls to 54.5 ± 0.5 kJ mol^–1. Complexes of the crown ether dithiocarbamates with Ni, Cu, Cr, Fe, Co, and Mo have been prepared and their electrochemistry investigated. Small shifts in the values of E_½ were observed in the presence of alkali-metal cations. The molecular structure of cobalt tris[(aza-15-crown-5)dithiocarbamate] has been determined by X-ray crystallography.