Carbon-13 nuclear magnetic resonance studies of synthetic [Fe4S4(SR)4]2–iron sulphur clusters

Abstract

Carbon-13 n.m.r. spectra of several synthetic [Fe₄S₄(SR)₄]^2– clusters have been recorded (R = CH₂CH₃, CH₂CH₂OH, Ph, C₆H₄Me-4, C₆H₄NH₂-3, or C₆H₄NH₂-4). Examination of the signs of the paramagnetic isotropic shifts leads to the conclusion that contact interactions dominate the shift mechanism. For alkanethiolates, a σ-spin delocalisation operates, and for arenethiolates both σ- and π-spin delocalisation pathways are observed. This behaviour parallels that observed in the corresponding ¹H n.m.r. spectra.