Multinuclear magnetic resonance studies on [Rh4(CO)12–xLx][L = P(OPh)3, x= 1–4]

Abstract

Direct ¹⁰³Rh n.m.r. studies on [Rh₄(CO)_12–xL_x][L = P(OPh)₃, x= 1–4] at low temperatures support the solution structures previously proposed and, although the apical rhodium resonance always occurs at lowest frequency, there is little variation in δ(¹⁰³Rh) with increasing ligand substitution. Measurements of ¹³C-{¹⁰³Rh} allow unambiguous assignment of the ¹³C n.m.r. spectra when x= 1 and 3 and δ(¹³CO_ax) is always at lowest frequency with ¹J(¹⁰³Rh^–13CO_ax)≃¹J(¹⁰³Rh^–13CO_ap) < ¹J(¹⁰³Rh^–13CO_rad); this suggests a new assignment for the ¹³C n.m.r. spectrum of [Rh₄(CO)₁₂].