Reducing the NMR line widths of quadrupole nuclei by employing supercritical solvents

An outline of the use of supercritical solvents in NMR spectroscopy is give n, with emphasis on instrumentation and applications. Especially the advant ages of the low viscosity of supercritical solvents, resulting in appreciab le reductions of the line widths of NMR resonances of quadrupole nuclei (I > 1/2), are discussed. The main focus of the review is on the development o f transition metal and N-14 NMR spectroscopy, to aid the analysis of transi tion metal complexes. The choices of the supercritical solvent and ligand m odifications are discussed in the context of solubility and reduction of th e line width.