Transition metal (Cr-53, Co-59, Zr-91, and Mo-95) and N-14 NMR spectroscopy of coordination compounds containing nitrogen donor ligands in low-viscosity fluids

Appreciable decreases of the Line widths of NMR resonances of the quadrupol ar nuclei N-14, Cr-53, Co-59, Zr-91, and Mo-95 have been obtained in superc ritical solvents and in low-viscosity Liquefied gases. Several a-diimines ( RN)-N-1=C(R-2)-C(R-2)=NR1 and their coordination compounds have been studie d. Regarding the solubility of two a-diimines and some Cr, Zr, and Mo compl exes it appears that the addition of small amounts of a modifier (acetone, CH2Cl2, THF) results in enhanced solubility of compounds without detrimenta l effects On the Line widths. The use of HP NMR tubes (with and without pre ssure sensor) is very appropriate for measurements of NMR spectra under hig h pressure in supercritical fluids and liquefied gases of low viscosity. In several cases it appeared that the use of Liquefied gases is more straight forward than the use of supercritical fluids, and gives similar or better r esults in terms of reduction of line widths.