Theoretical Study of Two-Dimensional COSY Experiments for S = 7/2 Spins: Application to 59Co in the Tetrahedral Cluster HFeCo3(CO)11PPh2H

Abstract

The first investigation and analysis of 59Co 2D NMR homonuclear chemical shift correlation spectra are reported for the tetrahedral mixed-metal cluster HFeCo3(CO)11PPh2H. For this cluster in solution, the 59Co 2D COSY and DQF COSY NMR spectra prove the existence of a scalar coupling between 59Co nuclei. In order to obtain a value of this coupling, the 2D COSY and DQF COSY NMR spectra for a three-spin 7/2 AX2 system have been simulated by numerical density matrix calculations. The comparison between experimental and theoretical 2D NMR spectra gives a spin-coupling constant ‖1J(59Co − 59Co)‖ = (115 ± 20) Hz for this cluster. Experimental measurements of T1 and of the line widths for cobalt 59 as well as theoretical 59Co 1D NMR spectra are reported and support our findings.