The ¹⁰³Rh NMR spectroscopy and relaxometry of the rhodium formate paddlewheel complex

The nuclear magnetic resonance (NMR) spectroscopy of spin-1/2 nuclei with low gyromagnetic ratio is challenging due to the lowNMRsignal strength. Methodology for the rapid acquisition of Rh-103 NMR parameters is demonstrated for the case of the rhodium formate "paddlewheel" complex Rh-2(HCO2)(4). A scheme is described for enhancing the Rh-103 signal strength by polarization transfer from H-1 nuclei, which also greatly reduces the interference from ringing artifacts, a common hurdle for the direct observation of low-. nuclei. The Rh-103 relaxation time constants T-1 and T-2 are measured within 20 min by using H-1-detected experiments. The field dependence of the Rh-103 T-1 is measured. The high-field relaxation is dominated by the chemical shift anisotropy mechanism. The Rh-103 shielding anisotropy is found to be very large: |Delta sigma| = 9900 +/- 540 ppm. This estimate is compared with density functional theory calculations.