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 low NMR signal strength. Methodology for the rapid acquisition of ¹⁰³Rh NMR parameters is demonstrated for the case of the rhodium formate "paddlewheel" complex R h 2 (H C O 2 ) 4 . A scheme is described for enhancing the ¹⁰³Rh signal strength by polarization transfer from ¹H nuclei, which also greatly reduces the interference from ringing artifacts, a common hurdle for the direct observation of low-γ nuclei. The ¹⁰³Rh relaxation time constants T₁ and T₂ are measured within 20 min by using ¹H-detected experiments. The field dependence of the ¹⁰³Rh T₁ is measured. The high-field relaxation is dominated by the chemical shift anisotropy mechanism. The ¹⁰³Rh shielding anisotropy is found to be very large: |Δσ| = 9900 ± 540 ppm. This estimate is compared with density functional theory calculations. [ABSTRACT FROM AUTHOR]