Rapid Acquisition of 103Rh Solid-State NMR Spectra by 31P Detection and Sideband Selective Methods

103Rh solid-state nuclear magnetic resonance (NMR) spectroscopy is potentially a powerful method for investigating the molecular and electronic structure of rhodium compounds. However, 103Rh is a difficult nucleus to study by NMR spectroscopy because of its small gyromagnetic ratio, broad chemical shift range, and long spin-lattice relaxation times (T1). While there are many prior reports demonstrating acquisition of 103Rh solution NMR spectra, there are few reports establishing a facile method with high sensitivity for acquiring 103Rh solid-state NMR spectra. Here, we utilize the large 31P-103Rh J-couplings (80-200 Hz) to efficiently acquire 31P-detected high-resolution 103Rh SSNMR spectra. We use sideband selective SSNMR techniques originally developed for wideline 195Pt SSNMR experiments. Notably, using these methods, we were able to acquire MAS 103Rh SSNMR spectra in experiment times on the order of 30 minutes to a few hours and from only a few mg of materials. The sideband selective experiments offer significant time savings as compared to existing direct detection methods, which require days of acquisition to obtain a directly detected MAS spectrum, or only yield low-resolution static powder patterns. Numerical fits of the spectra provide chemical shift tensor parameters, with the experimental spectra agreeing well with the DFT-calculated spectra.