Structure and bonding in rhodium coordination compounds: a 103 Rh solid-state NMR and relativistic DFT study.

This study demonstrates the application of 103 Rh solid-state NMR (SSNMR) spectroscopy to inorganic and organometallic coordination compounds, in combination with relativistic density functional theory (DFT) calculations of 103 Rh chemical shift tensors and their analysis with natural bond orbital (NBO) and natural localized molecular orbital (NLMO) protocols, to develop correlations between 103 Rh chemical shift tensors, molecular structure, and Rh-ligand bonding. 103 Rh is one of the least receptive NMR nuclides, and consequently, there are very few reports in the literature. We introduce robust 103 Rh SSNMR protocols for stationary samples, which use the broadband adiabatic inversion-cross polarization (BRAIN-CP) pulse sequence and wideband uniform-rate smooth-truncation (WURST) pulses for excitation, refocusing, and polarization transfer, and demonstrate the acquisition of 103 Rh SSNMR spectra of unprecedented signal-to-noise and uniformity. The 103 Rh chemical shift tensors determined from these spectra are complemented by NBO/NLMO analyses of contributions of individual orbitals to the 103 Rh magnetic shielding tensors to understand their relationship to structure and bonding. Finally, we discuss the potential for these experimental and theoretical protocols for investigating a wide range of materials containing the platinum group elements.