NMR Signatures of Transition-Metal Nuclei: From Local Environments and Electronic Structures to Reactivity Descriptors in Molecular and Heterogeneous Catalysis.

This Perspective summarizes the current state of the art in understanding the local environments of metal sites across homogeneous and heterogeneous catalysts by means of solid-state nuclear magnetic resonance (NMR), augmented with first-principles density functional theory (DFT) calculations, focusing on transition-metal nuclei and emphasizing the potential of this approach for understanding reactivity. We illustrate in particular how NMR parameters of transition-metal nuclei provide unique insights into the electronic structures and coordination environments of metal sites, complementary to information that can be obtained from C, N, or O NMR parameters of metal-bound ligands. Using the examples of solid-state NMR analyses of supported and molecular systems containing NMR-active transition-metal nuclei (Mo, Pt, Ag, W, V, and Ti), we show how NMR parameters can be determined and related to structural and electronic features of molecular and surface metal sites. Moreover, analyzing the origins of the chemical shift tensors of these metal nuclei through DFT computations helps to connect NMR signatures to specific local coordination environments and electronic structures (frontier molecular orbitals) and the corresponding reactivity of specific metal sites, thereby opening the possibility of establishing structure-activity relationships across catalytic systems, including industrially relevant heterogeneous catalysts.