Natural abundance 195Pt-13C correlation NMR spectroscopy on surfaces enabled by fast MAS dynamic nuclear polarization

Surface organometallic chemistry has developed as an effective strategy for the rational design and synthesis of well-defined, single-site Pt-based heterogeneous catalysts. Given its high sensitivity to changes in electronic structure, ¹⁹⁵Pt solid-state NMR spectroscopy offers a unique approach to investigate the chemical structure and local environment of Pt surface sites, providing invaluable insights for establishing structure-activity relationships. However, this approach is typically hindered by severe sensitivity issues, due to the low loading of Pt sites and the often-encountered large ¹⁹⁵Pt chemical shift anisotropies. To overcome this limitation, ¹⁹⁵Pt NMR signature of surface metal centers can be indirectly detected through protons. Indirect detection on ¹³C spins, has also been demonstrated to be feasible by combining isotopic labeling with dynamic nuclear polarization (DNP). Here, we extend this methodology to a supported Pt complex at natural abundance. The material was prepared by grafting (COD)PtMeOSi(OtBu)₃ (COD = 1,5-cyclooctadiene, Me = methyl and tBu = tert‑butyl) onto partially dehydroxylated silica. DNP enhanced two-dimensional through-bond ¹³C{¹⁹⁵Pt} heteronuclear correlation experiments were successfully implemented at fast magic angle spinning. They enabled the detection of the 0.37 % NMR-responsive surface species, thereby showcasing the remarkable sensitivity of this approach and its broad applicability. Key bonding information was obtained by measuring the correlated ¹³C and ¹⁹⁵Pt isotopic chemical shifts as well as ¹J(¹³C-¹⁹⁵Pt) coupling constants, confirming directly the coordination structure of the surface Pt sites.