Long-range through-bond heteronuclear communication in platinum complexes

Four analogous platinum stilbene- and stilbazole-based complexes exhibit unusual long-range heteronuclear spin-spin coupling in solution. Single crystal analysis and NMR experiments show that the ¹⁹F, ³¹P, and ¹⁹⁵Pt nuclei communicate over large distances (0.9-1.3 nm) through bond rather than through space. Spin-spin couplings between ¹⁹⁵Pt and ¹⁹F over seven bonds and between ³¹P and ¹⁹F over eight bonds are observed with ⁷J_PtF = 2.9 Hz and ⁸J_PF = 11.8 Hz. Remarkably, a very large spin coupling between ¹⁹⁵Pt and ¹⁹F over six bonds (⁶J _PtF = 40.1 Hz) is also observed in a structurally related pyridinium complex. Experimental and gNMR (version 5.0) simulated ¹⁹F{ ¹H}, ³¹P{¹H}, and ¹⁹⁵Pt{ ¹H} spectra of the complexes reveal a three-spin AMY system (A = ³¹P, M = ³¹P, Y = ¹⁹F) or a five-spin AMY3 flanked by a four-spin AMXY or a six-spin AMXY3 system (X = ¹⁹⁵Pt), respectively. Density functional theory calculations at the PBE0/SDD level of theory show a π-conjugated metal-ligand network, which may contribute to the experimentally observed spin-spin interactions.