Exploring Spin-Orbit Effects in a [Cu₆Tl]⁺ Nanocluster Featuring an Uncommon Tl−H Interaction

Reaction of [CuH(PPh₃)]₆ with 1 equiv. of Tl(OTf) results in formation of [Cu₆TlH₆(PPh₃)₆][OTf] ([1]OTf]), which can be isolated in good yields. Variable-temperature ¹H NMR spectroscopy, in combination with density functional theory (DFT) calculations, confirms the presence of a rare Tl−H orbital interaction. According to DFT, the ¹H chemical shift of the Tl-adjacent hydride ligands of [1]⁺ includes 7.7 ppm of deshielding due to spin-orbit effects from the heavy Tl atom. This study provides valuable new insights into a rare class of metal hydrides, given that [1][OTf] is only the third isolable species reported to contain a Tl−H interaction.