Novel porphyrin–thallium–platinum complex with “naked” metal–metal bond: multinuclear NMR characterization of [(tpp)Tl–Pt(CN)5]2− and [(thpp)Tl–Pt(CN)5]2− in solution

The novel porphyrin–thallium–platinum complexes with “naked” metal–metal bond, with the composition [(tpp)Tl–Pt(CN)5]2− (1) and [(thpp)Tl–Pt(CN)5]2− (2) (tpp = tetraphenylporphrin and thpp = tetrakis(4-hydroxyphenyl)-porphine), were synthesized and characterised by multinuclear NMR (205Tl, 195Pt, 13C and 1H) and Raman spectroscopies in solution. The presence of a direct Pt–Tl metal–metal bond in the complexes is convincingly confirmed by a very strong one-bond 195Pt–205Tl spin–spin coupling (47.8 and 48.3 kHz for 1 and 2, respectively) detected in both Pt and Tl NMR spectra. The corresponding force constant in molecule 1, 1.92 N cm−1, was calculated using Raman stretching frequency of the Pt–Tl vibration and is characteristic for a single metal–metal bond.