The bicyclic backbone of [4](OTf) was further confirmed by XRD (Fig. ). For the best of our knowledge, [4](OTf) represents the first crystallographically characterized sulfur-based trypticene analog, which we suggest to call thiatriptycenium. Similarly to phosphatroptycenes, the apical S atom in [4](OTf) is significantly more pyramidalized compared to that in a simple triphenylsulfonium cation or in its phosphinefunctionalized analog L1 (Σangles = 291.26° vs 314.39°, respectively). On the other hand, the C-S bond lengths of 1.788Å (av.), typical to other sulfonium cations, appear unaffected by the ring strain. In fact, similar geometric features were observed in the zwitterionic 9-sulfonium-10boratriptycenes recently introduced by Chardon (Fig. ). 8.09 ppm, compared to the free ligand (Figure ), a downfield shift considerably larger than those observed for the rest of the aromatic protons (0.3-0.5 ppm). Such a pronounced deshielding strongly supports coordination of the sulfur atom to a highly electrophilic Pt 2+ center in this compound. The fourth coordination site in [5](OTf)3 (assuming a typical square planar geometry of the Pt(II) center) is most likely occupied by a weakly coordinated MeCN. Although anion coordination cannot be completely ruled out, it appears less likely, based on the the 19 F NMR of this complex, which shows only a single sharp peak at δ = -78 ppm, characteristic of a free triflate anion (Fig. ). Furthermore, analogues of [5](OTf)3 with non-coordinative anions, which were prepared for comparison (Scheme 3b), exhibited nearly identical 31 P and 1 H NMR spectra. Despite multiple attempts, no XRD-quality single crystals of complex [5](OTf)3 (or its anion-exchanged analogues) could be grown, prompting us to resort to DFT calculations (ωB97X-D3/Def2-TZVP). The optimized model complex [5*] 3+ (where the t-Bu and Ph groups are replaced by H atoms, Fig. ) exhibited a Pt-coordination sphere nearly identical to that previously calculated for [6*] 3+ , the analogously simplified Pt(II)(MeCN) complex of the 2nd generation ligand (see Table for a detailed comparison). Given the excellent fit between the optimized geometry of the latter and the XRD structure of [6](BF4)3 (Scheme 4a), we believe that the true geometry of [5](OTf)3 is also reliably represented by its optimized model.