Control of the coordination geometry around platinum by a supramolecular capsule

The coordination geometry around a platinum atom can be controlled by a diphosphane capsule composed of a tetracationic xantphos-type ligand and a tetraanionic calix[4]arene. Reaction of the diphosphane capsule with the platinum precursor [PtCl2(MeCN)2] yields the bisligated biscalix[4]arene trans-platinum capsule, whereas the same diphosphane in the absence of calix[4]arene prefers the formation of the monoligated cis-platinum complex, as indicated by 31P{1H} NMR and ESI-MS. The two calix[4]arenes stabilize the kinetic product (trans-Pt), and slow the formation of the thermodynamic product (cis-Pt).