Further insights into platinum carbonyl Chini clusters

The oxidation of [Ph3P(CH2)12PPh3][Pt15(CO)30] with CF3COOH in THF afforded [Ph3P(CH2)12PPh3][Pt18(CO)36] as a precipitate which was re-crystallized from dmf/iso-propanol. This salt self-assembles in the solid state adopting an unprecedented morphology which consists of infinite chains of [Pt9(CO)18]– units. The solid state structure of [Ph3P(CH2)12PPh3][Pt18(CO)36] may be viewed as a snapshot in which [Pt9(CO)18]– units are approaching and ready to exchange outer Pt3(CO)6 fragments. The reactions of Chini clusters with isonitriles proceed via redox-fragmentation, at difference with those involving phosphines that may occur both via non-redox substitution and redox fragmentation, depending on the experimental conditions. Thus, the reaction of [Pt6(CO)12]2– with CNXyl afforded Pt5(CNXyl)10, whereas Pt9(CNXyl)13(CO) was obtained from the reaction of [Pt15(CO)30]2– with CNXyl. These two new neutral clusters have been structurally characterized as their Pt5(CNXyl)10·2toluene and Pt9(CNXyl)13(CO)·solv solvates. DFT studies on the CO exchange of [Pt6(CO)12]2– suggest an associative interchange mechanism, which may be extended also to larger Chini clusters and the initial steps of their reactions with other soft nucleophiles.