Globular molecular platinum carbonyl nanoclusters: Synthesis and molecular structures of the [Pt26(CO)32]- and [Pt14+x(CO)18+x]4- anions and their comparison to related platinum "browns"

The thermal decomposition of [Pt3n(CO)6n]2- (n=2-10) Chini clusters results in the formation of globular molecular platinum carbonyl clusters, whose nature depends of the nuclearity of the parent cluster as well as the counter-ion and solvent employed. Among these, the new [Pt14+x(CO)18+x]4- (x=0,1) and [Pt44(CO)45] n-, as well as the previously reported [Pt15(CO)19]4-, [Pt19(CO)22]4-, [Pt24(CO)30]2-, [Pt26(CO)32]2-, [Pt33(CO)38]2- and [Pt38(CO)44]2- have been identified. Oxidation of [Pt14+x(CO)18+x]4- (x=0,1) with HBF4·Et2O affords [Pt26(CO)32]2-, which is further oxidized to the related [Pt26(CO)32]- mono-anion. Oxidation of [Pt19(CO)22]4-, under similar conditions, affords the unstable [Pt19(CO)22]2- di-anion, that rearranges during crystallization into the new [Pt36(CO)44]2-. Conversely, the reduction of [Pt19(CO)22]4- with Na/naphthalene results in the [Pt19(CO)22]5- penta-anion which, after work-up, is transformed into the new [Pt23(CO)27]2-. The new clusters [Pt14+x(CO)18+x]4- (x=0,1) and [Pt26(CO)32]- have been fully characterized by means of single crystal X-ray diffractometry as their [NEt4]4[Pt14+x(CO)18+x]·MeCN (x=0.18) and [NEt4][Pt26(CO)32]·2.12thf·0.38C6H14 salts. Conversely, in the case of the new [Pt23(CO)27]2-, [Pt36(CO)44]2- and [Pt44(CO)45] n-, due to the poor quality of their crystals, only a partial structural determination has been possible. [Pt14+x(CO)18+x]4- (x=0,1) displays a distorted bcc structure, [Pt26(CO)32]- and [Pt23(CO)27]2- adopt hcp structures, [Pt36(CO)44]2- presents a distorted ccp metal core, whereas [Pt44(CO)45] n- possesses a twinned hcp/ccp ABCBA structure. The structures of the metal cores of these clusters is compared to previously reported globular platinum carbonyl nanoclusters ("platinum browns").