The catalysis of hydrogen-deuterium equilibration by platinum-gold cluster compounds

Heterosite Effects in Novel Heteronuclear Clusters [Os2Ru(CO)11(PPh3)] and [Os2Ru(CO)10(2‐acetylpyridine‐N‐isopropylimine)]

“…The observed photochemical reactivity of 3 differs significantly from that of the homonuclear clusters [Ru 3 (CO) 8 (μ-CO) 2 (α-diimine)]. [17] Although visible excitation of the latter clusters also resulted in the formation of open-structure photoproducts like biradicals and zwitterions, the efficiency of these processes is significantly lower due to the persistent presence of bridging carbonyl ligands in the excited state.…”

“…Starting from [Os 3 (CO) 12 ], the linear cluster [Os 3 (CO) 12 -(Br) 2 ] was obtained by oxidation with Br 2 in refluxing CH 2 Cl 2 [step (i)]. After the addition of Br 2 , rapid removal of the heating bath is required in order to prevent the reaction of [Os 3 (CO) 12 (Br) 2 ] with additional Br 2 producing at this stage undesired [Os 2 (CO) 8 (Br) 2 ] that is known to transform into [Os 2 (CO) 6 (Br) 2 ] at elevated temperatures. [27] Similar oxidative addition of X 2 (X = Cl, Br, I) to [Ru 3 (CO) 12 ] was reported [28,29] to yield the mononuclear complex cis-[Ru(CO) 4 (X) 2 ] as the initial product, which reflects the increasing stability of the metal-metal bonds towards oxidation on descending the periodic table.…”

“…[31] As [Ru(CO) 4 ] 2-is extremely air-and moisture-sensitive and readily converts to [Ru(CO) 4 H] -, the reduction of [Ru 3 -(CO) 12 ] was performed at reduced pressure (3 × 10 -4 Pa) on a high-vacuum line. After the completion of the reaction, the product must be dried extensively, as small traces of ammonia proved to react instantaneously with [Os 2 (CO) 8 12 ] by less than six equivalents of sodium. Thus, although the number of impurities and their percentages are significantly reduced in comparison with the established synthetic procedures, [22][23][24] the purity of cluster 1 and its substitution products remains difficult to control, even when employing this novel synthetic route.…”

“…Purification of the crude product was established by column chromatography (activated neutral alumina, hexane/ CH 2 Cl 2 gradient elution). After precipitation from THF at 190 K, the product was obtained as a yellow powder in yields varying between 86 and 135 mg (40-63 % based on [Os 2 (CO) 8 31 P{H} NMR spectra were recorded with a Bruker AMX 300 spectrometer. Field Desorption (FD), Fast Atom Bombardment (FAB) and Electron Impact (EI) mass spectra were collected with a JEOL JMS SX/SX102A four-sector mass spectrometer.…”

“…[5] Apart from the general expectation that different transition metal atoms in close proximity of each other could initiate novel reactions by synergistic interactions, the different reactivity of adjacent metal centres in mixed-metal clusters may provide additional bior multifunctional activation pathways and increase the selectivity of substrate-cluster interactions. [6] Although catalysis by mixed-metal clusters in a number of cases indeed resulted in higher catalytic activity [7,8] or different product selectivity [9,10] than observed for their homonuclear analogues, the mechanistic insight into the role of the different metal centres in the catalytic cycle is generally limited. This problem mainly has its origin in scarcely available series of isostructural mixed-metal clusters, which precludes a systematic study of their bonding properties and reactivity.…”