Platinum carbonyl clusters

Phosphine palladium and phosphine platinum carbonyl cluster compounds. N. K. Eremenko, E. G. Mednikov and S. S. Kurasov, Russ. Chem. Rev. (Engl Transl.), 1985, 54, 394 (69). 

Large platinum carbonyl clusters have been investigated as models for the adsorption of carbon monoxide on platinum surfaces and on platinum electrodes. An issue is how large the clusters must be before they adopt the properties of the bulk metal. Teo et al. have investigated the magnetic properties of the clusters [Pt6(CO)12]2+, [Pt9(CO)18]2+, [Pt y(CO)22f+, and... 

The [Pt6(CO)12]2- dianion can be used as starting material for the synthesis of other platinum carbonyl cluster complexes.1,3... 

Iron-platinum carbonyl clusters, characteristics, 8, 415 Iron reagents, in Kumada-Tamao-Corriu reaction, 11, 21 Iron-rhodium clusters, as heterogeneous catalyst precursors,... 

Fukuoka, A., Higashimoto, N., Sakamoto, Y., Sasaki, M., Sugimoto, N., Inagaki, S., Fukushima, Y. and Ichikawa, M. Ship-in-bottle synthesis and catalytic performances of platinum carbonyl clusters, nanowires, and nanoparticles in microporous and mesoporous materials, Catal. Today, 2001, 66, 23-31. 

Lawrence F. Dahl Platinum carbonyl cluster dianions ( tinker toy construction) with trigonal prismatic configuration... 

The linear CO stretching frequency for the carbonylated platinum colloid while lower than that found for surface bound CO, is in the range reported for the platinum carbonyl clusters [Pt 3 (CO) 6 ] n / sind we find that the carbonylated colloid is easily transformed into the molecular cluster [Pt 12 (CO) 24 ] (10) reaction with water. The cluster was isolated in 50 yield based on platinum content of the precipitate by extraction with tetraethylammonium bromide in methanol from the aluminum hydroxide precipitated when water is added to the aluminoxane solution. The isolation of the platinum carbonyl cluster reveals nothing about the size or structure of the colloidal platinum particles, but merely emphasizes the high reactivity of metals in this highly dispersed state. The cluster isolated is presumably more a reflection of the stability of the [Pt3(CO)6]n family of clusters than a clue to the nuclearity of the colloidal metal particles - in a similar series of experiments with colloidal cobalt with a mean particle size of 20A carbonylation results in the direct formation of Co2(CO)8. 

K.-I. Machida, A. Fukuoka, M. Ichikawa, M. Enyo, Preparation of chemically modified electrodes attachement of platinum carbonyl clusters, and their efficient electrocatalytic action in anodic oxidation of methanol. J. Chem. Soc. Chem. Commun. 1987, 1486-1487. 

Weaver and co-workers [150] carried out potential-dependent infrared spectroscopy to characterize adsorption of CO on nanosized platinum particles. Large particles of diameter 4 nm and above show C-0 stretching frequencies similar to those of platinum macroelectrodes. Small particles of diameter 2-4 nm, on the other hand, show a red shift in C-0 frequency, approaching that of platinum carbonyl clusters. The authors ascribe this observation to the changes in the platinum surface coordination number, consistent with pseudo-spherical packing-density considerations. A time-resolved IR absorption technique has also been used to monitor electrocatalytic reactions using platinum nanoparticles [151]. 

Chemistry similar to that described above for iridium clusters has also been observed for rhodium clusters. Several authors [16-18] have prepared [Rh6(CO)i6] in NaY zeolite [R1i4(CO)i2] has also been formed [18], and each of these has been decarbonylated with minimal changes in the metal frame, as shown by EXAFS spectroscopy [18]. Thus there appears to be some generality to the method of forming small clusters in zeolite cages by synthesis of stable metal carbonyl precursors followed by decarbonylation. However, the method is limited. Attempts to use it to prepare zeolite-supported platinum clusters that are structurally simple and uniform have apparently not been successfiil. The literature of platinum carbonyl clusters in zeolites is not considered here because it is still contradictory. 

The effect of Pt particle size on oxidation of methanol has been studied by several researchers. Machida et al. [67] introduced several platinum-cluster-attached graphite electrodes and reported enhanced electrocatalytic activity in anodic methanol oxidation with Pt clusters ranging in size from Pt9 to Ptis [67]. The catalytic activity of supported Pt clusters is significantly higher than that of conventional Pt electrodes. They used platinum carbonyl clusters of the type Pt3n,(CO)6n (u= 3,5) as well as HRu3(CO)n. Modification of the graphite surface... 

An extreme case of chemisorption-induced restructuring of metal surfaces is coirosive chemisorption as observed by SFG. In this circumstance, metal atoms break away from step or kink surface sites and form bonds with several adsorbate molecules. Carbon monoxide can form several carbonyl ligand bonds with platinum atoms leading to the creation of metal-carbonyl species. Thus, metal-metal bonds are broken in favor of forming metal-carbonyl clusters that are more stable at high CO pressures. The SFG vibrational spectra detect the reversible formation of new adsorb carbon monoxide species above 1(X) Torr on Pt(l 11), that appear to be platinum-carbonyl clusters Pt (CO) , with (m/n) > 1 and a CO commensurate overlayer. 

In 1977 we reported a method based on graph theory for study of the skeletal bonding topology in polyhedral boranes, carboranes, and metal clusters Q). Subsequent work has shown this method to be very effective In relating electron count to cluster shape for diverse metal clusters using a minimum of computation. Discrete metal clusters treated effectively by this method Include post-transition metal clusters (, ) > osmium carbonyl clusters (O, gold clusters, platinum carbonyl clusters (J., 7 ) > and... 

Platinum carbonyl clusters have also been formed in zeolite cages, but the literature does not yet present a consistent picture of the chemistry. [40-42] Several groups [40-42] have suggested the formation of [Pt9(CO) g] in zeolites occurs by reductive carbonylation. A discussion of the chemistry and a comparison of the results from several laboratories appears in a recent publication. [43]... 

Similarly, EXAFS data used to characterize platinum carbonyl clusters as being [Pt9(CO)i8] are open to question because the Pt-CO interactions are not evident above the noise in the spectra, and it is not dear that the data quality was suffident for the reported multiple shell analysis. [41, 42]... 

Mixed ligand triangular platinum carbonyl clusters... 

Selective reduction of biomolecules by dihydrogen using soluble platinum carbonyl clusters and redox active dyes as catalysts are known (see S. Bhaduri et al, J. Am. Chem. Soc., 1998, 120, 12127-12128). Based on this work, suggest a plausible catalytic scheme for the reduction of dinitrogen to ammonia by dihydrogen. 

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