Nickel-platinum cluster

The non-metallic atoms (C and H) are described by the 6-31G basis set of double zeta quality with p polarization functions in hydrogen atoms and d polarization functions in carbon atoms. In aU the clusters, the nearest-neighbour distances were taken from the bulk and are 2.77483 A for platinum, 2.75114 A for palladium and 2.49184 A for nickel. These clusters form compact sections of the corresponding ideal surfaces. 

The initial observation of remarkable size-dependent reactions of deuterium with clusters of cobalt and niobium was rapidly followed by other reports of dihydrogen addition reactions with clusters of many metals, in some cases containing more than 100 atoms. Further work was reported for nio-bium " and cobalt as well as for iron, vanadium, " nickel, platinum, rhodium, tantalum, and aluminum. ... 

E5.4 Formation of platinum and palladium clusters with carbonyl and phosphine ligands E5.5 Reactivity and flexibility in platinum metal clusters E5.6 Excited state properties of the low-valent bi- and trinuclear complexes of palladium and platinum E5.7 Interstitial nickel carbonyl clusters... 

Palladium forms clusters of these types far less readily than nickel and platinum, unless they are stabilized by o-donor ligands such as phosphines. This may be due to the lower energy of Pd-Pd bonds as reflected in the sublimation energies, 427, 354 and 565 kJ mol for Ni, Pd and Pt. 

This Study has shown that reasonably uniform platinum crystallites can be made on y-alumlna, and that platinum and palladium can be segregated and maintained In that form for the most part even after exposure to high temperature oxidation-reduction conditions. Highly dispersed clusters of palladium, nickel, cobalt, and Iron can be observed. Cluster size determination could not be accurately made because of the lack of contrast between the cluster and the support. The marginal detectability by EDS for these clusters enabled elemental Identification to be made, however, mass uniformity determinations could not be made. 

The cluster, Ni4(CO)6[P(CH2CH2CN)3]4, has been obtained in low yield (ca. 5%) by the reaction of Ni(CO)4 with P(CH2CH2CN)3 in boiling methanol17, 183, and the structure of this compound has already been reported in Fig. 12. Whereas the nickel species, Ni(CO)2(PR3)2, are generally stable, the corresponding platinum species decompose spontaneously50 ... 

A stabilization of low valencies of metals and an induction time before cluster formation have been observed as well in the case of iridium [105], platinum [53], palladium [147], copper [94], or nickel [115]. 

Nickel forms organometallic clusters with three to six metal atoms. Among these some unusual structures and bonding situations occur which were mentioned in Chapter 2. The cluster chemistry of palladium is rather poor, and the outstanding features of platinum are a considerable number of trinuclear heterometallic complexes and the chimney-like structures of the clusters [Pt3(C0)g]. ... 

The reactions of [Fe2S2(NO)4]2 with complexes of nickel (30) and platinum (32) to yield heterometallic Fe2MS2 clusters have already been described (Section II,B,2). 

Heteronuclear Clusters Containing Platinum and the Metals of the Iron, Cobalt, and Nickel Triads... 

More emphasis should be placed in future endeavors on routes to metal -isocyanide clusters, since those of nickel (21) and platinum (47-49) are proving to have a rich chemistry. 

To date, only nickel, palladium, and platinum have formed homoleptic metal(O) isocyanide clusters. This may be due to two factors, either the greater tendency to nucleation in the group or simply the ready access to the highly labile metal(O) precursors M(COD)2 [M = Ni (137), Pt (138)]. 

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