Octahedral metal clusters

The octahedron is classified into the c/o o-structure by Wade [3,4]. Closo-structures with n skeletal atoms are stable when they have 4n-i- 2 valence electrons. Wade s rules predict that the 26 (= 4 x 6 + 2) valence electrons could stabilize the regular octahedrons since n is 6 for the octahedron. This prediction is contained in our 6N + 14 (N= 2) valence electron rule. Our rule also predicts the stability of octahedral metal clusters with the other numbers (14 and 20) of valence electrons. 

Fig. 5.9 The inter-cluster halogen (i.e., iodine) bridging between the octahedral metal clusters in the structures of both Na[(Zr6B)Cl3.9ho.i] and Cs[(Zr6B)Cl2.2hi.8...

The chemistry of octahedral metal clusters culminates in the center of the Periodic Table with the heavy transition metals Nb, Ta, Mo, W, and Re. There is a plethora of clusters where the M-M bonded core is surrounded (and shielded) by non-metal ligands. When moving to the left of the Periodic Table the decrease in valence electron concentration calls for a stabilization through incorporation of interstitial atoms into the cluster core. Actually, the stabilization of the cluster occurs... 

The octahedral metal clusters that have long been familiar features of the lower halide chemistry of niobium, tantalum, molybdenum, and tungsten represent a category of cluster different from those so far considered in that their metal-metal bonding is best treated as involving four AO s on each metal 49, 133,144,165,178). 

Figure 1.25 The structures of (a) TijTe (b) Gd2Cl3 and (c) KM03S3 formed by condensation of octahedral metal clusters. (After Simon, 1981.)...

Exercise 3.12. The Au cluster, [Au6C(PR3)6]2+ exhibits an octahedral metal-cluster structure and contains an interstitial C atom. Justify composition and cluster geometry. 

Consider the putative synthesis of a capped octahedral metal cluster shown in the diagram below. Postulate a reasonable structure for each of the intermediate species 1 and 2 in the reaction scheme given the structures of the reactants and product. Briefly justify your structures using established ideas of cluster bonding. 

Figure 10. New pathway for the scrambling of metal vertices in 86-electron octahedral metal clusters. The proposed edge-shared bitetrahedral and capped square pyramidal intermediates (or transition states) both maximize connectivity and preserve the 86-electron count...

As discussed in section 2.8, relativistic effects on the valence electronic structure of atoms are dominated by spin-orbit splitting of (nl) states into (nlj) subshells, and stabilization of s- and p-states relative to d- and f-states. Here we examine consequences of relativistic interactions for cubo-octahedral metal-cluster complexes of the type [M6X8Xfi] where M=Mo, Nb, W and X=halogen, which have a well defined solution chemistry, and are building blocks for many interesting crystal structures. 

Some mixed octahedral metal cluster units of the type MnM 5 Xi2 have been prepared (288). Coreduction of mixtures of the pentachlorides of tantalum and molybdenum with aluminum metal in a fused mixture of... 

The structure of Gd2lFe2 reinforces the notion that our present state of understanding is incomplete. On the other hand, the remarkable abundance of octahedral metal clusters, whether empty or filled, justifies our focusing on this type of... 

The intercalation capacity depends weakly on the chalcogen nature for Mo Xg compounds with octahedral metal-clusters and Lig. Mo Sg/2/, Lig. gMogSeg,Lig. gMo TCg intercalates have been obtained. 

Ternary chalcogenides, M MoeXs (M = a transition metal, rare earth, etc. and X = S, Se, or Te) a class of ORR active materials, were for the first time synthesized by Chevrel et al. [167] and are referred as Chevrel compounds. These complex chalcogenides have a central octahedral metal cluster wherein the delocalization of the electrons leads to high electronic conductivity and these clusters act as a reservoir for electronic charge carriers. The substitution of Mo atoms by other transition metal atoms causes an alteration in the position of the Fermi level in such a way that it is suitable for the redox potential of the O2/H2O [19] couple. 

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