Clusters with Interstitial Atoms

Table 25.9 Some metal carbonyl clusters with interstitial atoms...

Hoffmann DK, Ruedenberg K, Verkade JG (1977) Molecuar Orbital Bonding Concepts in Polyatomic Molecules - A Novel Pictorial Approach. 33 57-96 Hogenkamp HPC, Sando GN (1974) The Enzymatic Reduction of Ribonucleotides. 20 23-58 Housecroft CE (1997) Clusters with Interstitial Atoms from the p-Block How Do Wade s Rules Handle Them 87 137-156 Huber R, see Romao MJ (1998) 90 69-96... 

The last example of a cluster with interstitial atoms we will deal with is the hexaanion [Ni32(CO)36(C)6]6, whose molecular structure is shown in Figure 54.24... 

Abstract This chapter reviews the methods that are useful for understanding the structure and bonding in Zintl ions and related bare post-transition element clusters in approximate historical order. After briefly discussing the Zintl-Klemm model the Wade-Mingos rules and related ideas are discussed. The chapter concludes with a discussion of the jellium model and special methods pertaining to bare metal clusters with interstitial atoms. 

Clusters with Interstitial Atoms Available Internal Volume... 

This consideration also applies to 8-vertex clusters with interstitial atoms. The most spherical 8-vertex deltahedron, namely the bisdisphenoid (Eig. 1), appears to have too small a cavity for an interstitial transition metal. Plowever, the square antiprism has two fewer edges and can be partially flattened to make a puckered eight-membered ring, which can accommodate a transition metal in the center (Pig. 8). Known clusters of this type include M E8" (M = Cr [98], Mo [98], Nb [99] E = As, Sb n = 2,3 for Cr and Mo = 3 for Nb). The transition metal in such structures can be considered to be eight-coordinate with flattened square antiprismatic coordination. The Eg ring (E = As, Sb) can be considered formally to be an octaanion, isoelectronic with the common form of elemental sulfur, Sg. Thus in M Eg (M = Cr, Mo E = As, Sb), the central transition metal has the formal oxidation state of +6. Similarly in Nb Eg , the central niobium atom has its d formal oxidation state of +5. 

The chemistry of bare metal clusters with interstitial atoms is clearly the new frontier as indicated by two recent serendipitous discoveries ... 

Note that in both interstitial transition metal carbides and the molecular clusters with interstitial atoms, the octahedral metal arrangement changes to trigonal prismatic as the d-electron count increases. That is, octahedral carbides are found for d4 or d5 metals as exemplified by ZrC and NbC and trigonal prismatic carbides are found for d6 metals as in WC. 

Figure 25.13 Metal frameworks of some Ru and Os carbonyl clusters with interstitial atoms, (a) [Ru8(H)2(CO)2i] (octahedron and face-sharing trigonal bipyramid) the second H is probably at the centre of the octahedron. (b) [Ru8(C)2(CO)n(PPh2)2] (octahedron and face-sharing square pyramid) PPh2 ligands bridge the pairs of shaded Ru atoms, (c) [Os7(H)2C(CO)i9] (tetrahedron and 3 irregularly spaced metal atoms) H atoms probably bridge two edges of the tetrahedron.

Clusters with interstitial atoms are an interesting class of polynuclear complexes. Several examples of compounds with interstitial atoms (H, C, Ge, N, P, S, etc.) have been reported. These compounds exhibit special behavior because the presence of main-group atoms in the cluster cage influences the chemical reactivity and stability of the system and its geometric structure. In the following section we consider some of these peculiarities, related both to the stability and to the electronic properties of clusters with interstitial elements. 

Mathematical cluster chemistry/Metal-metal interactions in transition metal clusters with donor ligands/Electron count versus structural arrangement in clusters based on a cubic transition metal core with bridging Main Group elements/Metalloboranes/ Clusters with interstitial atoms from the p-block How do Wade s rules handle them /Diverse naked clusters of the heavy Main Group elements Electronic regularities and analogies... 

B1.4 Clusters with interstitial atoms from the p-block How do Wade s rules handle them ... 

Figure 5-48. Schematized bonding in systems with discrete and condensed clusters (i) empty metal clusters in an environment of nonmetal atoms, (ii) clusters with interstitial atoms in an environment of nonmetal atoms, and (iii) bare clusters with interstitial atoms (see text).

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