Edge-sharing clusters

An example of an edge-sharing cluster is [RuioC2(CO)24]2 (condensation of two octahedral clusters of the type [Ru6(CO)18]2-) another example may be the structure of the ion [Re4(CO)i6]2 which can be described as the edge-sharing condensation of two triangular structures of the neutral cluster type Os3(CO)i2. 

A fascinating variety of discrete (or occasionally polymeric) polynuclear halogeno complexes of As, Sb and Bi have recently been characterized. A detailed discussion would be inappropriate here, but structural motifs include face-shared and edge-shared distorted (MXe) octahedral units fused into cubane-like and other related clusters or cluster fragments. Examples (see also preceding paragraph) are ... 

Cs2Ti4Nb6Clis06. (c) A tetrameric propellerlike (Ti4CI]206) unit in Cs2Ti4Nb6Chg06 built from four (TiLj) octahedra that share edges, (d) Cluster unit in PbLusNbeChsOe. 

Fig. 6.7 (a) Perspective of Ti2Nb5Cli404 structure in the [001] direction, (b) Cluster layer in Ti2Nb6Cli404. (c) Zigzag chain of edge-sharing [TiCl402] octahedra in Ti2Nb6Cli404. 

Figure 4.28. Schemes of octahedral cluster condensation, (a) Vertex-sharing, (b) edge-sharing and (c) face-sharing. In these examples octahedra centred by interstitial atoms are shown.

Edge-sharing and face-sharing poly-condensed clusters. Polyhedra... 

Further treatment with NH3 at 553 K promoted neither the catalytic performance nor further growth of the Re clusters. Thus the 120 min NH3 treatment gave the best performance of the Re-CVD/HZSM-5 catalyst for phenol synthesis. DFT calculations of Rejo cluster structures embedded in the pore of HZSM-5 revealed the most stabilized structure in the pore of HZSM-5 to be as shown in Scheme 10.4b. The edge-shared Rejo structure may be due to the structure and size of the pore ofthe HZSM-5 zeolite. A broader peak at 5 3.6 ppm than that of fresh HZSM-5 in the Al solid-state NMR spectrum implies a positive interaction between the A1 sites and the Reio clusters inside the pore of HZSM-5. 

The compound Bai 14Mo8016 contains similar rhomboidal clusters of Mo4 in the infinite chains (114). One is more regular, with five Mo—Mo bonds in the edge-shared bitriangle (2.578(1)—2.616(1) A), and another is rather distorted with two long and three short Mo—Mo bonds (2.546 -2.847 A). The CVE is 18.26 this can be divided into 10 for the more regular cluster and 8.26 for the distorted cluster, and the distortion can be understood from the viewpoint of electron deficiency. 

Fig. 1.85 Defect complexes of wustite. (a) Basic structure (Roth cluster) (b) edge-sharing tetrahedra (6 2 complex) (c) cornersharing tetrahedra (Koch-Cohen complex).

The isopoly anions may be considered to be portions of a closest packed array of oxide ions with the metal ions occupying the octahedral holes. The edge-sharing array found in [V n02S]6 consists of ten octahedra stacked as shown in Fig. 16.10a. This seems to be the largest stacked-octahedral isopoly anion cluster compatible with metal-metal repulsions, and the remaining edge-shared structures represent portions of this unit.46... 

The sharing of imperfect cluster faces of the clathrate-like clusters can be viewed as a thermodynamic tendency to minimize the negative entropies of solution. The tendency for face- or edge-sharing of individual solvation clusters, as Stillinger (1980) pointed out, is the same as the tendency for clustering of pure supercooled water. 

FIGURE 22 The structure of PrgFeuPb. Praseodymium, iron, and lead atoms are drawn as medium gray, black filled, and open circles, respectively. The layers of edge-sharing PbPrio polyhedra are separated by the iron cluster units. For details see text. 

Reaction of the rhenium hydride complex ReH7(PR3)2 (where R = Ph or p-tol) with Au(PPh3)N03 has yielded the heteronuclear cluster compounds [Au5Re(H)4(PR3)2(PPh3)5](PF6)2 (148) in which the metal cores are based on edge-shared bitetrahedra with the rhenium atom at one of the two most-connected vertices. This is illustrated in Fig. 24. A... 

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