Hexanuclear compounds

The hexanuclear compound 21 is a particular case of dendrimer in that a [Rh(ju-Cl)2Rh]4+ moiety can be identified as the core. The photophysical properties of this compound [40] indicate that the bimetallic core plays the role of insulator with respect to the peripheral luminescent Ru(II)-based units. 

Chemical Properties. Compound 2 is readily decarbonylated upon exposure to UV irradiation.5 Irradiated solutions of 2 readily yield addition products of sulfur containing small molecules such as COS, CS2, and H2S. In the absence of reagents it will form the hexanuclear compound Os6(CO)17(/r4-S)2. It reacts with other metal complexes to form higher nuclearity osmium clusters and heteronuclear metal cluster compounds.5,11,12... 

Since the time of the original preparation due to Hieber and Lagally (75) the synthesis of Rh6(CO)i6 has been considerably improved, and the best methods now available arc shown in Scheme 2. This hexanuclear compound is sparingly soluble in organic solvents and its purification is rather difficult. However, thermal decomposition of Rh4(CO)i2 in solution affords analytically pure microcrystals (98). 

The reaction of M3(CO)12 with both open-chain and cyclic poly-alkenes has attracted some attention, especially in the case of Ru3(CO)i2. In most of the examples reported, the organic fragment bonds to the metal framework in such a way as to interact with more than one of the three metal atoms (68-77). There are some exceptions to this general statement, however. One is the reaction of Ru3(CO)j 2 with cyclopentadiene, in which a mononuclear complex is obtained (78). In other cases, tetranuclear and hexanuclear compounds are obtained (79 81). Cluster breakdown has also been observed in the case of a rhodium complex upon reaction with ethylene (55) as shown in Fig. 3. 

A hexanuclear compound with mixed bridges was described by Sheng and Vahrenkamp (196). In the mixed-valent [CpFe (dppe)(CN)]4[Fe (N03)... 

Figure 1 Hexanuclear compounds formed via mercuriophilic interactions in the solid-state structures of [L3Hg30][N03] ...

For the mononuclear and dinuclear compounds, except V(CO)e, the number of valence electrons per metal atom is 18. The BAN (effective atomic number) of the metal is the number of electrons of the d" configuration added to twice the number of CO groups, one electron being further added in the case of metal-metal bonded dinuclear systems. For trinuclear, tetranuclear, and hexanuclear compounds (metal-carbonyl clusters), the cluster valence electron counting is 48, 60, and 86, respectively. As the [K(cryptand 2.2.2)]+ derivative. As the tetraalkylammonium derivative. As the tetrachloroaluminate. 

The dihalides of W", WCI2, WBr2 and WI2 are in reality the hexanuclear compounds W2X12 which contain the cluster (Figure 43). The metal atoms occupy the corners of an... 

In the hexanuclear compound [K4Sb2(/46-0)(OBu )8(thf)4] the central 0x0 ligand is in a distorted octahedron formed by the four potassiums and two (cis) antimony atoms. In the highly symmetrical molecule [K4Sb4(/44-0)2(OPr )i2] the /44-oxo ligands are... 

The latter bpy molecule, evidenced in Fig. 30.10, plays a particular role in the crystal packing of 12. Actually, the hexanuclear compound self-assembles, generating the supramolecular structure shown in Fig. 30.11. 

Hexanuclear Organometallic Clusters. Although the octahedral arrangement of metal atoms is the most representative one for hexanuclear cluster compounds, a number of other geometries have also been observed. The structural characteristics of a selected group of hexanuclear compounds are briefly described in Table 2.6. The different types of structures found for these clusters are illustrated schematically in Fig. 2.25. 

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