Cluster complexes tetrahedral

For tetranuclear cluster complexes, three stmcture types are observed tetrahedral open tetrahedral (butterfly) or square planar, for typical total valence electron counts of 60, 62, and 64, respectively. The earliest tetracarbonyl cluster complexes known were Co4(CO)22, and the rhodium and iridium analogues. The... 

In a non-stoichiometric oxide of the type Mi jO (where M is a metal), the association of the vacancy and the positive hole, or M + ion, can form the simplest cluster complex for Fei , 0. X-ray and neutron diffraction measurements (Roth 1960) suggested that some Fe + ions are in tetrahedral sites (flgure 1.11(a)). An... 

The structural relationship between the molecular and solid-state compounds has been a hot issue in inorganic chemistry for some time (25-27). The extrusion (or excision) from preformed solid-state cluster compounds is one of the major synthetic methods of the preparation of cluster complexes (26). Use of cluster complexes as precursors to solid-state cluster compounds is the reverse reaction of excision. Both reactions utilize the structural similarity of the metal cluster units. The basic cluster units of polyhedra (deltahedra) or raft structures are triangles, and both molecular and solid-state clusters with octahedral, tetrahedral, and rhomboidal cores have been reported. Similarity of other properties such as electronic structures based on the cluster units is also important. The present review is concerned with the syntheses and structures of the cluster complexes of the group 6 metals and with their relationships to solid-state chemistry. 

We have mentioned only in passing other cluster complexes in which a tetrahedral core of 1 carbon and 3 metal atoms is present. Such complexes in which the metal atoms are nickel, ruthenium, and osmium have been prepared XIII (81), XIV (82, 83), and XV (66, 82). Their chemistry remains largely unexplored, except for the transformations of compound XV in strong acid medium which we mentioned in the previous section. 

In terms of its coordination chemistry, the silver(I) ion is typically characterized as soft . Although originally believed to only bind ligands in a linear arrangement, it was soon shown that it can adopt a variety of coordination environments, the most common one being a four-coordinate tetrahedral geometry. Square-planar complexes are not rare, and various silver(I) cluster complexes also contain three-and five-coordinate sUver(I) ions. 

Geometrically, the main group element tends to retain a tetrahedral nearest neighbor environment, whereas the transition metal element tends to retain an octahedral environment. As a consequence, transition metal clusters with more than six metal atoms have a tendency toward ligand loss, leading to the formation of condensed clusters (multiple interstitial metal atoms). This leads eventually to close-packed structures that mimic bulk metal structures (see Polynuclear Organometallic Cluster Complexes). On the... 

Some solid-state metal hydrides are commercially (and in some cases potentially) very important because they are a safe and efficient way to store highly flammable hydrogen gas (for example, in nickel-metal hydride (NiMH) batteries). However, from a structural and theoretical point of view many aspects of metal-hydrogen bonding are still not well understood, and it is hoped that the accurate analysis of H positions in the various interstitial sites of the previously described covalent, molecular metal hydride cluster complexes will serve as models for H atoms in binary or more complex solid state hydride systems. For example, we can speculate that the octahedral cavities are more spacious in which H atoms can rattle around , while tetrahedral sites have less space and may even have to experience some expansion to accommodate a H atom. 

The NacNac ligand, N(Dipp)C(Me)CHC(Me)N(Dipp), has been extensively employed as an ancillary ligand in f-element chemistry and this area has been reviewed elsewhere [78,79]. Recently, the NacNac ligand has been used to stabilize an approximately tetrahedral Yb(II) cluster complex [ Yb(NacNac)(THF) 2 p-Yb(Fp) ] (36 Fp = [Fe(Cp)(CO)2] ), unusually exhibits four Fe—Yb bonds to the same Yb(II) center. Compound 36 was initially isolated as a minor product from the decomposition of [Yb(NacNac)(I)(THF)(p-Fp)]2 in a non-coordinating solvent, however it was found that 36 could be rationally synthesized by the 2 1 reaction of [Yb(NacNac)(I)(THF)(p-Fp)l2 with [Yb(Fp)2(THF)3l2 [80] (Scheme 23). 

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