Metal cluster halides

J.D. Corbett, Structural and bonding principles in metal halide cluster chemistry. In Modem Perspectives in Inorganic Crystal Chemistry (E. Parthe, ed.), p. 27. Kluwer, 1992. 

Fig. 32, Structures of the octahedral metal-halide clusters (MosClg) and (Nb6Cli2)2+ (49, 133, 144, 165, 178).

Early transition metal halide clusters, see Group 5 metal halide clusters Group 6 metal halide clusters... 

Coordination complexes that have metal halide clusters as their central cations represent a unique branch of coordination chemistry. The [M6X12]" cluster... 

All the hexamethylbenzene metal halide cluster cations exhibit characteristic electronic spectra which can be used for their identification in their green or brown solutions. Various attempts to obtain derivatives of [Nb3(/i-Cl)6(C6Me6)3] under the action of donors or organometallic reagents failed. 

A second feature of metal halide cluster chemistry is that the early transition metals are more prone to form metal -metal bonds than are the later noble metals and coinage metals. Again the polynuclear metal carbonyls differ in this facet of metal-metal bond behavior, and, in fact, metal carbonyl clusters become more common on going from the left to the right of the Periodic Table. 

Fig. 4.15 Some metal/halide clusters described in 1969 by Cotton, Ref. [122].

Reduction of [Mo CIg] and [Mo ClgX ] anions (X = Cl, Br, or I) by certain tertiary phosphines gave complexes of stoicheiometry MOgClgX3(PR3)3, which are formulated to have an ionic structure [MOgCl8(PR3)g] [Mo Clg]X in which the cation is a derivative of the previously unknown [Mo Clg] cluster. The use of photoelectron spectroscopy to determine structures of metal halide clusters has been reviewed. " A detailed study of the force fields for MojXg anions (X = Cr or Br) has indicated that 6 bonds do not play a significant part in the M—M bond strength of molybdenum halides. ... 

D. Redox Chemistry and Photophysics of the Group 6 Metal Halide Clusters... 

Early synthetic procedures for the group 6 metal halide clusters relied on disproportionation reactions of the intermediate halides, MoC13, MoBr3, WC14, and WBr4, at elevated temperatures to produce the clusters MgX (11, 12). These reactions suffered from inherently poor yields and the need to synthesize and isolate the reactive intermediate metal halide. McCarley and co-workers (13) introduced the use of sodium tetrahaloaluminate melts to reduce the halides MoX5 and WX (X = Cl, Br) with aluminum at lower temperatures ... 

Electronic structure calculations carried out at a variety of levels on these octahedral metal-halide clusters vary in detail (90-104). Our view of the metal-based orbitals responsible for metal-metal bonding in the M6Y8 4+ unit has evolved very little since Cotton and Haas semiempirical treatment in 1964 (90). Undoubtedly the importance of symmetry in the calculations has led to the consistent description of the bonding scheme. Only a brief summary emphasizing the relation between the proposed models to the physical and chemical properties of the clusters is presented here. For a more detailed discussion of the bonding numerous reviews are available (105-109). 

IV. Materials Chemistry Derived from Soluble Metal Halide Clusters A. Higher Nuclearity Clusters... 

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