Chloride clusters

The number of valence electrons in niobium oxychloride clusters decreases as the number of oxide hgands increases (Table 6.4). The compound Cs2LuNbi Cli70 has the VEC of 16 as found in most chloride clusters, suggesting that the presence of one oxide ligand per cluster does not tip the balance between the Nb-Nb bonding and Nb-L anti-bonding contributions to the a2u state. The VEC of most clusters... 

Sunner, J. Role of Ion-Ion Recombination for Alkali Chloride Cluster Formation in Liquid Secondary lon-MS. J. Am. Soc. Mass Spectrom. 1993,4,410-418. 

Table IV lists specific examples of compounds related through this form of dimensional reduction, By far, the majority of these are zirconium chloride and iodide phases, in which case lower main group and even transition metals have been found to incorporate as interstitial atoms. A few analogues are known with hafnium (135), and very recently it has been shown that nitrogen can be substituted for carbon in tungsten chloride clusters adopting the centered trigonal-prismatic geometry (see Fig. 2) (32). It is hoped that a variability similar to that exposed for the octahedral zirconium clusters will be attainable for such trigonal-prismatic cluster phases.

Recently, the new kinetic ion mobility mass spectrometer (KIMMS) was used to determine the rate constants for the SN2 reactions of a distribution of chloride cluster ions, Cr(CHCl3)o 2, with MeBr and Mel in N2 buffer gas at atmospheric pressure232. 

The versatility of transition-metal-ligand combinations in stabilizing localized, partially localized and delocalized cluster bonding is evident in the three examples discussed to this point. But we still have no analog of a late metal-carbonyl cluster that follows the main-group counting paradigm for an octahedral shape. Centered zirconium chloride clusters provide an example of an octahedral cluster with seven... 

P. Amara, J.E. Straub, Energy minimization using the classical density distribution application to sodium chloride clusters. Phys. Rev. B 53 (1996), 13857. 

The XRD diffraction patterns of the zeolites impregnated with copper(II) chloride were identical to that of the parent materials. This shows that no copper chloride clusters had been formed with diameters above 2.5 nm, the minimum detectable size [11]. 

CT term is lowest in energy followed by a LF term lying about 200 cm above. Orbital schemes are proposed for both compounds.The temperature dependence of the luminescence of the hexanuclear Mo(II) chloride cluster [Mo Cl, ] has been investigated over the rauige 1.4-300 K and analysed in terms of the emission from several Boltzmeuin populated triplet sublevels. The lowest triplet state was identified as t, and is due to the tjg to t y orbital excitation.A flash photolysis study of the quenching of [Mo Cl, ] by [IrCl ] shows it to occur by a one electron transfer process from the cluster medium euid pressure effects have been noted.An investigation of the... 

C Critchley and AM Sargeson (1984) A manganese chloride cluster as a functional centre of the O2 evolving enzyme in photosynthetic systems. FEBS Lett 177 2-5... 

Hakkinen H, Barnett R N and Landman U 1995 Energetics, structure, and excess electrons in small sodium-chloride clusters Chem. Phys. Lett 232 79... 

A wide variety of substitution reactions specific to the unique subsite have been carried out in aprotic solvents such as acetonitrile, DMF, and Me2SO at ambient temperature (33, 216-219). A number of these rections are depicted in Figs. 23 and 24, and underscore the reactivity of chloride cluster 37 and the utility of the ligand design. The chloride-thiolate interchange 37-39 in Fig. 23 is quantitative in both directions with stoichiometric quantities of reagents (33). The first examples of [4Fe-4S] double cubanes were obtained by reactions with dithiolates (40) and sulfide (41) (216). Reaction with cyanide is complete with one equivalent to yield 42. Earlier,... 

All reactions in Fig. 24 afford products in which the coordination number at the unique subsite is 5 or 6. Of product clusters 49-55, 50 is the first organometallic derivative of a [4Fe-4Sp cluster, and 49, 51, and 55 are the initial examples of six-coordinate subsites. Another example of a substituted cluster identified by H NMR is provided by the spectrum in Fig. 25. Here 1 equivalent of tacn (1,4,7-triazacyclononane) reacts quantitatively with 37 to afford 49, the 4-Me, 5-H, and 6-Me resonances of which are substantially shifted from their positions in the chloride cluster. The spectrum is indicative of trigonal symmetry. Certain of the clusters 40-55 are considered in subsequent sections. 

The just dry salts were again dispersed in Aqua Regia and steps (2) and (3) were repeated. This treatment provides gold chloride clusters of greater than 11 atoms. 

Always return any mistakes to the Aqua Regia bottle, such over dried dark red chloride clusters. The finished product may appear "wrong" but do not throw it away. A secret of the process is always to reuse it as raw material and repeat the process. 

FIGURE 7.3 Structures of common metal chloride clusters. 

In contrast to the synthetic accessibility of the above complexes using solution approaches, the synthesis of octahedral rhenium chalcogenide clusters requires the implementation of high temperature solid-state reactions, or the conversion of cluster-containing solids into soluble molecular species by the methods of cluster excision or dimensional reduction (see Section 7.2.2.1.8). While cluster excision has produced the mixed sulfide(selenide)-chloride clusters [Re6E4+ Clio 2 ] " ( = 1-3), the latter approach has led to the isolation of complexes with rhenium-chalcogenide cores [RegEgXg] - (E = S, Se X = C1, Br, I). 

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