Polynuclear entities

In symmetrical dinuclear entities, each of the central atoms is of the same element and they are identically ligated. Below, additive names of several formats are given to a number of 

The general procedure for naming a symmetrical dinuclear entity is as follows. 

The ligands are represented in the usual way and the multiplicative affix di is added immediately before the name of the central atom. The name of the central element is modified to the ate form if the compound is an anion. 

A bond between the two central atoms, if there is one, is indicated by adding to the name the italicized symbols for those two atoms, separated by an em dash and enclosed in parentheses. 

In bridged dinuclear species, bridging ligands are indicated by the Greek letter p, placed before the ligand name and separated from it by a hyphen. The whole term, e.g. p-chlorido , is separated from the rest of the name by hyphens. If the bridging ligand occurs more than once, multiplicative prefixes are employed (see also Sections IR-9.1.2.10 and IR-9.2.5.2). 

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IR-1.5.3.2 Compositional nomenclature IR-1.5.3.3 Substitutive nomenclature IR-1.5.3.4 Additive nomenclature IR-1.5.3.5 General naming procedures IR-1.6 Changes to previous IUPAC recommendations IR-1.6.1 Names of cations IR-1.6.2 Names of anions IR-1.6.3 The element sequence of Table VI IR-1.6.4 Names of anionic ligands in (formal) coordination entities IR-1.6.5 Formulae for (formal) coordination entities IR-1.6.6 Additive names of polynuclear entities IR-1.6.7 Names of inorganic acids IR-1.6.8 Addition compounds IR-1.6.9 Miscellaneous... 

The system developed in Ref. 11 for additive names of dinuclear and polynuclear entities has been clarified and to some extent changed for reasons of consistency the order of citation of central atoms in names is now always the order in which they appear in Table VI, the element occurring later being cited first (see Sections IR-7.3.2 and IR-9.2.5.6). 

IR-7.1.2 Choosing a central atom or atoms, or a chain or ring structure IR-7.1.3 Representing ligands in additive names IR-7.1.4 Ions and radicals IR-7.2 Mononuclear entities IR-7.3 Polynuclear entities... 

The proposed general procedure for constructing a coordination-type additive name for a polynuclear entity is as follows ... 

An efficient feed injection system produces extremely small droplets that vaporize quickly. Rapid vaporization minimizes the amount of non-vaporized hydrocarbons that block the active sites. An effective feed nozzle system must instantaneously vaporize and crack asphaltenes and polynuclear aromatics to lower boiling entities. 

Amino acid is one of the most important biological ligands. Researches on the coordination of metal-amino acid complexes will help us better understand the complicated behavior of the active site in a metal enzyme. Up to now many Ln-amino acid complexes [50] and 1 1 or 1 2 transition metal-amino acid complexes [51] with the structural motifs of mononuclear entity or chain have been synthesized. Recently, a series of polynuclear lanthanide clusters with amino acid as a ligand were reported (most of them display a Ln404-cubane structural motif) [52]. It is also well known that amino acids are useful ligands for the construction of polynuclear copper clusters [53-56], Several studies on polynuclear transition metal clusters with amino acids as ligands, such as [C03] [57,58], [Co2Pt2] [59], [Zn6] [60], and [Fe ] [61] were also reported. 

Polynuclear species with monocyclic MS4 entities such as WjSi discussed separately. 

The number of central atoms joined in a single coordination entity or cluster by bridging ligands or by metal-metal bonds. Such complexes are referred to as being dinuclear, trinuclear, tetranuclear, polynuclear, etc. 

Hydrolysis of polynuclear hydroxo-bridged chromium (III) complexes in concentrated solutions of strong acid yields the corresponding mononuclear species. Such cleavage reactions are fast in comparison with the hydrolysis in dilute acid and proceed with retention of configuration of the mononuclear entities. A few representative examples are shown in Eqs. (46)-(49) (40, 42,161, 252). 

The nx)st imponam ring system of organic chemistry is (he benzene nng. either as a separate entity or in polynuclear hydrocarbons such as naphthalene, anthracene, and phenanthrene. Inorganic chemistry has two (at (east) analogues ofbenzene borazincs. and trimeric cyclophosphazene compounds. 

This coal of intermediate rank has rather extensive polynuclear formation and polar functional groups. Thus we would expect dispersion, polarizability, and dipolar interactions between the substrate entities and the sorbate molecules. The polar portion of the substrate as well as the highly conjugated pi-bonded electrons most assuredly are involved in the sorption process. Such a concept is quite suggestive and compatible with the polarization theory for sorption processes (9, 13, 14), where the energetics are predicted to follow the relationship... 

IR-9.2.4.3 Comparison of the eta and kappa conventions IR-9.2.4.4 Use of donor atom symbol alone in names IR-9.2.5 Polynuclear complexes IR-9.2.5.1 General IR-9.2.5.2 Bridging ligands IR-9.2.5.3 Metal-metal bonding IR-9.2.5.4 Symmetrical dinuclear entities IR-9.2.5.5 Unsymmetrical dinuclear entities... 

IR-9.2.5.7 Polynuclear clusters symmetrical central structural units IR-9.3 Describing the configuration of coordination entities IR-9.3.1 Introduction... 

A comprehensive review appeared on the chemistry and structure of polynuclear clusters containing triphenylphosphine-stabilized Au and Pd or Pt. Many of the clusters contain also additional metals, such as Ag, Cu or Hg. The nuclearity (number of metal atoms) of the clusters ranges from 3 (e.g. 56) to 25 (e.g. 57). The spectroscopic techniques used for structural characterization of these entities were NMR, fast-atom-bombardment MS (FAB-MS), UVV and XPS. Several applications in catalysis were also reviewed164. 

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