Coordination compounds polynuclear

Alfred Werner s research on polynuclear coordination compounds, G. B, Kauffman, Coord. Chem. Rev., 1972, 9, 339-363 (115). 

Werner apparently did not realize that the polynuclear complexes which he investigated so extensively95 constituted a transition between the usual mononuclear coordination compounds and the infinite structure of the crystal lattice. It remained for Paul Pfeiffer, Paul Niggli (1888—1953) and others to point out that crystal structures were in beautiful agreement with his coordination theory, as revealed by the then new experimental technique of X-ray diffraction.96... 

The present discussion of isomerism in coordination compounds is not, nor was it intended to be, comprehensive and exhaustive. The examples considered are an eclectic selection, and many important systems may have been neglected through ignorance. An obvious omission is any detailed consideration of polynuclear complexes139,256"259 and it is, of course, a quite arbitrary decision not to include any consideration of organometallic species. Other neglected issues, such as the development of a truly comprehensive system of stereochemical nomenclature, are perhaps not yet capable of solution. Nevertheless, it is to be hoped that the principal factors to be considered... 

This expression is sufficient in the simplified simulation of magnetic susceptibility in polynuclear coordination compounds, where the case of very weakly interacting centers occurs. A non-trivial inquire is whether the HDVV is literaly valid for strongly bonded system—the present discussion having as implicit goal the corresponding answer. 

In this respect, a classification was reported whose basis is the nature of ligands together with the characteristic bonding and structural peculiarities of the metal complexes [112,113], This allowed the identification of four types of coordination compounds molecular complex compounds (MCC) metal-cyclic complex compounds, metal chelates (MC) complexes with multicenter coordination bonds (CMCB) and di- and polynuclear coordination compounds (DPCC). The expediency of such a classification is based on the following considerations. 

The ideas on the syntheses of di- and polynuclear complexes with phosphorus bridge by the method of direct (immediate) interaction of ligands and metal source can be received from the literature, summarized in Sec. 2.2.4.3, and related to the coordination compounds 239, 241, and 253. In this respect, we note that chelates can also participate as a metal source, for example in the transformation (3.68) [80] ... 

A change of salt anions allows us to carry out controlled syntheses of definite types of coordination compounds. Thus, metal halides are widely used to prepare molecular (Sec. 3.1.1.1) and ti-complexes (Sec. 3.1.1.3). Metal acetates are mostly applied in the syntheses of metal chelates and, especially, inner-complex compounds (Sec. 3.1.1.2). Di- and polynuclear structures are formed under use of the anions mentioned above, which, in some cases, determine (see Sec. 3.1.1.4) a type and donor centers of bridge fragments. At the same time, the mentioned approach to choice of salts of metal complex-formers has many exceptions, although it is useful. 

Copper complexes are known in oxidation states ranging from 0 to +4, although the +2 (cupric) and the +1 (cuprous) oxidation states are by far the most common, with the divalent state predominating. Only a relatively small number of Cu complexes have been characterized and the Cu° and oxidation states are extremely rare. A few mixed valence (see Mixed Valence Compounds) polynuclear species have also been isolated examples include a CuVCu species and a Cu /Cu catenane. The coordination numbers and geometries (see Coordination Numbers Geometries) of copper complexes vary with oxidation state. Thus, the majority of the characterized Cu complexes are square planar and diamagnetic, as is common for late transition metals with d electronic configurations. 

The vast majority of the coordination compounds of Os that have been prepared are in the oxidation states 11 and III. Moreover, many of these compounds show reversible or well defined Os / couples in which the electronic and redox properties at the metal are controlled by the a-donor, 7r-acceptor, and r-donor properties of the ligands. Indeed, the study of the redox behavior in Os / and Ru / species, metal ions in which octahedral coordination is almost universally retained in both redox partners, has been central in recent developments to parameterize metal centered redox processes as a function of ligand donor and acceptor capacity. The chemistries of Os and Os are, therefore, intimately linked, and have been extended to studies of important mixed valence Os / binuclear and polynuclear species (see Mixed Valence Compounds). For the purposes of brevity and convenience, this section will deal with Os and Os complexes together. The extensive literature on Os / complexes has been developed with a very wide range of donor ligands a comprehensive assessment of this work is beyond the scope of this article, and the reader is directed to published comprehensive reviews. " ... 

Carbene Complexes Carbonyl Complexes ofthe Transition Metals Cyanide Complexes of the Transition Metals Dinuclear Organometallic Cluster Complexes Electron Transfer in Coordination Compounds Electron Transfer Reactions Theory Electronic Structure of Organometallic Compounds Luminescence Nucleic Acid-Metal Ion Interactions Photochemistry of Transition Metal Complexes Photochemistry of Transition Metal Complexes Theory Polynuclear Organometallic Cluster Complexes. 

The designation of central atom and ligands, generally straightforward in mononuclear complexes, is more difficult in polynuclear compounds where there are several central atoms in the compound to be named, e.g. in polynuclear coordination compounds, and chain and ring compounds. In each case, a priority order or hierarchy has to be established. A hierarchy of functional groups is an established feature of substitutive nomenclature Table VI shows an element sequence used in compositional and additive nomenclature. 

The reactions involved in the chrome-tanning process are those of coordination complexes. They involve the interaction between charged carboxyl groups on the collagen macromolecule and polynuclear chromium(III) coordination compounds. The most widely used chrome-tanning material is 33% basic chromium(III) sulfate produced industrially by reducing sodium dichromate with sulfur dioxide. 

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