Coordination chemistry work

To our knowledge, the results presented in this chapter provide the first example of enantioselective Lewis-acid catalysis of an organic reaction in water. This discovery opens the possibility of employing the knowledge and techniques from aqueous coordination chemistry in enantioselective catalysis. This work represents an interface of two disciplines hitherto not strongly connected. 

Of all the work described in this thesis, this discovery is probably the most significant. Given the fact that the arene - arene interactions underlying the observed enantioselectivity of ftie Diels-Alder reactions described in Chapter 3 are also encountered in other organic reactions, we infer that, in the near future, the beneficial influence of water on enantioselectivity can also be extended to these transformations. Moreover, the fact that water can now be used as a solvent for enantioselective Lewis-add catalysed reactions facilitates mechanistic studies of these processes, because the number of equilibria that need to be considered is reduced Furthermore, knowledge and techniques from aqueous coordination chemistry can now be used directly in enantioselective catalysis. 

There are several exceUent sources of information about the platinum-group metals. The exceUent reference work G. Wilkinson, R. D. GiUard, and J. A. McCleverty, eds.. Comprehensive Coordination Chemistry Pergamon Press, Oxford, U.K., 1987, contains iadividual chapters devoted to descriptive chemistry of each element. 

Exciting developments have occurred in the coordination chemistry of the alkali metals during the last few years that have completely rejuvenated what appeared to be a largely predictable and worked-out area of chemistry. Conventional beliefs had reinforced the predominant impression of very weak coordinating ability, and had rationalized this in terms of the relatively large size and low charge of the cations M+. On this view, stability of coordination complexes should diminish in the sequence Li>Na>K>Rb> Cs, and this is frequently observed, though the reverse sequence is also known for the formation constants of, for example, the weak complexes with sulfate, peroxosulfate, thiosulfate and the hexacyanoferrates in aqueous solutions. 

We should also like to acknowledge the way in which the staff at the publisher, particularly Dr Colin Drayton and his dedicated editorial team, have supported the editors and authors in our endeavour to produce a work which correctly portrays the relevance and achievements of modern coordination chemistry. 

The lithium phosphonium diyiides 1, first described by Wittig and Rieber (R=H) [45] were until recently mainly used as ligands in coordination chemistry [46]. These species also constitute excellent tools in organic synthesis [47], still recently attested by works described below (Scheme 9). 

Example provides more practice in working with the names of coordination compounds. Our Chemical Milestones Box describes the detective work that led to the birth of coordination chemistry. 

The choice of metal ion in this work is interesting since it has been known for a considerable time that Ag+ is a rare example of a d-block metal ion that does not disrupt the duplex DNA structure (172,173). Rationalization of this effect has tended to focus on the possible base-pair crosslinking due to the preferred linear coordination geometry of Ag1 ions (174). The importance of Ag+ DNA coordination chemistry to the procedure described is not clear. However, reports that other metal ions, e.g., Pdri (175), can be plated to DNA to fabricate metallic wires (Fig. 51) suggests that this may not be essential. 

The trivalent Co coordination chemistry of amines is simply immense. Amines, both mono- and multidentate, are typically thermally and air stable, often commercially available, easily deriva-tized, and are well matched to the electronic needs of trivalent Co. Space does not permit a discussion of all categories of amines that have been investigated since CCC(1987) nor their limitless permutations when bound to mostly six-coordinate Co. Much of the synthetic and mechanistic work that underpins Co amine chemistry has long been known and will not be restated here. The emphasis here will be on novelty rather than breadth. That is, recent innovative aspects of the structure, reactivity, and applications of selected, but representative, collections of these simple but ever-present compounds will be our focus. 

The basic properties of nickel and the coordination chemistry of nickel reported until 1983 have been comprehensively described in Comprehensive Coordination Chemistry (CCC, 1987). Hence, work published prior to 1983 will not be mentioned here, and the reader should generally refer to the respective chapters of CCC—only at some points specific reference to CCC is given. Also, the basic geometric preferences and the electronic and spectromagnetic properties of nickel in its various oxidation states will not be recapitulated, since an excellent overview is included in the first edition and only selected recent advances are added in this second edition. 

This review cannot claim to be a comprehensive account of all the coordination chemistry of zinc since the early 1980s. The approach has been to attempt selection of references by key workers or important results in areas where much work has been carried out. It is hoped that it will be possible by following the key references and articles to gain an overview of achievements and advances in the important areas. In many cases, examples where X-ray structural data is included have been selected preferentially for inclusion. 

Over the subsequent three decades I have often wondered whether there would not be an alternative road to enter the bioEPR field for those of us, like myself, who choose to work in an intrinsically multidisciplinary area such as biochemistry (or microbiology, coordination chemistry, medical chemistry, et cetera) where some practical and theoretical knowledge is required on a broad range of advanced methods and instrumentation. Could one envision a way to short-cut the unpractically time-consuming requirement to work one s way through the physics of EPR without... 

In view of the versatility of A-heterocyclic carbenes as ligands and their structural diversity in silver(i) coordination chemistry, an extension of the work to ligands with two or more carbene moieties was reported. A dinuclear silver(i) complex 52 (Figure 21) with an o-phenylenedimethylene-bridged bis(carbene) ligand has been synthesized in 66% yield from silver(i) oxide and the bis(imidazolium) salt.88 The reaction to synthesize 52 has to be carried out in... 

Although the self-assembly process is easy and convenient to operate, success in obtaining the expected object is still a challenge for chemists. The aims of this article are to summarize the coordination chemistry of amino acids, to review our recent work on 3d-4f heterometallic clusters bearing amino acid ligands, and to expound the effects of several factors of influence on self-assembly, such as presence of a secondary ligand, lanthanides, crystallization conditions, the ratio of Cu2+ to amino acids, and transition metal ions. We hope that our systematic researches on the 3d-4f amino acid clusters can provide a useful framework of reference for the study of other self-assembly systems. 

The chemistry of coordination compounds comprises an area of chemistry that spans the entire spectrum from theoretical work on bonding to the synthesis of organometallic compounds. The essential feature of coordination compounds is that they involve coordinate bonds between Lewis acids and bases. Metal atoms or ions function as the Lewis acids, and the range of Lewis bases (electron pair donors) can include almost any species that has one or more unshared pairs of electrons. Electron pair donors include neutral molecules such as H20, NH3, CO, phosphines, pyridine, N2, 02, H2, and ethyl-enediamine, (H2NCH2CH2NH2). Most anions, such as OH-, Cl-, C2042-, and 11, contain unshared pairs of electrons that can be donated to Lewis acids to form coordinate bonds. The scope of coordination chemistry is indeed very broad and interdisciplinary. 

Some of the important types of coordination compounds occur in biological systems (for example, heme and chlorophyll). There are also significant applications of coordination compounds that involve their use as catalysts. The formation of coordination compounds provides the basis for several techniques in analytical chemistry. Because of the relevance of this area, an understanding of the basic theories and principles of coordination chemistry is essential for work in many related fields of chemistry. In the next few chapters, an introduction will be given to the basic principles of the chemistry of coordination compounds. 

Preceding reviews on distibines, R2Sb-SbR25,7,66-68 feature mainly the structural aspects in relation to the thermochromic properties of some of these compounds, but also overviews on the earlier work of the coordination chemistry of distibine ligands have been reported.7,68 All the distibines that... 

Table I gives a selection of bare metal cation reactions with neural molecules. As Eller and Schwarz (9) comprehensively reviewed the area of bare metal ion reactions, most of the reactions discussed in this chapter will be of work later than 1990. Earlier work will be used if specific examples show interesting coordination chemistry or if the early examples differ from later work.

Having worked for many years on chemistry and the behavior of Lewis adducts in nonmetallic coordination chemistry, we realized in 1970 that conformational analysis, both experimental and theoretical, of such compounds needed to be developed. 

This review has no final conclusions. The whole matter of P.E. spectra of volatile metal compounds is still under investigation the results obtained until now yield only a partial picture, and there are several fundamental problems still open, so generalized conclusions are not warranted at the present stage of research. However, some points regarding the significance of the P.E. spectroscopic technique in coordination chemistry are already self-evident. We shall try to identify open problems, lines of future research, and precautions to be taken both in the experimental research and in the interpretive work, at least in the form and to the extent suggested by the present partial stage of the development of research in this field. 

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