Synthesis of coordination compounds

Coordination compounds have been produced by a variety of techniques for at least two centuries. Zeise s salt, K[Pt(C2H4)Cl3], dates from the early 1800s, and Werner s classic syntheses of cobalt complexes were described over a century ago. Synthetic techniques used to prepare coordination compounds range from simply mixing the reactants to employing nonaqueous solvent chemistry. In this section, a brief overview of some types of general synthetic procedures will be presented. In Chapter 21, a survey of the organometallic chemistry of transition metals will be presented, and additional preparative methods for complexes of that type will be described there. 

One of the techniques for producing coordination compounds is to simply combine the reactants. Some reactions may be carried out in solution, but others may involve adding a liquid or gaseous ligand directly to a metal compound. Some reactions of this type are the following  

The product obtained during the second reaction, [Cr(en)3]2(S04)3(s), is a solid mass. It has been found advantageous to dissolve ethylenediamine in an inert liquid that has a high boiling point such as toluene. Refluxing this solution while adding solid Cr2(S04)3 slowly gives a finely divided product 

An example of a synthesis utilizing a nonaqueous solvent is a common procedure that is used to prepare [Cr(NH3)s]Cl3. The reaction is 

It has been found that this reaction is catalyzed by sodium amide, NaNH2. The function of the catalyst 

It should be mentioned that the premier reference work on reactions of complexes in solution is the book by F. Basolo and R. G. Pearson, Mechanisms of Inorganic Reactions (see reference list). 

Because of the large number of types of coordination compounds, it should not be surprising to find that a wide variety of synthetic methods are used in their preparation. A brief survey of several of the widely used methods will be presented here, but others used in preparing complexes of olefins and metal carbonyls will be described in Chapter 21. The suggested readings at the end of this chapter give a more detailed treatment of this topic. 

The use of coordination compounds in SCFs is rather larger than one might initially expect [1]. The major applications can be divided into two broad categories (1) the transport of metals, which includes selective extraction, deposition of metal and oxide films and impregnation of metals as a route to composite materials and (2) synthesis and reactions, which covers a wide range of topics from the synthesis of oxides and other solid state materials to the reactions of organometallic compounds. This chapter focuses on the synthesis of organometallic compounds because this is the area where the majority of the new experimental techniques have been developed. The chapter complements chapter 3.1 and 3.2 which cover, respectively, vibrational and NMR spectroscopy, because IR spectroscopy, and to a lesser extent NMR, have been key tools in the exploration of this chemistry. 

The chapter is divided into four parts Strategy, which explains the rationale for carrying out these reactions in SCF solution Chemistry, which outlines what the reactions are Equipment, which describes some of the key components and introduces a modular approach to high pressure experiments and Synthesis, which gives details of how to make particular compounds, including the use of flow reactors and semiflow reactors. It concludes with a brief summary and outlook. 

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Synthesis of coordination compounds and catalysis with participation of fluoro derivatives of alkaloids 98KK3. 

Chiral cyclic esters of phosphonic acid in the synthesis of coordination compounds and homogeneous asymmetric catalysis 99KK83. 

The application of reaction mechanisms to the synthesis of coordination compounds. J. L. Burmeis-ter, Prep. Inorg. React., 1968, S, 1-43 (211). 

The purpose of this review is to provide the reader with a scenario of what can be accomplished with nickel complexes. It is useful to do this via a series of broad schemes, hypothetical in some cases, which show the main reaction patterns, without considering mechanistic details. Examples will illustrate the various processes, but extension to other substrates or to different conditions often requires use of alternative ligands or solvents, or a change from a neutral complex to a cationic or anionic species, as indicated above. For references to syntheses with nickel see Baker et al. (10). For criteria for the synthesis of coordination compounds and stability of organotransition metal complexes in general, see references (11. 12). Organometallic literature has been collected periodically by Bruce (13). 

Baghurst, D.R., Cooper, S.R., Greene, D.L., Mingos, D.M.P. and Reynolds, S.M., Application of microwave dielectric loss heating effects for the rapid and convenient synthesis of coordination compounds, Polyhedron, 1990, 9, 893. 

In relation to the synthetic direction of the present monograph, we would like especially to mention that the theoretical approach of Lewis is the basis of preparative techniques in the synthesis of coordination compounds described later (Chap. 3) interaction of the ligands with metal salts or carbonyls (Sec. 3.3.1) is described by Schemes (1.1) and (1.2), ligand exchange (Sec. 3.3.2.1) by Schemes (1.3) and (1.6), metal exchange (Sec. 3.2.2) by Schemes (1.4) and (1.7) ... 

It is worth noting that preparative techniques for the synthesis of coordination compounds, formed by ligands such as N2, 02, H-, Hal-, CN-, CO, NO, COS, and CS2, are treated in an excellent handbook [113]. 

Kukushkin, V.Yu., Kukushkin, Yu.N. Theory and Practice of the Synthesis of Coordination Compounds. Nauka Leningrad, 1990, 260 pp. 

Direct Synthesis of Coordination Compounds. (Edit. Skopenko, V.V.). Ventury Kiev, 1997, 172 pp. 

Other Kinds of Direct Synthesis of Coordination Compounds... 

Other important methods of synthesis of coordination compounds are discussed in detail [1,3,10,11,53,201,202,206,207,316,318,322,690]. In this respect, we emphasize the synthesis of metal-polymers [690,691] and preparation of complexes in the solid phase (mechano- or tribosynthesis) [10,201,202,206]. Additionally to the above-described techniques, the general methods and principles of synthesis of coordination compounds are used to obtain metal-polymers (immediate interaction of polymer ligands and metal salts, template electrosynthesis, polymer-analogous transformations). The last method consists of the polymerization of metal-monomers (metal-containing monomers) and fixation of metal complexes on the polymer... 

Synthesis of Coordination Compounds with Programmed Properties... 

This type of synthesis of coordination compounds (which could be named controlled, selective, guided, or programmed ) is related with obtaining metal complexes having beforehand programmed quantitative and qualitative composition, structure, physicochemical, and practically useful properties. 

An approach to the regioselective synthesis of metal complexes was offered based on the joint use of chemical and electrochemical methods of synthesis of coordination compounds departing from the same ligands [11], for instance transformation (4.37). As a result of these reactions, chelates with the participation of different N atoms of the imidazole ring, of the ligand in coordination, are formed ... 

SOME APPLICATIONS OF PROGRAMMED SYNTHESIS OF COORDINATION COMPOUNDS... 

Neutral polydentate ligands are widely used for the synthesis of coordination compounds of transition metal ions. -i When different synthetic routes are possible for a given ligand, those which give the highest yields with the least number of steps and minimize the number of possible isomeric or by-products will obviously be preferred. The above criteria may be exemplified by a series of neutral tetradentate ligands of the tripod or umbrella type with a nitrogen atom as the top donor these may be described as 2-substituted triethylamine derivatives (I) ... 

Although known for many years, perfluorinated alkanes and ethers are becoming widely used as solvents for biphasic catalysis. They have not been employed as solvents for the synthesis of coordination compounds although metal complexes dissolve in them when suitable modifications are made to the ligands (see Chapter 1.38). 

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