Synthesis from Ionic Complexes

Anionic metal complexes may react with organic dihalogeno compounds to form carbene complexes. Similarly, metal carbenes may be obtained by reactions of hydrido complexes with compounds possessing active hydrogen. 

Like the organic dihalides, dialkyl(chloromethylene)ammonium chlorides react with many transition metal complexes. This method allows preparation of carbene complexes in which central atoms possess high oxidation states. 

---

The only reports of directed synthesis of coordination complexes in ionic liquids are from oxo-exchange chemistry. Exposure of chloroaluminate ionic liquids to water results in the formation of a variety of aluminium oxo- and hydroxo-contain-ing species [4]. Dissolution of metals more oxophilic than aluminium will generate metal oxohalide species. FFussey et al. have used phosgene (COCI2) to deoxochlori-nate [NbOa5] - (Scheme 6.1-1) [5]. 

The direct synthesis of neutral phosphenium complexes was reported from ionic... 

The above characterizations primarily concern the interactions between molecular solutes and ILs. However, ILs are also good solvents for ionic compounds, and have been studied extensively as media for transition metal catalysis [4, 38, 219] and for the extraction of heavy metals [23]. ILs are capable of solvating even simple salts, such as NaCl, to some degree [219], and in fact the removal of halide impurities resulting from synthesis can be a considerable challenge [68]. However, ionic complexes are generally far more soluble than simple salts [220], and we focus our attention on these systems as they have received greater study and are more relevant to the processes noted above. 

Figure 2.27 ORTEP diagram of [Na(DB18C6)H20][Tb(L )2] with the thermal ellipsoids drawn at the 30% probability level and the hydrogen atoms removed for clarity [59]. (Reprinted with penmssion from P.N. Remya, S. Bijn, M.L.P. Reddy, A.H. Cowley and M. Findlater, ID Molecnlar ladder of the ionic complex of terbinm-4-sebacoylbis( 1 -phenyl-3-methyl-5-pyrazolonate) and sodium dibenzo-18-crown-6 synthesis, crystal structure, and photophysical properties, Inorganic Chemistry, 47, 7396-7404, 2008. 2008 American Chemical Society.)...

The second factor which frequently leads to difficulties in isolation and purification arises from the exceptional solvent properties of amides—both liquid and solid. Many ionic compounds such as salts, water, and a large variety of covalent compounds, including aromatic hydrocarbons, have an appreciable solubility in many amides. The amides, in turn, may exhibit an appreciable solubility in very diversified solvents. Clearly, this situation may bedevil a synthesis with extremely complex solubility distribution coefficient problems. Vapor phase chromatography has been used in our laboratories to advantage in determining whether the amide has been adequately separated from... 

Synthesis of supported bimetallic and multimetallic particles. Supported bimetallics have been prepared from combinations of monometallic or from bimetallic cluster precursors. In the ideal case, the resulting metals are segregated on an oxide surface, sometimes with one metal present as zerovalent aggregates and the other present as ionic complexes. Occasionally, the metals are found in small bimetallic clusters, whereas the product formed from separate monometallic precursors may yield aggregates of segregated metals. 

Catalysis at interfaces between two immiscible liquid media is a rather wide topic extensively studied in various fields such as organic synthesis, bioenergetics, and environmental chemistry. One of the most common catalytic processes discussed in the literature involves the transfer of a reactant from one phase to another assisted by ionic species referred to as phase-transfer catalyst (PTC). It is generally assumed that the reaction process proceeds via formation of an ion-pair complex between the reactant and the catalyst, allowing the former to transfer to the adjacent phase in order to carry out a reaction homogeneously [179]. However, detailed comparisons between interfacial processes taking place at externally biased and open-circuit junctions have produced new insights into the role of PTC [86,180]. 

---