Group 13 elements chelates

Metal hydroxides of first- and second-group elements can enhance ortho substitution, the degree of which depends on the strength of metal-chelating effects linking the phenolic oxygen with the formaldehyde as it approaches the ortho position. Transition metal ions of elements such as Fe, Cu, Cr, Ni, Co, Mn, and Zn as well as boric acid also direct ortho substitutions via chelating effects (Fig. 7.9). 

Halet )-F, Saillard )-Y (1997) Electron Count Versus Structural Arrangement in Clusters Based on a Cubic Transition Metal Core with Bridging Main Group Elements. 87 81-110 Hall DI, Ling JH, Nyholm RS (1973) Metal Complexes of Chelating Olefin-Group V Ligands. 15 3-51... 

With the exception of a brief report of a dimethylaluminum complex [5], the coordination chemistry of the monomeric anion in (4) has not been investigated. By contrast, Stahl and co-workers have carried out extensive studies of both main group element and transition-metal complexes of the chelating dianion in the cube (7), which have been summarized in a recent review [9]. A noteworthy feature of the ligand behaviour of this N,N chelating dianion is the additional in-... 

Although chelating resins were widely used to preconcentrate and to separate elements and group elements in seawater [209], the first report on related HPCIC was made by Moyers and Fritz [210] in late 1977. The main principles of HPCIC were later formulated and studied by Timerbaev et al. [211] and Jones et al. [212]. 

The methine proton in the keto form and the hydroxyl proton in the enol form of jS-diketones are acidic and their removal generates 1,3-diketonate anions (2), which are the source of an extremely broad class of coordination compounds referred to generically as diketonates or acetylacetonates. The synthesis, structure and properties of these compounds form the focus of this chapter. Di-ketonate anions are powerful chelating species and form complexes with virtually every transition and main group element. The scope of this chemistry is very large and it has been assessed earlier in several excellent reviews.9-14... 

The heterocyclic complexes incorporating other main group element atoms have been prepared via the reaction of RBiBr2 with an appropriate difunctional salt or chelating ligand (see equations 7 and 8). The compound (21) is reported to have anticoccidial and insecticidal properties, as do other RBi(SR)2 compounds. 

Table 9. Dark conductivities (compressed powders) of some N4-chelates containing IVa-group elements and oxygen in the chain...

Alternatively, the ligand may occupy a terminal site, as shown in 4 or 5 (X=S). The tendency for the new ligand formed as a result of aminometallation to behave in a bidentate fashion, as in 3, 6, or 7, depends on whether the metal or metalloid has adequate Lewis acidity and is otherwise coordinatively unsaturated. Consequently, among main group elements M, chelation or bridging is most frequently found among the s-block, group IIIB, or electropositive (e.g., Sn", raher than SP) elements and is commonly encountered in transition metal complexes. 

The product (with en = 1,2-ethanediamine chelated) can be isolated readily. The transition metal carbonyls are usually far more robust than those formed by main group elements for example H3B(CO) decomposes below room temperature, whereas Cr(CO)6 can be sublimed without decomposition. 

Addition of an aqueous phase chelating reagent such as EDTA enhanced the separation factors to 2.2 for adjacent yttrium group elements. Addition of DTPA enhanced the separation factor to 3.5 for adjacent cerium group elements. 

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