Ligand-ligate complexes

Ligand-ligate complexes able to form in solution may not be able to form when one of the components is immobilized on a porous support. The interference may derive from the nearby support material itself or from other adsorbed proteins (especially... 

Fig. 9.1. Schematic illustration of the elements involved in bio-affinity chromatography. The solute (Lt) is retained on the stationary phase (S) by specific interaction with the ligand (Ln). The ligand is covalently attached to a spacer arm (SP) which is in turn attached to the stationary phase. Elution as shown here is achieved by specific ligand competition by another solute (Lt ). Alternatively the ligand-ligate complex can be disrupted by reversible denaturation using low pH solvent or mild chaotropic salts, e.g.

A number of highly active ethylene polymerisation catalysts have resulted from the combination of functionalised NHC ligands with Ti, the first of these was the bis(phenolate)carbene ligated complex 3 [8], Upon activation with modified MAO (MMAO), this species gave an activity of 290 kg-mol bar h in the one test reported, making it one of the most active carbene-based olefin polymerisation catalysts known. In later work the same complex was evaluated with straight MAO activation, and activities of up to ca. 100 kg mol -bar" -h" were reported for linear polyethylene production [9],... 

Phosphites have been used as ligands in Rh-catalyzed hydroformylation from the early days since their introduction in 1969.205 206 Identification of complexes occurred more recently. Ziolkowski and Trzeciak have studied extensively the use of phosphite ligands in the Rh-catalyzed hydroformylation of alkenes.207-210 The ligand tris(2-/er/-butyl-4-methylphenyl) phosphite (65) leads to extremely fast catalysis and in situ spectroscopy showed that under the reaction conditions only a mono-ligated complex [Rh(H)(CO)3(65)], (66), is formed due the bulkiness of the ligand.211-213... 

On mixed ligated complexes of palladium(II) and platinum(II), the cis coordination of the NHC and a phosphine ligand is thermodynamically favored. i27,261,262 Thermal isomerization was reported for tra i -[(NHC)2Cr(CO)4] (M = Cr, Mo) to the ds-complex. For [(NHC)2Mo(CO)4] this proceeds even in the solid state. A barrier of rotation due to a double-bond character of the metal-NHC bond could not be determined so far. This is in agreement with the single-bond character of the metal-carbon bond. Barriers of rotation determined so far are due to steric hindrance. 

AP as well as HRP as part of a ligand/ligate (antigen/antibody) complex is detected very sensitively by chemiluminescence. 

The assembly formation of heterobidentate ligated complexes was studied in detail using bidentate ligand 13"b as a typical example (Figure 8.8). UV/Vis titrations and NMR spectroscopy experiments showed that the pyridyl moiety of b selectively coordinates to thezinc(ii)porphyrinl3withabindingconstantofK(ib) = 3.8x lO m. An increase in the Kfor 13 b to 64.5 X lO was observed in the presence of metal... 

Chromium complexes (continued) organohalide activation, 5, 381 with phosphine-based supporting ligands, 5, 365 porphyrin-ligated derivatives, 5, 364 pyridinebis(imine) ligand derivatives, 5, 361 salen-ligated complexes, 5, 379 surface chemistry on oxides, 12, 525 tetradentate [04] compounds, 5, 352 tetradentate thioether derivatives, 5, 365 thiolate-bridged, Fe- and Rh complexes, 5, 308 with Ti(IV), 4, 627... 

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