Bidentate and tridentate

Poly(pyrazolyl)borato ligands offer a variety of coordination modes according to their degree of substitution. Bis and tris(pyrazolyl)hydro-borato derivatives tend to adopt bidentate and tridentate coordination modes almost exclusively (5), while the tetrakis(pyrazolyl)borato ligand... 

The structure of [pzTp]2GaMe, determined by x-ray diffraction, demonstrates that the [pzTp] ligands adopt both bidentate and tridentate coordination. However, in solution, the complexes [Tp]2GaMe and [pzTp]2GaMe are fluxional on the NMR time scale at room temperature, exhibiting a single set of resonances for the pyrazolyl groups. 

The 1,2,4-triazole system has been found to be particularly suited towards generating spin crossover behaviour in Fe(II)N6 derivatives of the simple molecule and in bidentate and tridentate systems containing at least one... 

Ai,Ai -Diphenylbenzamidine undergoes metaUation in toluene, the crystalline precipitate (232) is probably polymeric and contains solvating toluene (average 0.7 mol per Li atom). The lithium imidinate solid produced in the presence of HMPA is dimeric (233) whereas the solids obtained in the presence of bidentate and tridentate ligands (e.g. TMEDA and PMDTA) are monomeric (234 and 235). The products were characterized by H NMR spectra and XRD crystallography, except for 232, for which no crystals suitable for XRD could be prepared . 

There are numerous examples of this type of complex. The majority are seven-coordinate some representatives are given in Table 8. With bidentate and tridentate ligands, when the... 

The advances that have taken place over the past five years in catalytic, enantioselective aldol addition reactions is evident in a number of important respects. The types of transition metals and their complexes that function competently as catalysts have been expanded considerably. Thus, in addition to B(III), Ag(I), Au(I), Sn(II), and La(III), chiral catalysts prepared from Cu(II), Ti(IV), Ln(III), Si(IV), Pt(II) and Pd(II) have been introduced. The expansion in the use of transition metals has taken place hand-in-hand with the design and synthesis of new bidentate and tridentate organic ligands based on nitrogen, oxygen, and phosphorus donors. Additionally, whereas the older methods primarily relied on the use of Lewis-acids for the activation of... 

A variety of Cr(III)- and Co(III)-nucleotides have been synthesized and their diastereomers separated and characterized. Since these metals form octahedral hexacoordinate complexes, some of the coordination positions must be occupied by ligands other than the nucleotide in monodentate, bidentate and tridentate metal-nucleotide complexes. The most widely used Cr(III) complexes contain coordinated water at these positions, although those with coordinated ammonia are also known. The known, stable Co(III) complexes contain ammonia at the additional coordination positions. Although other nitrogen ligands can also be used, complexes with coordinated water are too unstable to be isolated and characterized under the usual laboratory conditions. 

The reactions of these trihalo-tetracarbonyl anions with monodentate, bidentate/ and tridentate donor ligands also have been investigated. 

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