Neutral bidentate complexes

Oximes can act both as anionic and neutral ligands. Complexes of Box (134), DBox (135), Fox (136), BMox (137) and DAMox (138) with lanthanide chlorides have been reported. These oximes act as bidentate ligands coordinating through the oxygen of the C=0 or the C-O—H group and the oxime group. 

Solution studies on the compounds [BU4N] [M(R2NCS2)3] (M = Zn or Cd R = Me or Et) show the zinc complex (unlike the cadmium complex) to be some 90% dissociated into the neutral bis complex and the free ligand anion. This is in accord with the structure of the solid complex,907 which shows that only one dithiocarbamato group is bidentate, the other two being formally unidentate. 

Neutral bidentate [N2] supporting ligands, chromium complexes, 5, 359... 

Neutral bidentate [P2] ligated derivatives chromium(II) complexes, 5, 365... 

In solution, at room temperature Ru(bpy) does not undergo a photo-induced ligand substitution over a wide pH range, whereas at 95°C complete lab Llization occurs in a few hours. In acidic solution Cr(bpy)3 is photo-inert. At room temperature at neutral or alkaline pH, a bidentate complex is formed rapidly... 

Whereas the enolates of 41a-c function as bidentate ligands towards iron(III) ions and form the neutral mer-complexes 42a-c, the enolates of the same compounds 41a-c should function as tridentate ligands towards iron(II) ions and afford, by spontaneous self-organization [102,103,132], neutral three-dimensional coordination polymers [132-153],... 

At pH 2.0 diols are not ionized and hence complexation occurs with neutral diol molecule. Above pH 2.0 diols are ionized and become bidentate complexing agent. The absorption spectra of lanthanide complexes with the following diols,... 

Studies other than preparative-type transformations have so far been limited to B-pyrazolylpyrazaboles. For example, the latter compounds have been found to react with R BX (where X is a readily leaving group) to form polynuclear boron spiro-cations (see Sect. V.A). It has also been shown that the pyrazolylpyrazaboles offer themselves as a class of neutral bidentate chelating ligands For example, the complexes H2B(pz)jB(pz)2ZnCl2 and Cl2Zn(pz)2B(pz)2B(pz)jZnCl2 were readily accessible by combination of the two reactants in an appropriate solvent. Obviously, a more detailed study of this feature is mandated. 

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