Imidazolate anion ligand

Reed (94,95) treated Fe(III) and Mn(III) tetraphenylporphyrins with imidazolate anions to obtain polymers that precipitate in high yields. When the ligand is added in excess, the simple 1 2 complex is formed. In the X-ray crystal structure of the Mn(III) polymer, a zig-zag chain is... 

Scheme 11 Direct synthesis of [99mTc(OH2)(L2)(CO)3] from [99mTc04] in water in the presence of [H3BC02H], 30 min, 95 °C, where L2 represents bidenate anionic ligands such as imidazole-carboxylic acid, picolinic acid or 2,4(5)-dipicolinic acid...

Turning to 2-D systems, Fig. 5(a) shows a very simple example in which nickel ions are connected via square planar coordination by imidazolate anions to form a very simple neutral layered structure.16 A more complex case based upon a combination of rare-earth ions with isophthalic acid is shown in Fig. 5(b) the thiophene derivatized version of the same ligand combined with Tb3+ yields a product with enhanced... 

Typical geometries observed for anionic complexes relevant to biological systems include the 2-methylimidazolate (2.002 A (Fe-Nax), 0.65 A out of the mean plane of the porphyrin core), phenolate (1.937A, 0.56 A out of plane), thiolate (2.36-2.37 A, 0.4-0.5 A out of plane) and acetate (2.03 A, 0.64 A out of plane) complexes. Note that in cases where the picket fence porphyrin was used, the anionic ligand (imidazolate, thiolate, " and acetate ) is on the same side of the porphyrin plane as the pivalamide pickets . 

Vanadium(II) heterocyclic amine complexes of the type [VX2L4] and [VL6]X2 (L = heterocyclic amine, e g. pyrazole, imidazole, 2-methylimidazole, benzimidazole, isoquinoline X = anionic ligand) have been known for some time and more recent examples of such complexes include polypyridyl V complexes of the type [V(terpy)(bipy)L] +. Such complexes are obtained as a result of the disproportionation reaction of [V (terpy)Cl3], which yields [V (terpy)2] + and [V 0] + in CH2CI2 suspensions. ... 

Fignre 3 Vanadium-51 chemical shifts for the complexes [CpV(CO)3L], where L is a neutral ligand (g = 0) or an anionic ligand (9=— ). Curly brackets indicate functionalities py = pyridine im = imidazole... 

A case story is represented by histidine (his, 19), whose R substituent is an imidazolyl group. Imidazole itself (imH) is not an ambidentate ligand, but in presence of two Cu ions it releases a proton and, as the imidazolate anion (im ), bridges the two metal centres [33]. Very importantly, the two Cu" ions have to be prepositioned, i.e. they must occupy some fixed position in a given coordinative framework. Moreover, their distance must fit the bite of the ambidentate im ligand. Finally, each copper centre must have a vacant coordination site. 

Iron(III) porphyrins with imidazole anion(s) as ligands have been synthesized in non-aqueous media"" , and are potential models for heme-containing enzymatic species. Metalloporphyrin vr-cation radicals generated electrochemically (but never from iron porphyrins) are models for compound I or horseradish peroxidase " (see 14.8.5.3.2). 

When imidazole is added to ferric-porphyrin complexes of other anionic ligands,... 

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