Perchlorate group, complexes with

In a similar manner, the potentially sexadentate macrocycle (21) yields Pb(n) and Cd(n) complexes which have unusual geometries (Drew etal., 1979). With Pb(n), the stereochemistry is hexagonal pyramidal with one axial site occupied by a water molecule and the other filled by a sterically-active lone pair of electrons on the metal ion. The Cd(n) complex is eight-coordinate (with a water molecule and a perchlorate group occupying axial positions) however the cadmium ion is not held centrally in the macrocyclic hole but is displaced to one side, presumably reflecting the... 

Coordination of the aluminum atom of the reducing complex was proposed to take place both to the oxygen atom of the hydroxy group and to the nitrogen atom of the amino group. The asymmetric reduction of enamine perchlorates and ketimines with menthol and bomeol chiral auxiliary reagents (50,51) presumably involves coordination of aluminum to the nitrogen atom of the substrate. 

Figure 2.10. Example of a donor-acceptor fluoroionophore in which the electron-withdrawing character of the acceptor (carbonyl group of the coumarine) is cation-controlled. Absorption and fluorescence spectra of ClS3-crown(Oj) and its complexes with perchlorate salts in acetonitrile. (Adapted from Ref. SO.)...

Castellani Bisi (98) has synthesized complexes of lanthanide perchlorates with DMP which have a L M of 8 1 for the lighter lanthanide and 7 1 for the heavier lanthanide complexes. These complexes were prepared by reacting the respective metal salts with an excess of the ligand. When the complexes were prepared under conditions of lower concentrations of the ligand, complexes of DMP with a L M of 6 1 were obtained. The perchlorate groups in all three groups of complexes are ionic. 

Substitution at the 2-position of the pyridine ring in PyO introduces steric hindrance to coordination as is evident from the formation of Heptakis-2-MePyO complexes with lanthanide perchlorates (167) and pentakis-2-MePyO complexes with the corresponding bromides (168), iodides (162) and chlorides (169). The lanthanide nitrate complexes prepared by Ramakrishnan and Soundararajan (170) have the formula Ln(2-MePy0)3(N03)3 -xH20in which all the nitrate groups are bidentate. 

Vicentini and Dunstan (227) have obtained tetrakis-DDPA complexes with lanthanide perchlorates in which the perchlorate groups are shown to be coordinated to the metal ion. DDPA also yields complexes with lanthanide isothiocyanates (228) and nitrates (229). All the anions in these complexes are coordinated. DPPM behaves more or less like DDPA which is reflected in the stoichiometry of the complexes of DPPM with lanthanide perchlorates (230), nitrates, and isothiocyanates (231). Hexakis-DMMP complexes of lanthanide perchlorates were recently reported by Mikulski et al. (210). One of the perchlorate groups is coordinated to the metal ion in the lighter lanthanide complexes, and in the heavier ones all the perchlorate groups are ionic. 

Perchlorate ion complexes, 28 255-299 with cobalt group metals, 28 265-268 coordination types, 28 256-260 with copper group metals, 28 273-283 with early transition metals, 28 260-263 electronic spectra. 28 258-259 ESR spectra, 28 260 infrared and Raman spectra, 28 257-258 with iron group metals, 28 263-265 with lanthanides, 28 260-265, 287-288 magnetic susceptibility, 28 260 molar conductivities, 28 260 with nickel group metals. 28 268-273 X-ray crystal structure analysis, 28 256-257... 

Uniformly, within this group of cations, perchlorate ion accompanying the transition-element cation is replaced by nitrate (7,31), thiocyanate (7,52), or halide (7,6). Nitrate is probably replaced by thiocyanate, but a secondary change takes place in many systems, which makes direct comparison difficult (see below). If one then makes the further reasonable assumption that solvent interference can be used as an inverse measure of tendency to bind to the central metal cations, thiocyanate, whose competition with alcohol is less efficient (52) than that of chloride (6), should be somewhat replaceable with chloride. Comparisons between chloride and thiocyanate in acetonitrile show also that the formation of a complex with a given anion/cation ratio takes place much more readily with chloride than with thiocyanate (55, 34). By the same criterion, from experiments in alcoholic solution (55), bromide should replace chloride, and an extrapolation of the behavior to iodide seems reasonable. 

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