Perchlorates bridging ligand

With a view to determining the equilibrium constant for the isomerisation, the rates of reduction of an equilibrium mixture of cis- and rra/i5-Co(NH3)4(OH2)N3 with Fe have been measured by Haim S . At Fe concentrations above 1.5 X 10 M the reaction with Fe is too rapid for equilibrium to be established between cis and trans isomers, and two rates are observed. For Fe concentrations below 1 X lO M, however, equilibrium between cis and trans forms is maintained and only one rate is observed. Detailed analysis of the rate data yields the individual rate coefficients for the reduction of the trans and cis isomers by Fe (24 l.mole sec and 0.355 l.mole .sec ) as well as the rate coefficient and equilibrium constant for the cw to trans isomerisation (1.42 x 10 sec and 0.22, respectively). All these results apply at perchlorate concentrations of 0.50 M and at 25 °C. Rate coefficients for the reduction of various azidoammine-cobalt(lll) complexes are collected in Table 12. Haim discusses the implications of these results on the basis that all these systems make use of azide bridges. The effect of substitution in Co(III) by a non-bridging ligand is remarkable in terms of reactivity towards Fe . The order of reactivity, trans-Co(NH3)4(OH2)N3 + > rra/is-Co(NH3)4(N3)2" > Co(NH3)sN3 +, is at va-... 

Complexes of PyzO with lanthanide perchlorates (2 79) and hexafluorophosphates 180) are eight coordinate. However, La(III) perchlorate gives the complex La(Pyz0)7(C104)3 2 H20 in which both the water molecules are coordinated to La(III). In the case of complexes of PyzO with lanthanide chlorides 180), the number of coordinated ligands increases as the ionic radius of the lanthanide ion decreases. These complexes probably contain bridging ligands. 

A novel peroxocopper complex with -coordination is formed when copper(II) perchlorate is reacted with the tridentate ligand 4-methyl-2,6-bis(pyrrol-idinomethyl)phenol (HL) in methanol solution, in the presence of air, triethyl-amine base, and 3,5-di-teri-butylcatechol [142], The four copper(II) ions in [Cu4L2(02)(0Me)2(C104)] (32) form a near-planar rectangle, with alternate methoxo (Cu... Cu = 3.03 A) and phenolato (Cu... Cu = 2.99 A) bridging ligands. 

Stable as well as transitory perchlorate-coordinated species are convenient intermediates for the isolation of novel complexes. With four potential donor sites, the role of C104 acting as a bridging ligand perhaps has interesting possibilities yet to be revealed. 

Ti in [Ti(> 2-Cl04)4] and Ni" in [Ni(>j -C104)L2] where L is a chiral bidenlate organic ligand.Sometimes both and modes occur in the same compound. The biden-latc bridging mode occurs in the silver complex [Ag /x,>j -00(0)20- (m-xylene)2]- The structure of appropriate segments of some of these compounds arc in Fig. 17.23. The distinction between coordinated and non-coordinaied ( ionic ) perchlorate is sometimes hard to make and there is an almost continuous... 

Figure 17.23 F.xamples of monodentate. ehelaiing and bridging perchlorate ligands.

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