Polyoxometalate-Supported Transition Metal Complexes and Their Charge Complementarity:Synthesis and Characterization of [M(OH)_6Mo_6O_(18){Cu(Phen)(H_2O)_2}_2][M(OH)_6Mo_6O_(18){Cu(Phen)(H_2O) Cl}_2] centre dot 5H_2O (M = Al~(3+) Cr~(3+))

摘要

Two Anderson-type heteropolyanion-supported copper phenanthroline complexes,[Al(OH)_6Mo_6O_(18){Cu(phen)-(H_2O)_2}_2]~(1+) (1c) and [Al(OH)_6Mo_6O_(18){Cu(phen)(H_2O)Cl}_2]~(1-) (1a) complement their charges in one of the title compounds [Al(OH)_6Mo_6O_(18){Cu(phen)(H_2O)_2}_2][Al(OH)_6Mo_6O_(18){Cu(phen)(H_2O)Cl}_2] centre dot 5H_2O ident to [1c][1a] centre dot 5 H_2O ident to 1.Similar charge complementarity exists in the chromium analogue,[Cr(OH)_6Mo_6O_(18){Cu(phen)(H_2O)_2}_2][Cr(OH)_6Mo_6O_(18)-{Cu(phen)(H_2O)Cl}_2] centre dot 5 H_2O ident to [2c][2a] centre dot 5 H_2O ident to 2.The chloride coordination to copper centers of 1a and 2a makes the charge difference.In both compounds,the geometries around copper centers are distorted square pyramidal and those around aluminum/chromium centers are distorted octahedral.Three lattice waters,from theformation of intermolecular O-H.....O hydrogen bonds,have been shown to self-assemble into an "acyclic watertrimer" in the crystals of both 1 and 2.The title compounds have been synthesized in a simple one pot aqueous wet-synthesis consisting of aluminum/chromium chloride,sodium molybdate,copper nitrate,phenanthroline,and hydrochloric acid,and characterized by elemental analyses,EDAX,IR,diffuse reflectance,EPR,TGA,and single-crystal X-ray diffraction.Both compounds crystallize in the triclinic space group P1.Crystal data for 1:a = 10.7618(6),b = 15.0238(8),c = 15.6648(8) A,alpha = 65.4570(10),beta = 83.4420(10),gamma = 71.3230(10) deg ,V = 2182.1(2) A~3.Crystal data for 2:a = 10.8867(5),b = 15.2504(7),c = 15.7022(7) A,alpha = 64.9850(10),beta = 83.0430(10),gamam = 71.1570(10) deg ,V= 2235.47(18) A~3.In the electronic reflectance spectra,compounds 1 and 2 exhibit a broad d-d band at approx 700 nm,which is a considerable shift with respect to the value of 650-660 nm for a square-pyramidal [Cu(phen)_2L] complex,indicating the coordination of [M(OH)_6Mo_6O_(18)]~(3-) POM anions (as a ligand) to the monophenanthroline copper complexes to form POM-supported copper complexes 1c,1a,2c,and 2a.The ESR spectrum of compound 1 shows a typical axial signal for a Cu~(2+) (d~9) system,and that of compound 2,containing both chromium(III) and copper(II) ions,may reveal a zero-field-splitting of the central Cr~(3+) ion of the Anderson anion,[Cr(OH)_6Mo_6O_(18)]~(3-),with an intense peak for the Cu~(2+) ion.