Polyoxometalate-supported transition metal complexes and their charge complementarity: Synthesis and characterization of [M(OH) < inf > 6 < /inf > Mo < inf > 6 < /inf > O < inf > 18 < /inf > {Cu(phen)(H < inf > 2 < /inf > O) < inf > 2 < /inf > } < inf > 2 < /inf > ][M(OH) < inf > 6 < /inf > Mo < inf > 6 < /inf > O < inf > 18 < /inf > {Cu(phen)(H < inf > 2 < /inf > O)Cl} < inf > 2 < /inf > ]·5H < inf > 2 < /inf > O (M = Al < sup > 3+ < /sup > , Cr < sup > 3+ < /sup > )

Abstract

Two Anderson-type heteropolyanion-supported copper phenanthroline complexes, [Al(OH)6Mo6O18{Cu(phen)-(H 2O)2}2]1+ (1c) and [Al(OH) 6Mo6O18{Cu(Phen)(H2O)Cl} 2]1- (1a) complement their charges in one of the title compounds [Al(OH)6Mo6O18{Cu(phen)(H 2O)2}2][Al(OH)6Mo6O 18{Cu(phen)(H2O)Cl}2]·5H2O ≡ [1c][1a]·5 H2O ≡ 1. Similar charge complementarity exists in the chromium analogue, [Cr(OH)6Mo 6O18{Cu(phen)(H2O)2} 2][Cr(OH)6Mo6O18-{Cu(phen)(H 2O)Cl}2]·5 H2O ≡ [2c][2a]·5 H2O ≡ 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 the formation of intermolecular O-H⋯O hydrogen bonds, have been shown to self-assemble into an "acyclic water trimer" 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) Å, α = 65.4570(10), β = 83.4420(10), γ = 71.3230(10)°, V = 2182.1(2) Å3. Crystal data for 2: a = 10.8867(5), b = 15.2504(7), c = 15.7022(7) Å, α = 64.9850(10), β = 83.0430(10), γ = 71.1570(10)°, V = 2235.47(18) Å3. In the electronic reflectance spectra, compounds 1 and 2 exhibit a broad d-d band at ∼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)6Mo6O18]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 Cu2+ (d9) system, and that of compound 2, containing both chromium(III) and copper(II) ions, may reveal a zero-field-splitting of the central Cr3+ ion of the Anderson anion, [Cr(OH)6Mo6O18]3-, with an intense peak for the Cu2+ ion. © 2005 American Chemical Society.