Crystal structure and magnetic properties of a copper(II)-vanadium(IV) complex of an 'open-ended' dinucleating ligand

The heterodinuclear copper(II)/vanadium(IV) complex, [bpmpCu(Cl)VO(H2O)](ClO4)(2), where bpmp(-) is the ligand 2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenolate(1-), has been prepared in a one-pot reaction from Hbpmp, VCl3 and Cu(ClO4)(2) in air. The X-ray structure shows the complex to be monoclinic, space group C2/c with eight cations in a cell of dimensions a=23.445(3), b=16.392(3), c=20.612(3) Angstrom and beta=106.955(7)degrees. The structure refined to a final R-value of 0.064 for 3379 reflections and 504 variables. The copper and vanadium atoms are bridged by the phenolic oxygen atom of bpmp with V-O-phenolate=1.958(6) Angstrom and Cu-O-phenolate=2.361(5) Angstrom. Two dinuclear units are associated via chloride bridging between the Cu atoms with Cu-Cl= 2.280(3) and 3.226(2) Angstrom. The vanadium is incorporated as a vanadyl ion and also has a water molecule coordinated. Magnetic susceptibility measurements indicate a very weak ferromagnetic coupling (J=0.43 cm(-1)); this probably originates from a Cu ... Cu interaction in the tetranuclear units. The ESR spectrum of [bpmpCu(Cl)VO(H2O)](ClO4)(2) confirms the very weak coupling.