Structural and spectroscopic characterization of a dicyanooxomolybdenum(IV) complex with a tetradentate schiff-base ligand

Abstract

The reaction of protonated tetracyanodioxomolybdate(IV) ion with 2-acetylpyridine and ethane-1,2-diamine gave a new complex of formula [MoO(CN)₂(L–L–L–L)]·H₂O, where L–L–L–L =N,N′-bis[1-(pyridin-2-yl)ethylidene]ethane-1,2-diamine. The structure of this salt was determined by X-ray analysis. Principal dimensions (ranges or means; estimated standard deviation ±0.006 Å) are MoO 1.689, Mo–C 2.157 and 2.168, Mo–N 2.273–2.329 Å. The crystals are monoclinic, space group C2/c, a= 31.789(2), b= 8.194(1), c= 15.198(1)Å, β= 104.08(1)°, Z= 8, R= 0.032 for 4249 observed [F/σ(F) > 4] reflections. The molybdenum is seven-co-ordinated with the L–L–L–L ligand and oxygen in one plane and cyanide ligands above and below this plane. The structure contains water molecules which form a network of hydrogen bonds with cyanide ligands. The IR and ESR spectra, as well as the results of ion-exchange and electrophoresis experiments, are in agreement with this structure. The visible spectra in various solvents are dominated by metal-to-ligand charge-transfer bands with absorption maxima linearly dependent on the Reichardt E_T parameter. The complex undergoes one step, two-electron, reversible oxidation with E_½= 0.77 V.