Two Cobalt(II) Complexes Derived from the Hydrolysis Product of Di-Schiff Base Ligand N,N'-Bis-(1-benzimidazo-2-yl-ethylidene)-ethane-1,2-diamine:Preparation,Characterization and Crystal Structure of the 6-Coordinate Species [CoL_2]X·H_2O (X = ClO_4~-, NO_3~-)

The reactions of Co(ClO4)2·6H2O and Co(NO3)2·6H2O with the di-Schiff base ligand N,N'-bis-(1-benzimidazo-2-yl-ethylidene)-ethane-1,2-diamine (LA) in ethanol have been investigated. The reactions of LA with excess amount of cobalt salts yield the six-coordinate complexes CoL2](ClO4)2·H2O 1 and CoL2](NO3)2·H2O 2 as isolatable products (L = N-(1-benzimidazo-2-yl-ethylidene)-ethane-1,2-diamine), where L is a tri-dentate mono-Schiff base ligand, resulting from the hydrolysis of the precursor di-Schiff base LA. Both complexes were characterized by X-ray crystallography. Crystal data for complex 1: monoclinic, space group P21/c, a = 11.9214(10), b = 23.5828(17), c = 14.0387(12) , β = 135.219(4)o, C22H30Cl2CoN8O9, Mr = 680.37, V = 2780.1(4) 3, Z = 4, Dc = 1.625 g/cm3, μ(MoKα) = 0.876 mm-1, F(000) = 1404, the final R = 0.0725 and wR = 0.1530 for 5726 observed reflections (I > 2σ(I)). Crystal data for complex 2: monoclinic, space group P21/c, a = 18.2162(16), b = 10.0610(6), c = 18.593(2) , β = 130.099(3)o, C22H30CoN10O7, Mr = 605.49, V = 2606.5(4) 3, Z = 4, Dc = 1.543 g/cm3, μ(MoKα) = 0.722 mm-1, F(000) = 1260, the final R = 0.0619 and wR = 0.1429 for 5194 observed reflections (I > 2σ(I)). X-ray diffraction analysis reveals that each cobalt atom in the two complexes is chelated by six nitrogen atoms from two tridentate ligands L, exhibiting a slightly distorted octahedral coordination sphere. In both complexes, the strong hydrogen-bonding interactions between the lattice waters and N-H groups of the ligands result in 1D chains which are further connected by ClO4-(or NO3-) groups to form a 3D framework. In complex 2, the strong π-π interactions increase the stability of the structure.