Bridging chlorides and hydroxides: syntheses and crystal structures of binuclear and tetranuclear NiII complexes derived from a reduced Schiff-base ligand 2-(2-pyridylmethylamino)ethanesulfonic acid

Abstract

Two complexes, [Ni(pmt)(Cl)] (1) and [Ni4(pmt)4(OH)4]·8H2O (2) [Hpmt = 2-(2-pyridylmethylamino)ethanesulfonic acid], were synthesized by different experimental methods in methanol-water mixed solution. Compound 1 crystallizes in triclinic, space group P−1 with unit cell parameters: a = 8.315(2) Å, b = 8.383(2) Å, c = 9.128(2) Å, α = 103.654(2)°, β = 98.125(2)°, γ = 113.154(2)°, V = 548.6(2) Å3, Z = 2. A pair of chlorides is μ 2-bridges linking two NiII atoms in forming binuclear complex 1. The coordination environment at NiII is distorted square-pyramidal geometry. Compound (2) belongs to monoclinic, space group C2/c, with a = 16.5168(15) Å, b = 18.3718(17) Å, c = 17.5473(16) Å, α = γ = 90°, β = 93.3820(10)°, V = 5315.3(8) Å3, Z = 4. Four hydroxides are μ 3-bridges joining four NiII atoms to generate a cubic framework as a tetranuclear complex. The configuration at each NiII is distorted octahedral. Both π–π stacking of pyridine rings and intermolecular hydrogen bonds stabilize the solid state structures for 1 and 2.