Reactions of copper(II) nitrate with pyridazine (pydz) and crystal structures of catena-[Cu(µ-η2-pydz)(µ-OH)(µ-O2NO)]·H2O and [Cu3(µ-η2-pydz)4(pydz)2(µ-NO3)2(NO3)4]

Abstract

The reactions of Cu(NO₃)₂·3H₂O with pyridazine (pydz) in water and ethanol solutions have been investigated. In water, using a 1 : 1 salt : pydz molar ratio, the polymeric species catena-[Cu(µ-η²-pydz)(µ-OH)(µ-O₂NO)]·H₂O 1 was obtained, whilst with a ratio of 1 : 2 the trinuclear complex [Cu₃(µ-η²-pydz)₄(pydz)₂(µ-NO₃)₂(NO₃)₄]2was isolated. In ethanol a different species 3, not yet characterized, was obtained on employing a ratio of 1 : 1. With a salt:pydz molar ratio close to 1 : 2 the trinuclear species 2 was recovered through a cleaner reaction, while, when a ratio of ca. 1 : 3 was used the mononuclear complex [Cu(pydz)₃(O₂NO)(NO₃)]4 was obtained. The structures of compounds 1 and 2 have been characterized by single-crystal X-ray analysis: 1, monoclinic, space group I2/m(no. 12), a= 10.239(1), b= 6.643(1), c= 12.363(2)Å, β= 103.74(1)°, Z= 4, R= 0.022 for 651 [F_o > 4σ(F_o)] reflections; 2, monoclinic, space group P2₁/n(no. 14), a= 8.957(2), b= 13.687(4), c= 14.945(4)Å, β= 96.06(2)°, Z= 2, R= 0.038 for 2430 [F_o > 4σ(F_o)] reflections. Compound 1 is a linear polymer [Cu ⋯ Cu 3.3215(5)Å], with each metal atom pair symmetrically bridged by a η²-pydz molecule, a hydroxide group and a nitrate. Compound 2 contains a linear trinuclear centrosymmetric array of copper atoms, with the two equivalent Cu ⋯ Cu interactions [3.4057(8)Å] symmetrically bridged by two η²-pydz molecules and a nitrate. Both 1 and 2 exhibit strong exchange coupling between the copper atoms, the room-temperature µ_eff being reduced to 1.08 1 and 2.62 µ_B2.