Copper tetrafluoroborate complexes of the potentially binucleating ligand 1,4-di(2′-pyridyl)aminophthalazine. Mononuclear and polynuclear derivatives

Abstract

Three different copper tetrafluoroborate complexes are obtained from the reaction of copper tetrafluoroborate and the title ligand (PAP) in water. Two crystalline modifications of a six-coordinate mononuclear protonated derivative, [Cu(PAPH) 2 (H 2 O) 2 ](BF 4 ) 4 , a triclinic brown form (I) and a monoclinic green form (II), and a dark green polynuclear complex containing neutral ligand and formulated as [Cu 3 (PAP) 2 (OH) 2 ](BF 4 )(BF 3 OH) 3 •5H 2 O (III), are obtained from the same reaction mixture. The hydrolysis of BF 4 − in water is thought to be responsible for the formation of protonated PAP. In methanol a four-coordinate protonated derivative, [Cu(PAPH) 2 ](BF 4 ) 4 (IV) and a binuclear complex [Cu 2 (PAP) 2 (H 2 O) 2 ](BF 4 ) 4 •0.5MeOH (V), containing neutral ligand, are obtained. The molecular structures of both forms of [Cu(PAPH) 2 (H 2 O) 2 ](BF 4 ) 4 have been determined by single crystal X-ray diffraction. The brown triclinic form (I) belongs to space group [Formula: see text] with a = 9.856(1), b = 12.724(1), c = 9.401(1) Å, α = 101.691(8), β = 96.717(9), γ = 70.145(8)°, V = 1084.4 Å 3 , Z = 1. The green monoclinic form (II) belongs to space group P2 1 /n with a = 12.663(4), b = 9.573(3), c = 18.813(4) Å, β = 107.16(2)°, V = 2178.9 Å 3 , Z = 2. Both complexes have tetragonally distorted six-coordinate structures involving axially bound water molecules and two in plane bidentate protonated ligands. The major difference between the structures involves the axial Cu—O(W) bond lengths (triclinic 2.497(9) Å; monoclinic 2.426(9) Å).