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(H2O)2](BF4)4, a triclinic brown form (I) and a monoclinic green form (II), and a dark green polynuclear complex containing neutral ligand and formulated as [Cu3(PAP)2(OH)2](BF4)(BF3OH)3•5H2O (III), are obtained from the same reaction mixture. The hydrolysis of BF4− in water is thought to be responsible for the formation of protonated PAP. In methanol a four-coordinate protonated derivative, [Cu(PAPH)2](BF4)4 (IV) and a binuclear complex [Cu2(PAP)2(H2O)2](BF4)4•0.5MeOH (V), containing neutral ligand, are obtained. The molecular structures of both forms of [Cu(PAPH)2(H2O)2](BF4)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 Å3, Z = 1. The green monoclinic form (II) belongs to space group P21/n with a = 12.663(4), b = 9.573(3), c = 18.813(4) Å, β = 107.16(2)°, V = 2178.9 Å3, 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).

Copper complexes of polyfunctional phthalazines. Mononuclear and polynuclear derivatives

“…Previously reported copper complexes of PAP have included binuclear systems involving two metals bound to the same ligand (13) and mononuclear derivatives in which two bidentate ligands are bound to the same metal (19). Polynuclear derivatives involving three copper centres and a binuclear derivative involving two metals bound simultaneously to two tetradentate ligands have also been reported (19).…”

“…Polynuclear derivatives involving three copper centres and a binuclear derivative involving two metals bound simultaneously to two tetradentate ligands have also been reported (19). In a series of binuclear copper carboxylate derivatives of PAP the pKa of the corresponding carbox ylic acid determined whether or not the ligand was neutral or anionic.…”

“…Polyfunctional ligands derived from hydrazine (1 -3), pyrazole (4)(5)(6)(7)(8), pyridazine (4, 9-1 I), and phthalazine (4,9,11,(12)(13)(14)(15)(16)(17)(18)(19) form transition metal complexes in which the metals are brought into close proximity because of the presence of the N,, diazine, fragments in these systems. Antiferromagnetic exchange between the adjacent metal centres has been demonstrated in some of these complexes (4,11,13,15,16,18) and catecholase activity has been shown with binuclear copper complexes of the binucleating ligand 1,4-di(2'-pyridyl) aminophthal- 'To whom all correspondence should be addressed.…”

“…PAP has been shown to bind preferentially to two metal centres forming binuclear complexes with copper, cobalt, nickel, and zinc salts ( 13,15,16,18,19). Antiferromagnetic exchange exists between the metal centres in cobalt, nickel, and copper complexes of PAP (13,15,16,18).…”

“…I. PAP (R = H), PAP4Me (R = 4 methy I), PAP6Me (R = 6 methyl). mononuclear (l:2) complexes are obtained as initial products, in certain reactions, followed by binuclear or polynuclear derivatives containing neutral ligand (18,19).…”