Some Di- and Tri-nuclear Compounds of Copper(II) with 4-Amino-4-methylpentan-2-one Oxime; Structures and Magnetism

Abstract

Green [{Cu(amox)(amoxH)}₂](NO₃)₂ (amoxH = 4-amino-4-methylpentan-2-one oxime) has twofold symmetrical, oximato-bridged, dinuclear cations. Each copper(II) ion is bonded to the nitrogen atoms of one bidentate amox ^– and one bidentate amoxH (marked *) ligand {Cu–N_amine 2.039(4), 2.006(4)* Å and Cu–N_oxime 1.975(5), 2.192(5)* Å}. The dinuclear cations have bonds between each copper(II) ion and the oximato oxygen atom of the other (marked #) unit {Cu–O# 2.062(4) Å, Cu–Cu# 3.801(5) Å}. The copper(II) ion is in asymmetrical trigonal-bipyramidal coordination, with N_amine*–Cu–Noximate axial {176.5(2)˚}, and N_amine–Cu–O# {136.6(2)˚}, N_amine–Cu–N_oxime* {126.2(2)˚} and N_amine–Cu–O# {96.9(2)˚} equatorial [orthorhombic, Pbcn, a 12.218(1), b 23.361(3), c 12.275(1) Å, Z 4, R₁ 0.057 for 2239 reflections]. The magnetic susceptibility values follow the Curie Weiss relation, with q = –10(2) K. Dark-green [{{Cu(amox)}₃O}₂H] (ClO₄)₃·3H₂O has threefold symmetrical trinuclear cations, with each copper(II) ion chelated by the amine {Cu–N 1.977(3) Å} and oxime {Cu–N 1.994(2) Å} nitrogen atoms of one amox ^– ligand, and coordinated by the bridging oximato oxygen atom of another amox ^– ligand {Cu–O# 1.938(2) Å}. A central oxygen atom on the threefold axis completes square-planar tetracoordination about each copper(II) ion {Cu–O 1.910(1) Å}. Cu–Cu# distances are 3.283(2) Å, with the central oxygen atom 0.233(2) Å out of the Cu₃ plane. Two of these tri-nuclear cations are linked confacially by a proton on the common threefold axis {O–O# 2.474(1) Å}, to form novel hexanuclear clusters, with dihedral angles about the central Cu–O–O#–Cu# axis of 37.4(1)˚. Distances Cu–Cu# between the triangles are 3.180(5), 3.860(5) and 4.738(5) Å [trigonal, R3 – c, a 23.932(5), c 18.581(4) Å, Z 12, R₁ 0.034 for 1660 reflections]. The magnetic susceptibility values indicate extensive antiferromagnetic spin-coupling within the triangles. A blue compound of stoichiometry Cu(amox)(H₂O)(NO₃) has susceptibility values supporting a di-nuclear spin-coupled structure.