Synthesis, crystal structure, and spectroscopic properties of bis(rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)(μ-1,2,3,4-oxalato)dichloridozincate(II)(μ-1,2,3-oxalato)dichromium(III) tetrachloridozincate monohydrate

Abstract

A novel oxalato-bridged trinuclear heterometallic complex, cis-[Cr(cyc b)(μ-1,2,3,4-ox)ZnCl2(μ-1,2,3-ox)Cr(cyc b)]ZnCl4·H2O (1) (cyc b = rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane; C16H36N4, ox = oxalate; C2O42−), was prepared and its structure was determined by single-crystal X-ray diffraction analysis at 100 K. Complex 1 crystallizes in the orthorhombic system space group Pca21, with a = 31.702(6), b = 9.087(2), c = 17.677(4) Å, and Z = 4. The two [Cr(cyc b)]3+ units are bridged by the central Zn(II) atom through the oxalato groups, which present bis-bidentate (μ-1,2,3,4-ox) and bidentate-monodentate (μ-1,2,3-ox) modes. Each Cr(III) ion is coordinated by four N atoms from the cyc b ligand and two O atoms of the oxalato ligand in cis-V conformation. The central Zn(II) ion is coordinated in a distorted trigonal-bipyramidal geometry formed by two Cl atoms and two O atoms from μ-1,2,3,4-ox and one O atom from μ-1,2,3-ox. However, the ZnCl42− anion and the uncoordinated water molecule remain outside the coordination sphere. Infrared, UV–visible, and electron paramagnetic resonance spectroscopic analyses confirmed the structural data.