Linkage lsomerism in bis[hydrotris(1,2,4-triazolyl)borato]zinc from a molecular chelate complex to a three-dimensional co-ordination polymer

Abstract

The reaction of zinc salts with K[HB(C₂H₂N₃)₃] in water gave two crystalline polymorphic forms. A single-crystal X-ray study revealed that the fast crystallizing cubic platelets have the formula [Zn{HB(C₂H₂N₃)₃}₂]·6H₂O with the orthorhombic space group Pmcn and a= 20.98(1), b= 10.734(6). c= 11.747(3)Å and Z= 4. The borate acts as a tridentate chelate through the endodentate nitrogens to form zinc co-ordination octahedra embedded in layers of water molecules. The slowly crystallizing parallelepipeds as the second modification present a three-dimensional lattice built up by the borate bridging three zinc centres viathe exodentate nitrogen donor atoms The co-ordination polymer of the analytical formula [Zn{HB(C₂H₂N₃)₃}₂]·ca.1.5H₂O crystallizes in the monoclinic space group C2/c with a= 15.975(13), b= 8.900(6)Å, c= 17.930(15)Å, β= 121.36(5) and Z= 4.