LINKAGE ISOMERISM IN BIS[HYDROTRIS(1,2,4-TRIAZOLYL)BORATO]ZINC FROM A MOLECULAR CHELATE COMPLEX TO A 3-DIMENSIONAL COORDINATION POLYMER

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)}2].6H2O with the orthorhombic space group Pmcn and a = 20.98(1), b = 10.734(6), c = 11.747(3)Angstrom and Z = 4. The berate 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 berate bridging three zinc centres via the exodentate nitrogen donor atoms. The co-ordination polymer of the analytical formula [Zn{HB(C2H2N3)3}2]. ca. 1.5H(2)O crystallizes in the monoclinic space group C2/c with a = 15.975(13). b = 8.900(6), c = 17.930(15) Angstrom, beta = 121.36(5)degrees and Z = 4.