New structural forms in molecular metal phosphonates: Novel tri- and hexanuclear Zinc(II) cages containing phosphonate and pyrazole ligands

The reaction of ZnCl2 with tert-butylphosphonic acid and 3,5-dimethylpyrazole in the presence of triethylamine as a hydrogen chloride scavenger affords a trinuclear molecular zinc phosphonate [Zn3Cl2(3,5-Me(2)Pz)(4)(t-BUPO3)(2)]. The structure of this compound contains a planar trizinc assembly containing two bicapping mu(3) [t-BuPO3](2-) ligands and terminal pyrazole and chloride ligands. In contrast an analogous reaction of ZnCl2 with phenylphosphonic acid and 3,5-dimethylpyrazole affords a hexanuclear zinc phosphonate [Zn6Cl4(3,5-Me(2)PzH)(8)(PhPO3)(4)]. The six zinc centers are arranged in a chairlike conformation. The four phosphonates in this complex also act as bridging tripodal mu(3) [RPO3](2-) ligands.