The ordered [WO2F4](2-) anion

Crystallographic order of the [WO2F4](2-) anion has been achieved in the ne w compound [HNC6H6OH][Cu-(NC5H5)(4)(WO2F4)(2)]. This salt with two cations, tetrakis(pyridine)copper(II) [Cu(NC5H5)(4)](2+) and 5-hydroxy-2-methylpyri dinium [HNC6H6OH](+), results in three separate anion-cation contacts and e liminates the disorder common to the [WO2F4](2-) anion in the solid state. Two of those interactions are hydrogen bonds formed with [HNC6H6OH](+), thr ough the protonated amine and the hydroxyl group. The third contact is form ed with [Cu(py)(4)](2+). These results and observations explain the trans-d irecting nature of the [WO2F4](2-) anion and the distinctly different cis-d irecting nature of the group 6 analogue [MoO2F4](2-).