Crystal and molecular structure of [{Cu(pmdien)F(H2O)}2][BF4]2 (pmdien = N,N,N′,N″,N″-pentamethyldiethylenetriamine): a novel dimeric cation with extremely short O–H · · · F interactions

Abstract

The crystal and molecular structure of [{Cu(pmdien)F(H2O)}2][BF4]21 (pmdien = N,N,N′,N″,N″-pentamethyldiethylenetriamine) has been determined. The cation exists in the solid state as a unique dimer, held together by O–H· · ·F hydrogen-bonding interactions [O· · ·F 2.567(2), O–H 0.83(3), F· · ·H 1.74(3) Å, F· · ·H–O 178.5(23)°]. The O· · ·F separation is the shortest ligand fluoride–ligand water hydrogen-bonding interaction in any copper(II) complex. The copper atom is five-co-ordinate and has a square-based pyramidal geometry comprising equatorially located pmdien (mean Cu–N 2.052 Å), and fluoride [Cu–F 1.888(1) Å] and axially located water [Cu–O 2.211(1) Å].