Complexes of a bis-bidentate ligand with d10 ions: a mononuclear complex with Ag(I), and a tetrahedral cage complex with Zn(II) which encapsulates a fluoroborate anion

Complexes of the bis-bidentate ligand 2,3-bis[{3-(2-pyridyl)-pyrazol-1-yl}methyl]naphthalene (L2) with Ag(I) and Zn(II) have been prepared and structurally characterised. In [Ag(L2)][ClO4] both bidentate pyrazolyl–pyridine arms of L2 interact with the same Ag(I) centre, which has two short Ag---N bonds and two much longer, weaker interactions such that the coordination is best described as linear and bidentate. In contrast, in [Zn4(L2)6(BF4)][BF4]7 the ligands L2 act as bis-bidentate bridges; the structure consists of a tetrahedral cage of Zn(II) ions with a bridging ligand L2 along each of the six edges. The cavity at the centre of this three-dimensional tetrahedral cage accommodates a tetrafluoroborate anion which is completely encapsulated, and inverted with respect to the Zn4 tetrahedron. The F atoms of this encapsulated anion are involved in close F---HC contacts with parts of the bridging ligands. 11B and 19F NMR spectra show that the encapsulated anion does not exchange with free tetrafluoroborate anions in MeCN solution, even up to 70 °C.