Halometallate and halide ions: nucleophiles in competition for hydrogen bond and halogen bond formation in halopyridinium salts of mixed halide–halometallate anions

Abstract

The compounds (4-ClpyH)3[PtCl6]Cl (1), (4-XpyH)3[FeCl4]2Cl [X = Cl (2); X = Br (3)] and (3-IpyH)2[AuBr3X]X (X = Cl/Br) (4) [n-XPyH = n-halopyridinium] have been synthesised and crystallographically characterised. Their structures illustrate two potential problems of preparing crystals of halometallate salts using aqueous HCl, but provide an opportunity to examine the competition between halometallate [MXq]p− (q = 4, 6; p = 1, 2) and halide X− nucleophiles for both hydrogen bond (N–H⋯X) and halogen bond (C–X⋯X′) formation.