Hydrogen bonding in hexamminemetal(II) bromides Br2 (M2+=Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Cd2+) - synergetic effect of M2+

Article abstract of DOI:10.1016/0022-2860(95)08850-U

IR spectra of isotypic hexamminemetal(II) bromide salts Br2 (K2PtCl6-type structure for M²⁺=Ca²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cd²⁺; tetragonal structure related to the K2PtCl6-type structure for M²⁺=Cu²⁺) and of isotopically dilute samples (5percent deuterated) have been recorded in the range 400-4000 cm^-1 with regard to the influence of M²⁺ on the strength of N-H...X^- hydrogen bonds.This so-called synergetic effect does not correlate simply with either the ionic radii or electron configuration of M²⁺, but must be caused by a superposition of electronic and ionic radii effects.Arranging the metal ions with decreasing strength of their synergetic effect leads to the following series: Cu²⁺>>Co²⁺>Mn²⁺>Fe²⁺>Ni²⁺>=Cd²⁺>Ca²⁺.