Pressure-tuning infrared spectra of the three Magnus' Green salts, [Pt(NH3)4][PtCl4], [Pt(ND3)4][PtCl4] and [Pt(NH3)4][PtBr4]

► Infrared spectra of the three Magnus' Green salts have been examined at high pressures. ► Evidence of restricted rotation of the coordinated NH3 groups about the Pt-N bonds at high pressures. ► This restricted rotation may be the result of weak N-H⋯X (X = Cl, Br) hydrogen bonding interactions.