Studies on the nature and strength of Pt•••H(-N) interactions.: The crystal structures of chloro[N-(2-aminoethyl)-N(2-ammonioethyl)ethane-1,2-diamine]platinum(II)chloride and dichloro[4,7-diaza-1-azoniacyclononane]platinum(II)tetrachloroplatinate(II)- water (1/2) and a molecular mechanics analysis of the Pt•••H(-N) interactions

Two complexes, namely, chloro[N-(2-aminoethyl)-N-(2-ammonioethyl)ethane-1,2-diamine]platinum(II) chloride {[PtCl(tren+ H)]Cl-2} and dichloro[4,7-diaza-1-azoniacyclononane]platinum(II) tetrachloroplatinate(II)-water (1/2) {[PtCl2( tacn+H)](2)[PtCl4]. 2H(2)O}, have been prepared and structurally characterized by single-crystal X-ray diffractometry as part of a study of the nature and strength of Pt ... H(-N) interactions. Crystals of [PtCl( tren+ H)]Cl-2 are monoclinic, space group P2(1)/c, a 8.293( 2), b 14.396(6), c 11.305(3) Angstrom, beta 107.34( 2)degrees, Z 4, and the structure has been refined to a residual of 0.042 based on 1631 reflections. Crystals of [PtCl2(tacn+H)](2)[PtCl4]. 2H(2)O are monoclinic, space group P2(1)/a, a 12.834(4), b 8.206(4), c 13.116( 8) Angstrom, beta 93.01( 4)degrees, Z 2, and the structure has been refined to a residual of 0.035 based on 1974 reflections. In [PtCl(tren+H)](2+), the protonated amine forms hydrogen bonds with chloride anions and no close contacts with the metal ion. In [PtCl2(tacn+ H)](+), a short intramolecular contact is observed between the metal and the protonated amine and the results of molecular mechanics modelling are consistent with there being a Pt ... H hydrogen bond. Molecular mechanics modelling of [PtCl( tren+ H)](2+) and [PtCl2(dien+ H)](+) shows that the protonated amines could readily form close contacts with the metal. It is concluded that there is evidence for the formation of Pt ... H(-N) hydrogen bonds but these bonds are very weak, being similar or lower in energy than Cl ... H(-NPt) hydrogen bonds.