Two complexes, namely,
chloro[N-(2-aminoethyl)-N-(2-ammonioethyl)ethane-1,2-diamine]platinum(II)
chloride {[PtCl(tren+H)]Cl2}
and dichloro[4,7-diaza-1-azoniacyclononane]platinum(II)
tetrachloroplatinate(II)–water (1/2)
{[PtCl2(tacn+H)]2[PtCl4]·2H2O},
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)]Cl2 are monoclinic, space
group P21/c,
a 8.293(2), b 14.396(6),
c 11.305(3) Å, β 107.34(2)º, 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]·2H2O
are monoclinic, space group
P21/a, a
12.834(4), b 8.206(4), c 13.116(8)
Å, β 93.01(4)˚, 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.
