Hydrogen-Bonding Patterns in Oxime/Oximato Platinum(II) Species Providing the Formation of One-Dimensional Chains, Two-Dimensional Networks, and Cages

Heating
cis-[PtCl2(Me2COH)2]
in molten 2-propanone oxime affords the cationic complex
[PtCl(Me2CNOH)3]Cl. This compound reacts with 1 equiv of NaOH to give the neutral
complex
cis-[PtCl(Me2CNO)(Me2CNOH)2]
(1). Further, the reaction of
[PtCl(Me2CNOH)3]Cl with 2 equiv
of AgNO3 and successive addition of excess
oxime and NaSbF6 afford the chloride-free cationic complex
[Pt(Me2CNO)(Me2CNOH)3](SbF6).
When a
solution of NaOH, instead of NaSbF6, was added to the
reaction mixture, the neutral compound
[Pt(Me2CNO)2(Me2CNOH)2]·2H2O
(2) was isolated. The homoleptic complex
[Pt(Me2CNOH)4]Cl2
(3) was prepared both
by addition of excess HCl to
[Pt(Me2CNO)2(Me2CNOH)2]
(87% yield) and by prolonged heating of [PtCl(Me2CNOH)3]Cl and excess 2-propanone
oxime, although in the latter case the conversion of the starting
complex
did not exceed 5−10%. 1−3 were
characterized by X-ray diffraction. All three compounds display
interesting
hydrogen-bonding modes. In 1, two crystallographically
independent molecules of
cis-[PtCl(Me2CNO)(Me2CNOH)2] form the repeat unit for a novel
type of self-assembly that produces infinite
one-dimensional
polymeric chains held by strong H-bonds. 2, as compared
to vic-dioxime Pt(II) complexes, displays
stronger
intramolecular hydrogen bonds and shows the absence of columnar
stacking. In addition, the solvation H2O
molecules connect the Pt(II) building elements by intermolecular
H-bonds to form a layered two-dimensional
network. In 3, the counterion is involved in
(μ4-Cl-)·cis-[(···H−O−)2(···H−CH2−)2]
hydrogen bonding, thus
forming the caged complex. Another interesting structural feature
of 3 is the interaction between methyl
hydrogens
and platinum.