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

Abstract

Heating cis-[PtCl2(Me2COH)2] in molten 2-propanone oxime affords the cationic complex [PtCl(Me2CNOH)3]Cl. This compound reacts with 1 equiv of NaOH to give the neutral complex cis-[PtCl(Me2CNO)(Me2CNOH)2] (1). Further, the reaction of [PtCl(Me2CNOH)3]Cl with 2 equiv of AgNO3 and successive addition of excess oxime and NaSbF6 afford the chloride-free cationic complex [Pt(Me2CNO)(Me2CNOH)3](SbF6). When a solution of NaOH, instead of NaSbF6, was added to the reaction mixture, the neutral compound [Pt(Me2CNO)2(Me2CNOH)2]·2H2O (2) was isolated. The homoleptic complex [Pt(Me2CNOH)4]Cl2 (3) was prepared both by addition of excess HCl to [Pt(Me2CNO)2(Me2CNOH)2] (87% yield) and by prolonged heating of [PtCl(Me2CNOH)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(Me2CNO)(Me2CNOH)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.