Synthesis, Characterization, and Stability of α‐Keggin‐Type Polyoxotungstate‐Coordinated Mono‐Platinum(II) Complex

The first example of mono‐platinum(II) complex composed of mono‐lacunary α‐Keggin‐type polyoxotungstate is described. The mono‐platinum(II)‐containing polyoxotungstate [(CH3)4N]4H[α‐PW11O39{cis‐PtII(Me2ppz)}]·5H2O (Me2ppz = N,N′‐dimethylpiperazine) (TMA‐1) was synthesized by a 1:1 stoichiometric reaction of mono‐lacunary α‐Keggin polyoxotungstate, [α‐PW11O39]7–, with cis‐PtCl2(Me2ppz) in an aqueous solution, followed by purification from water. The compound TMA‐1 was characterized by elemental analysis, thermogravimetric/differential thermal analysis (TG/DTA), and Fourier transform infrared (FTIR), ultraviolet‐visible (UV/Vis), and solution {1H, 13C, 31P, 195Pt, and 183W} nuclear magnetic resonance (NMR) spectroscopy. The characterization results indicated that a platinum(II) moiety, [cis‐Pt(Me2ppz)]2+, was coordinated to two oxygen atoms in a mono‐vacant site of [PW11O39]7– with asymmetric configuration, resulting in an overall C1 symmetry. The polyoxoanion [α‐PW11O39{cis‐PtII(Me2ppz)}]5– (1) was more stable in dimethylsulfoxide and water than the α‐Keggin‐type polyoxotungstate‐coordinated mono‐platinum(II) complex, [α‐PW11O39{cis‐Pt(NH3)2}]5–, which was also obtained by the reaction of [α‐PW11O39]7– with cis‐diamminedichloroplatinum(II) in an aqueous solution. We synthesized a tetramethylammonium salt of α‐Keggin‐type polyoxometalate‐coordinated mono‐platinum(II) complex [(CH3)4N]4H[α‐PW11O39{cis‐PtII(Me2ppz)}]·5H2O (Me2ppz = N,N′‐dimethylpiperazine) (TMA‐1), using cis‐PtCl2(Me2ppz) as the starting platinum(II) complex. The polyoxoanion 1 was more stable in dimethylsulfoxide and water than [α‐PW11O39{cis‐Pt(NH3)2}]5–.