Synthesis and characterization of stable bis(methoxo)platinum(IV) complexes. A facile synthesis via fluorenylidene-philic interactions

Stable mono- and bis(methoxo)platinum(IV) species via the oxidation of Pt^II to Pt^IV have been prepared and characterized. The reaction of [Pt^II(fpd)(dpda)] (fpd = 9-fluorenylidenepropanedioate; dpda = 2,2-dimethyl-1,3-propanediamine) with hydrogen peroxide in methanol at room temperature affords [pt^IV(OH)(OCH₃)(fpd)(dpda)], and further reaction at boiling methanol produces a bis(methoxo)platinum(IV) compound, [pt^IV(OCH₃)₂(fpd)(dpda)]. The bis(methoxo)platinum(IV) compound can be prepared by the direct reaction of [Pt^II(fpd)(dpda)] with hydrogen peroxide in boiling methanol or by the simple stirring of [Pt^IV(OH)₂(fpd)(dpda)] in boiling methanol. The crystal structures of [Pt^II(fpd)- (dpda)]·2(CH₃)₂NCHO (Pna2₁, a = 10.125(2) Å, b = 26.141(4) Å, c = 10.845(6) Å, V = 2870(2) ų, Z = 4, R = 0.0370), [Pt^IV(OH)₂(fpd)(dpda)]·3C₂ H₅OH (P2₁/a, a = 10.312(2) Å, b = 22.044(5) Å, c = 14.225(3) Å, β = 110.25(2)°, V = 3034(1) ų, Z = 4, R = 0.0572), and [Pt^IV(OCH₃)₂(fpd)(dpda)] ·1.5CH₃OH·0.5C₂H₅ OH·0.5H₂O (P1̄, a = 13.333(2) Å, b = 15.386(3) Å, c = 18.446(5) Å, α = 66.80(2), β = 69.06(2)°, γ = 68.84(1), V = 3140(1) ų, Z = 2, R = 0.0437) have been solved and refined. For [pt^IV(OCH₃)₂(fpd)(dpda)], the 9-fluorenylidene moiety of fpd ligand snugly interacts with the methoxo group (C(22)⋯C(9), 3.34 Å; C(22)-H⋯C(9), 2.65 Å). The mono- and bis(methoxo)platinum(IV) compounds are stable even in solution.