Synthesis, characterization, and acid-base properties of (N-N)PtIV(CH3)2(OH)2 - x(OCH3)x(x= 0, 1) complexes

(N-N)PtIV(CH3)2(OH)2 - x(OCH3)x(x= 0, 1; N-N = bipy, 4,4-(CH3)2bipy, 4,4-tBu2bipy, ArNC(CH3)-C(CH3)NAr (Ar = 3,5-(CF3)2C6H3, 3,5(CH3)2C6H3, 2,6-(CH3)2C6H3) complexes have been prepared by oxidation of the appropriate (N-N)PtII(CH3)2 complexes using H2O2/H2O. In methanol, the hydroxo-methoxy complexes are formed (x= 1), whereas in acetone, the dihydroxo complexes are formed (x= 0). A single-crystal X-ray structure determination establishes the structure of (4,4-(CH3)2bipy)PtIV(CH3)2(OH)2 as a dihydroxo compound with octahedral geometry, with the hydroxo ligands occupying apical coordination sites. The acidities of the protonated bipy hydroxo complexes, (4,4-R2bipy)PtIV(CH3)2(OH)(OH2)+ cations, were determined in methanol. The acidities closely matched that of Cl2CHCOOH (pKa= 6.38 in CH3OH).