Oxidation of Dimethylplatinum(II) Complexes with a Dioxirane: The Viability of Oxoplatinum(IV) Intermediates

The complexes [PtMe₂(NN)] (NN = 2,2′-bipyridine = bipy, <b>1a</b>; NN = di-2-pyridylamine = dpa, <b>1b</b>; NN = di-2-pyridyl ketone = dpk, <b>1c</b>) react with dimethyldioxirane in moist acetone to give the hydroxoplatinum­(IV) complexes [Pt­(OH)₂Me₂(NN)] (NN = bipy, <b>2a</b>; NN = dpa, <b>2b</b>, or [Pt­(OH)­Me₂(dpkOH)], <b>3</b>). Complex <b>2a</b> crystallizes as the hydrate <b>2a</b>·7H₂O, which has a complex supramolecular network structure formed through hydrogen bonding between PtOH groups and water molecules. Attempts to trap a potential oxoplatinum­(IV) intermediate in these reactions were unsuccessful, and computational studies suggest that oxoplatinum­(IV) intermediates are improbable. It is suggested that oxygen atom transfer from the dioxirane to platinum is coupled to proton addition to give the hydroxoplatinum group directly

Switching by Photochemical <i>trans–cis</i> Isomerization of Azobenzene Substituents in Organoplatinum Complexes

A diimine ligand, LL = 2-C₅H₄NCHN-4-C₆H₄NNPh, which carries a <i>trans</i>-azobenzene substituent, forms the dimethylplatinum­(II) complex [PtMe₂(LL)], which undergoes <i>trans</i> oxidative addition with MeI, PhCH₂Br, Br₂, and I₂ to give the corresponding organoplatinum­(IV) complexes [PtIMe₃(LL)], [PtBrMe₂(CH₂Ph)­(LL)], [PtBr₂Me₂(LL)], and [PtI₂Me₂(LL)], respectively. The ligand and the platinum­(II) and platinum­(IV) complexes are shown to undergo <i>trans–cis</i> isomerization of the azobenzene substituent upon irradiation, and the <i>cis</i> isomers then underwent slow thermal isomerization back to the more stable <i>trans</i> isomers

Hieracium dubium

Complexes [PtMe₂(NN)], with NN = 2,2′-bipyridine (bipy), 4,4′-di-<i>tert</i>-butyl-2,2′-bipyridine (bu₂bipy), di-2-pyridylamine (dpa), or di-2-pyridyl ketone (dpk), react easily with phthaloyl peroxide to give a mixture of the chelate complex [PtMe₂{κ²-<i>O</i>,<i>O</i>′-1,2-(O₂C)₂C₆H₄}­(NN)], which was structurally characterized when NN = bu₂bipy, and an oligomer or polymer [PtMe₂{μ-κ²-<i>O</i>,<i>O</i>′-1,2-(O₂C)₂C₆H₄}­(NN)]_<i>n</i>. In the case with NN = dpa, no phthalate chelate complex is formed. These complexes are easily hydrolyzed, and the complexes <i>cis</i>-[PtMe₂(OH)­{κ¹-<i>O</i>-O₂CC₆H₄-2-CO₂H}­(bipy)] and <i>trans</i>-[PtMe₂{κ¹-<i>O</i>-O₂CC₆H₄-2-CO₂H}­(dpkOH)] have been structurally characterized. It is argued that the oxidative addition of phthaloyl peroxide occurs by a polar mechanism and that the hydrolysis is easy because there is no special stability associated with the seven-membered platinum-phthalate chelate ring