Electron and ligand transfer reactions between cyclometallated platinum(II) compounds and thallium(III) carboxylates

Abstract

Reaction of trans-[(2-Me{2}NCH{2}C{6}H{4}{2}Pt}I{}I{] with Tl}I{}I{}I{(O{2}CR){3} (R = Me, i-Pr) gave direct elimination of Tl}I{(O{2}CR) and formation of the oxidative addition product [(2-Me{2}NCH{2}C{6}H{4}){2}Pt}I{}V{ (O{2}CR){2}], in two isomeric forms. A structure with the carbon ligands in trans positions is proposed for the main isomer, whereas the second isomer has the nitrogen ligands in trans positions. Conversion of the first isomer into the second was induced by addition of free carboxylic acid; evidence for rupture of a Pt@?O bond is given and a five-coordinate intermediate proposed. Pt@?O rupture does not occur for the trans-N-isomer.For [{2, 6-(Me{2}NCH{2}){2}C{6}H{3}}PtBr] with Tl(O{2}CR){3} (R = Me, i-Pr) two competing reactions have been observed, i.e. cis oxidative addition resulting in formation of cis-O-[{2,6-(Me{2}NCH{2}){2}C{6}H{3}}Pt(O{2}CR){2}Br] with elimination of Tl}I{(O{2}CR), and exchange of the bromide atom and a carboxylato group between the two metal centres. For R = Me a product has been isolated with stoichiometry [{2,6-(Me{2}NCH{2}){2}C{6}H{3}}Pt(O{2}CMe)]{2}.Tl(O{2}CMe)].2H{2}O, which is the adduct of some of the products of the above reactions. Adduct formation has been observed as the only reaction for [{2,6-(Me{2}NCH{2}){2}C{6}H{3}}Pt(O{2}CR)] and Tl(O{2}CR){3}, resulting in [{2,6-(me{2}NCH{2}){2}C{6}H{3}}Pt(O{2}CR).Tl(O{2}CR){3}]. The reactions of cis-[(2-Me{2}NCH{2}C{6}H{4}){2}Pt] and cis-[(2-Me{2}NC{6}H{4}CH{2}){2}Pt)] with Tl}I{}I{}I{(O{2}CR){3} (R = Me, i-Pr) are less well understood as compared with the corresponding reactions with Hg}I{}I{(O{2}CR){2}.In none of the reactions has evidence for covalent Pt@?Tl bonded intermediates been obtained. This result has been interpreted with an inner-sphere mechanism operating in electron transfer reactions involving Tl}I{}I{}I{(O{2}CR){3}.