Reactivity of diacetylplatinum(II) complexes: Oxidative addition of halogens and hydrogen halides

Diacetylplatinum(II) complexes [Pt(COMe)2()] ( = bpy, 3a; 4,4′-t-Bu2-bpy, 3b), obtained by the reaction of [Pt(COMe)2X(H)()] with NaOH in CH2Cl2/H2O, were found to undergo oxidative addition reactions with halogens (Br2, I2) yielding the platinum(IV) complexes (trans, OC-6-13)/(cis, OC-6-32) [Pt(COMe)2X2()] ( = bpy, X = Br, 4a/4b; I, 4c/4d;  = 4,4′-t-Bu2-bpy, X = Br, 4e/4f; I, 4g/4h). The diastereoselectivity of the reactions proved to be strongly dependent on the solvent. The oxidative addition of (SCN)2 resulted in the formation of (OC-6-13)-[Pt(COMe)2(SCN)2()] ( = bpy, 4i; 4,4′-t-Bu2-bpy, 4j). In a reaction the reverse of their formation, the diacetylplatinum(II) complexes 3 underwent oxidative addition with anhydrous HX (X = Cl, Br, I), prepared in situ from Me3SiX/H2O, yielding diacetyl(hydrido)platinum(IV) complexes [Pt(COMe)2X(H)()] ( = bpy, X = Cl, 5a; Br, 5b; I, 5c;  = 4,4′-t-Bu2-bpy, X = Cl, 5d; Br, 5e; I, 5f). Furthermore, diacetyldihaloplatinum complexes 4 were found to undergo reductive elimination reactions in boiling methanol yielding acetylplatinum(II) complexes [Pt(COMe)X()] ( = bpy, X = Br, 6b; I, 6c;  = 4,4′-t-Bu2-bpy, X = Br, 6e; I, 6f). All complexes were characterized by microanalysis, IR and 1H and 13C NMR spectroscopy. Additionally, the bis(thiocyanato) complex 4j was characterized by single-crystal X-ray diffraction analysis.

Diacetylplatinum(II) complexes (I) having 2,2′-bipyridine type coligands (NN) were found to react with halogens X2 (Br2, I2) yielding diacetyldihaloplatinum(IV) complexes (III) in a strongly solvent dependent diastereometric ratio (cis/trans). Thermally induced reductive elimination reactions of complexes III led to the formation of acetylhaloplatinum(II) complexes (IV). Reactions of I with HX (HCl, HBr, HI) under anhydrous conditions resulted in the formation of diacetyl(hydrido)platinum(IV) complexes (II). The reactivity of complexes I in these oxidative addition and reductive elimination reactions will be discussed with respect to that of the requisite dialkyl platinum complexes [PtR2(NN)].Figure optionsDownload as PowerPoint slideFigure optionsDownload as PowerPoint slideFigure optionsDownload as PowerPoint slide