CYCLOMETALATION AT CARBON ADJACENT TO OXYGEN IN PLATINUM(II) AND IRIDIUM(I) PHOSPHINE COMPLEXES

Heating trans-PtCl2(t-Bu2PCH2OCH3)2 at 125°C in 2-methoxyethanol yields a cyclometalated derivative, PtCl(t-Bu2PCH2OCH2)(t-Bu2PCH2OCH3). Adding excess NaI and 1,8-bis(dimethylamino)naphthalene accelerates the reaction and gives the iodide-substituted analog. Under the same conditions, trans-PtCl2(t-Bu2POCH2CH3)2 is also metalated at the methyl carbon atom. However, the slower rate of this reaction indicates that an α-oxygen atom has an electronic accelerating effect on the metalation process. Neither t-Bu2POCH3 nor t-Bu2PCH2CH2OCH3 give platinum(II) cyclometalated complexes; four- or six-membered chelate ring formation appears to be unfavorable. The t-Bu2PCH(CH3)OCH3 ligand also does not yield a platinum(II) metalated derivative. However, [IrCl(COT)2]2 (COT = cyclooctene) reacts at 25°C with both t-Bu2PCH2OCH3 and t-Bu2PCH(CH3)OCH3, to form iridium(III) metalated complexes by oxidative addition to the methyl CH bond. These coordinatively unsaturated compounds react with CO, yielding octahedral iridium(III) carbonyl hydride complexes. © 1979.