METHYL- AND PHENYL-BIS(TERTIARY PHOSPHINE) HYDROXO COMPLEXES OF PLATINUM(II): REACTIONS WITH WEAK ACIDS AND HYDRATION OF NITRILES CATALYSED BY HYDROXO AND N-BONDED CARBOXAMIDO COMPLEXES OF PLATINUM(II)

Article abstract of DOI:10.1016/S0022-328X(00)84529-5

Methyl- and phenyl-hydroxo complexes of platinum(II), Pt(OH)RL2 (R=Ph, L=Pcy3, P-t-Bu2Me, P-t-BuMe2, PEt3, PMePh2, Pme2Ph; R=Me, L=P-t-Bu2Me, P-i-Pr3) have been prepared by the action of KOH on cationic acetone complexes ⁺ generated in situ.All have mutually trans-phosphine ligands, except for Pt(OH)Ph(PMe2Ph)2, which was isolated in an impure state as a cis-trans mixture.The hydroxo complexes behave as strong bases and react with nitromethane, acetone or p-cresol to give, respectively, C-bonded nitromethyl-(CH2NO2), C-bonded acetonyl-(CH2COMe) and O-bonded p-cresolato-(p-MeC6H4O) platinum(II) complexes.Complexes in the first two of these classes can also be obtained in lower yield by reaction of PtClRL2 with nitromethane or acetone in the presence of silver oxide.Methyl cyanoacetate, NCCH2CO2Me, reacts with Pt(OH)PhL2 (L=PEt3, P-t-Bu2Me) to give N-bonded methoxycarbonyl-keteniminato complexes Pt(N=C=CHCO2Me)PhL2, but with Pt(OH)Me(dppp) the product is the C-bonded cyano(methoxycarbonyl)methyl complex PtMe(dppp).Both hydroxo complexes and N-bonded acetamido complexes Pt(NHCOMe)RL2 catalyse hydration of acetonitrile to acetamide at 80 deg C, but are less efficient than trialkylphosphine platinum(0) complexes.The order of activity for R=Ph is L=PEt3 > P-t-BuMe2 > PPh3 ca.PMe2Ph > P-t-Bu2Me >> Pcy3, while for a given tertiary phosphine the order of activity is R=Ph > Me.Hydration of acrylonitrile under similar conditions generally gives a mixture of acrylamide, β-cyanoethanol and β,β-dicyanoethyl ether, the last two products arising in irreproducible amounts by addition of water to the olefinic double bond.The mechanisms of these reactions are discussed in the light of the observed trends.