COMPLEXES INCLUDING ACETYLIDES FORMED FROM 3-DIPHENYLPHOSPHINOCAMPHOR AND PLATINUM OR PALLADIUM

Treatment of lithiated D-camphor with a half molar equivalent of PPh2C1 gives the 3-diphenylphosphino enolate anion [PPh2(C10H14O)]- as the only phoshorus-containing species. Treatment of lithiated D-camphor with one equivalent of PPh2C1 gives some of the enolate anion but the main product is the 3-exo substituted camphor derivative 3-exo-PPh2(C10H15O) together with some of the 3-endo-substituted derivative. On storage of the solution, the 3-endo substituted derivative becomes the main product with some of the 3-exo-substituted derivative still present. Treatment of a solution of the enolate ion with Na2PdCl4 . 4H2O gives [activated Pd{(PPh2)C10H14O}2] or with PtCl2(cyclo-octa-1,5-diene), cis-[activated Pt{(PPh2)C10H14O}2] is formed. Treatment of these bis-chelate complexes with hydrogen chloride opens up the chelate rings reversibly, giving dichloro-complexes of type [MCl2{(PPh2)C10H15O}2] {M = Pd (trans-isomer) M = Pt (cis-isomer)}. Treatment of ethanol or methanol solutions of these bischelate complexes with acetylenes, especially in the presence of traces of acetic acid also opens up the chelate rings to give di-acetylides of type [M(C = CR)2{(PPh2)C10H15O}2] {M = Pd or Pt; R = Ph or C(Me) = CH2}. When treated with HC = CH or EtC = CH the bis-chelate [activated Pd{(PPh2)C10H14O}2] gives the corresponding acetylides but these could not be isolated and reverted to the starting bis-chelate complex, i.e. acetylide formation is reversible.