Palladium(II) complexes with hemilabile etherdiphos ligands in the alternating copolymerization of carbon monoxide with olefins

The potentially hexadentate diphos ligands (ROCH2CH2)(2)P(CH2)(3)P(CH2CH2OR)(2) (1a-d) (R = Et (a), n-Bu (b), t-Bu (c), Cy (d)) are accessible by photochemically induced hydrophosphination of the vinyl ethers CH2=CH-OR with the diprimary phosphine H2P(CH2)(3)PH2. Treatment of 1a-d with (PhCN)(2)PdCl2 in CH2Cl2 leads to the dichlorodiphospalladium(II) complexes 2a-d, from which the dicationic palladium(II) complexes 3a-d were obtained by abstraction of the chlorides with AgBF4 in CH2Cl2. In 3a-d the etherdiphos ligands are coordinated in a eta(4)(O,P;O',P') fashion. A rapid chemical exchange between the eta(2)-(PO)-O-boolean AND chelated and the eta(1)-P coordinated part of the ligands in 3a-d was demonstrated by means of temperature-dependent C-13{H-1} NMR spectroscopy. Both Pd-O bonds in 3a-d are easily cleaved by polar solvents such as acetonitrile and water resulting in the formation of the adducts 3b . 2CH(3)CN, 3c . H2O, and 3c . 2H(2)O. The molecular structures of 2a and 3c . H2O were determined by single crystal X-ray diffraction methods. Under a total pressure of 60 bar ethene/CO and propene/CO, respectively, 3a-d are highly active catalysts in the copolymerization of olefins with carbon monoxide. GPC measurements revealed high molecular weights of these polyketones. (C) 1999 Elsevier Science S.A. All rights reserved.