Cationic palladium catalysts have been used to cooligomerize ethylene and carbon monoxide. At high ethylene/CO ratios (m /m = 10:1) in methylene chloride as a solvent, unsaturated alternating cooligomers of the general structure R[C(O)CH2CH2]mH ( m ≥ 1 ; R ≡CH2=CH-, CH2=CHCH2CH2- and CH3CH = CHCH2-) were obtained for the first time. Single component catalyst precursors [(allyl)Pd(P^X )]+Y- (P^X = Ph2P(CH2)nC(= O )OR, Ph2P(CH2)2P(=O)Ph2, Ph2P(CH2)n
Ph2P(CH2)2S (=O )Ph, n = 1 - 3 , R = Me, Et; Y- = BF4-, SbF6- ) with bidentate P,O- and P,S-ligands as well as in situ catalysts with unfunctionalized phosphine ligands were used. With P"Bu3 as a ligand, selectivities for ethylvinylketone of 40% based on the CO converted were obtained. The hemilabile phosphino-ester and phosphinothiophene ligands behave like monodentate phosphines under catalytic conditions.
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