ETA-3 AND ETA-1 TERMINAL-CARBON-BONDED COMPLEXES OF 2,4-PENTANEDIONE WITH PALLADIUM(II)

Dichlorobis(benzonitrile)palladium(II) reacts with 2, 4-pentanedione (acacH) in acetone at 0 °C to afford [PdCl(acac-O,O')]2 (5), which turns to a η3 acac complex [PdCl(acac-C1-C3)]2 (6) during a prolonged reaction at room temperature. Bridge-splitting reactions of 5 with triphenylphosphine and triphenylarsine yield PdCl(acac-O,O')L, where L is PPh3 (7a) or AsPh3 (7b). Corresponding mononuclear complexes PdCl(acac-C1-C3)L (L=PPh3 (8a) or AsPh3 (8b)) and M-[PdCl2(acac-C1-C3)] (M=PPh4 (9a) or AsPh4 (9b)) are similarly derived from 6. The isomeric pairs 7a-8a and 7b-8b manifest a novel type of linkage isomerism. The reaction of 6 with 2, 2'-bipyridine results in PdCl(acac-C1)(bpy), which exhibits the keto-enol tautomerism of the terminal-carbon-bonded acac, the equilibrium quotient [enol] / [keto] being 0.7 in CDC13 at 25 °C. © 1978, American Chemical Society. All rights reserved.