Cyclopalladated Complexes Derived from Phenylacetone Oxime. Insertion Reactions of Carbon Monoxide, Isocyanides, and Alkynes. Novel Amidines of the Isoquinoline Series

Abstract

Neutral and cationic six-membered C,N-palladacycles with the core “Pd{C,N-C6H4{CH2C(Me)═NOH}-2}” have been obtained by oxidative addition of the oxime BrC6H4{CH2C(Me)═NOH}-2 to “Pd(dba)2” (dba = dibenzylideneacetone) in the presence of mono- or bidentate ligands. The oximato complex [Pd{μ-C,N,O-C6H4{CH2C(Me)═NO}-2}(PTol3)]2 forms after dehydrobromination of the appropriate oxime complex with KtBuO, while the pincer derivative [Pd{C,N,N′-C6H4{CH2C(Me)═NOCH2py}-2}Br] results by attack of an in situ generated oximato complex to BrCH2py·HBr. Insertion of CO or RNC in some of the palladacycles causes a depalladation/coupling process, giving 1,2-dihydro-1-oxo-2-hydroxy-3-methylisoquinoline or 1,2-dihydro-1-imino(R)-2-hydroxy-3-methylisoquinoline, respectively, while the insertion of alkynes produces eight-membered alkenyl(oxime) palladacycles “Pd{C,N-C(R′)═C(R)C6H4{CH2C(Me)═NOH}-2}”. When using diphenylacetylene, a dimeric tetranuclear complex [{Pd(tbbpy)}2{μ-N,O-{η3-C6H4(C4Ph4){CH2C(Me)═NO}}}]24+ forms instead, in which a π-allyl-coordinated oximato, bearing a spirocyclic substituent, acts as the bridging ligand. The crystal structures of the oxime and of each type of complexes have been determined.