Cyclopalladated complexes derived from phenylacetone oxime. Insertion reactions of carbon monoxide, isocyanides, and alkynes. Novel amidines of the isoquinoline series

Article abstract of DOI:10.1021/om4010912

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 BrC₆H ₄{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 K^tBuO, while the pincer derivative [Pd{C,N,N′-C₆H₄{CH₂C(Me)=NOCH ₂py}-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(C ₄Ph₄){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.