Self-assembly of Schiff-base palladacycle-based discrete pseudo-macrocycles: Evidence for hemilability of oxalate ligand

Bis-bidentate tetra-coordinated oxalato bridged binuclear Schiff-base palladacycles [Pd{C,N-κ2-(4-R)C6H3CHdouble bond; length as m-dashNC6H3-2,6-i-Pr2]2(μ-η2-η2-C2O4) (R = H; OMe) were synthesized. Reactions of μ-oxalato bridged Schiff-base palladacycles [Pd{C,N-κ2-(4-R)C6H3CHdouble bond; length as m-dashNC6H3-2,6-i-Pr2]2(μ-η2-η2-C2O4) (R = H; OMe) with 1,4-bis(diphenylphosphino)butane (dppb) and 1,4-bis(diphenylphosphino)pentane (dppp) generated discrete pseudo-macrocycles with 1,1′-bicoordinated oxalato bridge. Unexpectedly, μ-oxalato bridged Schiff-base palladacycle [Pd(C,N-κ2-C6H4CHdouble bond; length as m-dashNC6H3-2,6-i-Pr2)]2(μ-η2-η2-C2O4) reacted with PPh3 to form unusual bidentate/monodentate tri-coordinated oxalato bridged binuclear cyclopalladated complex [Pd(C,N-κ2-C6H4CHdouble bond; length as m-dashNC6H3-2,6-i-Pr2)(PPh3)](μ-η2-η1-C2O4)[Pd(C-κ1-C6H4CHdouble bond; length as m-dashNC6H3-2,6-i-Pr2)(PPh3)].