Self-assembly Of Schiff-base Palladacycle-based Organometallic Macrocycles: Evidence For Hemilability Of O,O-chelate Ligands

In recent years, development of supramolecular chemistry is very rapidly. Since1990s the formation of discrete supramolecular structure via coordination-drivenself-assembly has become an active area of research and an important component ofsupramolecular chemistry and nanoscience. As a subset of discrete supramolecularcomplexes, the assemblies of organometallic supramolecule have attracted more andmore interest because of their potential application as promising molecular materials.Cyclometallated Pd(II) complexes with C,N-donor ligands as corner species haverarely been used for the construction of metallosupramolecular assemblies. Ifcyclometallated Pd(II) fragments with blocked C,N-donor ligands([Pd{C,N-κ2-(4-R)C6H4CH=NC6H3-2,6-i-Pr2}]+) were bridged by appropriatehemilabile linkers, it seems feasible for the assembly of metallamacrocycles viacleavage of the weaker metal-ligand bonds. In this thesis, organometallic macrocyclesare generated by reactions of μ-oxalate and μ-2,5-dihydroxy–p-benzoquinone bridgedcomplexes with P-donor ligands. The hemilability of O,O-chelate ligand is confirmed.The main contents were as follows:First of all, μ-chloro bridged palladacycles [Pd{C,N-κ2-(4-MeO)C6H4CH=NC6H3-2,6-i-Pr2}(μ-Cl)]2(R=H,1; R=OMe,2) are synthesized by reactions ofNa2PdCl4with Schiff base ligands [(4-R)C6H4CH=NC6H3-2,6-i-Pr2](R=H, L1; R=OMe, L2). And then complexes1and2react with AgNO3in CH3CN, subsequentlyreact with potassium oxalate solution, and generate[Pd{C,N-κ2-(4-R)C6H3CH=N-C6H3-2,6-i-Pr2}]2(μ-η2-η2-C2O4)(R=H,3; R=OMe,4). The complexes3,4react with PPh3,1,5-bis(diphenylphosphino)pentane(dppp),1,6-bis(diphenylphosphino)hexane(dpph) respectively, in CH2Cl2generatepalladacycles with two PPh3[Pd(C,N-κ2-C6H4CH=NC6H3-2,6-i-Pr2)(PPh3)](μ-η2-η1-C2O4)[Pd(C-κ1-C6H4CH=N-CH3-2,6-i-Pr2)(PPh3)](5), and macrocycles [Pd{C,N-κ2-(4-R)C6H3CH=NC6H3-2,6-i-Pr2]2(μ-η1-η1-C2O4)(μ-dppp)(R=H,6; R=OMe,7),[Pd{C,N-κ2-(4-R)C6H3CH=NC6H3-2,6-i-Pr2]2(μ-η1-η1-C2O4)(μ-dpph)(R=H,8; R=OMe,9). The above complexes were characterized by FT-IR spectroscopy and[Pd(C,N-κ2-C6H4CH=NC6H3-2,6-i-Pr2)(PPh3)](μ-η2-η1-C2O4)[Pd(C-κ1-C6H4CH=N-2,6-i-Pr2)(PPh3)](5), macrocycles [Pd{C,N-κ2-(4-R)C6H3CH=NC6H3-2,6-i-Pr2]2(μ-η1-η1-C2O4)(μ-dppp)(R=H,6; R=OMe,7) were characterized by1HNMR spectroscopy,31P NMR spectroscopy, elemental analysis and X-raycrystallography.Similarly, after complexes1and2react with AgNO3in CH3CN, subsequentlyreact with2,5-dihydroxy–p-benzoquinone salt solution, and generate[Pd{C,N-κ2-(4-R)C6H3CH=NC6H3-2,6-i-Pr2}]2(μ-η2-η2-dhpbq)(R=H,10; R=OMe,11). The complexes10,11reacte with PPh3,1,4-bis(diphenylphosphino)butane,1,5-bis(diphenylphosphino)pentane, in CH2Cl2generate palladacycles with two PPh3[Pd{C,N-κ2-(4-R)C6H3CH=NC6H3-2,6-i-Pr2}(PPh3)](μ-η2-η1-dhpbq)[Pd{C-κ1-(4-R)C6H3CH=NC6H3-2,6-i-Pr2}(PPh3)](R=H,12; R=OMe,13), and macrocycles[Pd{C,N-κ2-(4-MeO)C6H3CH=NC6H3-2,6-i-Pr2}]2(μ-η1-η1-dhpbq)(μ-dppb)(14),[Pd(C,N-κ2-C6H3CH=NC6H3-2,6-i-Pr2)]2(μ-η1-η1-dhpbq)(μ-dppp)(15). The abovecompounds were characterized by FT-IR spectroscopy and the complexes10,12,13were characterized by1H NMR spectroscopy. Besides the complexes11,12werecharacterized by X-ray crystallography.