Synthesis And Characterization Of Organometallic Macrocycles Based On Palladacycles

In the last few decades there has been a significant development in thepreparation of organometallic macrocycles which have shown potential application inmolecular recognition, catalysis and chemosensing. The square planar species ofplatinum（II） and palladium（II） have been extensively exploited to generatesupramolecular assemblies due to their rigid coordination environment. It is worthnoticing that in most examples the blocking ligands bound to platinum or palladiumcenters are symmetric diamines or diphosphines. However, cyclometallated Pd（II） orPt（II） complexes containing C,N-donor ligands as corner species to assemblesupramoleculars are very limited. In our opinion, readily synthesized μ-chloro bridgeddinuclear cyclometallated Pd（II） complexes [Pd{（4-R）C₆H₃CH=N-C₆H₃-2,6-i-Pr₂}（μ-Cl）]2（R=H; R=OMe）, with two blocked cis-coordination sites,seemed suitable for assembling of metalmacrocycles, if one could bridge the[Pd{（4-R）C₆H₃CH=NC₆H₃-2,6-i-Pr₂}]+fragments by appropriate linkers.In this thesis, bi-and tri-nuclear cyclometallated Pd（II） nitrato complexes witharomatic N-heterocycles or phosphines were synthesized. Organometallicmacrocycles were constructed by self-assembly of these bi-and tri-nuclearcyclometallated Pd（II） nitrato complexes as precursors. Also μ-C2O4and μ-C4O4bridged binuclear cyclometallated Pd（II） complexes were prepared. Binuclearmacrocycle [{Pd（C₆H₃CH=NC₆H₃-2,6-i-Pr₂）}]2（μ-C2O4）（μ-dppb） was constructed byreaction of μ-C2O4bridged binuclear cyclometallated Pd（II） complex with1,4-bis（diphenylphosphino）butane（dppb）. The details were summarized as follows:1. Complexes μ-Cl bridged binuclear cyclometallated Pd（II） complexes [Pd{（4-R）C₆H₄CH=NC₆H₃-2,6-i-Pr₂}（μ-Cl）]2（R=H,1; R=OMe,2） reacted withAgNO3in CH3CN and followed with2,5-bis（4-pyridyl）-1,3,4-thiadiazole（bpt）,4,4’-bipyridyl（bpy）,1,2-bis（4-pyridyl）ethylene（bpe）, generated binuclear nitratocomplexes [Pd{（4-R）C₆H₄CH=NC₆H₃-2,6-i-Pr₂}（ONPr₂）]2（μ-bpt）（R=H,4; R=OMe,5）,[Pd{（4-R）C₆H₄CH=NC₆H₃-2,6-i-Pr₂}（ONPr₂）]2（μ-bpy）（R=H,6; R=OMe, 7）,[Pd{（4-R）C₆H₄CH=NC₆H₃-2,6-i-Pr₂}（ONO₂）]2（μ-bpe）（R=H,8; R=OMe,9）.Complexes1and2reacted with2,4,6-tri（4-pyridyl）-1,3,5-triazine（tpt） in CH2Cl2produced trinuclear cyclometallated Pd（II） complexes[Pd{（4-R）C₆H₃CH=NC₆H₃-2,6-i-Pr₂}（Cl）]3（tpt）（R=H,10; R=OMe,11）. Treatmentof10and11with an excess AgNO3gave trinuclear cyclometallated Pd（II） nitratocomplexes [Pd{（4-R）C₆H₃CH=NC₆H₃-2,6-i-Pr₂}（ONO₂）]3（tpt）（R=H,12; R=OMe,13）. All these complexes were fully characterized by FT-IR,1H NMR spectroscopyand elemental analysis. The molecular structure of13was determined by the X-raycrystallography. Treatment of12and13with bpt in CH2Cl2produced macrocycles[{Pd（4-R）C₆H₄CH=NC₆H₃-2,6-i-Pr₂}6（bpt）3（tpt）2]（NO₃）₆（R=H,14; R=OMe,15）.Treatment of4with disodium terephthalate （dtpa） gave macrocycle[{Pd（C₆H₄CH=NC₆H₃-2,6-i-Pr₂）}₄（bpt）₂（dtpa）2]（16）, these three complexes werefully characterized by FT-IR,1H NMR spectroscopy and ESI-MS.2. Complexes μ-Cl bridged binuclear cyclometallated Pd（II） complexes [Pd{（4-R）C₆H₄CH=NC₆H₃-2,6-i-Pr₂}（μ-Cl）]2（R=H,1; R=OMe,2） reacted withAgNO3in CH3CN and followed with potassium oxalate monohydrate gave μ-C₂O₄bridged binuclear complexes [Pd{（4-R）C₆H₄CH=NC₆H₃-2,6-i-Pr₂}]2（μ-C₂O₄）（R=H,17; R=OMe,18）. Complex1and2reacted with AgNO3in CH3CN and followedwith3,4-dihydroxy-3-cyclobutene-1,2-dione（dhcbd） gave μ-C4O4bridged binuclearcomplexes [Pd（4-R）C₆H₃CH=NC₆H₃-2,6-i-Pr₂]2（μ-C4O4）（R=H,19; R=OMe,20）.Reaction of17with1,4-bis（diphenylphosphino）butane（dppb） in CH2Cl2, producedmacrocycle [Pd（C₆H₃CH=NC₆H₃-2,6-i-Pr₂）]2（μ-C₂O₄）（μ-dppb）（21）. All thesecomplexes were fully characterized by FT-IR,1H NMR spectroscopy and elementalanalysis. The molecular structure of17,18and21were determined by the X-raycrystallography.3. Complexes μ-Cl bridged binuclear cyclometallated Pd（II） complexes [Pd{（4-R）C₆H₄CH=NC₆H₃-2,6-i-Pr₂}（μ-Cl）]2（R=H,1; R=OMe,2） reacted withAgNO3in CH3CN and followed with1,4-bis（diphenylphosphino）butane（dppb）,1,3-bis（diphenylphosphino）propane（dppp）,1,1’-bis（diphenylphosphino）ferrocene（dppf）, generated binuclear nitrato complexes [Pd{（4-R）C₆H₄CH=NC₆H₃-2,6-i-Pr₂}（ONO₂）]2（μ-dppb）（R=H,22; R=OMe,23）,[Pd{（4-R）C₆H₄CH=NC₆H₃-2,6-i-Pr₂} （ONO₂）]₂（μ-dppp）（R=H,24; R=OMe,25）,[Pd{（4-R）C₆H₄CH=NC₆H₃-2,6-i-Pr₂}（ONO₂）]₂（μ-dppf）（R=H,26; R=OMe,27）. All these complexes were fullycharacterized by FT-IR,1H NMR spectroscopy and elemental analysis. The molecularstructure of23,24and25were determined by the X-ray crystallography. Reaction of23with disodium terephthalate （dtpa）, produced macrocycle[{Pd（4-MeO）C₆H₃CH=NC₆H₃-2,6-i-Pr₂}₄（dppb）₂（dtpa）₂]（28）, and the complex wascharacterized by FT-IR and1H NMR spectroscopy.