Pd complexes[Pd(P^(∩)P)(4-Sepy)_(2)]of 4-pyridylselenolate(4-Sepy)and diphosphines(P^(∩)P=dppe(1,2-bis(diphenylphosphino)ethane),dppf(1,1’-bis(diphenylphosphino)ferrocene)and Xantphos(4,5-bis(diphenylphosphino)-9,9...Pd complexes[Pd(P^(∩)P)(4-Sepy)_(2)]of 4-pyridylselenolate(4-Sepy)and diphosphines(P^(∩)P=dppe(1,2-bis(diphenylphosphino)ethane),dppf(1,1’-bis(diphenylphosphino)ferrocene)and Xantphos(4,5-bis(diphenylphosphino)-9,9-dimethylxanthene))have been developed as metallo-ligands.Their self-assembly reaction with[Pd(P^(∩)P)(OTf)_(2)](OTf-=CF_(3)SO_(3)^(-))successfully yielded the cationic macrocyclic complexes[Pd(P^(∩)P)(4-Sepy)]n(OTf)n.The major and minor products are assigned to the dimer(n=2)and tetramer(n=4)by nuclear magnetic resonance spectroscopy,electrospray ionization mass spectrometry and X-ray structural analysis.The equilibrium between the dimer and tetramer has been established in compounds of wide-bite-angle dppf.The same reaction for Xantphos as diphosphine produced a selenolato-bridged trinuclear complex with a free pyridyl group.A similar reaction with analogous 4-mercaptopyridine resulted in a mononuclear complex of Xantphos comprising Pd-O bond.Density functional theory calculations establish the stability of the macrocycles as tetranuclear(dppf)>dinuclear(dppf)>dinuclear(dppe).A low energy charge transfer transition has been identified from Se or Fe centers to unoccupied orbitals of mixed character.These macrocycles represent the first examples of metallo-supramolecular complexes constructed from selenolate groups and square-planar metal ions.The Pd complexes showed excellent catalytic activity with high turnover numbers(5×10^(7))in Suzuki C-C cross coupling reactions.展开更多
文摘Pd complexes[Pd(P^(∩)P)(4-Sepy)_(2)]of 4-pyridylselenolate(4-Sepy)and diphosphines(P^(∩)P=dppe(1,2-bis(diphenylphosphino)ethane),dppf(1,1’-bis(diphenylphosphino)ferrocene)and Xantphos(4,5-bis(diphenylphosphino)-9,9-dimethylxanthene))have been developed as metallo-ligands.Their self-assembly reaction with[Pd(P^(∩)P)(OTf)_(2)](OTf-=CF_(3)SO_(3)^(-))successfully yielded the cationic macrocyclic complexes[Pd(P^(∩)P)(4-Sepy)]n(OTf)n.The major and minor products are assigned to the dimer(n=2)and tetramer(n=4)by nuclear magnetic resonance spectroscopy,electrospray ionization mass spectrometry and X-ray structural analysis.The equilibrium between the dimer and tetramer has been established in compounds of wide-bite-angle dppf.The same reaction for Xantphos as diphosphine produced a selenolato-bridged trinuclear complex with a free pyridyl group.A similar reaction with analogous 4-mercaptopyridine resulted in a mononuclear complex of Xantphos comprising Pd-O bond.Density functional theory calculations establish the stability of the macrocycles as tetranuclear(dppf)>dinuclear(dppf)>dinuclear(dppe).A low energy charge transfer transition has been identified from Se or Fe centers to unoccupied orbitals of mixed character.These macrocycles represent the first examples of metallo-supramolecular complexes constructed from selenolate groups and square-planar metal ions.The Pd complexes showed excellent catalytic activity with high turnover numbers(5×10^(7))in Suzuki C-C cross coupling reactions.
