synthesis, structures, and catalytic properties of late-transition-metal...
TRANSCRIPT
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Synthesis, Structures, and Catalytic Properties of Synthesis, Structures, and Catalytic Properties of Late-Transition-Metal 2,6-Bis(2-Late-Transition-Metal 2,6-Bis(2-phosphaethenyl)pyridine Complexesphosphaethenyl)pyridine Complexes
Mariam IsraielMariam IsraielInstitutor: Dr. Hanae HaouariInstitutor: Dr. Hanae HaouariChemistry Department (NJCU)Chemistry Department (NJCU) Published: May 16, 2007
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OutlineOutline
• Synthesis of Rhodium(I) Complexes. [slide 5,6]
• Synthesis of Copper(I) Complex. [slide 7]
• Synthesis of Silver(I) Complex. [slide 8,9]
• Catalytic Hydroamidation of Enones. [slide 11]
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PurposePurpose
• Their recent effort has been focused on the development of transition-metal complexes coordinated with phosphaalkenes as low-coordinated phosphorus compounds.
• This property is useful for catalysis, leading to a highly efficient organic transformations.
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IntroductionIntroduction• In this study they have turned their
research interest to the synthesis of 2,6-bis(2- phosphaethenyl) pyridine as a tridentate ligand (PNP) with 9 and 11 group metals.
• PNP complexes consists of a σ-donative pyridine core and two π-accepting phosphaethenyl arms.
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Results and DiscussionResults and DiscussionSynthesis of Rhodium(I) ComplexesSynthesis of Rhodium(I) Complexes
► The PNP ligand reacted with Rh(I) metal [Rh(μ–Cl)(C2H4)2]2 in toluene at room temperature to give [RhCl(PNP)] 1a1a complex, which was isolated as a green crystalline solid.► Complex 1a1a was converted to rhodium triflate 1b1b by treatment with AgOTf► The same reaction conditions were used to prepare complexes 2a2a, 2b2b, and 2c2c.
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► The Rh–P lengths are shorter than those of Rh–Cl.► X-ray structure of 1a1a, adopts a distorted square planar geometry.
Molecular Structure of 1a ComplexMolecular Structure of 1a Complex
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► The Copper complex reacted with PNP in Et2O @ RT to give [Cu(MeCN)(PNP)]PF6 (33) complex, which showed a singlet at δ 269.0 in the 31P{1H} NMR.
Synthesis of Copper(I) ComplexSynthesis of Copper(I) Complex
► X-ray structure of complex of 33 shows typical length for single bonds between Cu–N1, Cu–N2, Cu–P1, and Cu–P2
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Synthesis of Silver(I) ComplexSynthesis of Silver(I) Complex
► PNP was treated with AgOTf in CH2Cl2 which resulted in the formation of OTf ligand and the isolation of Complex 44.
► Results were conformed By NMR and IR.
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Crystal Structure of 4 ComplexCrystal Structure of 4 Complex
► The silver complex connected with two phosphorous atoms of the PNP ligand and two oxygen atom of H2O and OTf ligands.
► Ag–P and Ag–O lengths are in typical bond range.► The Nitrogen atom of the PNP ligand is notably distant from
the silver atom due to the 18e configuration of the complex.► Which concludes that complex 44 is a distorted-tetrahedral
structure.
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Rhodium(I), Copper(I), and Silver(I) Rhodium(I), Copper(I), and Silver(I) Complex SummaryComplex Summary
►The difference in the PNP coordination modes between 33 and 44 is due to the sizes of Cu(I) and Ag(I).
►The long M–P bond in 44 compared with those in 33, put the nitrogen atom in a remote position were direct coordination to silver is not possible.
►The observation indicated the coordination ability of PNP is higher toward Rh(I) than toward Ag(I).
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Catalytic Hydroamidation of Enones
►The catalytic activity of PNP rhodium complexes 1a1a and 1b1b was evaluated in conjugate addition of benzyl carbamate to 2-cyclohexenone Eq. 5Eq. 5
►Highly Lewis acidic metal complexes shown to highly catalyze this reaction.
►The catalytic activity increased with the increasing amount of AgOTf.
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Summary►2,6-Bis(2-phosphaethenyl)pyridine (PNPPNP)
complexes of Rh(I), Cu(I), and Ag(I) have been prepared and examined by NMR and X-ray diffraction analyses.
►The PNP ligand adopts 3(P,N,P) coordination for Rh(I) and Cu(I) and 2(P,P) coordination for Ag(I).
►The rhodium complex [RhCl(PNP)] in combination with AgOTf catalyzes conjugate addition of benzylcarbamate to enones.
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Conclusion
►We have confirmed that 2,6-bis(2-phosphaethenyl)pyridine (PNP) successfully forms neutral and cationic complexes with Rh(I), Cu(I), and Ag(I) centers.
►The Rh(I) center forms a square planar complexes, however Cu(I) and Ag(I) centers adopt a distorted-tetrahedral geometry with the PNP ligand.
►The observation indicates a strong π-accepting ability of PNP ligand to afford a highly electron-deficient metal center.
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Works CitedWorks Cited
This was an Oral-Presentation of “Synthesis, Structures, and Catalytic Properties of Late-Transition-Metal 2,6-
Bis(2-phosphaethenyl)pyridine Complexes” Article Published in the Journal of Organometallic Chemistry on May 16th, 2007, by Akito Hayashi, Masaaki Okazaki, and
Fumiyuki Ozawa.