Tripodal Ligands (TMG3trphen-E) That Feature Heavy Pnictogen Elements (E = Sb(III), Bi(III)) And Tetramethylguanidinyl (TMG) Arms Have Been Explored In Stabilizing Cu(I) And Ag(I) Sites And Facilitating Nitrene-Transfer Chemistry. Compounds [(TMG3trphen-E)M3(Μ-X)3] (M = Cu(I), Ag(I); X = Cl, Br, I) Have Been Generated Upon Extraction Of M3(Μ-X)3 Units From MX Sources, Exhibiting Support Of The Crown-Shaped M3(Μ-X)3 Fragment By M-NTMG Bonds And Triply Bridging E → M3 Interactions. Orbital Interactions Between Cu(I) Sites And NTMG Residues Are More Dominant Than Sb/Bi → Cu3 Donor Interactions Between The Sb 5s Or Bi 6s Orbitals And Admixed Cu 4s/3d Orbitals, With Larger Interaction Energies Computed For Sb → Cu3. Nonhalogenated Copper Compounds [(TMG3trphen-E)2Cu2]2+2Y- (Y = PF6, B(C6F5)4) Have Been Synthesized Via Dechlorination By TlPF6 Or By Application Of Halide-Free Cu(I) Sources With TMG3trphen-E Ligands. Nitrene-Transfer To Olefins Mediated By [(TMG3trphen-E)Cu3(Μ-Cl)3] (E = Sb And Bi) Affords Aziridines In Good Yields, Primarily For Unencumbered Styrenes And With The More Robust Sb Catalyst. Amination Of C-H Bonds Is Most Effective With Sec-Benzylic Substrates And Requires A More Electrophilic Nitrene (NTces) To Achieve Practicable Yields With Halogenated Or Nonhalogenated Copper Precursors. Hammett Plots Indicate That The Competitive Amination Of Para-Substituted Ethylbenzenes Enabled By [(TMG3trphen-Sb)Cu3(Μ-Cl)3] Involves Stepwise C-H Functionalization.
Available at: http://works.bepress.com/amitava-choudhury/126/
National Institutes of Health, Grant R15GM117508