Click-triazole N2 coordination to transition-metal ions is assisted by a pendant pyridine substituent.
We report that 1-(2-picolyl)-1,2,3-triazole (click triazole) forms stable complexes with transition-metal ions in which the coordination involves the triazole N2 nitrogen atom and the pendant 2-picolyl group. This is exemplified by model compound 1-(2-picolyl)-4-phenyl-1H-1,2,3-triazole (L(x)) and its complexes with transition-metal ions of Pt(II), Pd(II), Cu(II), Ru(II), and Ag(I). The coordination was investigated experimentally and theoretically. Ligand L(x) easily reacted at room temperature with cis-[PtCl(2)(DMSO)(2)], [Pd(CH(3)CN)(4)](BF(4))(2), CuCl(2), [RuCl(mu-Cl)(eta(6)-p-cymene)](2), and AgNO(3) to give stable chelates [PtCl(2)L(x)] (1), [Pd(L(x))(2)](BF(4))(2) (2), [CuCl(2)(L(x))(2)] (3), [RuCl(eta(6)-p-cymene)L(x)]OTf (4), and [Ag(2)(L(x))(2)(NO(3))(2)] (5), respectively, in 60-98% yield. The structures of 1-5 were unambiguously confirmed by NMR spectroscopy and single-crystal X-ray diffraction analysis. Density functional theory calculations were carried out in order to theoretically investigate the stabilization factors in 1-5. A comparison of the chelating properties of ligand L(x) was made with structurally similar and isomeric 1-(2-aminoethyl)-substituted 1,2,3-triazole (L(y)) and 4-(2-aminoethyl)-substituted 1,2,3-triazole (L(z)). The complexation affinity of L(x) was attributed to pi-back-donation from the metal to the pendant pyridine side arm, whereas the stability of the complexes involving L(y) and L(z) mainly originates from efficient pi-back-donation to the triazole ring.
Urankar
Damijana
D
Faculty of Chemistry and Chemical Technology, University of Ljubljana, Askerceva 5, Ljubljana, Slovenia.
Pinter
Balazs
B
Pevec
Andrej
A
De Proft
Frank
F
Turel
Iztok
I
Kosmrlj
Janez
J
D003198:Computer Simulation; D018360:Crystallography, X-Ray; D007477:Ions / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry*; D028561:Transition Elements / Q000737:chemistry*; D014230:Triazoles / Q000737:chemistry*
D007477:Ions; D008024:Ligands; D009942:Organometallic Compounds; D011725:Pyridines; D028561:Transition Elements; D014230:Triazoles