Nickel complexes with “click”-derived pyridyl-triazole ligands: weak intermolecular interactions and catalytic ethylene oligomerisation

Abstract

The ligands 1-(cyclohexyl)-4-(2-pyridyl)-1,2,3-triazole (1), 1-(2,6-diisopropylphenyl)-4-(2-pyridyl)-1,2,3-triazole (2), 1-(4-butoxyphenyl)-4-(2-pyridyl)-1,2,3-triazole (3) and 1-(methyl)-4-(2-pyridyl)-1,2,3-triazole (4) were synthesized by the Cu(I) catalyzed "Click" reaction between 2-pyridylacetylene and the corresponding azides. The ligands were then reacted with NiBr(2)·3H(2)O to generate the complexes (1)(2)NiBr(2) (1a), (2)(2)NiBr(2) (2a), (3)(2)NiBr(2) (3a) and (4)(2)NiBr(2) (4a). Structural characterization of 1a confirmed the mononuclear and distorted octahedral environment around the Ni(II) center, with the pyridyl-triazole ligands coordinating in a bis-chelating fashion. Bond length analysis inside the 1,2,3-triazole ring shows a short N=N double bond that is flanked by two longer C-N and N-N bonds pointing to the existence of "azo" character in the ring. The highly polar five-membered 1,2,3-triazole ring makes its C-H bond acidic, and these bonds participate in an extended weak intermolecular C-H···Br interactions with the Br-groups of neighboring molecules, resulting in a 3-D network. The nickel complexes with these "Click" ligands were tested as pre-catalysts for ethylene oligomerization, and the complexes showed moderate activity in that reaction with good selectivity towards C4 oligomers.

Pyridine–triazole ligands for copper-catalyzed aerobic alcohol oxidation

“…Furthermore, for both complexes 1 and 3, the pyridyl N and the triazole N donors are mutually trans to each other. This structural arrangement has previously been observed in related octahedral bis(pyridine-triazolyl) complexes of Cu(II), 30 Ni(II), 31 and Zn(II) 32 as well as square planar Pd(II) complexes. showing 30% probability displacement ellipsoids and partial atom-labeling scheme.…”

Jahn–Teller distortion in 2-pyridyl-(1,2,3)-triazole-containing copper(ii) compounds

“…The packing of the [Cu(L 2 )2Cl2] compound (with ligand substituent R = CH3) is discussed here, as an example of the packing observed in the solid state for all the [Cu(L n )2Cl2] compounds (L n = L 2 , L 6 , L 7 , L 8 and L 9 ) of this study. The molecules are arranged in a head to tail arrangement, similar to the arrangements reported for complexes of Ni(II), Co(II) and Zn(II) metals with these pyridyl-triazole ligands [6,7,20]. The crystal structure of the [Cu(L 2 )2Cl2] complex is governed by extensive hydrogen bonding CH...Cl interactions, between the chloride coligands which are bound to the copper centres of one molecule, and three of the nearest C-H bonds on the L 2 ligand of a neighbouring molecule, as well as to a CH bond of a methyl substituent on another adjacent molecule; see Figure 6.…”

Novel dichloro(bis{2-[1-(4-methylphenyl)-1H-1,2,3-triazol-4-yl-κN3]pyridine-κN})metal(II) coordination compounds of seven transition metals (Mn, Fe, Co, Ni, Cu, Zn and Cd)

“…The existence of relatively basic nitrogen atoms in the 1,2,3-triazole rings, and the possibility of introducing additional donor groups in the substituents (Figure 1), made the CuAAC "click" reaction an attractive method to prepare differently substituted 1,2,3-triazoles. These compounds have been used as ligands to coordinate to various metal ions that display a range of applications such as in electrochemical and photochemical studies, in supramolecular chemistry, magnetism, metal-ion sensing and catalysis [4]. The reasons for the success of the "click" reaction, is that it is easy to carry out and is widely applicable.…”