Syntheses and crystal structures of 4-benzyl-1-ethyl-1,2,4-triazolium bromide and its corresponding NHC complexes of rhodium and iridium

Abstract

The syntheses and crystal structures of a triazolium salt, 4-benzyl-1-ethyl-1,2,4-triazolium bromide, and the corresponding N-heterocyclic carbene complexes, (4-benzyl-1-ethyl-1,2,4-triazol-5-yl­idene)chlorido­[(1,2,5,6-η)-cyclo­octa-1,5-diene]rhodium(I), (4-benzyl-1-ethyl-1,2,4-triazol-5-yl­idene)[(1,2,5,6-η)-cyclo­octa-1,5-diene](tri­phenyl­phosphane)iridium(I) tetra­fluorido­borate and (4-benzyl-1-ethyl-1,2,4-triazol-5-yl­idene)[(1,2,5,6-η)-cyclo­octa-1,5-diene](tri­cyclo­hexyl­phosphane)iridium(I) tetra­fluorido­borate dicholoro­methane sesquisolvate, are presented. All structures exhibit non-classical hydrogen-bonding inter­actions with the most acidic hydrogen atoms in two of them playing critical roles in the orientations of structural units.

The syntheses and crystal structures of a triazolium salt, 4-benzyl-1-ethyl-1,2,4-triazolium bromide, C₁₁H₁₄N₃⁺·Br⁻ (2), and the corresponding N-heterocyclic carbene complexes, (4-benzyl-1-ethyl-1,2,4-triazol-5-yl­idene)chlorido­[(1,2,5,6-η)-cyclo­octa-1,5-diene]rhodium(I), [RhCl(C₈H₁₂)(C₁₁H₁₃N₃)] (3), (4-benzyl-1-ethyl-1,2,4-triazol-5-yl­idene)[(1,2,5,6-η)-cyclo­octa-1,5-diene](tri­phenyl­phosphane)iridium(I) tetra­fluorido­borate, [Ir(C₈H₁₂)(C₁₁H₁₃N₃)(C₁₈H₁₅P)]BF₄ (5), and (4-benzyl-1-ethyl-1,2,4-triazol-5-yl­idene)[(1,2,5,6-η)-cyclo­octa-1,5-diene](tri­cyclo­hexyl­phosphane)iridium(I) tetra­fluorido­borate dicholoro­methane sesquisolvate, [Ir(C₈H₁₂)(C₁₁H₁₃N₃)(C₁₈H₃₃P)]BF₄·1.5CH₂Cl₂ (6), are presented. Complexes 2 and 6 crystallize in the monoclinic space group P2₁/c, complex 3 in the triclinic space group P1 and complex 5 in the triclinic space group P1 with two mol­ecules in the asymmetric unit. The three metal complexes 3, 5, and 6 have a distorted square-planar geometry around the metal ions. The N1—C1—N3 bond angle in the triazolium salt 2 is 107.1 (2)° and is observed in the range of 102.2 (3) to 103.8 (5)° in the NHC ligands in complexes 3, 5, and 6. The two substituent ‘wing tips’ in the NHC ligand (N-ethyl and N-benz­yl) are oriented in an anti-arrangement in compounds 2 and 3, a syn-arrangement in compound 6, and both syn and anti-arrangements in the two independent ion pairs in compound 5. All structures exhibit non-classical hydrogen-bonding inter­actions with the most acidic hydrogen atoms in complexes 2 and 3 playing critical roles in the orientations of structural units.