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

The syntheses and crystal structures of a triazolium salt, 4-benzyl-1-ethyl-1,2,4-triazolium bromide, CHN ·Br (), and the corresponding N-heterocyclic carbene complexes, (4-benzyl-1-ethyl-1,2,4-triazol-5-yl-idene)chlorido-[(1,2,5,6-η)-cyclo-octa-1,5-diene]rhodium(I), [RhCl(CH)(CHN)] (), (4-benzyl-1-ethyl-1,2,4-triazol-5-yl-idene)(1,2,5,6-η)-cyclo-octa-1,5-dieneiridium(I) tetra-fluorido-borate, [Ir(CH)(CHN)(CHP)]BF (), and (4-benzyl-1-ethyl-1,2,4-triazol-5-yl-idene)(1,2,5,6-η)-cyclo-octa-1,5-dieneiridium(I) tetra-fluorido-borate dicholoro-methane sesquisolvate, [Ir(CH)(CHN)(CHP)]BF·1.5CHCl (), are presented. Complexes and crystallize in the monoclinic space group 2/, complex in the triclinic space group 1 and complex in the triclinic space group 1 with two mol-ecules in the asymmetric unit. The three metal complexes , , and have a distorted square-planar geometry around the metal ions. The N1-C1-N3 bond angle in the triazolium salt is 107.1 (2)° and is observed in the range of 102.2 (3) to 103.8 (5)° in the NHC ligands in complexes , , and . The two substituent 'wing tips' in the NHC ligand (N-ethyl and N-benz-yl) are oriented in an -arrangement in compounds and , a -arrangement in compound , and both and -arrangements in the two independent ion pairs in compound . All structures exhibit non-classical hydrogen-bonding inter-actions with the most acidic hydrogen atoms in complexes and playing critical roles in the orientations of structural units.