(Chlorido/bromido)[(1,2,5,6-η)-cycloocta-1,5-diene](4-isopropyl-1-methyl-1,2,4-triazol-5-ylidene)rhodium(I)

The RhI atom in the title compound has a distorted square-planar coordination environment, defined by a bidentate cycloocta-1,5-diene (COD) ligand, an N-heterocyclic carbene and a chloride ligand with bromide substitutional disorder.

A new triazole-based neutral Rh I complex, [Rh(Cl 0.846 Br 0.154 )(C 6 H 11 N 3 )-(C 8 H 12 )], has been synthesized and structurally characterized. The Rh I atom has a distorted square-planar coordination environment, formed by a bidentate cycloocta-1,5-diene (COD) ligand, an N-heterocyclic carbene and a halide ligand that shows substitutional disorder (Cl:Br = 0.846:0.154). No significant intermolecular interactions other than van der Waals forces are found in the crystal structure. Diffraction data indicated a two-component inversion twin with a ratio of 0.95 (5):0.05 (5).
The molecular structure of the title complex, [Rh(Cl 0.846 Br 0.154 )(C 6 H 11 N 3 )(C 8 H 12 )] (3), is illustrated in Fig. 1. The coordination environment around the Rh I ion, formed by the bidentate cycloocta-1,5-diene (COD), NHC, and halide (Cl,Br) ligands is distorted data reports square-planar. The Rh-C(NHC) bond length is found to be 2.016 (5) Å . The C(NHC)-Rh-(Cl,Br) bond angle is 87.93 (14) . The N-(carbene)-N bond angle in the triazolebased carbene is 103.1 (4) . Fig. 2 shows the crystal packing diagram of the complex. No non-covalent interactions exist between atoms that are closer than the sum of the van der Waals radii.

Synthesis and crystallization
1-Methyl triazole (1) was purchased from Matrix Scientific and the subsequent syntheses, as shown in Fig. 3, were performed using reagent-grade solvents without further purification. NMR spectra were recorded at room temperature in CDCl 3 on a 400 MHz Varian spectrometer and referenced to the residual solvent peak ( in ppm and J in Hz). The triazolium salt (2) was prepared by reacting (1) with isopropyl (i-Pr) bromide in toluene at reflux for 24 h followed by isolation with diethyl ether. The title metal complex (3) was synthesized by in situ transmetallation from the silver carbene complex of (2) (Chianese et al., 2003). The pale-yellow complex (3)  Pale-yellow X-ray quality crystals of (3) were grown from 1:1, CH 2 Cl 2 / pentane by slow diffusion.

Figure 2
Crystal packing diagram of the title compound (3) along the a axis.

Figure 3
Reaction scheme summarizing the synthesis of the N-heterocyclic carbene ligand (2) and metal complex (3).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1. Using only the Cl ligand in the refinement did not account for all electron density at the ligand location, and therefore, a Cl/Br substitutional disorder was introduced for this site. The refinement was stabilized by forcing Cl and Br to have the same atomic coordinates and ADPs, using EXYZ and EADP instructions, respectively, in SHELXL (Sheldrick, 2015b). The resulting occupancies for Cl and Br were about 85% and 15%, respectively. The crystal was refined as a two-component inversion twin with a ratio of 0.95 (5)  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.65 e Å −3 Δρ min = −0.42 e Å −3 Absolute structure: Refined as an inversion twin. Absolute structure parameter: 0.05 (5)

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refined as a 2-component inversion twin.