Chlorido[(1,2,5,6-η)-cycloocta-1,5-diene](1-ethyl-4-isobutyl-1,2,4-triazol-5-ylidene)rhodium(I)

A new neutral triazole-based N-heterocyclic carbene rhodium(I) complex [RhCl(C8H12)(C8H15N3)], has been synthesized and structurally characterized. The complex crystallizes with two molecules in the asymmetric unit. The rhodium center has a distorted square-planar conformation, formed by a cycloocta-1,5-diene (COD) ligand, an N-heterocyclic carbene (NHC) ligand, and a chloride ligand.


Synthesis and crystallization
1-Ethyl-1,2,4-triazole (1) was purchased from Matrix Scientific.All other compounds used in the syntheses, detailed in Fig. 4, were obtained from Sigma-Aldrich and Strem and used as received; all syntheses were performed under a nitrogen atmosphere.NMR spectra were recorded at room temperature in CDCl 3 on a 400 MHz (operating at 100 MHz for 13 C and 162 MHz for 31 P) Varian spectrometer and referenced to the residual solvent peak (� in p.p.m.).The title compound (3) was crystallized by slow diffusion of pentane into a CH 2 Cl 2 solution.

Figure 1
Asymmetric unit of the title compound (3) showing the two molecular units.Displacement ellipsoids are drawn at the 50% probability level.
(15 ml), and the mixture was refluxed in the dark for 48 h.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

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.

Figure 2
Figure 2View of one molecule of the title compound (3) showing the ethyl and isobutyl wingtips oriented on the same side of the NHC ring and away from the COD ligand.

Figure 3
Figure 3 Crystal packing diagram of the title compound (3) viewed along the a axis.C-H� � �Cl non-standard hydrogen-bonding interactions are shown as dotted green lines.

Table 2
Experimental details.