(4-Butyl-1-ethyl-1,2,4-triazol-5-ylidene)[(1,2,5,6-η)-cycloocta-1,5-diene](triphenylphosphane)rhodium(I) tetrafluoridoborate

In the title triazole-based N-heterocyclic carbene rhodium(I) cationic complex with a tetrafluoridoborate counter-anion, the Rh center has a distorted square-planar coordination geometry with expected bond distances.


Synthesis and crystallization
1-Ethyl-1,2,4-triazole (1) was purchased from Matrix Scientific.All other compounds used in the syntheses were obtained from Sigma-Aldrich and Strem and used as received; all syntheses were performed under a nitrogen atmosphere.The reaction scheme for the synthesis of the title compound is shown in Fig. 3. 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 ppm).The title compound (4) was crystallized by slow diffusion of pentane into a CH 2 Cl 2 solution.

Figure 2
Crystal packing diagram of the title compound (4), viewed along the aaxis direction.C-H� � �F hydrogen bonds are shown as dotted green lines.

Refinement
All H atoms were placed geometrically and refined as riding atoms, with U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C).Two of the F atoms are disordered over adjacent sites in a 0.814 (4):0.186(4) ratio.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.

Table 2
Experimental details.