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

The title triazole-based N-heterocyclic carbene iridium(I) cationic complex with a tetrafluoridoborate counter-anion, crystallizes with two cations and two anions in the asymmetric unit. In the extended structure, non-classical C–H⋯F hydrogen bonds, one of which is notably short (H⋯F = 2.21 Å), link the cations and anions.

The molecular structure of the title complex, [Ir(C 8 H 12 )(C 18 H 15 P)(C 8 H 15 N 3 )][BF 4 ] (3), comprises an Ir I cation complex and a tetrafluoridoborate counter-anion, as shown in Fig. 1.No solvent molecules are found in the structure.Two cations (A containing Ir1 and B containing Ir1 0 ) and two anions are contained in the assymetric unit, which crystallizes in the monoclinic space group Pc.The distorted square-planar geometry around the iridium atoms is characterized by C1-Ir-P bond angles of 92.97 (14) � for cation A and 91.62 (15) � for cation B. The N-C-N bond angles of the NHC ligand are 102.8(4) and 102.6 (4) � for cations A and B, respectively.The metal-phosphorous and metal-carbene bond lengths of the title compound are similar to those of the previously published rhodium analogue (Lerch et al., 2024) with Ir-C NHC bond lengths of 2.035 (5) A ˚(cation A) and 2.034 (5) A ˚(cation B) and Ir-P bond lengths of 2.3145 (13) A ˚(cation A) and 2.3154 (13) A ˚(cation B).Fig. 2 shows the packing viewed along the a axis with non-classical C-H� � �F hydrogen bonds (Table 1) in the range of 2.21-2.49A ˚for the H� � �F contacts shown as dotted red lines.The shortest C-H� � �F contacts arise from interactions from the CH moieties of the NHC (C2 and C2 0 ) interacting with adjacent tetrafluoridoborate anions.

Synthesis and crystallization
4-Butyl-1-ethyl-1,2,4-triazolium bromide (1) was synthesized by a previously published procedure (Lerch et al., 2024).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 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 p.p.m.).The title compound (3) was crystallized by slow diffusion of pentane into a CH 2 Cl 2 solution.

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.

Fractional atomic coordinates and isotropic
Figure 1

Figure 2
Figure 2 Crystal packing diagram of the title compound (3), viewed along [100].C-H� � �F hydrogen bonds are shown as dotted red lines.

Figure 3
Figure 3Reaction scheme for the synthesis of (3).

Table 2
Experimental details.