[(1,2,5,6-η)-Cycloocta-1,5-diene](1-ethyl-4-isopropyl-1,2,4-triazol-5-ylidene)(triphenylphosphane)iridium(I) tetrafluoridoborate dichloromethane sesquisolvate

The synthesis and crystal structure of a new triazole-based N-heterocyclic carbene iridium(I) cationic complex with a tetrafluoridoborate counter-anion and solvating dichloromethane is reported. The IrI center of the cationic complex has a distorted square-planar conformation, formed by a bidentate cycloocta-1,5-diene (COD) ligand, an N-heterocyclic carbene, and a tripheylphosphane ligand. There are weak hydrogen-bonding interactions between C—H groupings of the iridium complex and F atoms of the [BF4]− counter-ions.

The molecular structure of the title complex (3), shown in Fig. 1, is characterized as an Ir I cationic complex with a tetrafluoridoborate counter-ion and incorporates 1.5 dichloromethane solvent molecules.The distorted square-planar geometry of the coordination sphere around the Ir I atom is formed by a bidentate cycloocta-1,5-diene (COD) ligand, the carbene C atom of the triazole NHC ligand, and the P atom of the triphenylphosphane ligand.The distorted square-planar geometry exhibits a P1-Ir1-C1 bond angle of 92.69 (7) � .The carbene C atom bonded to the central Ir I atom exhibits a bond angle that significantly differs from the expected sp 2 hybridization with an N1-C1-N3 bond angle of 103.5 (2) � , as observed in similar structures.An intramolecular C-H� � ��(ring) interaction is observed between a hydrogen atom on the isopropyl wingtip of the NHC (H6A) ligand and a phenyl phosphane ring (C8-C13) with an H� � �centroid distance of 2.67 A ˚and a C-H� � �centroid angle of 168 � .
In the extended structure, weak hydrogen-bonding interactions between a C-H grouping of the N-heterocyclic carbene and F atoms of the [BF 4 ] À counter-ion are observed along with interactions between the triphenyl phosphane ligand and the [BF 4 ] À counter-ion (Table 1).Fig. 2 shows the packing diagram of the title complex.
The crystal structure of the triazolium salt that was used in the synthesis of the title compound was previously determined (Maynard et al., 2023).Comparison of triazolium salt bond angles and lengths with the bond angles and lengths of the NHC in the title complex are summarized in Tables 2 and 3, respectively.The most significant changes occur for the carbon atom coordinating to the metal center: the N1-C1-N3 bond angle goes from 107 � in the triazolium salt to 103.5 (2) � when coordinating to the iridium atom as an NHC and the C-N bond lengths (C1-N1 and C1-N3) elongate by about 0.03 A ẘhen the NHC coordinates to the metal.

Figure 1
The molecular entities in the crystal structure of the title compound 3. Displacement ellipsoids are drawn at the 50% probability level.Fig. 3 were obtained from Sigma-Aldrich and Strem and used as received.All subsequent synthesis procedures were performed under an N 2 atmosphere using reagent grade solvents, which were used as received without further purification.NMR spectra were recorded at room temperature in CDCl 3 on a 400 MHz (operating at 162 MHz for 31 P) Varian spectrometer and referenced to the residual solvent peak (� in ppm).The title compound (3) was crystallized by slow diffusion of pentane into a CH 2 Cl 2 solution.

Refinement
Crystal data, data collection, and structure refinement details are summarized in Table 4.

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.The H atoms were placed in claculated locations (C-H = 0.95-0.99Å) and refined as riding atoms with U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C).

Figure 2
Figure 2 Crystal packing of 3 shown along the a axis direction.Non-classical hydrogen bonding interactions are shown as dotted green lines.C-H� � ��(ring) interactions are shown as dashed orange lines between hydrogen atoms and phenyl ring centroids.

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

Table 3
Comparison of bond lengths (A ˚) for NHC and triazolium salt.