Synthesis, crystal structure and Hirshfeld surface analysis of [bis(diphenylphosphanyl)methane-κP]chloridobis[2-(pyridin-2-yl)phenyl-κ2 N,C 1]iridium(III)

The title IrIII complex was synthesized from the substitution reaction between the (ppy)2Ir(μ-Cl)2Ir(ppy)2 (ppy = deprotonated 2-phenylpyridine, C11H8N−) dimer and 1,1-bis(diphenylphosphanyl)methane (dppm, C25H22P2) under an argon gas atmosphere. The IrIII atom is coordinated by two C,N-bidentate ppy anions, a unidentate dppm ligand and a chloride anion in a distorted octahedral IrC2N2PCl arrangement.


Chemical context
Iridium(III) complexes have been investigated for decades because of their stability (Jian et al., 2011;Lee et al., 2009;Tsuboyama et al., 2003), promising luminescent properties (Lin et al., 2011;Lowry et al., 2004;Tamayo et al., 2003) and medicinal applications, especially as anticancer agents (Hearn et al., 2018;Rubio et al., 2020;Xiao et al., 2018). The syntheses of cyclometallated iridium(III) complexes have mainly focused on the 2-phenylpyridine (ppy) ligand and its derivatives. The octahedral geometry of bis-complexes is commonly selected as the main backbone accompanied by various types of ancillary ligands. Most of them are N-donor ligands (Chi & Chou, 2010;Goldsmith et al., 2005;Lin et al., 2011) owing to the strong binding of the borderline acid metal and basic ligand. However, there are fewer reports of P-donor ancillary ligands. In this present work, we report the synthesis and characterization of the title photoactive complex, (I), obtained by the reaction between (ppy) 2 Ir(-Cl) 2 Ir(ppy) 2 ) dimer (ppy = deprotonated 2-phenylpyridine, C 11 H 8 N À ) with 1,1-bis(diphenylphosphanyl)methane under an inert gas atmosphere. ISSN 2056-9890

Structural commentary
The asymmetric unit of (I) shows a distorted octahedral molecular structure to overcome steric hindrance between the ligands ( Fig. 1) in space group P2 1 /n. The Ir III atom is linked to two C,N-bidentate 2-phenylpyridine (ppy) anions through five-membered chelate rings where the N1 and N2 atoms of the ppy pyridine rings exist in a trans orientation to each other [N1-Ir1-N2 = 170.97 (9) ] and C11 and C22 are in cis orientation  ]. The bond lengths of Ir1-N1, Ir1-N2, Ir1-C11 and Ir1-C22 are 2.051 (2), 2.062 (2), 2.004 (3) and 2.032 (3) Å , respectively. As expected, the averaged Ir-C and Ir-N bond lengths are much shorter than the Ir-Cl and Ir-P bonds, based on the sizes of the different species.

Figure 1
The molecular structure of the title compound, including atom labelling. Displacement ellipsoids are drawn at the 30% probability level.

Hirshfeld surface analysis
Additional insights into the weak intermolecular contacts in the crystal packing of (I) were gained from Hirshfeld surface analysis and the two-dimensional fingerprint plots (McKinnon et al., 2004;2007;Spackman & Jayatilaka, 2009) generated using Crystal Explorer 17.5 program (Turner et al., 2017). The Hirshfeld surfaces were mapped over the normalized contact distance (d norm ) with the functions d e and d i , which are the distances from an indicated area on the Hirshfeld surface to the nearest atoms outside and inside the surface, respectively. The white, red, and blue areas on the d norm -mapped Hirshfeld surfaces show intermolecular contacts that are equal to, shorter than, and longer than the sum of their van der Waals (vdW) radii, respectively. A pair of intermolecular contacts are shown as red spots on the Hirshfeld surface close to the Cl1 atom of the adjoining molecule and the H14 atom of the associated pyridine ring. The spots indicate hydrogen-bond donor-to-acceptor interactions of C14-H14Á Á ÁCl1 and vice versa (Fig. 5). The relative contributions of the various types of contacts to the total of intermolecular interactions across the Hirshfeld surface are represented in two-dimensional fingerprint plots. Total intermolecular interactions (100%) are shown in Fig Table 2 Hydrogen-bond geometry (Å , ).

Synthesis and crystallization
The title complex was synthesized from the reaction between (ppy) 2 Ir(-Cl)2Ir(ppy) 2 (0.5 mmol) and bis(diphenylphosphanyl)methane (1.25 mmol) in CH 2 Cl 2 solution. The reaction was carried out by refluxing the mixture under Ar gas for 20 h. The solution mixture was then cooled to room temperature and the solvent was evaporated. The crude yellow product thus obtained was washed with diethyl ether to remove excess ligands and impurities, and the complex was crystallized and recrystallized in mixed solvents of dichloromethane:diethyl ether (9:1) at room temperature three times, yielding yellowish crystals (

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. H atoms were included in calculated positions [C-H = 0.93 (aromatic) or 0.97 Å (Csp 2 )] and refined as riding with U iso (H) = 1.2U eq (C).  used to prepare material for publication: WinGX publication routines (Farrugia, 2012) and publCIF (Westrip, 2010).

[Bis(diphenylphosphanyl)methane-κP]chloridobis[2-(pyridin-2-yl)phenyl-κ 2 N,C 1 ]iridium(III)
Crystal data 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.