Crystal structure of bis[2-tert-butoxy-6-fluoro-3-(pyridin-2-yl-κN)pyridin-4-yl-κC 4](pentane-2,4-dionato-κ2 O,O′)iridium(III)

The IrIII atom in the title molecule adopts a distorted octahedral coordination sphere, being C,N-chelated by two main 2-tert-butoxy-6-fluoro-3-(pyridine-2-yl)pyridine-4-yl ligands and O,O′-chelated by one ancillary pentane-2,4-dionato ligand.


Chemical context
Iridium(III) compounds with fluorinated main dipyridyl ligands have attracted much attention due to their colour purity and high external quantum efficiency in organic lightemitting diodes (Lee et al., 2009;Park et al., 2013). In particular, heteroleptic Ir III compounds have many advantages such as easy tuning of emission energies and photophysical properties by modification of the ancillary ligands . Herein, we report the results of the crystal-structure determination of an iridium(III) compound, [Ir(C 14 H 14 F-N 2 O) 2 (C 5 H 7 O 2 )], with acetylacetonate (acac, O,O 0 ) as an ancillary ligand.

Structural commentary
The molecular structure of the title compound, Fig. 1, is generated by twofold rotation symmetry. The twofold rotation ISSN 1600-5368 axis passes through the Ir III atom and the central C atom (C15) of the acetylacetonate ligand. Therefore, the asymmetric unit consists of one Ir(III) atom on Wyckoff position 4e, one half of the acetylacetonate anion and one 2-tert-butoxy-6-fluoro-3-(pyridin-2-yl)pyridin-4-yl ligand. The Ir III atom is six-coordinated by the two main C,N-bidentate ligands and one ancillary O,O 0 -bidentate ligand, forming a distorted octahedral coordination sphere due to the narrow ligand bite angles, which range from 80.36 (7) to 88.65 (8) . The C,N-bidentate ligands, which are perpendicular to each other [dihedral angle between the least-squares planes = 89.95 (5) ], are arranged in a cis-C,C 0 and trans-N,N 0 fashion. The Ir-C bond length of 1.9760 (19) Å is shorter than the Ir-N bond length of 2.0344 (16) Å due to the electronegative fluorine substituent ( Table 1). The Ir-C, Ir-N, and Ir-O bond lengths are in normal ranges as reported for similar Ir III compounds, e.g.

Figure 2
Packing plot of the molecular components in the title compound. Yellow and black dashed lines represent intermolecular C-HÁ Á ÁF andstacking interactions, respectively. H atoms not involved in intermolecular interactions have been omitted for clarity.

Synthesis and crystallization
The title compound was synthesized according to a previous report . Yellow single crystals were obtained by slow evaporation from a dichloromethane/hexane solution.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.