Crystal structure of chlorido(2-{[2-(4-chlorophenyl)hydrazin-1-ylidene-κN 1](phenyl)methyl}pyridine-κN)(η5-pentamethylcyclopentadienyl)iridium(III) tetraphenylborate

The title compound, [Ir(η5-C5Me5)Cl(C18H14ClN3)]B(C6H5)4, is chiral at the metal center and crystallizes as a racemate. In the cation, the hydrazinylidenepyridine ligand is N,N-coordinated through the N-pyridyl and N-hydrazinylidene groups forming a five-membered metallacycle. An intramolecular C—H⋯Cl hydrogen bond is observed. In the crystal, centrosymmetrically-related cations are connected by C—Cl⋯π interactions, forming a dimeric structure. The crystal packing is further stabilized by weak interionic C—H⋯π interactions.

The cationic complex adopts a typical piano-stool geometry and it is chiral at the metal center. The salt crystallizes as a racemate in the triclinic space group P-1. In the cationic complex, the hydrazinylidenepyridine ligand is N,N-coordinated, the N-hydrazinylidene and the N-pyridyl groups forming with the iridium center a five-membered metallacycle. Upon coordination, the hydrazinylidenepyridine ligand is non-planar, an angle of 55.15 (6)° is observed between the planes formed by the pyridyl and {(4-chlorophenyl)hydrazinylene}methyl groups. Otherwise, all geometrical data around the iridium(III) center are similar to those found in related N,N-chelated pentamethylcyclopentadienyl iridium complexes (Prasad et al., 2010;Payne et al., 2013). An intramolecular C-H···Cl hydrogen bond is present (Table 1).

S3. Supramolecular features
In the crystal packing of the title compound, centrosymmetrically-related cations form through the pentamethylcyclopentadienyl and 4-chlorophenyl groups a dimeric structure, the chlorine atoms sitting above the centroids of the C 5 Me 5 rings at 3.58Å (Fig. 2). In addition, crystal packing is stabilized by weak interionic C-H···π interactions (Table 1).

S5. Refinement
Except for the amine H atom, which was located in a difference Fourier map and refined freely, all hydrogen atoms were included in calculated positions and treated as riding atoms, using SHELXL-97 default parameters, with C-H = 0.93Å for C arom and 0.96Å for CH 3 , with U iso (H) = 1.2 U eq (C) or 1.5 U eq (C) for methyl H atoms.

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level.

Figure 2
Dimeric structure involving two centrosymmetrically related cations.  Hydrogen site location: inferred from neighbouring sites H atoms treated by a mixture of independent and constrained refinement

Chlorido(2-{[2-(4-chlorophenyl)hydrazin-1-ylidene-κN 1 ](phenyl)methyl} pyridine-κN)(η 5pentamethylcyclopentadienyl)iridium(III) tetraphenylborate
where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.002 Δρ max = 1.58 e Å −3 Δρ min = −1.54 e Å −3 Special details Experimental. A crystal was mounted at 173 K on a Stoe Image Plate Diffraction System (Stoe & Cie, 2000) using Mo Kα graphite monochromated radiation. Image plate distance 100 mm, φ oscillation scans 0 -180°, step Δφ = 1.2°, 5 minutes per frame. 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.