Crystal structure of chlorido(η2-phenyl isothiocyanate-κ2 C,S)-mer-tris(trimethylphosphane-κP)iridium(I)

In this distorted octahedral iridium complex, the three PMe3 ligands are arranged in a meridional geometry, with the chloride ion cis to all three PMe3 groups and the phenyl isothiocyanate ligand bonded in an η2-fashion through the C and S atoms. The geometric parameters for the metal-complexed PhNCS group are compared with other metal-complexed phenyl isothiocyanates, as well as with examples of uncomplexed aryl isothiocyanates.


Chemical context
Various phenyl isothiocyanate complexes of metals have been characterized, all showing the effect of complexation of lengthening of N-C and C-S bonds and the bending of the N-C-S angle away from linearity. Complexation of an aryl isothiocyanate to a metal has a similar effect across a wide range of metal systems with the N-C bond length averaging about 1.26 Å , the C-S distance averaging about 1.74 Å and the N-C-S bond angle ranging from 137 to 142 .

Structural commentary
The molecule of the title iridium compound has a distorted octahedral coordination sphere with three PMe 3 ligands arranged in a meridional geometry, a chloride ion cis to all three PMe 3 groups and the phenyl isothiocyanate bonded in an 2 fashion to the C and S atoms (Fig. 1). The C atom is trans to the chloride ion and the S atom is significantly off from an ideal octahedral geometry [the P2-Ir1-S1 angle is 144.51 (5) instead of the expected angle near 180 ].
Upon complexation to the iridium cation in the title compound, the N-C bond in phenyl isothiocyanate lengthens to 1.256 (7) Å , the C-S bond lengthens to 1.757 (6) Å and the N-C-S bond angle bends to 137.2 (4) . These significant changes in geometry reflect the normal consequences of -bonding of the C-S -electrons to the metal and -backbonding from the metal to the *-orbitals of the ligand.

Database survey
A search of the Cambridge Crystallographic Database (Groom & Allen, 2014) on 28 January 2014 found 16 aryl isothiocyanates in which the SCN group is not disordered on coordinating to a metal. All of those structures display a nearly linear N-C-S geometry (ranging from 174-179 with an average of 176 ). The multiply bonded nature of both the C-S and C-N bonds is seen in the bond lengths. For C-N, the distances range from 1.14 to 1.17 Å with an average of 1.16 Å and the C-S distances range from 1.54 to 1.59 Å with an average of 1.57 Å . Of those 16, four structures of good precision with no disorder, ionic interactions or other complex interactions that could affect the geometry of the N-C-S group were chosen for comparison to contrast 'free' versus 'complexed' isothiocyanates. The first entry in Table 1 shows the average values for all 16 structures, the next four entries are the specific non-complexed aryl isothiocyanates, the next six entries are other examples from the CCDC in which phenyl isothiocyanate is complexed to a metal and the last entry is the data from the title compound. For the structures of several uncomplexed aryl isothiocyanates, see: Majewska et al. (2007Majewska et al. ( , 2008; Laliberté et al. (2004); Biswas et al. (2007). For the structures of a cobalt and a nickel complex of phenyl isothiocyanate, see: Bianchini et al. (1984). For the structure of a vanadium complex of phenyl isothiocyanate see: Gambarotta et al. (1984). For a phenyl isothiocyanate complex of molybdenum, see: Ohnishi et al. (2005). For a phenyl isothiocyanate complex of osmium, see: Flü gel et al. (1996). For a tris-trimethylphosphine nickel complex of phenyl isothiocyanate, see: Huang et al. (2013).

Figure 1
Displacement ellipsoid drawing of the title compound. Ellipsoids are drawn at the 50% probability level and hydrogen atoms are omitted for clarity. octadiene) and phenyl isothiocyanate in toluene solution. Suitable single crystals were grown from dichloromethane by the layering of diethyl ether.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were placed at calculated positions and refined using a model in which the hydrogen rides on the atom to which it is attached. For methyl hydrogen atoms U iso (H) = 1.5Ueq(C) and for the phenyl hydrogen atoms, U iso (H) = 1.2Ueq(C).

Chlorido(η 2 -phenyl isothiocyanate-κ 2 C,S)-mer-tris(trimethylphosphane-κP)iridium(I)
Crystal data [IrCl(C 7 H 5 NS)(C 3 H 9 P) 3 ] M r = 591.05 Monoclinic, P2 1 /n a = 8.964 (2)  Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.00040 (9) 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.