Pentacarbonyl{3-[(2S)-1-methylpyrrolidin-2-yl]pyridine}tungsten(0)

The title compound, [W(C10H14N2)(CO)5], contains five carbonyl ligands and a nicotine ligand in an octahedral arrangement around the tungsten atom. The metal atom shows cis angles in the range 87.30 (16)–94.2 (2)°, and trans angles between 175.2 (2) and 178.1 (4)°. The W—CO bond trans to the pyridine N atom [1.987 (6) Å] is noticeably shorter than the others, which range between 2.036 (3) and 2.064 (3) Å, possibly due to the well-known trans effect. The distance between the W atom and the pyridine N atom is 2.278 (4) Å.

The title compound, [W(C 10 H 14 N 2 )(CO) 5 ], contains five carbonyl ligands and a nicotine ligand in an octahedral arrangement around the tungsten atom. The metal atom shows cis angles in the range 87.30 (16)-94.2 (2) , and trans angles between 175.2 (2) and 178.1 (4) . The W-CO bond trans to the pyridine N atom [1.987 (6) Å ] is noticeably shorter than the others, which range between 2.036 (3) and 2.064 (3) Å , possibly due to the well-known trans effect. The distance between the W atom and the pyridine N atom is 2.278 (4) Å .
It is thus envisaged that during the preparation of the precursor it is likely that such compounds as W(CO) 5 Cl - [Abel et al. (1963); Baker (1998)] may be formed, which in turn react with a single molecule of the ligand, nicotine, forming the obtained product. There is less likelihood of a direct substitution of the carbonyl ligands (Tripathi & Srivasatva, 1970) or a redox mechanism (Heyns & Buchholtz, 1976) that would most likely lead to a disubstituted compound. The coordination of nicotine to tungsten, as observed, is via the imine nitrogen as shown in the crystal structure of the compound (See Figure 1).
The W-CO bond trans to the nitrogen [1.987 (6) Å] is noticeably shorter than the others, which range between 2.036 (3) and 2.064 (3) Å, possibly due to the known trans effect. The distance between the W atom and the nicotine imine N is 2.278 (4) Å.
The infrared absorption bands of the compound show five absorption peaks at 2006.8(m), 1921.9(w), 1884.3(s), 1816.6(m) and 1760.9(m) cm -1 . Also, there is a ~1ppm shift downfield in the positions of the alpha protons on the pyridine ring of the product in both the 1 H and 13 C NMR spectra compared to the reactants. The CO that is trans to the pyridinyl structure has the most significant shift upfield, possibly due to the trans effect. Only one peak is observed for the carbonyls in the 13 C NMR spectrum, possibly due to shielding by the ring electrons leading to a slow decay, and since they are so close they appear identical.

Experimental
The procedure by Colton and Tomkins (1966) and Schlenk techniques were used to prepare tungsten halocarbonyl [W(CO) 4 Cl 2 ]. This halocarbonyl (13.13 mmol) was then reacted in situ with the base, nicotine (31.13 mmol), dissolved in freshly distilled methanol (20 ml) at -78 °C and the mixture left to warm to room temperature while stirring. The solution was stirred at room temperature for 14 h after which the solvent was removed under vacuum and the residue washed with portions of dry freshly distilled methanol and rinsed with diethylether. A yellow product was obtained in medium yield.
The crystal was grown at 4°C using a slow diffusion of dichloromethane over hexane for several days.
supplementary materials sup-2 Refinement All H atoms for (I) were found in electron density difference maps. The methyl H atoms were put in ideally staggered positions with C-H distances of 0.98 Å and U iso (H) = 1.5U eq (C). The methylene, methine and phenyl Hs were placed in geometrically idealized positions and constrained to ride on their parent C atoms with C-H distances of 0.99, 1.00 and 0.95 Å, respectively, and U iso (H) = 1.2U eq (C). Fig. 1. : The structure of the asymmetric unit of (I) with its numbering scheme. Displacement ellipsoids are drawn at the 40% probability level for non-H atoms.

Special details
Experimental. 'crystal mounted on a Cryoloop using Paratone-N' 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. 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 Rfactors(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.