Crystal structure of (OC)5W(μ-dppe)W(CO)5

In the title complex two W(CO)5 moieties are bridged by a bis(diphenylphosphanyl)ethane (dppe) ligand. Both tungsten atoms have a slightly distorted octahedral coordination.


Chemical context
In 1976, Pickett and Pletcher studied the mechanism of reduction of a group 6 carbonyl complex in the presence of carbon dioxide (Pickett & Pletcher, 1976). Recently Grice & Saucedo (2016) have shown that group 6 metal-carbonyl complexes without 'non-innocent' ligands can electrocatalytically reduce CO 2 . Dickson et al. (1989) varied the ligand Ph 2 P(CH 2 ) n PPh 2 (n = 2, 4, and 5), finding that the predominate product in the reactions of n = 2 and 5 is the bridged complex (OC) 5 W[-Ph 2 P(CH 2 ) n ]PPh 2 )W(CO) 5 , whereas when n = 4 it was reported the chelated product is favored (W(CO) 4 [-Ph 2 P(CH 2 ) 4 PPh 2 ]. Tan et al. (1994) reported the separation of several diphosphine-bridged group 6 decacarbonyl complexes by HPLC, but no further characterization was reported. Keiter et al. (1981) and Gan et al. (1993) have reported group 6 heterobimetallic complexes using dppe as the bridging ligand. The title complex has been reported by Keiter & Shah (1972), Ozer et al. (1993), and El-Khateeb et al. (2002), but the structure has yet to be published. We report here its single crystal X-ray structure determination.

Structural commentary
The molecular structure of (OC) 5 W(-dppe)W(CO) 5 ( Fig. 1) consists of two six-coordinate tungsten(0) atoms, each in a slightly distorted octahedral environment. The coordination environment of tungsten has five carbonyl ligands and one phosphorus atom from the dppe ligand. The axial carbonyl ISSN 2056-9890 ligands have a bond length of 2.015 (3) Å and the average bond length for the equatorial carbonyl ligands is 2.048 (8) Å . The W1-P1 bond length is 2.5200 (8) Å and the P1-W1-C(axial) bond angle is 178.79 (9) . The average P1-W1-C(equatorial) bond angle is 90.10 (18) . Examination of the dppe backbone shows the P1-C13 bond length at 1.843 (3) Å and the C13-C13 bond length at 1.531 (6) Å . The molecule sits on a center of symmetry.

Supramolecular features
The two tungsten atoms in each of the molecules (OC) 5 W(dppe)W(CO) 5 are bridged by a diphosphine approximately along the c axis and the molecules themselves are stacked along the a axis. No significant van der Waals-type interactions such as C-HÁ Á Á orcontacts between adjacent molecules are observed.

Synthesis and crystallization
All synthesis and crystallization procedures were carried out using standard Schlenk techniques. Dichloromethane was added to a mixture of W(CO) 5 (NH 2 C 6 H 5 ) (0.10 g, 2.9 mmol) and dppe (0.12 g, 3.0 mmol) to produce a golden yellow solution. After two h, methanol was added to precipitate a yellow solid. The precipitate was collected and washed with methanol (3 x 20 mL). The resulting yellow solid was recrystallized from a 1:5 mixture of dichloromethane:methanol at 253 K.

Refinement
Crystal data, data collection, and structure refinement details are summarized in Table 1. The phenyl H-atom positions and the methylene H atoms on the ligand backbone have been positioned according to idealized C-H distances.

[µ-Ethane-1,2-diylbis(diphenylphosphane)-κ 2 P:P′]bis[pentacarbonyltungsten(0)]
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. Refinement. All nonhydrogen atoms were located in a single difference Fourier electron density maps and refined using anisotropic diplacement parameters. All C-H hydrogen atoms were placed in calculated positions with Uiso = 1.2xUeqiv of the connected C atoms