cis-[1,2-Bis(diphenylarsanyl)ethane-κ2 As,As’]tetracarbonylchromium(0)

In the title compound, [Cr(C26H24As2)(CO)4], the Cr atom is octahedrally coordinated by four carbonyl ligands and one bidentate 1,2-bis(diphenylarsanyl)ethane ligand, which chelates in a cis manner with an As—Cr—As bite angle of 82.513 (9)°. The dihedral angles between the pairs of benzene rings attached to each As atom are 84.63 (9) and 77.15 (8)°. In the crystal, molecules are linked by C—H⋯O interactions, forming infinite chains along the a axis. The crystal structure is further stabilized by C—H⋯π interactions.

In the title compound, [Cr(C 26 H 24 As 2 )(CO) 4 ], the Cr atom is octahedrally coordinated by four carbonyl ligands and one bidentate 1,2-bis(diphenylarsanyl)ethane ligand, which chelates in a cis manner with an As-Cr-As bite angle of 82.513 (9) . The dihedral angles between the pairs of benzene rings attached to each As atom are 84.63 (9) and 77.15 (8) . In the crystal, molecules are linked by C-HÁ Á ÁO interactions, forming infinite chains along the a axis. The crystal structure is further stabilized by C-HÁ Á Á interactions.
Related literature X-ray structure determinations of chromium carbonyls with arsine ligands are rare. A search of the Cambridge Crystallographic Structural Database (Allen, 2002) reveals only 12 complexes of chromium carbonyl disubtituted with tertiary arsines. For related structures, see: Bennett et al. (1971); Nowell et al. (1972). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986).
Cg1 is the centroid of the C7-C12 ring. Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 (Allen, 2002). The C-C bond length and the As-Cr-As bite angle of the title complex are comparable to similar complexes of chromium carbonyls substituted with bidentate arsine with two carbon atom backbone (Nowell et al.,1972). The title compound is isostructural to Cr(CO) 4 (Ph 2 P(CH 2 ) 2 PPh 2 ) and this gives further support that the formation of stable cis-M(CO) 4 L 2 compounds is prefered when the L 2 groups are combined in a chelating bidentate ligand (Bennett et al. 1971).
The Cr-As bond lengths show an average value of 2.449 Å and the As-Cr-As bite angle has a value of 82.51 (1)° (   Table 1) while in Cr(CO) 4 (Ph 2 P(CH 2 ) 2 PPh 2 ), the average of Cr-P bond lengths is 2.360Å and the P-Cr-P bite angle has a value of 83.41 (8).

Experimental
All manipulations were performed under a dry, oxygen-free nitrogen atmosphere using standard Schlenk techniques. All solvents were dried over sodium under dry oxygen free nitrogen. Chromium hexacarbonyl (200 mg, 0.909 mmol) and ethylenebisdiphenyl-arsanylethane (441.9 mg, 0.9086 mmol) in 35 ml of pet ether (100-130°C) was refluxed for 12 h.
Suitable single crystals were obtained by solvent-solvent diffusion in a mixture of dichloromethane/methanol.

Refinement
All hydrogen atoms were positioned geometrically and refined using ariding model with C-H = 0.93-0.97Å and U iso (H) = 1.2U eq (C). Fig. 1. The molecular structure, showing 50% probability displacement ellipsoids. Hydrogen atoms are shown as spheres of arbitrary radius.