(Benzoylacetonato-κ2 O,O′)dicarbonylrhodium(I)

In the title compound, [Rh(C10H9O2)(CO)2], a distorted square-planar coordination geometry is observed around the RhI atom, formed by the O atoms of the bidentate ligand and two C atoms from the carbonyl ligands. The RhI atom is displaced from the plane through the surrounding atoms by 0.017 Å. In the crystal, C—H⋯O interaction is observed between a methyl group of the bidentate ligand and a carbonyl O atom. Metallophilic interactions [3.308 (3) and 3.461 (3) Å] between neighbouring RhI atoms are encountered in the crystal, resulting in the formation of a metal chain along the b-axis direction.

In the title compound, [Rh(C 10 H 9 O 2 )(CO) 2 ], a distorted square-planar coordination geometry is observed around the Rh I atom, formed by the O atoms of the bidentate ligand and two C atoms from the carbonyl ligands. The Rh I atom is displaced from the plane through the surrounding atoms by 0.017 Å . In the crystal, C-HÁ Á ÁO interaction is observed between a methyl group of the bidentate ligand and a carbonyl O atom. Metallophilic interactions [3.308 (3) and 3.461 (3) Å ] between neighbouring Rh I atoms are encountered in the crystal, resulting in the formation of a metal chain along the baxis direction.

Carla Pretorius and Andreas Roodt Comment
Rhodium is one of the most studied transition metals due to its importance in various applications including catalysis and biological activity (Dutta & Singh, 1994). It is widely recognized as a good catalyst for several industrial processes such as the Monsanto process (Paulik & Roth, 1968) and hydroformylation (Evans et al., 1968). In turn, rhodium dicarbonyl complexes of the type [Rh(L,L′)(CO) 2 ] where (L,L′) represents a mono-anionic bidentate ligand have been widely studied as catalyst precursors (Brink et al., 2010).
The structural analysis of the title complex was undertaken to obtain a better understanding of the rhodium-ligand interactions in this type of compound and as a partial study of the effects that the different substituents in nonsymmetrical β-diketones have on the kinetics of substitution reactions of these complexes.
Metallophilicity has been defined as the interaction between electron densities of large metal centres with an associated energy in the same order as hydrogen-bonding (Doerrer, 2010). These metallophilic interactions lead to the construction of 1D metal chains and have been widely recognized for other square-planar Rh I molecules (Prater et al., 1999;Laurila et al., 2012;Real et al., 1989). The rhodium complex reported here showed stacking in such a way that the rhodium atoms of neighbouring molecules occupy the two remaining pseudo-octahedral positions almost perpendicular to the coordination polyhedron, with Rh···Rh distances of 3.308 (3) and 3.461 (3) Å respectively (see Figure 2). These values are slightly longer than the Rh···Rh distances reported for [Rh(acac)(CO) 2 ] (3.253 and 3.271 Å, Huq & Skapski, 1974).
For the benzoyl-1,1,1-trifluoroacetonatodicarbonylrhodium(I) complex these distances were reported as 3.537 Å (Leipoldt et al., 1977). The metallophilic interactions result in the formation of a 1D metal chain along the b-axis in the unit cell. This is consistent with the [Rh(acac)(CO) 2 ] complex and benzoyl-1,1,1-trifluoroacetonatodicarbonylrhodium(I), that also displayed chain growth along the shortest unit cell axis.
A substitutional disorder over two positions was observed for the hydrogen atoms of the methyl group on the pentenone backbone. Intermolecular C10-H10C···O3 hydrogen bonding in the order of 3.427 Å was observed with one of the carbonyl moieties.

Refinement
The methyl and aromatic H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H = 0.95 and 0.98 Å and U iso (H) = 1.5U eq (carrier C) and 1.2U eq (carrier C), respectively. The highest supplementary materials sup-2 Acta Cryst. (2012). E68, m1451-m1452 residual electron density was located 0.04 Å from C12 and the deepest hole was 0.17 Å from O4.

Figure 1
Molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
The metallophilic Rh···Rh interactions result in the formation of a 1D metal chain along the b-axis.