(Acetylacetonato-κ2 O,O′)carbonyl[tris(naphthalen-1-yl)phosphane-κP]rhodium(I) acetone hemisolvate

The title compound, [Rh(C5H7O2)(C30H21P)(CO)]·0.5C3H6O, has two different complex molecules in the asymmetric unit, with the RhI atoms in slightly distorted square-planar coordination environments. The molecules are packed as two monomeric molecules with one acetone solvent molecule sitting at the centre.

Financial assistance from the South African National Research Foundation (SA NRF), the Research Fund of the University of Johannesburg, TESP and SASOL is gratefully acknowledged. Mr S. Enus is acknowledged for the synthesis of this compound.
In the title compound, the Rh lies at the base of acetylacetonato ring. The coordination polyhedron around the Rh atom shows a slightly distorted square-planar arrangement. A larger trans influence of the phosphine ligand with respect to the carbonyl ligand is indicated by the longer Rh-O2 2.0633 (17) Å) bond compared to Rh-O3 2.0380 (17) Å) bond which is trans to the carbonyl ligand. The steric demand of the phosphine is indicated by the smaller O3-Rh1-P1 angle, 92.78 (5)°), compared to the carbonyl ligand (O2-Rh1-C1 = 90.07 (9)°). Similar geometries have been observed for related complexes [Brink et al. (2007);Leipoldt et al. (1978); Janse van Rensburg et al. (2006)].
Spectroscopic characteristics of the current compound are similar to that reported previously by Brink et al. (2007), and we refer at Brink et al. (2007) for additional discussion on the spectroscopy of these types of compounds.

Experimental
A solution of [Rh(acac)(CO) 2 ] (25.8 mg, 0.1 mmol) in acetone (5 cm 3 ) was slowly added to a solution of [P(C 10 H 7 )] (41.2 mg, 0.1 mmol) in acetone (5 cm 3 ) at room temperature, the mixture was then stirred for 10 min. Slow evaporation of the solvent afforded the title compound as a yellow crystalline solid.

Refinement
The aromatic, methine, and methyl H atoms were placed in geometrically idealized positions (C-H = 0.95-0.98) and constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (C) for aromatic and methine H atoms, and U iso (H) = 1.5U eq (C) for methyl H atoms respectively. Methyl torsion angles were refined from electron density.

Figure 1
Molecular structure of the title compound showing 50% probability displacement ellipsoids. 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.