Bis(triphenylphosphine)rhodium carbonyl chloride
Bis(triphenylphosphine)rhodium carbonyl chloride, often referred to as Wilkinson's carbonyl chloride complex, is a coordination complex of rhodium, with the chemical formula [RhCl(CO)(PPh3)2]. It is a bright yellow-orange solid, soluble in organic solvents.
This complex is primarily known as a precursor to homogeneous catalysts. It contains a rhodium(I) center coordinated to one carbonyl ligand (CO), two triphenylphosphine ligands (PPh3), and one chloride ligand (Cl). The geometry around the rhodium center is approximately square planar, although deviations from perfect planarity are common due to the steric bulk of the triphenylphosphine ligands.
Synthesis of bis(triphenylphosphine)rhodium carbonyl chloride typically involves the reaction of rhodium(III) chloride hydrate with triphenylphosphine in a suitable solvent such as ethanol or chloroform, under a carbon monoxide atmosphere. The carbon monoxide serves both as a ligand and as a reductant, reducing rhodium from the +3 to the +1 oxidation state.
The complex is air-stable to some extent, but prolonged exposure to air and moisture can lead to decomposition. It is commonly stored under an inert atmosphere to prevent degradation.
Reactions involving bis(triphenylphosphine)rhodium carbonyl chloride often involve the displacement of one or more of its ligands, allowing the rhodium center to coordinate to other substrates. It has been used in various catalytic reactions, including hydroformylation, hydrogenation, and carbonylation reactions, although it is not as widely used as other related rhodium complexes like Wilkinson's catalyst ([RhCl(PPh3)3]). The reactivity of the complex can be tuned by varying the phosphine ligands.