Bis(triphenylphosphine)rhodium carbonyl chloride
# Bis(triphenylphosphine)rhodium carbonyl chloride

Bis(triphenylphosphine)rhodium carbonyl chloride is the organorhodium complex with the formula $[RhCl(CO)(PPh_3)_2].$ This complex of rhodium(I) is a bright yellow, air-stable solid. It is the Rh analogue of Vaska's complex, the corresponding iridium complex. With regards to its structure, the complex is square planar with mutually trans triphenylphosphine $(PPh_3)$ ligands. The complex is a versatile homogeneous catalyst.

## Synthesis and reactions

Bis(triphenylphosphine)rhodium carbonyl chloride was originally prepared by treating $Rh_2Cl_2(CO)_4$ with triphenylphosphine. However, it is typically produced by the carbonylation of Wilkinson's catalyst:

    $RhCl[P(C_6H_5)_3]_3$ + CO → $RhCl(CO)[P(C_6H_5)_3]_2$ + $P(C_6H_5)_3$

In homogeneous catalysis, this conversion is typically an undesirable side-reaction since $[RhCl(CO)(PPh_3)_2]$ is a poor hydrogenation catalyst.

Bis(triphenylphosphine)rhodium carbonyl chloride is the precursor to tris(triphenylphosphine)rhodium carbonyl hydride, an important catalyst for hydroformylation.

    $RhCl(CO)[P(C_6H_5)_3]_2$ + $NaBH_4$ + $P(C_6H_5)_3$ → $RhH(CO)[P(C_6H_5)_3]_3$ + NaCl + $BH_3$
