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Bis(triphenylphosphine)rhodium carbonyl chloride

Bis(triphenylphosphine)rhodium carbonyl chloride is the organorhodium complex with the formula [RhCl(CO)(PPh<sub>3</sub>)<sub>2</sub>]. 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<sub>3</sub>) ligands. The complex is a versatile homogeneous catalyst.

Synthesis and reactions

Bis(triphenylphosphine)rhodium carbonyl chloride was originally prepared by treating Rh<sub>2</sub>Cl<sub>2</sub>(CO)<sub>4</sub> with triphenylphosphine. However, it is typically produced by the carbonylation of Wilkinson's catalyst:

RhCl[P(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>]<sub>3</sub> + CO → RhCl(CO)[P(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>]<sub>2</sub> + P(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>

In homogeneous catalysis, this conversion is typically an undesirable side-reaction since [RhCl(CO)(PPh<sub>3</sub>)<sub>2</sub>] 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<sub>6</sub>H<sub>5</sub>)<sub>3</sub>]<sub>2</sub> + NaBH<sub>4</sub> + P(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub> → RhH(CO)[P(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>]<sub>3</sub> + NaCl + BH<sub>3</sub>

References