Domain: Coordination chemistry

A lustrous, silvery-white, hard, higher melting transition metal when heated to about 400 degree C in a current of halogen, X_2, generates a red compound P. An aqueous suspension of P with a little quantity of hydrochloric acid solution when added with a concentrated KOH solution yielded a solid Q. Upon standing for drying, Q is converted into a pale-yellow powder R, as Q is quite an unstable compound. R is a highly soluble compound and it is comfortably dissolved in hydrochloric acid to form a yellow solution. On evaporation of this solution, a red compound S is obtained. S in ethanol is then added with a hot ethanolic solution of an organophosphorus ligand and the resulting mixture is subsequently refluxed under an inert atmosphere for about 2 h, producing a dark-red colored complex T. Identify the complex T.

Grading rubric:
criterion: Correctly identifies the transition metal as Rhodium (Rh) based on the physical properties and the specific color sequence of its halides.
weight: 10
criterion: Correctly identifies the red compound P as Rhodium(III) chloride, RhCl_3, formed via direct halogenation.
weight: 10
criterion: Correctly identifies the solid Q as the hydroxide intermediate Rh(OH)_3 formed by the reaction with potassium hydroxide.
weight: 10
criterion: Correctly identifies the pale-yellow powder R as a hydrated form of Rhodium(III) oxide, Rh_2O_3, resulting from the dehydration or aging of the hydroxide.
weight: 10
criterion: Correctly identifies compound S as the hydrated salt Rhodium(III) chloride trihydrate, RhCl_3·3H_2O, formed by dissolving the oxide in hydrochloric acid.
weight: 10
criterion: Correctly identifies the organophosphorus ligand as triphenylphosphine (PPh_3), a standard reagent for Wilkinson-type catalysts.
weight: 10
criterion: Correctly describes the final step as a reductive substitution where Rh(III) is reduced by excess phosphine to form a Rh(I) complex.
weight: 10
criterion: Correctly identifies the final dark-red complex T as tris(triphenylphosphine)rhodium(I) chloride.
weight: 10
criterion: Correctly provides the molecular formula for T as [RhCl(PPh_3)_3].
weight: 10
criterion: Correctly identifies the byproduct of the final reaction as triphenylphosphine oxide (OPPh_3).
weight: 10

Answer:
tris(triphenylphosphine)rhodium(I) chloride, [RhCl(PPh3)3]