A simple, high-yield synthesis is described that leads to the sodium salt of monosulfonated triphenylphosphane (TPPMSNa) as a pure product in large quantities without complicated workup techniques, The single-crystal X-ray structure of TPPMSNa center dot 2.5H(2)O is reported. The structure is built up by alternating layers of aquated sodium sulfonate units and hydrophobic triphenyl units. Thermogravimetric analyses show the loss of one molecule of water at 70 and one at 105 degrees C. Thermal decomposition occurs at temperatures above 400 degrees C. The anhydrous ligand is hygroscopic. The preparation of the free acid TPPMSH starting from the sodium salt is also reported. TPPMSH is an extremely hygroscopic solid that could not be isolated in the crystalline form.