Water-soluble phosphonate-functionalized triaryl phosphine ligands Na-2[Ph(2)P(4-C6H4PO3)]. 1.5H(2)O (4a), Na-2[Ph(2)P(3-C6H4PO3)]. 2H(2)O (4b), and Na-2[Ph(2)P(2-C6H4PO3)]. 2H(2)O (4c), were prepared in 54-56% yields by the transesterification and hydrolysis of the appropriate phosphonic acid diethyl ester precursors. The solubilities of 4a-c in water are compared and the spectroscopic properties studied in detail. The crystal structure of Na-2[Ph(2)P(4-C6H4PO3)(H2O)(3)(CH3OH)] . CH3OH (monoclinic, P2(1)/n, a = 6.4457(8) Angstrom, b = 8.1226(8) Angstrom, c = 46.351(3) Angstrom, beta = 92.902(8)degrees, Z = 4) shows a dimeric association via two bridging water molecules and four sodium ions. Reaction of 4a with PtCl2(PPh(3))(2) in a biphasic H2O/CH2Cl2 mixture gives cis- and trans-Na-4[PtCl2{Ph(2)P(4-C6H4PO3)}(2)]. 3H(2)O. Palladium dichloride and 4a in H2O/benzene catalyzes the carbonylation of benzyl chloride to give phenylacetic acid (91%).