Ligand displacement reactions of PtR2(cod) with water soluble tertiary phosphines such as 1,2-bis{di(hydroxymethyl)phosphino}ethane (DHMPE) or tris(hydroxymethyl)phosphine (THMP) gave new water-soluble diorganoplatinum(II) complexes PtR2L2 [L-2 = (HOCH2)(2)PCH2CH2P(CH2OH)(2): R = Me (1a); Et (1b); Ph (1c), L = P(CH2OH)(3): R = Me (2a); Et (2b); Ph (2c)] at room temperature. They were considerably stable in water and the thermolyses of 1b and 2b at 80 degreesC liberate ethylene and ethane via beta-hydrogen elimination and hydrolysis.