The present invention provides phosphinic acids and their sulfur derivatives, in accordance with the following formula (I) : wherein R1 and R2 are different and each of R1 and R2 is independently selected from an organic radical that branches at the alpha carbon and an organic radical that branches at the beta carbon, and each of X and Y is independently O or S, and wherein said compound is a liquid at room temperature. Compounds of formula (I) find utility for example as metal extractants. Also provided are methods for making compounds of formula (I) and their corresponding phosphine intermediates.