The parent phosphonium  is  as found in the iodide salt, phosphonium iodide. Salts of the parent  are rarely encountered, but this ion is an intermediate in the preparation of the industrially useful tetrakis(hydroxymethyl)phosphonium chloride:
:PH + HCl + 4 CHO → 
Many organophosphonium salts are produced by protonation of primary, secondary, and tertiary phosphines:
:PR + H → 
The basicity of phosphines follows the usual trends, with R = alkyl being more basic than R = aryl.