A salt useful as an active species in an organic reaction and represented by the following chemical formula (1): ##STR1##

wherein n stands for an integer of from 1 to 8, Z^n- represents an n-valent anion of an active hydrogen compound, a, b, c and d each stands for a positive integer, and Rs represent the same or different hydrocarbon groups. In addition, a simple and efficient process is provided for producing a poly(alkylene oxide) by polymerizing an alkylene oxide compound in the presence of the salt represented by the chemical formula (1).