Described herein is a catalyst precursor composition comprising at least one metal from Group 6 of the Periodic Table of the Elements, at least one metal from Groups 8-10 of the Periodic Table of the Elements, and a reaction product formed from (i) a first organic compound containing at least one amine group, and (ii) a second organic compound separate from said first organic compound and containing at least one carboxylic acid group. A process for preparing the catalyst precursor composition is also described, as is sulfiding the bulk mixed metal oxide catalyst precursor composition to form a hydroprocessing catalyst.