X0306 4 2015-10-28 1 0000899723 OM GROUP INC OMG 0001522796 Mullin Patrick S. FLATS EAST BANK BUILDING, 950 MAIN AVENUE, SUITE 1300 CLEVELAND OH 44113 1 0 0 0 Common Stock 2015-10-28 4 D 0 11973 34.00 D 0 D Phantom Stock 2015-10-28 4 D 0 1293.6429 34.00 D Common Stock 1293.6429 0 D Disposed of pursuant to a merger agreement, dated May 31, 2015, by and among Duke Acquisition Holdings, LLC, Duke Acquisition, Inc., MacDermid Americas Acquisitions, Inc., and the Issuer in exchange for the right to receive $34.00 in cash per share. Represents shares of phantom stock acquired by the reporting person (in exempt transactions) (including 624 shares otherwise payable on April 27, 2015) as deferred compensation pursuant to OM Group, Inc.'s Deferred Compensation Plan. Each share of phantom stock is the economic equivalent of one share of Issuer Common Stock, and the shares were to became payable in cash upon the reporting person's termination of service as a director of the Issuer. /s/ Valerie Gentile Sachs, as Attorney-In-Fact 2015-10-30