X0306 4 2013-02-28 0 0000899723 OM GROUP INC OMG 0001228169 SACHS VALERIE GENTILE 1500 KEY TOWER 127 PUBLIC SQUARE CLEVELAND OH 44114-1221 0 1 0 0 VP, Gen. Counsel & Secretary Common Stock 2013-02-28 4 D 0 7562 D 53331 D Common Stock 2013-02-28 4 F 0 13 24.715 D 53318 D This field is not applicable. These shares were forfeited due to failure to satisfy the performance criteria of OM Group, Inc. for the three-year period ending December 31, 2012. This reflects the surrender of shares to OM Group, Inc. to pay taxes applicable to the vesting of restricted stock in accordance with the applicable long-term incentive plan previously approved by the stockholders of OM Group, Inc. and the related agreement previously approved by the Compensation Committee of the Board of Directors of OM Group, Inc. /s/ Valerie Gentile Sachs, by Cipriano S. Beredo as attorney-in-fact 2013-03-04