X0304 4 2012-03-05 0 0000899723 OM GROUP INC OMG 0001203526 SCAMINACE JOSEPH 1500 KEY TOWER 127 PUBLIC SQUARE CLEVELAND OH 44114-1221 1 1 0 0 Chairman and CEO Common Stock 2012-03-05 4 P 0 15000 24.6892 A 239521 D This field is not applicable. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $24.64 to $24.75, inclusive. The reporting person undertakes to provide OM Group, Inc., any security holder of OM Group, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth in this footnote (2) to this Form 4. /s/ Joseph Scaminace, by Cipriano S. Beredo, as attorney in fact 2012-03-06