Under their agreement, Onexim will also buy a 27.5% stake in Open Investments and 91% of shares in the Soglasie insurance company from KM Invest.
KM invest manages the joint assets of Interros owner Vladimir Potanin and Onexim's Mikhail Prokhorov.
"We have managed to overcome all differences and sign a mutually beneficial deal," Potanin was quoted in Interros's statement. "I hope the conclusion of a major restructuring of the joint business will have a positive effect on the business climate in this country."
The billionaires have been involved in months of wrangling over how to divide their assets.
Prokhorov said in the statement circulated by Interros that the deal would allow the businessmen to get access to companies "of strategic importance" for the partners in the near future and "focus on their own projects."
The businessmen plan to close the deal before May 15, 2008.
KM Invest currently holds 39% in Rosbank, 8.1% in Norilsk Nickel metals giant, 7.4% in Polyus Gold producer, 100% in Prof Media diversified media company, 25.8% in Rusia Petroleum and other assets.