Mr. Usmanov said that, after the series of investments from 2009 until 2011, he and Mr. Milner owned about 9 percent of Facebook at one point, but now own about 6 percent and will hold about 4.5 percent after the initial public offering. The other shares they originally controlled have gone to other investors, clients of D.S.T. and corporate entities.
Mr. Usmanov earned his billions in the post-Soviet business world, managing steel mill subsidiaries for Gazprom before they were spun off as his own businesses, Gazmetal, later renamed Metalloinvest. Mr. Usmanov has said he took on debt in this transaction and others acquiring iron ore mines in Russia.
He said he would use money from investors who buy his shares in the Facebook I.P.O. to invest and pay down debt at his other Russian businesses.
This year, Russia’s second-largest cellphone company, MegaFon, which Mr. Usmanov partly owns, is expected to issue shares in London in its own I.P.O.
From his work with Gazprom, Mr. Usmanov is said to be close to Russia’s former president and current prime minister, Dmitri A. Medvedev, a former chairman of the Gazprom board. His ties to the Kremlin and Facebook have stirred concerns that he might influence the company’s policies in subtle ways to appease governments in markets where Facebook is also an important tool of political dissent, such as Russia.
Because he does not vote Facebook shares, however, Mr. Usmanov has no direct influence on policies for the site in Russia.
A native of Uzbekistan, Mr. Usmanov spent six years in an Uzbek prison after being convicted of fraud and embezzlement in the 1980s, charges he contends were politically inspired and the result of a power struggle among the Uzbek elite. Mr. Usmanov’s father was a prosecutor. He was sent to a remote prison camp where many men his father had convicted were serving time, apparently an intentional decision so he would be abused or killed.
Soviet courts later exonerated Mr. Usmanov and expunged his record. The Supreme Court of Uzbekistan in 2000 ruled that the K.G.B. had fabricated evidence against him and other children of top Uzbek officials in that period.
“I survived only because I loved my wife, and wanted to return to her, and because I wanted to prove I was innocent,” he said. “I am an example to innocent people in jail. A man like that can achieve something. I dedicated 25 years of my life to this idea.”
Evelyn M. Rusli contributed reporting from New York.