Refco Inc. (RFX) filed for bankruptcy and agreed to sell its core futures brokerage unit to an investor group for $768 million, a key step to help rescue the embattled commodities and futures brokerage from collapse.

The developments late on Monday followed a week in which customers pulled assets out of the New York-based firm after Chief Executive Phillip Bennett (search) was charged with securities fraud. He is accused of hiding $430 million owed to Refco by a company he controlled.

Refco agreed to sell its main futures brokerage unit to a group led by private equity fund J.C. Flowers & Co. LLC, which is run by former Goldman Sachs (GS) partner Christopher Flowers.

"Those businesses are solvent and the customers' assets are safe," Flowers said in a CNBC interview on Tuesday. "We have an option to buy the rest of it and we're very keenly interested in seeing if we can resuscitate all of Refco's business."

He added, "The entities that we're involved in are solvent and the bankruptcy court helps to alleviate the risk."

None of Refco's regulated subsidiaries -- including Refco Overseas Ltd., Refco Singapore Ltd, and its broker-dealer, Refco Securities LLC -- filed for bankruptcy protection, the company said in a news release.

Refco's Capital Markets group, an unregulated business that handles over-the-counter trading of derivatives and other securities, is not mentioned in Monday's press release. The fate of the business, which halted activity and froze accounts last week, remains unclear.

While a stream of Refco customers have bailed out of its accounts, other customers have remained loyal.

"It's pretty much business as usual," said Ken Hughes, commodities senior market strategist at Refco private client group in Chicago. "Most of our clients have been quite loyal to us. I've had a few clients take some money out, but the majority have stayed with us."

The New York Stock Exchange on Tuesday said it would delist Refco shares, which were suspended from trading last Thursday after plummeting 72 percent in four days to $7.90.

"In light of all the circumstances involving the company, the NYSE has determined that the company's common stock is no longer suitable for continued listing on the NYSE," the exchange said in a statement.

J.C. Flowers' investor group includes financial services investment firm Enstar Group Inc. (ESGR) -- of which Flowers is the major shareholder -- Silver Point Capital, MatlinPatterson Global Advisers LLC and Texas Pacific Group.

But the sale of the unit is far from sealed, with J.C. Flowers acknowledging there was no assurance a deal would be reached.

Dubai Investments, an investment arm of the Dubai government, has hired Blackstone Group to advise it on a potential $1 billion acquisition of the entire company, a source close to the matter said on Tuesday.

The firm's downfall has triggered a rush from its rivals to pick up its business, with Interactive Brokers LLC on Tuesday taking out a full-page advertisement in the Wall Street Journal saying it was ready to accept account transfers from Refco.

Refco said it expected the bankruptcy court would establish procedures for the submission of competing proposals, although it did not specify which assets it was referring to.

Before its recent troubles, Refco was one of the biggest market makers for commodities and financial futures, allowing funds and companies to trade contracts on commodities, bonds and currencies.

Under the terms of the preliminary agreement with J.C. Flowers, Refco will have an option to keep up to 20 percent of the equity value of the entities being sold. The company said it expected to reach definitive agreements shortly, but that there was no assurance a sale would take place.

Mark Winkelman, formerly head of Goldman Sachs' J. Aron & Co. commodities business and co-head of Goldman's fixed-income division, will serve as chairman of Refco LLC, Refco said.

In response to a question about customers fleeing Refco, Winkelman said on CNBC, "Our intention to continue with the business going forward will stem that flow, we hope, very soon, if not immediately."

Flowers left Goldman in 1998 to form a financial services buyout fund, which currently manages about $1 billion. The firm acquired and turned around a troubled Japanese bank, Long-Term Credit Bank, which was renamed Shinsei Bank and launched an IPO in Tokyo last year.

With Flowers as lead investor and Winkelman as chairman, Goldman's presence remains heavy within the company. The investment bank served both as an underwriter for Refco's initial public offering and as its financial adviser after Bennett was suspended and the stock collapsed.

Refco also hired Greenhill & Co. (GHL) last week to assist with advisory work. Refco said Greenhill would remain while Goldman ended its advisory services after the bankruptcy filing.