This week's $137.5 million settlement over Freeport-McMoRan Inc.'s acquisition of McMoRan Exploration was big news in M&A litigation, and with good reason: The deal is the third-largest ever in a shareholder derivative class action, and unlike other derivative settlements, the proceeds will go directly to investors.

But the next chapter of the Delaware Chancery Court litigation could be even more interesting. Credit Suisse Group AG, which advised Freeport's board in the McMoRan acquisition, is facing an imminent lawsuit over the controversial buyout. The plaintiffs in the now-settled Freeport case say they they'll sue the bank within the next several weeks, claiming that Credit Suisse overvalued McMoRan in order to please conflicted board members who desperately wanted to push the deal through at maximum price.

“We allege that the bank used numerous improper methods to inflate the numbers to rationalize a deal that could not otherwise be justified,” said Bernstein Litowitz Berger & Grossmann's Mark Lebovitch, one of the lead plaintiffs lawyers behind the Freeport-McMoRan settlement.