Lehman Brothers Holdings Inc may have grounds to sue Goldman Sachs Group Inc and Barclays Plc after they demanded $1.2 billion in additional margin to assume trading positions auctioned by a Chicago exchange, bankruptcy examiner Anton Valukas said.Goldman Sachs was the high bidder for Lehman’s equity derivatives at options and futures exchange CME Group Inc, and took $445 million of those assets at a private auction in September 2008, according to previously censored details of Valukas’s March 11 report. Barclays was the high bidder for Lehman’s energy derivatives and took $707 million in assets from CME.