Exelon Corp. and NRG Energy Inc. are two deal-happy independent power producers, which helps explain the exclusion of Skadden, Arps, Slate, Meagher & Flom LLP from Exelon's $6.2 billion hostile bid for NRG. Skadden represented Calpine Corp. in rejecting a $9.6 billion hostile bid by NRG May 22. Skadden also advised Exelon in its 2004 agreement to buy Newark, N.J.-based Public Service Enterprise Group Inc., which fell through for regulatory reasons. And Skadden's Robert Pincus and Erica Ward represented NRG on its $8.3 billion acquisition of Texas Genco LLC in 2005 and its successful defense against a Mirant Corp. bid in 2006.

With Skadden sitting this out, NRG tapped Stephen Fraidin, Thomas Christopher and Gerald Nowak of Kirkland & Ellis LLP. Nowak helped advise NRG on Texas Genco. Kirkland counseled NRG on its 2003 bankruptcy and still works with the company on corporate matters. NRG used Hunton & Williams LLP on the Calpine bid; NRG general counsel Drew Murphy ran the energy practice there before moving to NRG. NRG's board is using Wilmington, Del., law firm Potter Anderson & Corroon LLP's Michael Tumas, who played the same role in NRG's Texas Genco buy.

For banking advice, NRG tapped Kirk Andrews and Ralph Watts at Citigroup Inc. and James Welch at Credit Suisse Group, NRG's banker on the Calpine bid. Watts and Andrews aided NRG on Mirant's bid along with Citi's Sandip Sen and Bruce Chung. The bank also provided a bridge loan on the Texas Genco deal. NRG CEO David Crane was himself a Lehman Brothers Inc. banker from 1996 to 2000.

Exelon is using Frederick Lowinger and Thomas Cole at Sidley Austin LLP, both of whom advised Exelon in its PSEG bid and an attempt to buy Illinois Power Co. from Dynegy Inc. in 2003. For banking advice, Exelon tapped Barclays Capital Inc.'s John Lange and UBS' Jim Metcalfe, who helped on PSEG while at Lehman.