UPDATE, 7/25/13, 4:00 p.m. EDT: Wachtell lawyers working on the deal for CapitalSource have been added to the article's sixth paragraph.

PacWest Bancorp is depositing $2.3 billion in cash and stock into a transaction that will create California's sixth-largest publicly owned bank, with more than $15 billion in assets.

PacWest is acquiring CapitalSource Inc., with Sullivan & Cromwell and Wachtell Lipton Rosen & Katz advising the two Los Angeles–based banks, respectively, in a deal announced late Monday. PacWest will pay roughly $11.64 in cash and stock—composed of $2.47 in cash and 0.2837 PacWest shares—for each CapitalSource share. The deal price represents a premium of 18.4 percent over CapitalSource's Monday closing price.

PacWest is the parent company of Pacific Western Bank, which operates 75 branches in 10 California counties. The acquisition of CapitalSource would add another 21 branches and roughly $8.7 billion in assets to the company's portfolio. The deal, which is subject to the approval of regulators and both banks' shareholders, is expected to close in the first quarter of 2014.

S&C is representing PacWest in the acquisition with a corporate team led by Los Angeles–based partner Patrick Brown, as well as special counsel Ann Chen and associate Aaron Werner. Employee benefits partner Matthew Friestedt, tax partner Ronald Creamer, employee benefits special counsel Rebecca Coccaro, and M&A of counsel Janet Geldzahler are also working on the deal. Of counsel Stanley Farrar and special counsel Janine Waldman are advising on bank regulatory matters. Associates on the deal are Siaw Ching Lee, Guy Inbar, and Daniel Zharkovsky.

S&C's Brown has advised PacWest on a number of past acquisitions, including last year's purchase of Marquette Equipment Finance in a deal worth $189 million, including assumed debt. Jared Wolff, a former S&C attorney, serves as PacWest's general counsel.

For its part, CapitalSource has turned to Wachtell to advise on its sale. Corporate partners Edward Herlihy and Matthew Guest are leading a Wachtell team that also includes corporate partner Richard Kim, executive compensation and benefits partner Jeannemarie O'Brien, and tax partner Joshua Holmes. Associates Jacob Kling and Minsun Lee are also working on the matter, as is law clerk Emily Korinek.

Last November, Wachtell advised PacWest on its $231 million purchase of First California Financial Group.