Daniel Clivner, managing partner of Simpson Thacher & Bartlett’s Los Angeles office, is poised to leave the firm to open a Century City office for Sidley Austin as the latter prepares to celebrate its 35th anniversary in the city.

Clivner, 51, will serve as co-head of Sidley’s Los Angeles outposts. Sabina Lippman, a partner and co-founder of local legal recruiter Lippman Jungers, brokered Clivner’s move to Sidley. His decision to leave Simpson Thacher marks a rare lateral partner departure for the leading Am Law 100 firm.