Simpson Thacher & Bartlett announced Thursday that corporate partner William Dougherty has been named chairman of the 837-lawyer New York–based firm’s executive committee, effective immediately.

In taking over Simpson Thacher’s top management post, the 51-year-old Dougherty succeeds corporate partner Philip “Pete” Ruegger III, 63, who has led the firm since 2004. Ruegger told The Am Law Daily Thursday that he plans to retire from full-time practice later this year after 39 years and move into an of counsel role with the firm.