After 20 years at Wachtell, Lipton, Rosen & Katz, Gavin Solotar is set to become one of the rare partners to depart the top-ranked Am Law 100 firm on his way to becoming a managing director and the general counsel at New York–based boutique investment bank Greenhill & Co.

Greenhill announced Tuesday that Solotar, a veteran corporate partner at Wachtell, will make the move in-house in September. Greenhill CEO Scott Bok, who worked at Wachtell during the mid-eighties, said in a statement that his firm valued Solotar’s combination of experience in the financial and legal fields.

Before entering New York University School of Law, Solotar was an accountant at Ernst & Young from 1986 to 1989. During his time at Wachtell, which he joined in 1992, Solotar focused on M&A, corporate governance, and securities work.

In 2009, Solotar was part of a team from the firm that advised Schering-Plough on its $41 billion acquisition by rival drugmaker Merck. Earlier this month, Solotar was part of another Wachtell deal team representing Mexican billionaire Carlos Slim Helu’s America Movil on its purchase of a 4.1 percent stake in Telekom Austria.

In an e-mail to The Am Law Daily, Solotar said he had worked with Greenhill on a number of transactions over the years.

“On a personal level, I admired the culture of teamwork there. It is similar to Wachtell in that regard,” he wrote. “While it is difficult to leave a place like Wachtell Lipton, I am excited for the new adventures and opportunities that Greenhill presents.”

In departing Wachtell, Solotar is leaving behind a firm that—at nearly $4.5 million—had the highest profits per partner of any Am Law 100 firm last year, according to the most recent data compiled by The American Lawyer.

In his new role as managing director and general counsel at Greenhill, Solotar is replacing Ulrika Ekman, who is planning to retire. Ekman, a former Davis Polk & Wardwell partner, joined Greenhill in 2004. (A compensation table included in a proxy statement filed by Greenhill with the SEC in March shows that Ekman received nearly $1.6 million last year in the form of salary, stock, and other compensation.)

While partner departures from Wachtell are a rarity, there have been several notable losses in the last several years. Executive compensation partner Adam Chinn left the firm in 2007 for investment banking and private equity investment firm Centerview Partners. Chinn’s move came a year after another executive compensation partner, Michael Katzke, left Wachtell to pursue a career in social work. (Katzke, who worked closely with Solotar on several deals at Wachtell, returned to practicing law in 2009 at New York’s Bachelder Law Firm.)

This is not the first time Greenhill has dipped into the ranks of The Am Law 100 to make a high-profile hire. In 2002, the bank brought on Harvey Miller, the founder of the business finance and restructuring practice at Weil, Gotshal & Manges. Miller had been with Weil for 32 years when he left to become Greenhill’s vice-chairman, advising clients on corporate restructuring matters.

Greenhill went public with a $75 million IPO in 2004, and Miller, who collectively owned shares worth an estimated $25 million at the time of the listing, eventually returned to Weil in March 2007. (Since returning to Weil, Miller’s significant assignments have included guiding the firm’s work in the massive bankruptcy of defunct investment bank Lehman Brothers—a case on which Miller and his Weil colleagues have racked up nearly $400 million in legal fees.)

Former U.S. Senator and current Bryan Cave partner John Danforth serves on Greenhill’s board of directors, along with former Davis Polk partner Steven Goldstone, who now also manages his own private investment firm Silver Spring Group.

As for Wachtell, The Wall Street Journal reported last year that the firm was looking ahead to a new generation of leadership given that one of its most prominent partners, Martin Lipton, is well past the age when many lawyers have long since retired. Lipton, who turned 81 last Friday, shows no signs of slowing down. This month Lipton led a Wachtell team advising AOL in its proxy fight win over activist investors.

Senior reporter Brian Baxter contributed to this story.