Simpson Thacher & Bartlett Hong Kong corporate partner Leiming Chen is leaving to join longstanding client Alibaba Holdings's affiliate company Ant Financial Services Group as general counsel.

Chen will be based in Hong Kong and lead a team of 50 lawyers and compliance specialists. He will report directly to Ant Financial president Eric Jing.

Ant financial chief executive Lucy Peng said Chen's appointment was an "important step" in Ant's global financial services business strategy.

Chen has advised on overseas listings, fundraising and mergers and acquisition for Chinese companies since 1997.

In 2014, he was one of the lead partners that handled Alibaba's $25bn (£18bn) initial public offering (IPO) on the New York Stock Exchange.

Earlier in his career, he also worked on overseas listings for China Mobile Communications, Bank of China and Ping An Insurance.

Chen joined Simpson Thacher in 2006 from Shearman & Sterling, where he had been a partner for two years.

Ant Financial was formed in 2014 following the IPO and is controlled by Alibaba chairman Jack Ma.

The company runs China's most popular online payment system Alipay with over 300 million active users. The company is reported to be valued at over $40bn (£29bn) and planning for an IPO in 2016.

Legal Week was acquired by The Asian Lawyer publisher ALM in January. Click here to read more from The Asian Lawyer.