Groupon Inc sued two former sales managers who held confidential information before they quit the daily deal company to join Google Inc's competing daily deals site, a court filing showed.

The case filed in an Illinois court on October 21, named former Groupon employees Brian Hanna and Michael Nolan, who left the company in September to join Google Offers.

The court filing said Hanna and Nolan's employment at Google would result in the confidential trade secrets being revealed to Google.

The hiring of Hanna and Nolan by Google breaches their employment agreement with Groupon, which bars them from working with a direct competitor for 24 months after leaving the company, Groupon said.

Groupon seeks a court order to prevent the former employees from disclosing confidential information to Google, which would continue to irreparably harm it.

Last year, Groupon rejected a $6 billion buyout offer from Google. Groupon plans to raise as much as $540 million in an initial public offering. It aims to sell 30 million shares, or less than 5 percent of the company, at between $16 and $18 each, according to a regulatory filing on October 21.

Google and Groupon were not immediately available for comment.

The case is In re: Groupon Inc. v. Brian Hanna and Michael Nolan, Cook County, Illinois, Circuit Court, Chancery Division (Chicago), No. 11CH36731.

(Reporting by Megha Mandavia in Bangalore, editing by Bernard Orr)