The Wall Street Journal reports that Facebook is preparing to launch a version of its social networking service with a distinctly corporate twist—Facebook at Work. The new service is aimed at breaking into the already crowded but under-adopted workplace social networking tools market, going head to head with Microsoft’s Yammer, Google’s Apps for Business, IBM’s Connections, and the startup Slack Technologies.

Facebook at Work will initially be free and advertising-free. Companies that sign up for the service will have a private site for their employees, and the service will also provide document sharing, messaging, and collaboration services. There is no word on how long the service will be free or how Facebook will charge for Facebook for Work in the long term.

But Facebook’s move is counter to a trend in corporate social networking tools. For example, Microsoft has been moving to embed Yammer within its Office and Office 365 platform, infusing social networking in SharePoint and allowing users to share documents directly from Office applications. Slack integrates into Dropbox and a host of other cloud services, and it acts largely as a consolidated communications channel. Just how welcome Facebook will be in offices—particularly when many organizations have been trying to keep employees off Facebook during work for years—also remains an open question.