Web Service and Message Queue

We’re looking at creating a web services/REST API layer that will be consumed by web and mobile clients.

To make the solution more robust I was considering putting the commands from PUT, POST, and PATCH onto a message queue, which would mean that they would then be executed asynchronously.

Is there a standard HTTP response from a RESTful API that indicates that a command will be executed asynchronously?

Edit

Actually, if anyone had any thoughts on how sensible it is to have a message queue behind a web services layer I’d be interested to hear them.