iPhone 5 won't sync wirelessly with iTunes Mac

This has been posted in several discussions on this board but no one seems to be having the problems I am having.

I have an iPad 3 and an iPhone 5 (both running iOS 6) along with a MacBook Pro running iTunes 11.0.4 through Mountain Lion OS X 10.8.4.

I have wi-fi turned on for all three devices and they are all on the same network.

The iPad shows in iTunes wirelessly and syncs with the Mac.

The iPhone 5 will sync with the Mac if it is connected via USB, but it disappears from the Mac when I disconnect the USB cable. I havew "Sync with this iPhone over Wi-Fi" ticked on in the Options for the iPhone in iTunes. I have backed up and restored the iPhone through iTunes a couple of times, but nothing fixes the issue.

I'd love to sync the iPhone via wi-fi. Can anyone suggest what I could try to make this work for me?