It sounds as if you are way behind on all your software.
This article shows that your 2009 iMac is capable of running the current version of OS X - Mountain Lion:
If you were to upgrade to Mountain Lion, you would be able to load the current iTunes (11.0.4) and communicate to your iPhone 5.
Indicating the version of OSX that you are using would be helpful.
This discussion might be helpful - https://discussions.apple.com/thread/4330473?start=0&tstart=0
To use iTunes 11 you need:
- Mac computer with an Intel Core processor
- OS X version 10.6.8 or later
- 400MB of available disk space
- Broadband Internet connection to use the iTunes Store