itunes wont update from version 10.6.3 to 11.1. help!

i am unable to update my itunes. it is saying that my version (10.6.3) is the current version. when i go to plug in my iphone 5, it will not connect to itunes unless my itunes has been updated to 11.1

i went and tried to download the updated itunes from the website, but it says that i am unable to download it. please help!