It was/is challenging to transfer contacts from almost any phone for that matter in the 08/09 IS-F (all IS's) with the GEN5 Nav system. It's best to manually enter your most frequently used contacts into the car. The Gen 6 Nav system in the 2010 IS's transfers the contacts much better in my experience.
My understanding is that the iPhone does not support the right data transfer Bluetooth protocol. If you search on here, you'll see several threads on the issue and I don't think anyone has been able to transfer contacts from an iPhone, at least for pre-2010 cars.
I just find times when I have to spend a few minutes waiting in the car for some reason and spend that time inputting numbers into the car's phone book (and training the voice dial).