Can you replace 245-r75-16 tires with 225-r45-16 tires?

Absolutely not. The 45 series tire would be way too small in overall diameter. Your speedometer would read 46 mph at a true 60 mph. You are changing the overall diameter by 21% which is totally unacceptable as you should never go over or under 3%, You can install a 255/70-16 and it will work well.