I hope you got that in writing, since the right size for the back is 275/40/19 which has an identical diameter and almost identical (2mm) circumference to the front. The tyre you have (45/19) results in a 27mm difference in diameter and 85mm circumference difference front to rear within the set. With stories of how finicky the AWD system is on these I would double check.
On some other AWD platforms, having slightly different tread depths is enough to cause issues...