Well that is supposedly damaging to the processor. However, I believe (Read: Believe) that you can undervolt it to 1.5v in the bios.
The next thing is that you got the incorrect kit anyway. with a 3x4 kit, you can't take advantage of the Dual Channel feature that allows improved memory bandwidth and speed.
I would play it safe. Return it and get the correct 1.5v ram, and get a 2x4 kit. You don't need 12GB, trust me on this one. You don't.