I need to notch the bottom plate (pressure treated 2x4) that is sitting on a
concrete slab. I can't use a recipricating saw because of the concrete slab
below.

Can I use a 4" grinder to cut the notch? I have a diamond blade (for
concrete) and a metal blade but no wood grinder blade. Can I use the
diamond blade to cut the PT wood or will it "burn" and ruin the blade?

I guess the perfect tool would be one of those vibrating multi-cutter but I
don't want to buy a tool just to make one notch.

Ideas?