Yes, a brass fitting will leach copper into your reef. There are a number of instances reported on this board and others where this has resulted in tank wipeouts of inverts. Gte the converter in PVC.
I have a 125 gallon reef tank with 2 overflows, each driven by a Rio 2100. I want to replace the two pumps with one powerful enough to drive both overflows. I bought a Y connector but it is 3/4" while my pump is 1/2". I bought a brass converter but before I install it I want to make sure brass will not cause a problem down the road.
Brass is a copper alloy, and it will leach copper into your tank. I would avoid it. The fact that salt water will be coursing through it 24/7 is enough to make me say not to use it. Can't you get one out of PVC?
