I think Russia and China did not want a recurrence of the actions taken in Libya by NATO and the UN. There was no mandate for the hunting down and killing of Khadaffi and yet it's still happening. Any day now. They probably don't want that on their conscience, rightly so. Some people, it doesn't bother.
U.S., allies conduct 31 air strikes in Syria and Iraq against ISIS militants (Reuters)
from the article: Russia, China, thwart anti-Syria UN Security Council resolution