In advance of this potential conflict it is prudent of the Turks to advise the Russians of Turkey’s treaty obligations should Russia wage open war against Ukraine.
And Russia will not engage Turkey over this because to do so will mean Turkey will request that NATO honor Article V of the North Atlantic Treaty.
If Turkey closes the Bosporus to Russia but allows NATO shipping to reinforce or support Ukraine, Russia will be justified to do whatever is necessary to close the straits to all of its enemies. As for Article V obligations, do you really think any NATO member nation wants to go to war against Russia? NATO was formed to defend Western Europe against a massive Soviet invasion that never came, not to project offensive warfare in distant lands. For practical reasons (our allies' current military weaknesses) as well as political ones, America would have to carry that fight alone.
The idea of appeasing tyrants never works out well. In this case the feeble reaction to the invasion of Ukraine has the Russians now angling to attack a NATO member: Estonia.
http://www.reuters.com/article/2014/03/19/us-russia-estonia-idUSBREA2I1J620140319
NATO might not want to go to war with Russia but for damn sure Russia doesn’t care about going to war with NATO.