Given the performance of the Russian armed forces against Ukraine over the past 8 weeks, and their attrition rates, it is pretty obvious that for Putin to declare war on NATO (deliberately attacking any 1 NATO state amounts to the same thing), then the resultant defeat would be far reaching and inevitable. Sure, NATO forces would suffer some significant losses, but Russia would be forced to evacuate all the territory they have claimed, including all of East Ukraine and Crimea, and end up with zero military capability. Their only alternative would be to start a MAD WW3. Would the chain of command 'break down' if the order was given?
Not going to happen.