(Reuters) -Russia’s central bank more than doubled its key policy rate on Monday and introduced some capital controls as the country faced deepening economic isolation, but its governor said sanctions had stopped it selling foreign currency to prop up the rouble. The admission that restrictions had effectively tied the Bank of Russia’s hands underscores the ferocity of the backlash to Moscow’s invasion of Ukraine and Western allies’ success in restricting its ability to deploy some $640 billion of foreign exchange and gold reserves. “The central bank today increased its key rate to 20% as new …