LONDON—Confiscating the assets of companies that have fled Russia since the invasion of Ukraine would shatter investor confidence for decades and take Russia back to the calamitous days of the 1917 Bolshevik revolution, metals magnate Vladimir Potanin has said. Potanin, president and biggest shareholder of Norilsk Nickel, the world’s largest producer of palladium and refined nickel, said Russia should respond with pragmatism to its exclusion from swathes of the global economy. “We should not try to ‘slam the door’ but endeavour to preserve Russia’s economic position in those markets which we spent so long cultivating,” Potanin, 61, said on the Telegram messaging app. Potanin, one of the most prominent Russian billionaires who is not sanctioned by the West, said confiscating assets from companies that had left would put Russia out in the cold for decades, as far as investors were concerned: “It would take us back 100 years to 1917. …