By Ludwig Burger FRANKFURT (Reuters) -LetterOne will not take on Russian assets of Wintershall Dea and has not held talks with co-investor BASF on such a transaction, a spokesperson for the investment group said. A person familiar with the matter told Reuters earlier that BASF is looking into transferring Russian assets of its oil and gas business Wintershall Dea to partner LetterOne. “We have had no discussions with BASF about this and have no plans to take on Russian assets,” the spokesperson said. Offloading the assets would have advanced the German chemicals giant’s efforts to extricate it…