When it comes to the Eastern Orthodox Churches his friend is incorrect. According to canon law:
Can. 1127 §1. …Nevertheless, if a Catholic party contracts marriage with a non-Catholic party of an Eastern rite, the canonical form of the celebration must be observed for liceity only; for validity, however, the presence of a sacred minister is required and the other requirements of law are to be observed.
If he was married to someone who was free to marry and was married by a Russian Orthodox priest according to the Russian Orthodox norms of law then his marriage is considered **valid **by the Catholic Church. He would need a “full” annulment.