wrl281

"Reaction of WCl6 with CO under high pressure and in the presence of Na gives an anionic carbonyl complex A which shows 2 CO stretches in the IR region. Further reaction of A with CO under acidic conditions leads to complex B, a neutral carbonyl complex with a single CO stretch in the IR spetrum. Identify compounds A and B and draw their structures. Perform an electron count for A and B." Really not sure where to begin on this one if someone could please point me in the right direction?