14. Bis[μ‐Nitrido‐Bis(Triphenylphosphorus)(1+)] Tridecacarbonyltetraferrate(2‐) or [Bis(Triphenylphosphine)Iminium Tridecacarbonyl‐Tetraferrate] (2‐) [PPN] 2 [Fe 4 (CO) 13 ]