Extensive　DFT　calculations　are　performed　to　optimize　the　geometric　structures　of　O-rich　tungsten　oxide　clusters,　to　simulate　the　PES　spectra,　and　to　analyze　the　chemical　bonding.　The　ground-state　structure　of　W　4O14-　is　best　considered　as　W4O　12(O2-),　containing　a　side-on　bound　superoxide　ligand.　The　current　study　indicates　that　the　extra　electron　in　W　4O12-　is　capable　of　activating　dioxygen　by　non-dissociative　electron　transfer　(W　5d　→　O2　π*),　and　the　anionic　clusters　can　be　viewed　as　models　for　reduced　defect　sites　on　tungsten　oxide　surfaces　for　the　chemisorption　of　O2.