Activation of N2 by isolated small tungsten clusters at room temperature

•Reactions of N2 with H2O on gas-phase small tungsten clusters Wn+ (n=3–5) yielding N2O were observed at room temperature.•N2 is activated by W4+ and W5+ to a much greater extent than by W3+.•The N2 activation is made possible by bridge adsorption geometry of N2 on W4+ and W5+.•The activated N2 adsorption state survives at room temperature on the tungsten clusters.•This is due to the high dissociation barrier for the activated N2 on the small clusters.