This paper reports the first example of diruthenium phosphonate with kagome structure, namely, [NH3(CH2)(4)NH3][Ru-2(hedpH(0.5))(2)]center dot 2H(2)O (hedp = 1-hydroxyethylidenediphosphonate). The compound contains kagome layers that are linked by very strong hydrogen bonds into a nanoscale kagome structure. Ferromagnetic interactions are mediated between the paramagnetic diruthenium units.