An unusual β-diketone coordination mode is reported here for the first time. A dinuclear Mn(III) compound is obtained by reaction, in open atmosphere and basic medium, of a mononuclear, β- diketone like complex of the trinucleating ligand 1,3-bis(2-hydroxyphenyl)-1,3-propanedione with a Mn(II) salt. The aforementioned molecule is a potentially trinucleating ligand with three coordination sites: the most reactive is the central β-diketone moiety, while the outer are the less reactive. In the Mn(III) complex both metal ions are occupying the two outer sites. The compound bis(1,3-bis(2- hydroxyphenyl)-1,3-propanedione)tetrakispyridine dimanganese(III), C50H38N4O8Mn2, is monoclinic, space group P21/n, a=16.093(5), b=17.062(4), c=31.449(6) Å, β=93.09(2)°, V=8622.7 Å3, Z=8, Dx=1.44 Mg m-3, μ(Mo Kα)=6.20 cm-1 4516 final data for 259 refined parameters. R=0.076, Rw= 0.081. MnMn distance in the dinuclear compound is 5.295(2) Å. © 1990.