Dinitrogen reduction chemistry with scandium provides a complex with two side-on (N[double bond, length as m-dash]N) 2- ligands bound to one metal: (C 5 Me 5 )Sc[(µ-η 2 :η 2 -N 2 )Sc(C 5 Me 5 ) 2 ] 2 .

Although there are few reduced dinitrogen complexes of scandium, this metal has revealed a new structural type in reductive dinitrogen chemistry by reduction of bis(pentamethylcyclopentadienyl) scandium halides under N 2 . Reduction of (Cp* = C 5 Me 5 ) with potassium graphite (KC 8 ) under dinitrogen generates the dark blue paramagnetic complex , 1. This end-on bridging (N[double bond, length as m-dash]N) 2- complex is a diradical with a magnetic moment of 2.8 µ B . Upon further reduction of 1 with KC 8 , the orange diamagnetic trimetallic complex , 2, is obtained. This complex has an unprecedented structure in which two side-on bridging (N[double bond, length as m-dash]N) 2- ligands are bound to the central (Cp*Sc) 2+ moiety. Complex 2 can also be obtained directly from reduction of or a mixture of and with KC 8 . The reaction of with KC 8 in the presence of 18-crown-6 or 2.2.2-cryptand affords 2 along with small amounts of , 3, which is green at room temperature and purple at low temperature and displays a mixture of side-on and end-on bridging isomers in the crystal structure collected at -180 °C. Density functional theory (DFT) calculations are consistent with a triplet ground state for the end-on complex 1 and singlet ground states for the side-on complexes 2 and 3.