Steric Control in Low-Valent Mn Diamide Complexes: Contrasting Magnesium and Manganese in N₂ and Benzene Activation

Based on previous studies on Mg mediated N2 activation, the reduction chemistry of bulky MnII complexes with xanthene-based diamido ligands has been examined. Reduction of [(TripNON)Mn(THF)2] with 5% w/w K/KI leads to a MnI dimer [(K(TripNON)Mn)2] with a long Mn-Mn bond, while the sterically more demanding complex [(TCHPNON)Mn(THF)] does not allow dimerisation of metal centres upon reduction and thereby enables N2 binding instead, to give [(K(TCHPNON)Mn)2(-N2)]. However, in the absence of N2 the MnI intermediate “[K(TCHPNON)Mn]” is able to perform oxidative addition of aromatic C-H bonds, which is in contrast to the observed “Birch-type” reduction chemistry of its MgI analogue.