Three-coordinate bis(phosphinimino)methanide derivatives of ‘open shell’ [M(II)] (M = Mn, Fe, Co) transition metals

An alternative two-step synthesis of the previously reported bis(diphenylphosphinimino)methane [CH2(Ph2P = NC6H3iPr2-2,6)2] involving bromine oxidation of dppm and metathesis with 2,6-diisopropylaniline is described. [CH2(Ph2Pdouble bond; length as m-dashNC6H3iPr2-2,6)2] is readily deprotonated by the transition metal silylamides [M{N(SiMe3)2}2] (M = Mn, Fe and Co) to provide a series of exclusively three-coordinate derivatives [{CH(Ph2PNC6H3iPr2-2,6)2M{N(SiMe3)2}] which have been characterised by elemental analysis, magnetic measurements and, in the case of the Fe derivative, X-ray structural analysis. Reactivity studies have shown that even such sterically demanding bis(phosphinimino)methanide ligands are prone to protonolysis and reductive [P(V) to P(III)] degradation which limits their utility as stable platforms for further M(II) derivitisation.