Tuning low-coordinate metal environments: high spin d5–d7 complexes supported by bis (phosphinimino)methyl ligation

Treatment of FeCl2 with the lithium derivative of [CH2(Ph2PNC6H2Me3-2,4,6)2] in THF and crystallisation from Et2O gave the ate complex [{CH(Ph2PNC6H2Me3-2,4,6)2}Fe(µ-Cl)2Li(THF)(OEt2)] in which the iron is fourcoordinate and the chlorides bridge to lithium. Treatment of [M{N(SiMe3)}2](M = Mn, Fe, Co) with [CH2 (Ph2PNC6H2Me3-2,4,6)2] in toluene afforded the complexes [{CH(Ph2PNC6H2Me3-2,4,6)2}MN(SiMe3)2] which all feature essentially planar N(1)–N(2)–N(3)–M coordination. The carbanionic character of the bis(phosphinimino) methyl ligand results in close C(1)–M contacts in both the Mn and Co complexes effectively raising the coordination number to four. The analogous iron compound is strictly three-coordinate as demonstrated by Xray crystallography and 57Fe M?ssbauer. However protonolysis of this compound with Ph3COH yields the iron alkoxide [{CH(Ph2PNC6H2Me3-2,4,6)2}FeOCPh3] that features a close C(1)–Fe contact of 2.375 . Although the iron centre in this complex is only marginally pyramidalised by this contact, its 57Fe M?ssbauer spectrum indicates a significant perturbation to the local electronic environment at the metal.