Synthesis, characterisation and structural studies of amidinate and guanidinate alkaline earth–transition metal bonded complexes

Reaction of magnesium amidinate complexes of the form [{MesC(NR)2}MgBr(OEt2)]2 (R = i Pr, Dipp, Mes) with the potassium salts of transition metal anions K[CpFe(CO)2] (K[Fp]) and K[Co(CO)3(PCy3)](THF)2 gave the complexes {MesC(NR)2}MgFp(THF) and {MesC(NR)2}Mg{Co(CO)3(PCy3)}(THF). Single crystal X-ray diffraction studies of {MesC(NR)2}Mg{Co(CO)3(PCy3)}(THF) for R = i Pr and Dipp confirm these to have Mg‒Co bonds in the solid state. Reaction of the structurally similar magnesium guanidinate complex {Me2NC(NDipp)2}MgI(OEt2) with the aforementioned transition metal anions and additional K[Co(CO)3(PPh3)](THF) gave the series of complexes [{Me2NC(NDipp)2}MgFp]2, {Me2NC(NDipp)2}Mg{Co(CO)3(PCy3)}(OEt2) and {Me2NC(NDipp)2}Mg{Co(CO)3(PPh3)}(OEt2). Structural authentication by X-ray crystallography showed [{Me2NC(NDipp)2}MgFp]2 to be a very rare example of a base-free alkaline earth‒transition bonded complex, having two Mg‒Fe bonds. IR and diffusion NMR spectroscopy were carried out to gain further insight into the solid state and solution phase structures.