Iron and Manganese Complexes of 2‑Carbonyl Pyrrolyls: Scorpionate Sandwich Anions and Extended Structures

Attempts to synthesize complexes of Fe and Mn­(II) with 2-amidopyrrolyl ligands (N–O) were unsuccessful, and only small amounts of the trivalent tris complexes M­(N–O)₃ were detected, although unusually in the case of Fe­(III) a fac structure is observed. In contrast the 2-benzoylpyrrolyl systems give M­(II) complexes, and in all instances thus far where Na⁺ is present, a scorpionate fac-[M^II(N–O)₃]⁻ unit self-assembles into sandwich anions [M^II(N–O)₃Na­(O–N)₃M^II]⁻ in which the central metal is efficiently encapsulated by interdigitation of the aryl units. Extended structures are readily made through the use of a 2-(4-pyridinoyl)­pyrrolylamide ligand. When Li⁺ is used, the scorpionate ligand is not assembled, and instead [M­(N–O)₂] units give rhombic 2D grids. The Fe system displays spin-crossover at 120 K.