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-[MII(N–O)3]− unit self-assembles into sandwich anions
[MII(N–O)3Na­(O–N)3MII]− 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.