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)<sub>3</sub> were detected, although unusually in the case of Fe­(III) a <i>fac</i> structure is observed. In contrast the 2-benzoylpyrrolyl systems give M­(II) complexes, and in all instances thus far where Na<sup>+</sup> is present, a scorpionate <i>fac</i>-[M<sup>II</sup>(N–O)<sub>3</sub>]<sup>−</sup> unit self-assembles into sandwich anions [M<sup>II</sup>(N–O)<sub>3</sub>Na­(O–N)<sub>3</sub>M<sup>II</sup>]<sup>−</sup> 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<sup>+</sup> is used, the scorpionate ligand is not assembled, and instead [M­(N–O)<sub>2</sub>] units give rhombic 2D grids. The Fe system displays spin-crossover at 120 K.