Applications of manganocene in the synthesis of Mn(ii) amide and imide cages

Abstract

The reactions of manganocene, Cp₂Mn (Cp = C₅H₅), with 2-aminopyrimidines give similar, octameric amido/imido cage complexes of general formulae [{CpMnNHR}{MnNR}]₄ [R = 4,6-Me₂pm (1a), 4-MeO-6-Mepm (1b), 4,6-(MeO)₂pm (1c); pm = pyrimidinyl]. The structures of these complexes can be visualised as being composed of central Mn₄N₄ imido cubane units that are coordinated at their peripheries by four [CpMnNHpm] monomers. In contrast, less acidic 2-aminopyridine (2-NH₂py) and 8-aminoquinoline (8-NH₂quin) are only singly deprotonated under similar conditions, giving the unusual hexanuclear amido complex [Cp₂Mn₃(NHpy)₄]₂ (2) and the dimer [CpMn(μ-8-HNquin)]₂ (3). N,N′-Dibenzylethylenediamine [(BnNHCH₂)₂] only forms the simple adduct [(η¹-Cp)(η⁵-Cp)Mn{(BnNHCH₂)₂}] (4) (Bn = CH₂Ph) with Cp₂Mn, in which no deprotonation of the organic acid has occurred. The X-ray structures of the new complexes 1b–c, 3 and 4 are reported (1a and 2 having been communicated previously).