Synthesis of Anionic Triple‐Decker Complexes Having Closed 30e Valence Shells by Stacking of Sandwich Anions with Cr(CO)3 Fragments

The addition of a 12e metal carbonyl fragment to an 18e sandwich anion, which was predicted to be facile, gave the first 30e triple-decker anion. Thus, [CpFe(C4H4BPh)]⊖ reacted regiospecifically with the fragment Cr(CO)3, prepared from [Cr(CO)3(NH3)3], to give the 30e anion 1, which could be isolated as its [NMe3Ph]⊕ salt. The 30 valence electron rule plays the same role for triple-decker complexes as the 18e rule for mononuclear organometallic complex. For example, neutral, stable 30e complexes are known.