A Structural Diversity of Molecular Alkaline‐Earth‐Metal Polyphosphides: From Supramolecular Wheel to Zintl Ion

A series of molecular group 2 polyphosphides has been synthesized by using air‐stable [Cp*Fe(η(5)‐P(5))] (Cp*=C(5)Me(5)) or white phosphorus as polyphosphorus precursors. Different types of group 2 reagents such as organo‐magnesium, mono‐valent magnesium, and molecular calcium hydride complexes have been investigated to activate these polyphosphorus sources. The organo‐magnesium complex [((Dipp)BDI−Mg(CH(3)))(2)] ((Dipp)BDI={[2,6‐( i )Pr(2)C(6)H(3)NCMe](2)CH}(−)) reacts with [Cp*Fe(η(5)‐P(5))] to give an unprecedented Mg/Fe‐supramolecular wheel. Kinetically controlled activation of [Cp*Fe(η(5)‐P(5))] by different mono‐valent magnesium complexes allowed the isolation of Mg‐coordinated formally mono‐ and di‐reduced products of [Cp*Fe(η(5)‐P(5))]. To obtain the first examples of molecular calcium‐polyphosphides, a molecular calcium hydride complex was used to reduce the aromatic cyclo‐P(5) ring of [Cp*Fe(η(5)‐P(5))]. The Ca‐Fe‐polyphosphide is also characterized by quantum chemical calculations and compared with the corresponding Mg complex. Moreover, a calcium coordinated Zintl ion (P(7))(3−) was obtained by molecular calcium hydride mediated P(4) reduction.