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

Abstract

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 organomagnesium, mono-valent magnesium, and molecular calcium hydride complexes have been investigated to activate these polyphosphorus sources. The organo-magnesium complex [( Dipp BDIÀ Mg(CH 3 )) 2 ] ( Dipp BDI = {[2,6-i Pr 2 C 6 H 3 NCMe] 2 CH} À ) reacts with [Cp*Fe(η 5 -P 5 )] to give an unprecedented Mg/Fesupramolecular 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 ) 3À was obtained by molecular calcium hydride mediated P 4 reduction.

Snapshots of sequential polyphosphide rearrangement upon metallatetrylene addition

“…Since the pioneering synthesis of the air-stable pentaphosphaferrocene [Cp*Fe( η 5 -P 5 )] by Scherer, 9 it has been used as a well-established building block in coordination 10 and supramolecular chemistry. 11 The reactivity has been investigated extensively with reactive transition metal complexes, 12 and with highly reducing lanthanide compounds. 13 Redox reactions with [Cp*Fe( η 5 -P 5 )] often involve the cyclo -P 5 moiety without alteration of the ring itself.…”

Signet-Ring-Shaped Octaphosphorus–Cobalt Complexes: Synthesis, Structure, and Functionalization Reactions with Carbene Analogs

“…Though a considerable amount of reactions of P 4 with alkali metals, alkaline earth metals, and also transition-metals were reported to form large polyphosphide compounds, − selectivity control presents as a big challenge in these reactions. Moreover, large polyphosphide compounds have structural variety, which also adds difficulty to their selective synthesis. − Probably associated with these difficulties, selective syntheses of large polyphosphorus compounds from P 4 coupling reactions are rarely known, which renders further reactivity exploration on large polyphosphorus compounds difficult.…”