Bis-[3]Ferrocenophanes with Central >E-E'< Bonds (E, E'=P, SiH): Preparation, Properties, and Thermal Activation.

Invited for this month's cover picture are the groups of Professors Rudolf Pietschnig at the University of Kassel, Professor Dietrich Gudat at the University of Stuttgart and Professor László Nyulászi at the Budapest University of Technology and Economics. The cover picture shows the thermally induced homolytic cleavage of the central P-P bond in a phosphorus-rich bis-ferrocenophane furnishing P-centered radicals (as evidenced by the computed spin-density highlighted in blue). The central P6 unit in the title compound is a structural analog of the connecting unit in Hittorf's violet phosphorus, which links the orthogonally arranged tubular entities. A portrait of the German physicist Johann Wilhelm Hittorf is included. Read the full text of their Full Paper at 10.1002/open.201900182.

Bis-[3]Ferrocenophanes with Central >E-E'< Bonds (E, E'=P, SiH): Preparation, Properties, and Thermal Activation.

A series of bis-[3]ferrocenophanes of the general type Fe(C5H4E')2E-E(E'C5H4)2Fe (E=P, SiH and E'=PtBu, NneoPentyl, NSi(CH3)3) with an isolobal molecular framework have been prepared and characterized by heteronuclear NMR spectroscopy and X-ray crystallography. The thermal dissociation behavior with respect to homolytic fission of the central bond generating phosphorus centered radicals was investigated using EPR spectroscopy and quantum chemical calculations.

Controllable access to P-functional [3]ferrocenophane and [4]ferrocenophane frameworks.

Condensation of secondary 1,1'-diaminoferrocenes with phosphorus trihalides (PCl3 or PBr3) yielded either P-halo-1,3-diaza-2-phospha[3]ferrocenophanes or 1,1'-diaminoferrocenediyl-bis(dichlorophosphines), respectively. The latter provide controlled access to both [3]- and [4]ferrocene frameworks. Thus, reductive coupling with magnesium gave diaza-diphospha[4]ferrocenophane-annelated tetraphosphetanes, while a reaction with LiNMe2 produced a P-chloro-diazaphospha[3]ferrocenophane. Condensation of diaminoferrocenes and aminodichlorophosphines were mostly unselective, but afforded in one case a 3-amino[3]ferrocenophane. All reaction products were characterised by spectroscopic and single-crystal XRD studies. DFT studies indicate that the product selectivity in the reactions studied depends on a combination of kinetic and thermodynamic effects, which correlate subtly with the steric bulk of the N-substituents. Cyclic voltammetry measurements revealed that the ferrocenophanes can undergo multiple oxidation events, the first of which may according to DFT studies be located in both the ferrocene and aminophosphine units. The quantum chemical studies provided also insight into stereochemical aspects like ring strain in the ferrocenophane units.

PBP bridged [3]ferrocenophane: a bisphosphanylborane with a redox trigger.

Stereospecific access to the unprecedented P-B-P bridged [3]ferrocenophane Fe(C5H4PtBu)2BMes is presented. In contrast to acyclic ferrocenylphosphanes, we find evidence for a shift of spin-density from Fe to P upon pyramidal inversion of the P centers in the mono-cation; the latter has a lifetime of τ = 0.31(4) s.