Andreas E. Seitz

P4 activation by main group elements and compounds.

An overview about the activation of white phosphorus, P4 with main group elements and compounds is given.

Transfer Reagent for Bonding Isomers of Iron Complexes

The cothermolysis of As4 and [Cp″2Zr(CO)2] (Cp″ = η5-C5H3tBu2) results in the formation of [Cp″2Zr(η1:1-As4)] (1) in high yields and the arsenic-rich complex [(Cp″2Zr)(Cp″Zr)(μ,η2:2:1-As5)] (2) as a minor product. In contrast to yellow arsenic, 1 is a light-stable, weighable and storable arsenic source for subsequent reactions. The transfer reaction of 1 with [Cp‴Fe(μ-Br)]2 (Cp‴ = η5-C5H2tBu3) yields the unprecedented bond isomeric complexes [(Cp‴Fe)2(μ,η4:4-As4)] (3a) and [(Cp‴Fe)2(μ,η4:4-cyclo-As4)] (3b). In contrast, the analogous reaction with the CpBn derivative [CpBnFe(μ-Br)]2 (CpBn = η5-C5(CH2(C6H5)5) leads exclusively to the triple decker complex [(CpBnFe)2(μ,η4:4-As4)] (4) possessing the tetraarsabutadiene-type ligand analogous to 3a. To elucidate the stability of the bonding isomers 3a and 3b, DFT calculations were performed. The oxidation of 4 with AgBF4 affords [(CpBnFe)2(μ,η5:5-As5)][BF4] (5), which is a product expanded by one arsenic atom, instead of the expected complex [(CpBnFe)2(μ,η4:4-cyclo-As4)]+.

Facile storage and release of white phosphorus and yellow arsenic

The storage of metastable compounds and modifications of elements are of great interest for synthesis and other, e.g., semiconductor, applications. Whereas white phosphorus is a metastable modification that can be stored under certain conditions, storage of the extremely (light- and air-)sensitive form of arsenic, yellow arsenic, is a challenge rarely tackled so far. Herein, we report on the facile storage and release of these tetrahedral E4 molecules (E = P, As) using activated carbon as a porous storage material. These loaded materials are air- and light-stable and have been comprehensively characterized by solid-state 31P{1H} MAS NMR spectroscopy, powder X-ray diffraction analysis, nitrogen adsorption measurements, and thermogravimetric analysis. Additionally, we show that these materials can be used as a suitable E4 source for releasing intact white phosphorus or yellow arsenic, enabling subsequent reactions in solution. Because the uptake and release of E4 are reversible, these materials are excellent carriers of these highly reactive modifications.White phosphorus and yellow arsenic represent useful elemental sources for synthetic applications, but their poor stabilities make their storage highly challenging. Here, Scheer and colleagues encapsulate P4 and As4 molecules within porous activated carbons and demonstrate their use in subsequent chemical reactions.

Different Reactivity of As4 towards Disilenes and Silylenes

The activation of yellow arsenic is possible with the silylene [PhC(NtBu)2 SiN(SiMe3 )2 ] (1) and the disilene [(Me3 Si)2 N(η1 -Me5 C5 )Si=Si(η1 -Me5 C5 )N(SiMe3 )2 ] (3). The reaction of As4 with 1 leads to the unprecedented As10 cage compound [(LSiN(SiMe3 )2 )3 As10 ] (2; L=PhC(NtBu)2 ) with an As7 nortricyclane core stabilized by arsasilene moieties containing silicon(II)bis(trimethylsilyl)amide substituents. In contrast, the compound [Cp*{(SiMe3 )2 N}SiAs]2 (4) containing a butterfly-like diarsadisilabicyclo[1.1.0]butane unit is formed by the reaction of As4 with the disilene 3. Both compounds were characterized by single-crystal X-ray diffraction analysis, NMR spectroscopy, and mass spectrometry. The reaction outcomes demonstrate the different reaction behavior of yellow arsenic (As4 ) compared to white phosphorus (P4 ) in the reactions with the corresponding silylenes and disilenes.