German Edition: DOI: 10.1002/ange.201702903 Polyarsenides International Edition: DOI: 10.1002/anie.201702903 Arsenic-Rich Polyarsenides Stabilized by Cp*Fe Fragments Monika Schmidt, David Konieczny, Eugenia V. Peresypkina, AlexanderV. Virovets, Gabor Balµzs, Michael Bodensteiner, Felix Riedlberger, Hannes Krauss, and Manfred Scheer* Dedicated to Professor Wolfgang Schnick on the occasion of his 60th birthday Abstract: The redox chemistry of [Cp*Fe(h 5 -As 5 )] (1, Cp* = h 5 -C 5 Me 5 ) has been investigated by cyclic voltammetry, revealing a redox behavior similar to that of its lighter congener [Cp*Fe(h 5 -P 5 )]. However, the subsequent chemical reduction of 1 by KH led to the formation of a mixture of novel As n scaffolds with n up to 18 that are stabilized only by [Cp*Fe] fragments. These include the arsenic-poor triple-decker com- plex [K(dme) 2 ][{Cp*Fe(m,h 2:2 -As 2 )} 2 ](2) and the arsenic-rich complexes [K(dme) 3 ] 2 [(Cp*Fe) 2 (m,h 4:4 -As 10 )] (3), [K(dme) 2 ] 2 - [(Cp*Fe) 2 (m,h 2:2:2:2 -As 14 )] (4), and [K(dme) 3 ] 2 - [(Cp*Fe) 4 (m 4 ,h 4:3:3:2:2:1:1 -As 18 )] (5). Compound 4 and the poly- arsenide complex 5 are the largest anionic As n ligand complexes reported thus far. Complexes 2–5 were character- ized by single-crystal X-ray diffraction, 1 H NMR spectroscopy, EPR spectroscopy (2), and mass spectrometry. Furthermore, DFT calculations showed that the intermediate [Cp*Fe(h 5 - As 5 )]  , which is presumably formed first, undergoes fast dimerization to the dianion [(Cp*Fe) 2 (m,h 4:4 -As 10 )] 2 . Ferrocene, [Cp 2 Fe] (Cp = h 5 -C 5 H 5 ), and its derivatives belong to the most frequently used compounds in organome- tallic chemistry, for example, for catalysis [1] and bioorgano- metallic [2] purposes. As [Cp 2 Fe] is redox-active, it has also been applied in redox-switchable systems [3] or as a reference in cyclic voltammetry. While the oxidation of [Cp 2 Fe] to [Cp 2 Fe] + is a simple reversible one-electron process, and its reduction goes along with a structural change, the electro- chemical oxidation and reduction of the isolobal derivative [Cp*Fe(h 5 -P 5 )] (Cp* = h 5 -C 5 Me 5 ) are more complex. [4] Here, [Cp*Fe(h 5 -P 5 )] is either oxidized or reduced to [Cp*FeP 5 ] + (17 valence electrons (VE)) or [Cp*FeP 5 ]  (19 VE), followed by immediate dimerization to [(Cp*FeP 5 ) 2 ] 2+ or [(Cp*FeP 5 ) 2 ] 2 , respectively. Recently, both species as well as the doubly reduced dianion [Cp*Fe(h 4 -P 5 )] 2 have been isolated and characterized by using KH or K as the reducing agent. [5] Moreover, the chemical reduction of [Cp*Fe(h 5 -P 5 )] by divalent lanthanide complexes has been studied, enabling the stabilization of the formally singly ([(Cp*Fe) 2 (P 10 )] 2 ) or doubly ([Cp*FeP 5 ] 2 ) reduced fragments in the coordination sphere of the samarium moieties. [6] In contrast, little is known about the redox chemistry of the heavier congener [Cp*Fe(h 5 -As 5 )] (1; Scheme 1). Inter- estingly, comparative studies on the charge distribution [7] as well as DFT calculations [8] predict only small differences in the electronic structure of [Cp*Fe(h 5 -E 5 )] (E = P, As (1)). However, first reactivity studies [8, 9] showed differences, and the reduction of 1 by divalent samarium complexes led to a rearrangement of the former cyclo-As 5 ligand of 1 to form either [(Cp’’Sm)(m,h 4:4 -As 4 )(Cp*Fe)] or [(Cp’’Sm) 2 As 7 - (Cp*Fe)] (Cp’’ = h 5 -1,3- t Bu 2 C 5 H 3 ). [10, 11] This indicates inter- esting behavior for this compound as a potential As source because arsenic-rich polyarsenides in particular are rare to date. Most of them have been obtained from reactions of the Zintl ion As 7 3 with transition-metal and main-group-metal precursors (Scheme 1). [12] An outstanding example is the synthesis of [PBu 4 ] 3 [As@Ni 12 @As 20 ], which contains an ico- sahedral [Ni 12 (m 12 -As)] 3 core incorporated into a fullerene- like As 20 cage. [12d] In 1988, Haushalter and co-workers reported on [Rb(crypt)] 4 [As 22 ]·dmf (dmf = dimethylforma- mide, crypt = 4,7,13,16,21,24-hexaoxa-1,10-diazatricyclo- [8.8.8]hexacosane), which is, to the best of our knowledge, the largest polyarsenide that has been reported thus far. [12b] Apart from the use of Zintl ions as starting materials, which usually led to charged polyarsenides, only few neutral arsenic- containing complexes could be obtained starting from yellow Scheme 1. Arsenic sources used for the synthesis of polyarsenides aside from As(SiMe 3 ) 3 : As 7 3 (left) and As 4 (middle). [Cp*Fe(h 5 -As 5 )] (1) (right) was expected to be a suitable precursor for arsenic-rich complexes. [*] Dr. M. Schmidt, M. Sc. D. Konieczny, Dr. E. V. Peresypkina, Dr. A.V. Virovets, Dr. G. Balµzs, Dr. M. Bodensteiner, M. Sc. F. Riedlberger, Dr. H. Krauss, Prof. Dr. M. Scheer Institut für Anorganische Chemie Universität Regensburg Universitätsstrasse 31, 93053 Regensburg (Germany) E-mail: manfred.scheer@ur.de Homepage: http://www.uni-regensburg.de/chemie-pharmazie/ anorganische-chemie-scheer/ Dr. E. V. Peresypkina, Dr. A. V. Virovets Nikolaev Institute of Inorganic Chemistry SB RAS Ak. Lavrentiev prosp. 3, 630090 Novosibirsk (Russia) and Novosibirsk State University Pirogova str. 2, 630090 Novosibirsk (Russia) Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10. 1002/anie.201702903. A ngewandte Chemi e Communications 1 Angew. Chem. Int. Ed. 2017, 56,1–6  2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim These are not the final page numbers! Ü Ü