Arsenic‐Rich Polyarsenides Stabilized by Cp*Fe Fragments

Abstract

The redox chemistry of [Cp*Fe(η -As )] (1, Cp*=η -C Me ) has been investigated by cyclic voltammetry, revealing a redox behavior similar to that of its lighter congener [Cp*Fe(η -P )]. However, the subsequent chemical reduction of 1 by KH led to the formation of a mixture of novel As scaffolds with n up to 18 that are stabilized only by [Cp*Fe] fragments. These include the arsenic-poor triple-decker complex [K(dme) ][{Cp*Fe(μ,η -As )} ] (2) and the arsenic-rich complexes [K(dme) ] [(Cp*Fe) (μ,η -As )] (3), [K(dme) ] [(Cp*Fe) (μ,η -As )] (4), and [K(dme) ] [(Cp*Fe) (μ ,η -As )] (5). Compound 4 and the polyarsenide complex 5 are the largest anionic As ligand complexes reported thus far. Complexes 2-5 were characterized by single-crystal X-ray diffraction, H NMR spectroscopy, EPR spectroscopy (2), and mass spectrometry. Furthermore, DFT calculations showed that the intermediate [Cp*Fe(η -As )] , which is presumably formed first, undergoes fast dimerization to the dianion [(Cp*Fe) (μ,η -As )] .

Durch Cp*Fe‐Fragmente stabilisierte, Arsen‐reiche Polyarsenide

“…Ausgewählte Bindungslängen []und -winkel [8 8]von 3:As1-As2 2.3722-(12), As2-As3 2.3728(12), As3-As4 2.3697(11), As4-As5 2.4366(9), As1-As5 2.4360(11),A s5-As5' 2.4408 (14);A s1-As5-As4 81.25(3), As1-As5-As5' 93.00(4), As4-As5-As5' 92.51 (4). [31] Abbildung 2. Molekülstruktur des Anions von 4 im Kristall.…”

“…[28] (14);A s1-As2-As3 106.30(6), As1-As5-As4 106.77(6), As1-As5-As6 98.55(5), As1-As2-As7 99.02(5), As2-As1-As5 102.15 (5), As2-As1-As1' 97.50 (7), As2-As3-As4 106.51(5), As3-As2-As7 80.60(4), As3-As4-As5 106.26 (5), As4-As5-As6 81.82(5), As5-As1-As1' 97.39(6), As5-As6-As7 106.20 (5). [31] Angewandte Chemie Zuschriften längen sind. [23] Lediglich der As10-As11-Abstand (2.5738-(13) )i st gegenüber einer As-As-Einfachbindung deutlich vergrçßert.…”

Element‐Element‐Bindungsbildung durch Oxidation und Reduktion

“…In diesen Reaktionen reagiert der Polyphosphorligand in [Cp*Fe(η 5 ‐P 5 )] auf die Aufnahme oder Abgabe eines Elektrons entweder mit der Faltung des P 5 ‐Rings oder mit der Bildung einer neuen exocyclischen P‐P‐Bindung . Die Redoxchemie der analogen Arsenverbindung [Cp*Fe(η 5 ‐As 5 )] führt im Falle einer Reduktion zu einem Gemisch anionischer Spezies, die As 4 ‐, As 10 ‐, As 14 ‐ und As 18 ‐Liganden enthalten, während alle Versuche in Richtung einer Oxidation bisher fehlgeschlagen sind . Ein ähnliches Verhalten, einschließlich der Bildung exocyclischer E‐E‐Bindungen bei der Oxidation, wurde für die Komplexe [{CpMo(CO) 2 } 2 (μ,η 2 :η 2 ‐E 2 )] (E=P–Bi) berichtet, was für E=P, As zur Bildung der Komplexe C und D (Schema ) führte …”

The Influence of β‐diiminato Ligands on As4 Activation by Cobalt Complexes

“…[3] In contrast, the reactivity of As 4 has been less explored and only afew reports have been published during the last few years. [4] Most of the synthesized compounds have cyclopentadienyl (Cp R )and strongly donating carbonyl ligands,f or example [(Cp R Co) 2 As 4 ]( A), [5] [(Cp iPr4 Ni) 2 As 4 ]( B), [6] and [(Cp*(CO)Co) 2 As 4 ]( C) [7] (Scheme 1). Recently,c omplexes containing b-diiminato ligands (L) have gained increasing importance because of their exceptionally mild and selective reactivity towards small molecules such as O 2 ,N 2 ,and P 4 .…”

“…[9] Fort he analogous Co I -mediated reactions,d inuclear complexes [(LCo) 2 (m-h 4:4 -P 4 )] (L = L 0 ,L 1 ,L 2 ,L 3 (E)) are formed exclusively,w ith each of them stabilizing similar rectangular and neutral [P 4 ] 0 ligands. [10] Recently,i nt he case of the heavier congener antimony,t he synthesis of [(L 3 Ga) 2 Sb 4 ] (F) [11] and [(LMg) 4 Sb 8 ]( G) [12] was reported. However,t he only reported reaction of a b-diketiminato complex with As 4 yielded [(L 3 Cu) 2 (m-h 2 :h 2 -As 4 )] (H), [13] which contains an intact [As 4 ] 0 tetrahedron fixed between two [L 3 Cu] fragments.…”