Niedervalente Eisen(I)‐Amido‐Olefinkomplexe als Promotoren von Dehydrierungsreaktionen

Abstract

Fe I -Verbindungen einschließlichH ydrogenasen [1a] zeigen bemerkenswerte Stoffeigenschaften und Reaktivitäten. [2][3][4][5][6] Das Anion [Fe(C(SiMe 3 ) 3 ) 2 ] À ist ein Einzelmolekülmagnet mit hoher Anisotropiebarriere. [2a] In stçchiometrischen Reaktionen wurden Eisen(I)-Diketiminate,E isen(I)-Tris(phosphino)borate und verwandte Spezies als Modellverbindungen für die N 2 -Aktivierung [4a-c,l, 5a,f] sowied ie Spaltung und Kupplung von CO 2 etabliert. [4d,e] Die Entwicklung wohldefinierter Eisen(I)-Komplexef ür katalytischeU msetzungen bleibt jedoche ine Herausforderung. Die wenigen Beispiele umfassen Kreuzkupplungen, [2b,3] Hydrierungen terminaler Olefine [4f] und Azidfunktionalisierungen. [4h, 5i] Hier berichten wir über die Herstellung und Eigenschaften bimetallischer Komplexe[ MFe I (trop 2 dae)(solv)] mit einer d 7 -Fe-low-spin-Valenzelektronenkonfiguration (M = Na, solv = 3thf (1); M= Li, solv = 2Et 2 O( 2 ); trop = 5H-Dibenzo[a,d]cyclo-hepten-5yl, dae = (N-CH 2 -CH 2 -N)). Verbindungen 1 und 2 induzieren die Dehydrierung von N,N-Dimethylaminboran, und 1 ist ein Präkatalysator für die dehydrierende Alkoholyse von Silanen. Es wurden keine Hinweise auf heterogene Katalyse gefunden. Vora llem mit [NaFe I (trop 2 dae)(thf) 3 ]( 1 )w urden hohe Aktivitäten und vollständige Umsätze erzielt. Schema 1. Synthese der Komplexe 1 und 2 ausgehend von [FeCl 2 -(thf) n ]; 1: n=1.5; 2: n = 0.

Mono- and Dinuclear Neutral and Cationic Iron(II) Compounds Supported by an Amidinato-diolefin Ligand: Characterization and Catalytic Application

“…The Fe(I) compound [NaFe(trop 2 dae)(THF) 3 ] (12) has very recently been reported as an efficient homogeneous precatalyst for the dehydrogenative coupling of PhSiH 3 and 1,4-benzene-dimethanol (dae = N−CH 2 −CH 2 −N). 12 Compared to 12, the use of precatalyst 9 results in a slower reaction (43 min vs 5 min until full conversion) but yields a product with a molecular weight that is more than two times higher (≥24 vs ≥9 repeating units).…”

“…The base metal catalyzed dehydrogenative alcoholysis of silanes has been discussed as a tool for introducing silyl protection groups in organic synthesis 48 and as a means of on-demand-H 2 generation. 49 We became interested in this type of reaction for the synthesis of poly silylethers, 12 an approach which was introduced by Kawakami et al and has been only little exploited so far. 50,51 The catalysts employed for this transformation were typically based on the precious metals Pd and Rh.…”

Stabilization of Low‐Valent Iron(I) in a High‐Valent Vanadium(V) Oxide Cluster

“…Low‐valent iron centers are discussed as reactive sites in the nitrogen‐to‐ammonia reduction in nitrogenase and the Haber–Bosch process . Further, low‐valent iron complexes play a key role in a multitude of technologically important organic conversions including C−C bond formation, C−H activation, hydrogenations, and dehydrogenations, as well as small‐molecule activation …”

Low-Valence Anionic α-Diimine Iron Complexes: Synthesis, Characterization, and Catalytic Hydroboration Studies

“…As a result, the synthesis of low-valence α-diimine iron complexes bearing an unsaturated hydrocarbon as second ligand has attracted significant interest over the last two decades (Figure ). − In these complexes, the hydrocarbon is supposed to act as a “placeholder”, which is easily replaced by other substrates to initiate the catalytic cycle. These hydrocarbons are typically simple arenes as used for example in net-neutral complexes A – E shown in Figure synthesized by the groups of Zenneck ( A ), Chirik ( B ), Song ( C ), and Findlater ( D and E , all Figure ).…”

“…In contrast to the research on neutral heteroleptic iron α-diimine complexes, there are only three reports about anionic complexes, coming from the groups of Lichtenberg, de Bruin, and Grützmacher ( L – N ). In these complexes, the olefin and α-diimine ligands were combined in one framework using a trop 2 dad ligand (trop = 5 H -dibenzo­[ a,d ]­cycloheptene-5-yl, dad = diazadiene) . The central iron atom of complex L adopts an almost square-planar geometry.…”