Demetallierung von Tricarbonyl(cyclopentadienon)eisen-Komplexen durch eine Ligandenaustauschreaktion mit NaOH – Röntgenstrukturanalyse eines Komplexes mit nahezu quadratisch-planar koordiniertem Natrium

Abstract

Durch sequentiellen Austausch eines Carbonylliganden durch einen Hydridliganden mit NaOH und einen Iodliganden mit Iodpentan und anschließende Umsetzung mit Säure werden Tricarbonyl(η4‐cyclopentadienon)eisen‐Komplexe in Dicarbonyl(η5‐hydroxycyclopentadienyl)iodeisen‐Komplexe überführt. Diese demetallieren beim Kontakt mit Luft an Tageslicht hochselektiv zu den entsprechenden freien Liganden. Unter basischen Bedingungen reagiert der Iodkomplex zu einem anionischen Dicarbonyl(η4‐cyclopentadienon)iodeisen‐Komplex, der im Festkörper dimer vorliegt und dessen Natrium‐Gegenion nahezu quadratisch‐planar koordiniert wird.

Air‐Stable, Nitrile‐Ligated (Cyclopentadienone)iron Dicarbonyl Compounds as Transfer Reduction and Oxidation Catalysts

“…Unfortunately its major practical limitation is its air sensitivity. While 1 is stable for a brief time in the air, it must be stored at −30 °C under an inert atmosphere 6b,9…”

“…Using the established procedure, a series of five nitrile‐ligated iron compounds was synthesized from 3 , which is air‐stable and accessible in two steps from commercial chemicals (Table 1). 9,13 All of the iron nitriles in Table 1 could be purified by flash chromatography and all were air‐stable, orange solids.…”

Cooperative Transition‐Metal and Chiral Brønsted Acid Catalysis: Enantioselective Hydrogenation of Imines To Form Amines

“…The use of other simple iron salts or the Morris complex 6 led to no amine at all. However, dicarbonylhydro[2,5‐di(trimethylsilyl)‐3,4‐butylene‐1‐hydroxy(η 5 ‐cyclopentadienyl)]iron ( 5 ), which was first synthesized by Knölker et al.,20 yielded N ‐phenyl‐1‐phenylethylamine in 81 % yield with 94 % ee (Table 1, entry 11)! The combination of 5 with other chiral phosphates also created active catalysts; however, the reaction yields and enantioselectivities were lower (Table 1, entries 14–18).…”

General and Highly Efficient Iron‐Catalyzed Hydrogenation of Aldehydes, Ketones, and α,β‐Unsaturated Aldehydes

“…First, we synthesized eight different tricarbonyl(h 4 -cyclopentadienone)iron complexes (1 a-f and 2 a-b) in a straightforward two-step procedure starting from either commercially available 1,6-heptadyines or 1,7-octadiynes, iron pentacarbonyl, and chlorotrialkylsilanes in excellent yield (Scheme 1 and Table 1). [12] In contrast to the known complex 3, [13] and Milsteins pincer complex, [9] all synthesized iron complexes can be handled without special precautions. In fact, they are stable in air and water, and can be purified by column chromatography on silica gel.…”

“…Next, we wondered if the hydrogenation of carbonyl compounds would be possible by using an in situ Hieber base reaction to activate the tricarbonyl(h 4 -cyclopentadienone)iron complexes. [13,14] Considering the industrial importance of 1-arylethanols, our initial catalytic investigations were carried out using the hydrogenation of acetophenone (4 a) as a benchmark reaction (Table 1). As expected the blank reaction without the iron catalyst did not show any activity (Table 1, entry 1).…”