Der elektronische Grundzustand von [Fe(CO)₃(NO)]⁻: eine spektroskopische und theoretische Studie

Abstract

Fe‐katalysierte Reaktionen haben sich in den vergangenen 10 Jahren fest in der organischen Synthese etabliert. Das ursprünglich von Hogsed und Hieber beschriebene komplexe Ferrat [Fe(CO)3(NO)]− zeigt katalytische Aktivität in zahlreichen organischen Reaktionen und wird allgemein als isoelektronisch zum [Fe(CO)4]2− betrachtet. Allerdings zeigt der letztgenannte Komplex kaum katalytische Aktivität. Die hier vorgestellten spektroskopischen und quantenchemischen Untersuchungen zeigen, dass das komplexe Ferrat [Fe(CO)3(NO)]− nicht wie angenommen als eine Fe−II‐Spezies, sondern vielmehr als eine Fe0‐Spezies, in der das Metall kovalent über zwei π‐Bindungen an ein NO− gebunden ist, aufgefasst werden sollte. Eine Metall‐N‐σ‐Bindung wird nicht beobachtet.

Stable Salts of Heteroleptic Iron Carbonyl/Nitrosyl Cations

“…[3] However, from a fundamental perspective, the long-known flexible bonding motifs and bonding fashions of the NO ligand [4] are still under discussion and reinvestigation today. [5] And as much as the chemistry of Fe II and Fe III is well established, as much is yet to learn about the chemistry of iron in the unusual oxidation state of + I. The synthesis of such compounds is mainly achieved by the reduction of Fe II precursors, usually stabilized by bulky strong donor ligands such as [C{Si(CH 3 ) 3 } 3 ] À , [6] cyclic (alkyl)-(amino)carbenes [7] or N-heterocyclic carbenes (NHCs).…”

“…[8] But especially in the absence of those strong and sterically demanding ligands, an undisturbed insight to iron(I) systems is scarce. With that in mind, we made use of the versatility of carbon monoxide (CO) as a ligand by starting from Fe(CO) 5 as a Fe 0 source in combination with an oxidative approach. In order to compensate for the lability of the Fe À CO bond in the resulting iron cations, we utilized the weakly coordinating anion (WCA) [F-{Al(OR F ) 3 } 2 ] À (R F = C(CF 3 ) 3 ) [9,10] [11] In regard to ternary carbonyl/nitrosyl cations, the only currently known examples are [Cr(CO) 5 -(NO)][WCA], reported by us [12] and [Co(CO) 2 (NO) 2 ]-[WCA].…”

“…[13] And although the neutral Fe(CO) 2 (NO) 2 [14] and anionic [Fe(CO) 3 (NO)] À (the Hieber anion) [15] shown in Figure 1 were discovered more than half a decade ago and found their applications as useful starting materials or catalysts, [16] as of yet, their cationic counterparts have been mostly untouched. [ ** ] Our oxidative syntheses started from NO[F-{Al(OR F ) 3 } 2 ] and Fe(CO) 5 in dichloromethane (CH 2 Cl 2 ). Conveniently, this reaction can be done with an excess of Fe(CO) 5 or even with impure NO[F-{Al(OR F ) 3 } 2 ], since [Fe(CO) 4 (NO)][F-{Al-(OR F ) 3 } 2 ] (1) is only poorly soluble in CH 2 Cl 2 (Scheme 1 a).…”

Endlich homoleptisch: Synthese und vollständige Charakterisierung stabiler Salze des Mangantetranitrosylkations

“…[ [11] Weiterhin reichen fürd as berühmte [Fe(H 2 O) 5 NO)] 2+ -Kation die postulierten Oxidationsstufen von Fe I (NO + )z uF e III (NO À ). [ [11] Weiterhin reichen fürd as berühmte [Fe(H 2 O) 5 NO)] 2+ -Kation die postulierten Oxidationsstufen von Fe I (NO + )z uF e III (NO À ).…”

Iron‐Catalysed Hydrofunctionalisation of Alkenes and Alkynes

“…[37] On the basis of the ambivalent nature of NO ligands, the actual oxidation state of iron in complex 46 may be as high as iron(III). Plietker found that complex 46 efficiently catalysed the addition of both aromatic and aliphatic thiols 47 to a,b-unsaturated ketones 48 and nitriles.…”