Endlich homoleptisch: Synthese und vollständige Charakterisierung stabiler Salze des Mangantetranitrosylkations

Abstract

Trotz der ¾hnlichkeit zu Kohlenmonoxid ist die Chemie von homoleptischen Stickstoffmonoxidkomplexen im Unterschied zu ihren Carbonylanaloga bislang grundlegend unerforscht. Hier beschreiben wir die Synthese des ersten echten homoleptischen Übergangsmetallnitrosylkomplexes als Salz der schwachk oordinierenden Anionen (WCAs) [Al(OR F ) 4 ] À und [F{Al(OR F ) 3 } 2 ] À (R F = C(CF 3 ) 3 ). Diese Salze sind in guten Ausbeuten phasenrein zugänglichu nd wurden vollständig durch IR/Raman-, NMR-und UV/Vis-Spektroskopie sowiem ittels Einkristallstrukturanalyse und Pulverdiffraktometrie charakterisiert. Sie kçnnten als bisher beispiellose Modellsysteme fürtheoretische und experimentelle Studien zu Nitrosylkomplexen fungieren.ImLaufe der letzten Jahrzehnte waren Übergangsmetallnitrosylkomplexe hauptsächlich wegen der wichtigen Rolle von NO in biochemischen Prozessen im Fokus. [1,2] Nahezu 4000 Kristallstrukturen von Übergangsmetallnitrosylkomplexen mit mindestens einem NO-Liganden sind in der CCSD (Stand 05/2019) hinterlegt. Obwohl -o der gerade weil -s ie so vielzählig sind, fällt auf,d ass bis heute nur ein einziger homoleptischer und vollständig charakterisierter Nitrosylkomplex publiziert wurde:d as anionische [Fe(NO) 4 ] À (Tabelle 1). [3] Dies ist gerade im Vergleich mit der sehr gut untersuchten Chemie der artverwandten Carbonylkomplexe verwunderlich, da dort seit langer Zeit zahlreiche Beispiele von anionischen, neutralen oder kationischen homoleptischen Kom-Angewandte Chemie

Stable Salts of Heteroleptic Iron Carbonyl/Nitrosyl Cations

“…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.…”

“…However, similar reactions showed that the more accessible alternative [Al-(OR F ) 4 ] À anion is not suitable for this system: although the [Fe(CO) 4 4 ]. [11] Therefore, we limit our report to the use of the more stable and less-symmetric [F-{Al(OR F ) 3 } 2 ] À anion. With this anion, the reactions in Scheme 1 led to phase-pure crystals of 1 and 2 (cf.…”

“…[Fe(CO) 4 [11] [Co(CO) 2 (NO) 2 ] + [B(CF 3 ) 4 ] À [13] ñ(CO/NO) IR [cm À1 ] 2183 (vvw) 2144 (sh) [b] 2137 (mw) [b] 2119 (m) 1904 (m) 2168 (vvw) 2114 (vvs) 2114 (vvs) 2096 (vvs) 1905 (w) n(CO) (A 1 ) n(CO) (A 1 ) [b] n(CO) (B 1 ) [b] n(CO) (B 2 ) n(NO) (A 1 ) [d] [a] C 2v /C 3v symmetry @BP86def2/TZVPP-D3BJ, no scaling factor was applied. For comparison, the experimental d FeC in Fe(CO) 5 is 181.4 pm [18] and the calculation at the same level of theory gives 180.4 pm; [b] the assignment of the shoulder is ambiguous; [c] distances and angles averaged over all positions (CO and NO); [d] ligand, we conducted AIM charge analyses on the cations of compounds 1 and 2 and compared them to the fully characterized isoelectronic and pseudo-isostructural analogues [Co(CO) 5 ] + , [13] [Mn(NO) 4 ] + [11] as well as [Co(CO) 2 -(NO) 2 ] + [13] ( In conclusion, we discovered a simple pathway to two novel heteroleptic iron carbonyl/nitrosyl cations, stabilized by a weakly coordinating anion. Both complexes are the first of their kind, exhibit the unusual oxidation state + I, were fully characterized and are accessible as phase pure materials in good to excellent yields.…”

Synthesis and Application of a Perfluorinated Ammoniumyl Radical Cation as a Very Strong Deelectronator

“…However, the identification of the crystals as 7 was unambiguous (molecular structure, see Figure 2). Presence of the assigned cationic species was verified by IR spectroscopic analysis showing a strong vibrational band of the single coordinated carbonyl moiety with a stretching frequency of 2057 cm À1 , which is, as expected due to the better WCA performance of our counterion, slightly (8). Data collected at 100 K. H atoms, counterions and (co-crystallized) oDFB were omitted for clarity.…”

“…However, the generated neutral NO is likely to undergo further ligand-substitution, for example, with transition-metal complexes. [8] Moreover, nitrosyl salts show a noticeable solvent dependency of their formal potential and are known to form colored charge transfer complexes with arenes as the first step towards electrophilic substitution, thus lessening their applicability. [9] Another class of deelectronating agents, and part of the work documented herein, are ammoniumyl radical cations, first observed over 100 years ago by Wieland.…”