The Reincarnation of the Hieber Anion [Fe(CO)₃(NO)]^– – a New Venue in Nucleophilic Metal Catalysis

Abstract

Nowadays demand for selective, energy-efficient, and sustainable chemical transformations has spurred an increasing interest in the development of "sustainable metal catalysis". This expression defines a type of catalytic transformation in which non-toxic, readily available and inexpensive, stable metal complexes are used for catalysis. The increasing prices for energy and noble metals, which are commonly used for catalysis, represent an economical and ecological dilemma. If the price for a catalyst exceeds the savings on the energy side an industrial application does not make sense. As a consequence of this dilemma, chemists are looking for exit stra-

Benign Catalysis with Iron: Unique Selectivity in Catalytic Isomerization Reactions of Olefins

“…Using Collman's reagent or a combination of HCl and Collman's reagent, which is known to form the dihydride complex [H 2 Fe(CO) 4 ], no activity at all was observed ( Table 2, entries 7-8). [43,44] When using [Fe 2 (CO) 9 ] instead of [Fe(CO) 5 ], the reaction solution turned red after 2 h. Interestingly, [Fe 3 (CO) 12 ] produced the red active-catalyst solution after a few minutes. When the isomerization process was started with [Fe(CO) 5 ], the same monomeric iron anion [HFe(CO) 4 ] À was formed upon reaction with 3 equiv of NaOH or KOH.…”

“…We initially studied the reactivity of different iron hydride carbonyl complexes with 1-octene as the model system ( Table 2). For the selective generation of hydride species through a water-gas shift reaction, [43,44] adding water and base proved to be essential. Using only iron carbonyl complexes without water and base resulted in a mixture of internal olefins ( Table 2, entry 1).…”

“…After a few hours, this species was converted to the same red-colored trinuclear anion. [43,44] When using [Fe 2 (CO) 9 ] instead of [Fe(CO) 5 ], the reaction solution turned red after 2 h. Interestingly, [Fe 3 (CO) 12 ] produced the red active-catalyst solution after a few minutes. This explains the higher activity of this precatalyst relative to all the other iron carbonyl complexes.…”

Photocatalytic Hydrogen Generation from Water with Iron Carbonyl Phosphine Complexes: Improved Water Reduction Catalysts and Mechanistic Insights

“…[IrA C H T U N G T R E N N U N G (bpy) 2 A C H T U N G T R E N N U N G (ppy) 2 ]PF 6 , [17c] [HNEt 3 ]A C H T U N G T R E N N U N G [HFe 3 (CO) 11 ], [36] [NEt 4 ]A C H T U N G T R E N N U N G [HFe(CO) 4 ], [46] [NEt 4 ][(NO)Fe(CO) 3 ], [47] [FeA C H T U N G T R E N N U N G (bda)(CO) 3 ], [48] trisA C H T U N G T R E N N U N G (pyrollyl)phosphine, [49] and [Fe(CO) 3 A C H T U N G T R E N N U N G (PPh 3 ) 2 ]…”

Iron Catalysis in Organic Synthesis: A Critical Assessment of What It Takes To Make This Base Metal a Multitasking Champion

“…Other low valent iron complexes such as [CpFe(C 2 H 4 ) 2 ][Li(tmeda)] ( 12 ) (Scheme 6) 71 or [Fe(CO) 3 (NO)][Bu 4 N] also found promising applications as nucleophilic catalysts. 143 …”