Heterolytic Cleavage of Dihydrogen by Frustrated Lewis Pairs Derived from α-(Dimesitylphosphino)ferrocenes and B(C₆F₅)₃

Abstract

Treatment of the α-dimethylamino[3]ferrocenophane system 3 with methyl iodide followed by dimesitylphosphine (Mes2PH) gave the α-(dimesitylphosphino)[3]ferrocenophane 5. This forms a frustrated Lewis pair [5/8] with B(C6F5)3 (8) that rapidly reacts with dihydrogen under ambient conditions to probably give the phosphonium cation/hydrido borate anion salt [5-H+/H-8 −]. This, however, is unstable under the applied reaction conditions with regard to replacement of the newly formed phosphonium leaving group at the ferrocenophane α-position for hydride from the [HB(C6F5)3 −] counteranion to eventually yield the unfunctionalized [3]ferrocenophane product (10) and Mes2PH·B(C6F5)3 (11)both characterized by independent syntheses. Analogously, Ugi’s amine (6) was converted to (1-(dimesitylphosphino)ethyl)ferrocene (7). The frustrated pair [7/8] consumes dihydrogen under similar conditions to yield the reduction products ethylferrocene (14) and Mes2PH·B(C6F5)3 (11).

Frustrated Lewis Pairs: Metal‐free Hydrogen Activation and More

“…Thus employing a catalytic amount of B(C 6 F 5 ) 3 in the presence of an imine substrate (and H 2 ), it was indeed possible to effect the catalytic reduction of the imine to the corresponding amine. In this fashion, the simple combination of an imine substrate and H 2 results in reduction of imines (82-84) to amines (86)(87)(88) under conditions similar to those described in Section 6.1 for the phosphino-borane catalysts. Mechanistically these reductions proceed by H 2 cleavage and protonation of the imine to give iminium cations which are then attacked by hydridoborate affording the amine (Scheme 36).…”

Frustrierte Lewis‐Paare: metallfreie Wasserstoffaktivierung und mehr

“…Die selektive 1,4-Hydrierung von 133 zum Produkt 134 gelang mit dem Katalysatorsystem 27 a (Schema 49). [63] Der [65,87] Die analoge Reaktion wurde auch bei einem Beispiel aus der verwandten [3] [87] Überraschend liefert die analoge Umsetzung der eng verwandten ortho-Brom-und ortho-Iod-substituierten [88] …”

Synthesis and Characterization of a Family of Air-Stable Ferrocene- and Ruthenocene-Containing Primary, Secondary, and Tertiary Phosphines

“…26 The crystal of 8b was nonmerohedrally twinned (see supporting information for twin law). The twin fraction of the minor domain refined to a value of 0.4120 (7). The structures for 8b, 8c, 10, 11, and 12 were solved using the SHELXT program.…”

“…The twin fraction for the minor domain refined to a value of 0.4120 (7). The twin law is given below: Figure S22.…”

“…4c,4d,4o Phosphines bearing ferrocene (Fc) substituents combine the desirable characteristics of phosphines and ferrocene, and often exhibit surprising stability towards air and moisture. 4f,4k,4m Consequently, they have been utilized as rigid and potentially redox-active ligands for transition metals, e.g., in Pd(dppf)Cl 2 4 [dppf = 1,1'-bis(diphenylphosphino)ferrocene], 5,6 as Lewis bases in frustrated Lewis pairs, e.g., 5, 7 and in the synthesis of metal-containing polymers and polymer networks, e.g., 6. 4m,4o,8 While the properties of ferrocene-based phosphines have been widely explored, reports on ruthenocene (Rc) analogs are relatively scarce throughout the literature.…”