Formation of 2-Azaallyl Cobalt(I) Complexes by Csp³–H Bond Activation

Abstract

Three novel unsymmetrical η3-2-azaallyl cobalt­(I) complexes, [(2-PPh2)­C6H4]­CHN­[CHC6H4­(4-R)]­Co­(PMe3)2 (4–6) (R = H (4); Cl (5); and OMe (6)), were synthesized by the reactions of Schiff base ligands [(2-PPh2)­C6H4]­CHN­[CH2C6H4­(4-R)] (1–3) (R = H (1); Cl (2); and OMe (3)) with CoMe­(PMe3)4 via sp3 C–H bond activation under mild reaction conditions. Complex {[(2-PPh2)­C6H4]­CHNCH3­[CHC6H4­(4-R)]­Co­(PMe3)2}I (7) as an 18e cobalt­(III) salt was obtained through the reaction of 4 with iodomethane. The substitution reaction of complex 4 with carbon monoxide afforded the dicarbonyl cobalt­(I) complex [(2-PPh2)­C6H4]­CH­[NCHC6H4­(4-R)]­Co­(CO)2­(PMe3) (8). The molecular structures of complexes 4–8 were determined by single crystal X-ray diffraction.

3d Transition Metals for C–H Activation

“…735 After these early efforts, cyclometalation could also be achieved with thioketones 402, ketones 209, 736−739 NH imines 199, 738,740 vinylpyridines 326, 741 aryl and benzyl phosphines 407, 742,743 thioether 409, 744 and even on C(O)−H 745 and C(sp 3 )−H bonds. 746,747 It is noteworthy that the versatile complex [Co(CH 3 )(PMe 3 ) 4 ] is also a potent reagent for challenging C−F activation. 737,738 As these examples deliver the favored 5membered metallacycle, Klein and co-workers also succeeded in forming a less-favored six-membered cobaltacycle using 8methylnaphtalen-1-yl phosphane 411.…”

“…Later, Li found a similar reaction with a hydroxy group as additional donor group . After these early efforts, cyclometalation could also be achieved with thioketones 402 , ketones 209 , − NH imines 199 , , vinylpyridines 326 , aryl and benzyl phosphines 407 , , thioether 409 , and even on C­(O)–H and C­(sp 3 )–H bonds. , It is noteworthy that the versatile complex [Co­(CH 3 )­(PMe 3 ) 4 ] is also a potent reagent for challenging C–F activation. , As these examples deliver the favored 5-membered metallacycle, Klein and co-workers also succeeded in forming a less-favored six-membered cobaltacycle using 8-methylnaphtalen-1-yl phosphane 411 . The size of the formed ring could even be reduced to strained 4-membered rings, as was shown for phosphines, , thioles, and thioethers 409 .…”

Diiodido-bis{N-[2-(diphenylphosphino)benzylidene]benzylamine-κ2N,P}dicopper(I)

“…To investigate whether ligands bearing an imine group, as shown in Scheme 1, also form photophysically interesting complexes, the synthesis of a copper(I) iodide complex was undertaken with R = benzyl. The ligand with R = Bn is not new but has already been used for the complexation of Re(I) [33], Fe [34], Co [35], Pd [36][37][38][39][40], Rh [41], Ru [42], Au [9,43], Pt [9,44], Ir [45], and Cu [46].…”

Synthesis of an elusive, stable 2-azaallyl radical guided by electrochemical and reactivity studies of 2-azaallyl anions

“…7 Despite over 100 years of research into 2-azaallyl anions and their different forms of reactivity, electrochemical and structural data on these reactive species remain underdeveloped. 8,[15][16][17][18][19][20][21] Notably, electrochemical analysis of aryl and alkyl halide substrates reduced by 2-azaallyl anions reveal E pc values approaching À2.4 V versus ferrocene (Fc/Fc + ) (À2.0 V vs. SCE). 22 The SET reactivity observed with 2-azaallyl anions is reminiscent of organic super electron donors (SEDs), which have garnered attention due to their potential advantages over transition metal reducing agents, including lower costs and toxicities (Scheme 2A).…”