Carbon–Carbon Bond Formation from Azaallyl and Imine Couplings about Metal–Metal Bonds

Abstract

Typical C-C bond-forming processes feature oxidative addition, insertion, and reductive elimination reactions. An alternative strategy toward C-C bond formation involves the generation of transient radicals that can couple at or around one or more metal centers. Generation of transient azaallyl ligands that reductively couple at CH positions possessing radical character is described. Two C-C bonds form, and the redox non-innocence of the resulting pyridine-imines may be critical to formation of a third C-C bond via dinuclear di-imine oxidative coupling. Unique metal-metal bonds are a consequence of the chelation.

First-Row Transition Metal and Lithium Pyridine-ene-amide Complexes Exhibiting N- and C-Isomers and Ligand-Based Activation of Benzylic C–H Bonds

“…35 Incorporating PI precursors into a nacnac framework 36−39 permitted the isolation of carbon radical character, leading to C−C bond formation (C), 40 but in related tetradentate ligands, electrostatic stabilization of a 14e − π-system afforded very stable Fe(II) complexes (D). 41,42 Finally, a tetradentate di-PI ligand revealed five redox states (E) that were quite stable, while the metal formally remained Ni(II).…”

Disparate reactivity from isomeric {Me 2 C(CH 2 N CHpy) 2 } and {Me 2 C(CH NCH 2 py) 2 } chelates in iron complexation

“…The generation of 2-N(TMS) 2 , and the ensuing thermolysis, suggested the potential for carbon-carbon bond formation in the system [3][4][5]7], hence a hydrazine derivative, 1,2-diphenyl-1,2-dimethylhydrazine, was added to oxidatively release organic product from the metal. For example, 1 equiv dmp(PM) 2 and 1 equiv hydrazine were placed in C 6 D 6 with 10% Fe{N(TMS) 2 } 2 (THF), and a new organic product formed after 2 d at 23°C.…”

“…Lithium bis(trimethylsilyl)amide was purchased from Aldrich and recrystallized from hexanes prior to use. Ligands dmp(PM) 2 and dmp(PI) 2 have been previously reported [4,7]. NMR spectra were obtained using an INOVA 400 and 500 MHz spectrometers.…”

“…As part of an investigation involving 1,3-di-(2-pyridyl)-2-azaallyls [1][2][3][4][5][6][7][8] and related species as chelating agents, imines that can serve as azaallyl precursors were incorporated into tetradentate platforms. In Fig.…”

“…In Fig. 1, treatment of dibasic metal amides M{N(TMS) 2 } 2 (THF) n (M = Cr, Co) or ½ equiv [Ni(NPh 2 ) 2 ] 2 with Me 2 C(HC@NCH 2 (2-py)) 2 (dmp(PM) 2 ) afforded dimeric complexes [{Me 2 C(HC@NCH(2-py)) 2 } 2 M 2 ] (M 2 ) M = Cr, Co, Ni) upon loss of two equiv HN(TMS) 2 [4]. The dichromium complex has a triple bond, whereas the Ni 2 and Co 2 species possess unusual, relatively weak metal-metal interactions derived from sigma/pi-mixing.…”