Novel Azine Reactivity: Facile NN Bond Cleavage, CH Activation, and NN Coupling Mediated by Rh^I

Abstract

Azines (R 2 C¼NÀN¼CR 2 ) are very useful compounds. For example, they undergo unusual [1,3] dipolar cycloaddition reactions (the crisscross addition) with dienophiles, which provide a convenient route to five-membered rings. [1] They also participate in [3þ2] cycloaddition reactions as an ene fragment. [2] Applications of azines include possible nonlinear optical materials [3] and conducting polymers (polyazines). [4] Relevant to dinitrogen fixation, the formation of azines by metal-mediated functionalization of N 2 was demonstrated. [5] Azine derivatives display important biological properties and are of importance for drug development. [6] Complexes of titanium, [7] zirconium, [7c] cobalt, [7c] uranium, [8] and iron [9] are capable of cleaving the N À N bond in azines. In all the reported cases, the azine NÀN bond is cleaved symmetrically forming two imide units, ÀN¼CR 2 , coordinated to a metal center. No metal-complex-catalyzed reactions were reported. Herein we report a novel type of azine reactivity, the rhodium-promoted catalytic "nonsymmetrical" NÀN bond cleavage accompanied by C À H activation, which leads to an imine and benzonitrile. This is the first metal-promoted nonsymmetric cleavage of the NÀN bond in an azine [10] and the first metal-catalyzed NÀN activation in an azine.When a toluene solution of the PCP-pincer rhodium complex 1 [11] was treated with one equivalent of benzalazine at À30 8C, three complexes were formed (Scheme 1). One of them, tentatively identified by NMR spectroscopy as the [(PCP)Rh(benzalazine)] complex 2 (precedents exist for azine complexes [7] ), is an intermediate, which converts into [*] Prof.

C−F Bond Cleavage and Unexpected C−CN Activation by Cobalt Compounds Supported with Phosphine Ligands

“…Interest in azine and diazine compounds either for pharmaceuticals or as building blocks for various applications with materials and in supramolecular chemistry has led to a variety of experimental and theoretical studies. 5c, Cleavage of the N−N bond in azines by transition metal complexes has been occasionally observed. , …”

Reactivity and Structure of Complexes of Small Molecules: Dinitrogen

“…Accordingly, coordination of N 2 at these fragments is sufficient to allow isolation of the 16 electron complexes, yet N 2 is readily displaced by many two electron donors en route to catalysis. 426 , 427 An equilibrium between terminal and bridging end-on complexes has been observed (scheme 116). 428 Unlike what was presented above, reaction of PhCHN 2 formed a stable adduct only at low temperature.…”

Non-Pincer-Type Arene Ru(II) Catalysts for the Direct Synthesis of Azines from Alcohols and Hydrazine under Aerobic Conditions

“…These compounds have been recently used as nonlinear optical (NLO) materials, 9 conducting materials, 10 as ion-selective optical sensors, 11 and in supramolecular chemistry. 12,13 Furthermore, azines act as beneficial candidates for drug development in pharmacological industries possess and some derivatives displayed antifungal, anticancer, antihypertensive, antibacterial, antimicrobial activities 14 (Figure 1).…”