Activation of Nitrogen-Rich Substrates by Low-Valent, Redox-Active Aluminum Species

Abstract

Reactivity of low-valent Al II species containing redox-active dpp-dad or dpp-Bian ligand (L a = dpp-dad = [(2,6-iPr 2 C 6 H 3 )NC(CH 3 )] 2 ; L b = dpp-Bian = 1,2-[(2,6-iPr 2 C 6 H 3 )NC] 2 C 10 H 6 ) toward nitrogen-rich substrates is described. Reactions of dialumanes [L 2− Al−AlL 2− ] (L a , 1a, or L b , 1b) with azides (Me 3 SiN 3 , BenzylN 3 ) or azobenzene at room temperature lead to the facile elimination of dinitrogen (in the case of azides) and formation of dimeric imido-complexes [L •− Al(μ 2 -NR) 2 AlL •− ] (2a−2d). During the reaction, the initially dianionic ligands (L 2− ) and Al II ions are oxidized into monoanions (L •− ) and Al III in the products, respectively, while the [NR] 2− imides are produced by a four-electron reductive cleavage of the NN double bond of azides or azo compounds. The monoanionic α-diimine ligands in 2 can be reduced again by Na, yielding analogous products with (L a ) ̇•− /(L a ) 2− or (L a ) 2− /(L a ) 2− ligands (3, 4a, and 4b). Treatment of 1a with benzyl azide at −30 °C in the presence of Na results in [(L a ) 2− Al(μ 2 -N 3 Benzyl) 2 Al(L a ) 2− ]•[Na(THF)] 2 ( 5), with unprecedented bridging triazene groups, while reaction with trimethylsilyldiazomethane (Me 3 SiCHN 2 ) or diphenyldiazomethane (Ph 2 CN 2 ) affords dinuclear complexes with doubly reduced diazo dianions as the bridges (6a and 6b). All the products were structurally and spectroscopically characterized. The results clearly demonstrate the unique reactivity of α-diimine-ligated dialumanes 1a and 1b, which can activate nitrogen-rich molecules by cooperation of metal and the redox ligand.

Hydrocarbon Soluble Alkali‐Metal‐Aluminium Hydride Surrog[ATES]

“…Solution studies on the crystals of 2 in C 6 D 6 confirmed the above observation as the β‐CH 2 (TMP) protons were found to be split into three separate multiplets in the 1 H NMR spectrum (2H, 1H, and 1H respectively), of which two protons appear shielded at −0.02 (1H) and −0.30 ppm (1H) respectively (See Supporting Information, Figure S14) indicating the close interaction of the sodium centre to the axial H‐ atoms of the TMP moiety in the donor‐free aluminate. The structures of 2 and 2 a bear significance on the grounds of the paucity of structures of bisamido bridged sodium aluminates with only a few crystallographically characterised examples present in the literature from the Fedyushkin and Chivers groups [21a,b] …”

Stepwise reduction of a base-stabilised ferrocenyl aluminium(iii) dihalide for the synthesis of structurally-diverse dialane species

“…An interesting possibility for controlling the reactivity of Al–Al species is the introduction of redox-active ligands at the Al centres, and a handful of low-valent aluminium compounds have been prepared with redox-active organic ligands. 13 However, the incorporation of classical redox-active organometallic substituents such as ferrocenyl groups has not been demonstrated. Redox-active ligands bound to a metal centre play an important role in controlling the reactivity of the complex, 14 and their nature depends on redox-active moieties, either bound as ligands or in the second coordination sphere of a metal cofactor, to catalyse challenging reactions.…”

Reactivity of Transition Metal Gallylene Complexes Toward Substrates with Multiple Carbon–Element Bonds

“…It finds use in molecule activation, olefin polymerization, asymmetric transformations, coupling reactions, and other catalytic applications . Earlier, we had made a few attempts for investigation of reactivity of the gallium–dpp-bian system and found it useful for activation of small molecules and heteroallenes − as well as for polymerization of cyclic ethers (Scheme ). Due to this peculiar cooperative capability of the gallylene [(dpp-bian)­Ga], we hypothesized its transition metal complexes − (Scheme ) that consist of three reactive centers, a redox-active ligand, a main group low-valent metal atom, and a transition metal atom, to be useful for the activation of organic molecules.…”