Al–Sc Bonded Complexes: Synthesis, Structure, and Reaction with Benzene in the Presence of Alkyl Halide

Abstract

An alumanyl anion possessing N, N′-bis(2,6-diisopropylphenyl)-1,3-propanediamine ligand was synthesized and characterized. Transmetalation of this Al anion with diaminoscandium chloride precursors afforded the corresponding Al−Sc complexes possessing an unprecedented Al−Sc bond. The Al−Sc[N(SiMe 3 ) 2 ] complex underwent intramolecular C−H cleavage to form a bridged dinuclear complex with μ-hydrido and μ-methylene ligands. The Al− Sc(N i Pr 2 ) 2 complex reacted with benzene in the presence of alkyl bromide to furnish a 1,4-dialuminated cyclohexadiene product with a concomitant formation of the alkyl−alkyl coupled product. Although the latter product seems to form through the radical mechanism, DFT calculations revealed an ionic mechanism involving bimetallic reaction pathways to react with alkyl bromide and benzene, which provides new insight into the chemistry of metal−metal bonded compounds.

Inducing Nucleophilic Reactivity at Beryllium with an Aluminyl Ligand

“…Within this surge of activity was a report in 2018 of a nucleophilic aluminyl anion (along with its gallium analogue) {K­[E­(NON)]} 2 (E = Al, 1 ; Ga, 2 ; NON = 4,5-bis­(2,6-diisopropylanilido)-2,7-di tert -butyl-9,9-dimethylxanthene) . The potent nucleophilicity of compound 1 (and related aluminyl systems) has been harnessed to prepare a range of complexes featuring aluminium–metal bonds, many of which display unique behavior because of the powerful electron-donating properties of this aluminyl “metalloligand.” − …”

The emerging chemistry of the aluminyl anion

“…A new addition to the family of N,N 0 -(diamido) aluminyl anions has been reported and the chemistry of its bimetallic complex with scandium investigated. 86 Compound 161 undergoes a thermal (room temperature) activation of a methyl group from SiMe 3 to afford a methylene-/hydrido-bridged species 163. When the NiPr 2 derivative 162 was reacted with Ph 2 CHBr in benzene, a dialuminated 1,4-cyclohexadiene product 164 was isolated that derives from the dearomatisation of C 6 H 6 .…”

“…A new addition to the family of N , N ′-(diamido) aluminyl anions has been reported and the chemistry of its bimetallic complex with scandium investigated. 86 The relatively simple 1,3-propanediamido ligand [DippN(CH 2 ) 3 NDipp] 2− ([NC 3 N] 2− ) supports the potassium aluminyl that has been isolated as the CDP 159 and the [K(crypt-222)] + SIP, 160 (Scheme 17). Metathesis reactions with Sc(NR 2 ) 2 Cl(THF) n (R = SiMe 3 , n = 1; R = iPr, n = 2) affords the bimetallic Al–Sc complexes, (NC 3 N)Al–Sc(NR 2 ) 2 (THF) 161 (R = SiMe 3 ) and 162 (R = iPr).…”

An acyclic aluminyl anion

“…[6][7][8][9][10][11] The groups of Kinjo and Yamashita have recently contributed a series of 5-membered aluminyl anions, stabilised by bidentate alkyl(amido) (VI-VII) and dialkyl (VIII) ligands. [12][13][14] Even though the range of ligands used to isolate 'free' aluminyl anions appears to be diverse, to date all of these are dianionic chelating ligands. 1,[6][7][8][9][10][11][12][13][14] This is in fact the case for nearly all reported group 13 E(I) anions (boryl, aluminyl, gallyl, indyl), with no mononuclear acyclic boryl, aluminyl or indyl anions bearing s-block cations being reported.…”

“…[12][13][14] Even though the range of ligands used to isolate 'free' aluminyl anions appears to be diverse, to date all of these are dianionic chelating ligands. 1,[6][7][8][9][10][11][12][13][14] This is in fact the case for nearly all reported group 13 E(I) anions (boryl, aluminyl, gallyl, indyl), with no mononuclear acyclic boryl, aluminyl or indyl anions bearing s-block cations being reported. 15,16 Herein, we report the first acyclic aluminyl anion, stabilised by two bulky monodentate, monoanionic amido ligands and explore its structure and reactivity.…”