Hydroalumination of Nitriles and Isonitriles

Abstract

Hydroalumination of H5C6-C≡N with di(tert-butyl)aluminum hydride 1or the corresponding diethyl compound 2yielded the products tBu2Al-N=C(C6H5)H 3and Et2Al-N=C(C6H5)H 4, respectively, both of which form dimers possessing Al2N2 heterocycles with two exocyclic C=N double bonds. NMR spectroscopic data indicate the occurrence of cis/trans isomers in solutions of compound 4. The dimerization of the imide via Al-N interactions was prevented by employing the hydride [(Me3Si)2HC]2AlH 6bearing the bulky bis(trimethylsilyl)methyl substituents. Its reaction with benzonitrile yielded the compound R2Al-N=C(C6H5)H(N≡C-C6H5) 7[R = CH(SiMe3)2], in which the coordinative saturation of the aluminum atoms was achieved by adduct formation with one molecule of the starting nitrile. In these cases the C≡N triple bond inserted completely into the Al-H bond of the hydride. In contrast, the reaction of tert-butyl isonitrile afforded the product tBu2Al-C(H)=NC6H5 8by the insertion of its terminal carbon atom into the Al-H bond. Hence, it has a geminal arrangement of the aluminum and hydrogen atoms. Dimerization of 8yielded a six-membered heterocycle. Hydroalumination does not occur upon treatment of the hydride 1with trimethylsilylnitrile. Instead, the Si-CN bond was cleaved, and the aluminum cyanide (tBu2Al-C≡N)4 9was isolated in a high yield.

Facile Synthesis of an Unsaturated Spiro Germane by Hydroalumination and Intramolecular 1,1-Carbalumination

“…n -Pentane, n -hexane, and cyclopentane were dried over LiAlH 4 , toluene, and diethyl ether over Na/benzophenone. The dialkylaluminum hydride R 2 Al−H (R = CH(SiMe 3 ) 2 ) was obtained according to a literature procedure . Tetrakis(phenylethynyl)germane was synthesized in high yield by a slight modification of a method described by Wrackmeyer .…”

Hydroalumination of dialkynylgermanes—synthesis of alkenyl–alkynylgermanes with intramolecular aluminium–carbon interactions

“…n-Hexane, n-pentane and cyclopentane were dried over LiAlH 4 , diethyl ether over Na/benzophenone, and 1,2-difluoro-and pentafluorobenzene over molecular sieves (4 A ˚). The starting compounds (tBuCH 2 ) 2 AlH, 19 tBu 2 AlH 20 and [(Me 3 Si) 2 CH] 2 AlH 21 were obtained according to literature procedures. Commercially available Cl 2 GeMe 2 and Cl 2 Ge(C 6 H 5 ) 2 (Aldrich) were applied as purchased.…”

Three different product types from reactions of lithiated cyclic aminals with trivalent organometal chlorides

“…Although different anions are observed in the products 4 and 5, this demonstrates that in the presence of (trivalent) metals like Y or Ga such cleavage reactions of the tmtac ring can take place. The N-methylimido ligand MeNQCH À has earlier been described by Uhl and Matar in an aluminiumanalogous compound to 5, [(Me 3 C) 2 Al-CHQN(CMe 3 )] 2 , but this was prepared by the insertion of the isonitrile Me 3 C-NC into the Al-H bond of (Me 3 C) 2 Al-H. 12 The 1,3,5-trimethyl-2-methylamidomethyl-1,3,5-triazacyclohexane ligand in 4 is a novel donor-functionalised version of tmtac, the protonated form of which would require a difficult protocol in an intentionally planned synthesis, namely the co-condensation of three equivalents of methylamine, two equivalents of formaldehyde and one equivalent of H 2 NCH 2 NHMe, which itself is an aminal made up from formaldehyde methylamine and ammonia. This ligand has also some similarity to the triazacyclononane (tacn) derivative, N-tert-butyl-2-(4,7dimethyl[1,4,7]triazacyclonon-1-yl)ethylamine, 11 which reacts with a tripodal tacn-ligands with an anionic amide side-arm with rare-earth metal alkyls, however, since already tacn itself is a very expensive or tedious to prepare ligand, the formation of the new ligand system in 4 in two steps from the cheap bulk chemical tmtac bears obvious advantages.…”

“…[(Me 3 C) 2 Al-CHQN(CMe 3 )] 2 12. The C-N double bond in the latter is 1.285(2) A ˚, while it is 1.271(2) A ˚in 5.…”