Hydroalumination of Oligoalkynylgermanes and ‐digermanes – Reactions with Heterocumulenes by Al–C or Ge–C Bond Activation and Formation of a Hexazenedialuminum Complex

Abstract

Hydroalumination of the dialkynylgermane Ph2Ge(C≡CtBu)2 (1) and the digermanes Phn(tBuC≡C)3–nGe–Ge(C≡CtBu)3–nPhn (2a: n = 2; 2b: n = 1) with two equivalents of H–AltBu2 or H–AlEt2 yielded the mixed Al/Ge compounds Ph2Ge[C(AltBu2)=CH‐tBu]2 (3), [Ph2GeC(AltBu2)=CH‐tBu]2 (4a), and [Ph2GeC(AlEt2)=CH‐tBu]2 (4b). Reactions of 2b with both aluminum hydrides afforded inseparable mixtures of products. 3 reacted with heterocumulenes by retrohydroalumination. Phenyl isocyanate gave insertion of the C=N group into the resulting Ge–C(≡C–tBu) bond (5), whereas the NCS and NCN groups of phenyl isothiocyanate and a carbodiimide inserted into Al–Cvinyl bonds (6 and 7) with unaffected terminal Ge–C≡C–tBu moieties. The generation of 5 represents the first example of the insertion of a heterocumulene into a Ge–C bond, which may be favored by the activation of the isocyanate group by the Lewis acidic Al atom and the increased polarity of the N=C=O fragment as determined by NBO calculations. The reactions of the digermanes 4 with heterocumulenes were unselective and afforded inseparable mixtures. Treatment of 4a with the azide (4‐tBu)C6H4CH2–N3 led interestingly to reductive coupling of two azide molecules, and the hexazene complex (tBuC6H4CH2N3–N3C6H4tBu)(AltBu2)2 (8) was isolated in moderate yield. Six nitrogen atoms form a dianionic chain, which coordinated two AltBu2 fragments by formation of two joint AlN4 heterocycles.

1,2‐Bis(triazolyl)tetraphenyldigermanes: Synthesis, Structure and Properties

“…; [14] R 2 Ge[C≡CH] 2 , [15] [−Ph 2 GeC≡CBu‐ t ] 2 studied by Uhl et al. ; [16] cyclo ‐[‐ o ‐C 6 H 4 C≡CGeR 2 GeR 2 C≡C−] 2 [17] and cyclo ‐[−Me 2 GeGeMe 2 C≡C−] 2 [18] investigated by Mochida et al. ; and recent other examples [19] ), further application of molecular Ge−Ge derivative 1 in synthesis by cross‐coupling and metallation reactions opens wide prospects.…”

“…Interestingly, under these conditions the GeÀ Ge bond was stable, and the target [HC�CÀ GePh 2 À ] 2 (1) was obtained in high yield (76 %). Moreover, along with other ethynyl derivatives known to date (e. g., R 2 Ge[C�CH] 2 and germanium [n]pericyclynes based on them, developed by Kakiuchi et al; [14] R 2 Ge[C�CH] 2 , [15] [À Ph 2 GeC�CBut] 2 studied by Uhl et al; [16] cyclo-[-o-C 6 H 4 C�CGeR 2 GeR 2 C�CÀ ] 2 [17] and cyclo-[À Me 2 GeGeMe 2 C�CÀ ] 2 [18] investigated by Mochida et al; and recent other examples [19] ), further application of molecular GeÀ Ge derivative 1 in synthesis by cross-coupling and metallation reactions opens wide prospects. Although ClGePh 2 À GePh 2 Cl [20] is known, we develop its effective simple synthesis in mild conditions; it consists in the action of a suspension of ammonium chloride in dichloromethane on (TfO)Ph 2 Ge-GePh 2 (OTf) [21] (74 % yield).…”

Silicon–Halogen Bond Activation in Mixed Si/Al Compounds and an Approach to Intramolecular Stabilized Silylium Ions

“…The relatively selective reaction yielded the chlorosilane 3j and the dimeric aluminium imide 7 (Scheme ) which were unambiguously identified in the reaction mixture by their characteristic NMR resonances. This reaction likely proceeds via retro hydroalumination, with the formation of the chlorosilane 3j and t Bu 2 AlH, which in the following step added to the C≡N triple bond of the isonitrile to afford the imide 7 .…”

Reactions of Tetra(o‐tolyl)diborane(4) with Organic Azides: Formation of Fluorescent Boron‐Fused Hexazenes

“…Transmetallation of the resulting M 2 N 6 species with other metals was also demonstrated to produce Li/Zn‐ and Al 2 ‐containing M 2 N 6 compounds [4c,6] . It should be noted that digermane compound possessing two (dialkylalumanyl)alkenyl substituents was reported to react with aryl azide to form the Al 2 N 6 structure [7] …”

“…[4c,6] It should be noted that digermane compound possessing two (dialkylalumanyl)alkenyl substituents was reported to react with aryl azide to form the Al 2 N 6 structure. [7] Recently, we reported some characteristic reactivity of aryl-substituted diborane(4) compounds [Scheme 1(b)]. [8] The tetra(o-tolyl)diborane(4) (1) reacted with H 2 to furnish a dimeric hydrodiarylborane through HÀ H and BÀ B bond cleavage.…”