New Ga/N-based Active Lewis Pairs, Trifunctional Ga–Ga Compounds, Reactions with Cyanamide and Dual Insertion of Isocyanate

Abstract

Hydrogallation of Me3Si–C≡C–NR'2 with R2Ga–H (R = tBu, CH2tBu, iBu) yielded Ga/N-based active Lewis pairs, R2Ga–C(SiMe3)=C(H)–NR'2 (7). The Ga and N atoms adopt cis-positions at the C=C bonds and show weak Ga–N interactions. tBu2GaH and Me3Si–C≡C–N(C2H4)2NMe afforded under exposure of daylight the trifunctional digallium(II) compound [MeN(C2H4)2N](H)C=C(SiMe3)Ga(tBu)–Ga(tBu)C(SiMe3)=C(H)[N(C2H4)2NMe] (8), which results from elimination of isobutene and H2 and Ga–Ga bond formation. 8 was selectively obtained from the ynamine and [tBu(H)Ga–Ga(H)tBu]2[HGatBu2]2. 7a (R = tBu; NR'2 = 2,6-Me2NC5H8) and H8C4N–C≡N afforded the adduct tBu2Ga-C(SiMe3)=C(H)(2,6-Me2NC5H8)·N≡C–NC4H8 (11) with the nitrile bound to gallium. The analogous ALP with harder Al atoms yielded an adduct of the nitrile dimer or oligomers of the nitrile at room temperature. The reaction of 7a with Ph–N=C=O led to the insertion of two NCO groups into the Ga–Cvinyl bond to yield a GaOCNCN heterocycle with Ga bound to O and N atoms (12).