Jutta Kiesgen

Ringerweiterungs- und -verengungsreaktionen bei BN-Vier- und -Sechsringen / Expansion and Contraction Reactions with BN Four- and Six-Membered Rings

By the addition of iminoboranes RB≡NR′ (1a—d) to the corresponding diazadiboretidines (RBNR′)2 (2a—d), a ring expansion is observed, borazines (RBNR′)3 (3a—d) being formed. The particular iminoborane iPrB≡NiPr (la) can be added to the diazadiboretidines 2c—g to give borazines B3N3R2R′2iPr2 with an unsymmetrical set of ligands. From PhB=NtBu (1j) and (PhBNtBu)2 (2j), the Dewar borazine 3j′ is formed, which crystallizes in the space group P2,/c. The diazadiboretidines 2b—i, the borazines 3b—d,f, and the Dewar borazine 3e′ are split into the corresponding iminoboranes RB≡NtBu at 500-600 °C in the gas phase. The molten borazines 3b—d,f and Dewar borazines 3e′, j′ are contracted to the corresponding diazadiboretidines 2b—f, j at 160-320 °C. [Ligands R/R′: iPr/iPr (a), Me/tBu (b), Et/tBu (c), Pr/tBu (d), ¡Pr/ tBu (e), Bu/tBu (f), iBu/tBu (g), tBu/tBu (h), tBu(Me3Si)N/tBu (i), Ph/tBu (j).]

Neue Iminoborane und ihre Reaktionen / Novel Iminoboranes and their Reactions

Abstract The iminoboranes RB≡NR′, 2a-f, are formed by the elimination of Me3SiHal from the corresponding aminoboranes 1a-f. Stabilization occurs either through cyclodimerisation (→3b-d,f), cyclotrimerisation (→4e), bicyclotrimerisation (→5b) or cyclotetramerisation (→6a). Trialkylboranes BX3 are added to give the diboryl amines . 7a-f. The Δ2:-tetraazaborolines . 8a-f, are the (3+2)-cycloaddition products from 2a-f and azides X′N3. A CH-bond of cyclopentadiene adds to one of the BN bonds of 2f, giving a mixture of the corresponding 1,3- and 1,4-cyclopentadienyl boranes. 9f, 9′f.