Reaktionen der Azadiboriridine: Clusterbildung und Ringerweiterung

Reactions of the Azadiboriridines: Formation of Clusters and Ring Expansions * Nine bis(haloboryl)amines 1 were synthesized by haloboration of iminoboranes RB = NR” with dihaloboranes R'BHal 2 [R/R'/R” = Et/iPr/ t Bu ( 1b) , Et/sBu/ t Bu ( c ), i Pr/ i Pr/ i Pr ( d ), i Pr/ t Bu/ i Pr ( e ), t Bu/Me/ t Bu ( g ), t Bu/Et/ t Bu ( h ), t Bu/Et/SiMe 3 ( k ), t Bu/ t Bu/SiMe 3 ( 1 ), t Bu/Cl/ t Bu n )]. The borane 1n can be transformed into 1o (R' = NMe 2 ) by the reaction with Me 3 SiNMe 2 ; an equilibrium between 1o and the four‐membered ring 1o ' is observed, 1o ' being formed from 1o by intramolecular B – N coordination. On reduction with lithium, the nido ‐diazahexaboranes 3b – e , g , h are formed from the corresponding bis‐(haloboryl)amines 1 . In the case of 3e , g , h , the ligands R and R' are unsymmetrically distributed to axial and equatorial positions of the fragment structure derived from the pentagonal bipyramid. In particular cases, azadiboriridines of type 2 are either isolated or proven as intermediates on the way from 1 to 3 . The three‐membered ring of the known azadiboriridines 2i , m (R/R'/R” = t Bu/ i Pr/ t Bu, t Bu/ t Bu/ t Bu) is expanded to the five‐membered ring of the corresponding azadiborolines 4i , m by the reaction with 3‐hexyne. The products 4i , m are reduced to the dilithium azadiborolinates 5i , m by the action of lithium; the molecular structure of a closo ‐azadicarbadili‐thiaheptaborane is recognized in crystals of 5i . The threemembered ring of 2m is also expanded by the reaction with the iminoborane EtB ≡ N t Bu giving the diazatriborolidin 6m , which crystallizes in the space group Pca2 1