Collect. Czech. Chem. Commun. 1997, 62, 1299-1309

Opening of Closed Azadecaboranes RNB9H9 by Amines

Martin Roth, Franc Meyer and Peter Paetzold

Institut für Anorganische Chemie, Technische Hochschule Aachen, D-52066 Aachen, Germany


The aza-closo-decaborane RNB9H9 (4a; R = 4-ClC6H4) is opened to give the nido-cluster RNB9H9(tmeda) (7a) by the addition of Me2N(CH2)2NMe2 (tmeda). The cluster 7a contains the same type of asymmetric hydrogen bridge as is present in the isoelectronic nido-anion [RNB9H10]- (10b, 10c; R = Ph, PhCH2), obtained by the action of KBHEt3 on the corresponding arachno-cluster RNB9H11(NH2t-Bu) (9b, 9c). Secondary amines HNR1R2 yield the azaboranes RNB9H10(NR1R2) (11a-11c; R1/R2 = H/t-Bu, Et/Et, i-Pr/i-Pr). From 2D-1H/11B NMR correlations, concerning the two non-terminal H atoms, and from the 11B NMR shifts, a nido/arachno hybrid structure is deduced for 11a-11c, governed by the contribution of pi-bonding between the lone pair of the amino group and the neighbouring B atom. Amines, like nucleophiles generally, attack the closo-boranes RNB9H9 at one of the B atoms adjacent to the N atom, as expected.

Keywords: Azadecaboranes; Cluster opening; nido/arachno Hybrids.