Reactions of B2(o-tolyl)4 with Boranes: Assembly of the Pentaborane(9), HB[B(o-tolyl)(μ-H)]4

Reactions of the diborane(4) B-2(o-tolyl)(4) and monohydridoboranes are shown to give B(o-tolyl)(3) and (o-tolyl)BR2 (R-2=(C8H14) 3, cat 4, pin 5, (C6F5)(2) 6) as the major products. The corresponding reaction with BH3-sources gives complex mixtures, resulting from hydride/aryl exchange, dimerization and borane elimination. This led to the isolation of the first tetra-substituted pentaborane(9) HB[B(o-tolyl)(mu-H)](4) 8. The reaction pathways are probed experimentally and by computations.

Automated summary

The reactions of diborane(4) B-2(o-tolyl)(4) and monohydridoboranes were found to produce B(o-tolyl)(3) and (o-tolyl)BR2 as the main products, while reactions with BH3 sources resulted in complex mixtures. Through experimental and computational studies, a new tetra-substituted pentaborane(9) compound HB[B(o-tolyl)(mu-H)](4) was isolated.