Monomere Phosphinoborane: Synthese eines Tetraalkylphosphinoborans und seine Umwandlung unter Retro- und Re-hydroborierung zu einem dimeren Phosphinoboran sowie Synthese eines Triphosphinoborans

The first monomeric tetralakylphosphinoborane ^tBu₂BP^tBu₂ was synthesized from ^tBu₂BBr and LiP^tBu₂. It decomposes above −20°C via double retro-hydroboration and elimination of isobutene, undergoes subsequent re-hydroboration and dimerisation to give stable bis(phosphinoborane)ⁱBu(H)BP^tBu₂]₂, whose molecular structure was determined by X-ray diffraction. It contains a planar, almost square (BP)₂ four-membered ring. The BP distances are 2.004(4)/2.022(4) Å. The first monomeric triphosphinoborane, Me₂PB(PMes₂)₂, was synthesized similarly. All compounds have been characterized by NMR spectroscopy.