Isomeric hypho borane structures B5H9.L [L =(Ph2P)2CH2, (Ph2PCH2)2, or (Me2NCH2)2]; X-ray crystal and molecular structures

Abstract

The X-ray crystal structures of the 1 : 1 complexes, containing hypho boron polyhedra, derived from pentaborane(9) and the ligands bis(diphenylphosphino)-methane (dppm), bis(diphenylphosphino)ethane (dppe), and tetramethylethylenediamine (tmed) are reported; the dppm and dppe structures both show the phosphorus atoms bridging the apical and basal atoms of a flattened pyramidal B₅ framework (with rearrangement of the hydrogen atoms), the tmed complex differing markedly, with the ligand chelating one of the originally basal boron atoms, which becomes singly bonded to the apical boron atom and is separated from the remaining basal atoms by typical non-bonded contact distances.