Synthesis and characterisation of a bulky chelating bis(phosphine) ligand, 1,2-bis(diⁿbutylphosphino)ethane (DBPE), and its iron metal coordinated complexes, Fe(DBPE)₂Cl₂ and Fe(DBPE)₂(CCC₆H₅)₂

The synthesis of a bulky chelating bis(phosphine) ligand, 1,2-bis(diⁿbutylphosphino)ethane, ⁿBu₂PCH₂CH₂PⁿBu₂ (1) (Bu = Butyl = C₄H₉) (DBPE) is reported. This ligand was coordinated to iron by treatment with FeCl₂ to yield Fe(DBPE)₂Cl₂ (2) which is an important precursor of a variety of σ-acetylide complexes, e.g. Fe(DBPE)₂ (CCC₆H₅)₂ (3). Complex 2 is paramagnetic in solution at room temperature and diamagnetic in the solid state. The optical absorption spectrum of 3 shows strong absorptions associated with π-π{black star} transition of the acetylenic unit.