Steric Influence on the Constitution of Beryllium Phosphine Complexes

The phosphine complexes of beryllium chloride, bromide and iodide, [(PMe2Ph)(2)BeX2], [(PMePh2)(2)BeX2] and [(PPh3)BeX2](2) (X=Cl, Br, I) were prepared and characterised with multinuclear NMR spectroscopy. Additionally the molecular structure of dinuclear [(PPh3)BeCl2](2) was determined with single crystal X-ray diffraction techniques. The threshold cone angle of the phosphines, below which two ligands can coordinate to the beryllium dihalide fragments, is between 136 degrees and 145 degrees. Halide-chloride exchange in dichloromethane is observed for [(PPh3)BeBr2](2) and [(PPh3)BeI2](2), which leads to the formation of [(PPh3)BeCl2](2). Due to the relatively low Lewis basicity of PPh3, it almost exclusively acts as a spectator ligand with only little formation of phosphonium cations.

Automated summary

In this study, the phosphine complexes of beryllium chloride, bromide and iodide were prepared and characterized using multinuclear NMR spectroscopy. The molecular structure of one of the complexes was determined using single crystal X-ray diffraction techniques. The study found that the threshold cone angle of the phosphines for coordination to beryllium dihalide fragments is between 136° and 145°. Halide-chloride exchange was observed in dichloromethane, leading to the formation of [(PPh3)BeCl2](2).