Abstract The synthesis of the isomeric compounds 1,8-bis(diphenylphosphino)biphenylene (1) and 1,5-bis(diphenylphosphino)biphenylene (2) is reported. Compound 1 was used as bidentate ligand towards late transition metal chlorides giving rise to six complexes 1·MCl₂ (M=Ni, Pd, Pt) and 1·MCl (M=Cu, Ag, Au), which have been fully characterized. The electronic bond characteristics of the polar-covalent M–P and M–Cl bonds of 1·MCl₂ (M=Ni, Pd, Pt) and 1·MCl (M=Cu, Ag, Au) were determined by a computational real-space bonding indicator (RSBI) analyses including the atoms-in-molecules, electron localizability indicator, and non-covalent interactions (NCI) index methods based on the molecular structures established by single crystal X-ray diffraction. Consistent with the electronegativity differences, the polarity of the M–Cl bonds is found to be systematically higher compared to the M–P bonds. In addition, there is a tendency for decreasing bond polarities downwards the column (Ag–P is an exception). Consequently, the highest bond polarities are observed for the Ni–Cl and Cu–Cl bonds, whereas the lowest polarities are observed for the Pt–P and Au–P bonds.