Scheme 1. Spatial arrangement of silyl cations I-IV with different coordination numbers (CN).

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.

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The reaction of 2,6-dihalophenyllithium 2,6-X 2 C 6 H 3 Li (X = F, Cl, Br) with the chlorosilanes ClMe 2 SiSiCl 2 Me, SiCl 4 , and HSiCl 3 afforded the diaryldisilanes (2,6-X 2 C 6 H 3 SiMe 2 ) 2 [X = F (1a), Cl (1b), Br (1c)] and the diaryl-and triarylsilanes (2,6-X 2 C 6 H 3 ) 2 SiCl 2 [X = F (3a), Cl (3a)], (2,3-Br 2 C 6 H 3 ) 2 SiCl 2 (4c), (2,6-F 2 C 6 H 3 ) 3 SiH (6a), and (2,6-X 2 C 6 H 3 ) 2 Si(H)Cl [X = Cl (7b), Br (7c)], respectively. The formation of 4c was rationalized on the basis of an equilibrium that exists * Prof. Dr. J. Beckmann E-Mail: j.beckmann@uni-bremen.de [a] 1034 between the aryllithium isomers 2,6-Br 2 C 6 H 3 Li and 2,3-Br 2 C 6 H 3 Li . Reduction of 3a, 3b, 4c, 7b, and 7c using LiAlH 4 provided the diarylsilanes (2,6-X 2 C 6 H 3 ) 2 SiH 2 [X = F (2a), Cl (2b), Br (2c)] and (2,3-Br 2 C 6 H 3 ) 2 SiH 2 (5c), respectively. The products were characterized by multinuclear NMR spectroscopy ( 1 H, 13 C, 19 F, 29 Si) and in case of 1a, 1b, 2a, 2b, 2c, 5c, and 6a also by X-ray crystallography.