Synthesis, characterisation and electronic properties of naphthalene bridged disilanes

Synthesis of naphthalene bridged disilanes 2_R (R = Me, Ph) was performed via catalytic dehydrocoupling. Using RhCl(PPh₃)₃ as a catalyst, an intramolecular Si-Si bond was readily formed from the corresponding disilyl precursors 1_R (R = Me, Ph). For catalytic reactions using (C₆F₅)₃B(OH₂), bridged siloxanes (3_Ph and 3_Me) were observed. Attempts to install the 1,8-naphthalene bridge directly onto a disilane resulted in an unusual product (4), containing two silicon centres bridged through one naphthyl group, and another naphthyl group attached to a single Si centre. In order for this product to form, both a Si to Si hydrogen shift rearrangement as well as Si-Si bond cleavage occurred. The effects of phenyl and methyl substitutions on the structure and electronic properties of the synthesised compounds was investigated by single crystal X-ray diffraction, as well as IR and multinuclear NMR spectroscopic analysis. In addition, theoretical UV-Vis absorption maxima were evaluated using density functional theory (TD-SCF) on a B3LYP/6-31(++)G** level of theory and compared with experimental UV-Vis spectroscopic data.