Organic Monolayers by B(C ₆F ₅) ₃-Catalyzed Siloxanation of Oxidized Silicon Surfaces

Abstract

Inspired by the homogeneous catalyst tris(pentafluorophenyl) borane [B(C ₆F ₅) ₃], which acts as a promotor of Si–H bond activation, we developed and studied a method of modifying silicon oxide surfaces using hydrosilanes with B(C ₆F ₅) ₃ as the catalyst. This dedihydrosiloxanation reaction yields complete surface coverage within 10 min at room temperature. Organic monolayers derived from hydrosilanes with varying carbon chain lengths (C ₈–C ₁₈) were prepared on oxidized Si(111) surfaces, and the thermal and hydrolytic stabilities of the obtained monolayers were investigated in acidic (pH 3) medium, basic (pH 11) medium, phosphate-buffered saline (PBS), and deionized water (neutral conditions) for up to 30 days. DFT calculations were carried out to gain insight into the mechanism, and the computational results support a mechanism involving silane activation with B(C ₆F ₅) ₃. This catalyzed reaction path proceeds through a low-barrier-height transition state compared to the noncatalyzed reaction path.