Activation of water at disiladicarbene: from the perspective of modification of silicon surface with organo-silicon compounds

Silicon is one of the most important components of electronic devices. Surface passivation of a silicon wafer is an active area of research. The Si(OH)₂ sites of partially oxidized silicon surface could exist as hydroxylated [Si(OH)₂] or hydrated silanone [SiO∙(OH₂)]. The previously reported disiladicarbene (cAAC)₂Si₂ has been reacted here with water to obtain elusive, hydrated silanone (3) co-crystallized with its silanol analog (2) in a 1:3 molar ratio. The mass spectrometric characterization of acyclic silanone, followed by the isolation and characterization of the zwitterionic hydrated silanone, has been achieved. The detailed energy decomposition analysis coupled with natural orbital for chemical valence (EDA-NOCV) calculations revealed that the central Si(O)OH unit of the hydrated silanone possesses a covalent electron sharing σ- and a dative σ-bonds (C_L−Si, Si←C_L) with hydrogen-containing cyclic alkyl(amino) carbene ligands. These two bonds are stabilized by 49% coulombic interaction and 47.8% orbital interaction. The presence of N-atoms at the hydrogenated and/or protonated carbene part (cAACH/cAACH₂) has reduced the stability of these species. The electron pair on the N-atom of the cAACH unit displays a sort of anomeric effect relevant to the cyclic form of the sugar molecule.

Graphical abstract

A disiladicarbene containing two Si(0) centres reacts with water to produce a mixture of co-crystallized products in a 3:1 molar ratio. EDA-NOCV analyses further analysed the bonding and stability of zwitterionic-hydrate-silanone to probe the nature of chemical bonds in it. This species has further been characterized by ES-MS spectrometry.