Nitrogen-silicon bonds lone-pair interaction

The participation of the germanium dimers in nucleophilic/electrophilic or Lewis acid/base reactions has been the subject of several investigations on the Ge(100)-2x1 surface [16,49,255,288,294,313-318]. As for the case of silicon, adsorption of amines has provided an excellent system for probing such reactions. Amines contain nitrogen lone pair electrons that can interact with the electrophilic down atom of a tilted Ge dimer to form a dative bond via a Lewis acid/base interaction (illustrated for trimethylamine at the Si(100)-2 x 1 surface in Ligure 5.17). In the dative bond, the lone pair electrons on nitrogen donate charge to the Ge down atom [49]. 

The contraction of the Si-O-N angle in molecules such as (4) has been danon-strated to be the result of the attraction between the lone pair of nitrogen and silicon s positive o-hole on the extension of the X-Si bond [109], (This is the o-hole that is best positioned to interact with the nitrogen lone pair.) Of lesser importance but still significant are secondary (often repulsive) interactions between the lone pair and the substituents Y and Z. 

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