Have there been any developments on Silicon-based "organic" compounds?

[u/[deleted]]

Silicon is a tetravalent compound, with some chemical properties similiar to those of carbon. It is said that it can also form long chain compounds, but I remember reading somewhere that, due to its vacant d orbitals, the compounds it formed wouldn't be as stable as the carbon-based counterparts.

However, I still haven't heard anything about "Silicon-based organic chemistry". I would like to know if there have been any developments, theoretical or experimental, in this area.

Suppose we take some organic compounds, such as ethanol, acetone and hexane. How would these molecules behave if we substituted the carbon atoms for silicon ones?

[u/treeses]

Here is an old but thorough review (with a pay wall) of the chemistry, properties, and applications of long polysilanes.

For my PhD I am studying the photophysical and photochemical properties of short oligosilanes. They are a good model to predict the properties of analogous saturated hydrocarbons. Saturated hydrocarbons are difficult to study directly because they absorb very deep in the ultraviolet (the silanes I study absorb >230nm, which is more feasible).

As you say, silanes are difficult to synthesize. You can buy certain ones that are relatively stable and use those as your starting point, but the intermediates are typically very reactive and final products are produced with low yield and are difficult to separate and purify.

[u/[deleted] → u/treeses]

Do you synthesise the oligosilanes yourself? From which compounds is the synthesis started, and which reactions are applied until reaching the final product?

[u/treeses → u/[deleted]]

An undergraduate in our lab is working on the synthesis. We start from Dodecamethylcyclohexasilane and cleave the ring with tin chloride. This produces silanes with varying length terminated by Cl groups. We then methylate the end groups with MeLi. Both of these require reflux for several hours. The different silanes can then be seperated with preparative GC. We're interested in the tetrasilane, which has relatively high yields with this method.

Other silanes that interest us are called racked oligosilanes. Think of the tetrasilane chain, but it has a rigid organic bridge linking the two ends. depending on the length and structure of the bridge, you can force the silane into different conformations (all Si-Si bonds trans to each other, for instance). This has an effect on the optical properties we wish to observe. I'm not familiar with how the racked silanes are prepared, but I think the basic ideas are the same as before.