Tag Team, Back Again

So it's been a while since my last post...I've been spending a lot of time learning the laser lab and reorganizing the ol' disiloxane synthesis project. My biggest problem at the moment is getting my hands on a reliable supply of hydrogen iodide, which we use in turn to make silyl iodide using phenylsilane. Matheson TG has stopped selling it, probably because it wasn't economically sound to offer it. During the synthesis I use, which involves red phosphorus, iodine, and water, unwanted byproducts tend to coat the iodine shards and insulate the valuable inner iodine from reacting. Thus, I decided I'm going to beat the hell out of the iodine, grounding it into a powder with a large surface area (and releasing some stored-up anger in the process).

The alternative to perfecting the syntheses of HI and silyl iodide is making a different halosilane from (pre-bought, hooray!) hydrogen bromide or chloride. The strange thing is, most of the halosilane literature I've looked at used silyl chloride or silyl bromide. Where my advisor got the idea for silyl iodide, I have no idea. Perhaps the disiloxane hydrolysis doesn't work quite as well with bromide or chloride. Yet, hexamethyldisiloxane is made using silyl chloride.

Cloush is in Ohio for a conference this week. When the cat is away, the mice will play... :-D

Enter the Matrix

My lab's matrix IR apparatus is almost done, and naturally the guy I'm working with just had to have a baby. In the meantime, I get to watch over it and get things ready for our first target molecule, chlorosilylene. It is the silicon analogue of the one, the only chlorocarbene.

Herzberg was the first to investigate this molecule, having produced it in 1964 by flash photolysis of chlorosilane. As research on CVD intermediates picked up steam, a number of research groups obtained varied results on the extent to which chlorosilylene is produced during CVD. The Clouthier group, of which I am a humble member, revived spectroscopic studies of the radical by performing laser-induced fluoresence experiments on it in 1997. They obtained a whole slew of rotational constants, geometric parameters, and most importantly vibrational frequencies exhibited by the molecule. That's right, a whole slew.

Our goal is to observe HSiCl's ground-state vibrational frequencies directly by jolting trichlorosilane in an electric discharge and performing matrix IR.

Pictures of the apparatus to follow soon!

Bromosilane go BOOM!

Well ladies and gentlemen, I've reached a milestone...I caused my first explosion in lab yesterday. I was cleaning out a flask after a cold-trap separation of the reaction products of the bromosilane synthesis reaction:

PhSiH3 + HBr --> SiH3Br + C6H6

I believed that no bromosilane (or perhaps a negligibly small amount) remained in said flask. I was wrong. Set the flask inside the hood, put a little heat on it to vaporize things, took a step back to walk away, and BAM! A huge, quick flame burst out of the flask's mouth, accompanied by a horrible noise like a gunshot. Incredibly, the flask was just fine, save for a few brown spots that 48% HF took care of right away. Nothing got burned in the hood either. It was just a really loud, scary noise and a few flames. Doesn't mean it didn't scare the pants off me, of course.

The picture, for your viewing pleasure, is the LUMO of bromosilane.