The Vespiary

The Hive => Novel Discourse => Topic started by: psytech on July 24, 2003, 12:14:00 AM

Title: ZrCl4/NaBH4
Post by: psytech on July 24, 2003, 12:14:00 AM

NaBH4 (1.51 g, 40 mmol) is added to a solution of ZrCl4 (2.39 g, 10 mmol) in THF (35 mL) at room temperature under nitrogen. How necassary is a nitrogen atmosphere? I Have read the MDSD on both, neither is very dangerous.I know often that researchers use in for mmole scale.

Title: Tips for the preparation of Zirconium Borohydride
Post by: Rhodium on July 24, 2003, 06:55:00 AM

I have experimented with Zr(BH₄)₄, and it works great without a nitrogen atmosphere. You need to protect the reactants and reaction mixture from atmospheric moisture though, as both ZrCl₄ and Zr(BH₄)₄ decomposes in the presence of water.

Also, watch out when you prepare the ZrCl₄ solution in THF, as the dissolution is exothermic, and some THF may splatter if you only add a few milliliters at first, so preferably chill the THF in an ice-bath before adding it to the Zr(BH₄)₄ and add at least half of the intended amount of solvent in one go. The addition of NaBH₄ is also exothermic, and creates foam, so do that too slowly, use good magnetic stirring, and choose a reaction flask large enough as to not get more than 1/3 full with all the initial THF added.

Title: Addition speed
Post by: Aurelius on July 24, 2003, 08:32:00 PM

Rhodium, when adding solvent, have you ever had a problem with super-heating? (to the point of being dangerous, not just splattering?) 

I'm assuming good stirring will eliminate any possibility of this being a problem.

Title: Adding the powdered reagents to the solvent...
Post by: Lilienthal on July 24, 2003, 08:50:00 PM

Adding the powdered reagents to the solvent solves the problem  :)

Title: Powder
Post by: Aurelius on July 24, 2003, 08:55:00 PM

Well, that option made sense to me, but the way it was phrased above made me believe that there might be an advantage to that method.

Title: order of addition
Post by: Rhodium on July 25, 2003, 05:51:00 AM

Adding the moisture-sensitive and very dusty solid ZrCl₄ will easily suspend particles in the air, as well as expose it to the air for a longer time (depending on your local air humidity this may or may not be a problem). It is also always easier to add liquids to a solid in a flask than the other way around if working with the apparatus sealed from the atmosphere.

Title: Duh
Post by: Aurelius on July 27, 2003, 01:12:00 AM

How easily the obvious escapes us.   :-[

Title: Hm.. I got 100g Zirconium wet with water (for...
Post by: josef_k on July 27, 2003, 06:21:00 PM

Hm.. I got 100g Zirconium wet with water (for transportation purposes apparently) for free when buying some other stuff, and I haven't known what to do with it until now. Is it possible to make ZrCl4 out of it without killing yourself? You make it out like it's not so friendly to work with.

Title: ZrCl4 is preferably bought, not made yourself
Post by: Rhodium on July 27, 2003, 10:18:00 PM

Nope, the synthesis of ZrCl₄ is not suitable for the home lab.