Sciencemadness Discussion Board

Substituting transitional metal catalysts

CrimpJiggler - 7-1-2012 at 18:40

I'm reading a patent which gives claims that a handful of 1st row transitional metal halide of catalysts can be used for the reaction but it gives it gives various "exemplary embodiments" in which the catalyst is always is CoCl2. I'm guessing exemplary embodiment means ideal conditions. All their procedure examples used CoCl2 and gave >95% yields. They didn't give any info on what yields one would get with other catalysts though. Will using other catalysts such as NiCl2 or CuCl2 result in lower yield or will it just reduce the reaction rate? Since they are all 1st row metal halides, I assume they all participate in the same kind of catalytic cycle so I would be inclined to assume that the yield will not change, only the rate will change. Is that correct?

[Edited on 8-1-2012 by CrimpJiggler]

ThatchemistKid - 7-1-2012 at 19:03

if yields were all in the 95% range they would have most certainly reported it. I doubt that your thinking is correct.

Arrhenius - 8-1-2012 at 13:19

Quote:

Since they are all 1st row metal halides, I assume they all participate in the same kind of catalytic cycle so I would be inclined to assume that the yield will not change, only the rate will change. Is that correct?


This is certainly not the case. Foremost, you really ought to clue your peers into exactly what transition metal catalyzed reaction(s) you're interested in - at least reference the patent you're reading. In general, the valence of the metal within a particular complex is what determines its reactivity and propensity to undergo a redox catalytic cycle. In that regard, particular reactivity is not found broadly across the 'transition metals'. Following general trends for the periodic table, one would expect transition metals from the same 'group' to behave similarly. Sometimes metals in the adjacent group will behave similarly as well. For instance:

Group 10 metals are all useful as hydrogenation catalysts, and are competent catalysts for cross-coupling reactions.

Also, certain palladium (group 10) complexes are competent catalysts for allylation reactions, as are certain iridium (group 9) complexes.

Copper (group 11) is also a frequently employed metal center. This is because it can readily access +1, +2 and +3 oxidation states. Group 11 metals are highly alkynophilic, whereas neighboring groups 10 and 12 are less so. Hence, copper finds particular utility in Sonogashira-type couplings, the Glaser coupling, and other alkyne substitution reactions due to the propensity to form a copper acetylide intermediate. You would be hard pressed to substitute another metal here.

[Edited on 8-1-2012 by Arrhenius]

ScienceSquirrel - 8-1-2012 at 17:52

Quote: Originally posted by CrimpJiggler  
I'm reading a patent which gives claims that a handful of 1st row transitional metal halide of catalysts can be used for the reaction but it gives it gives various "exemplary embodiments" in which the catalyst is always is CoCl2. I'm guessing exemplary embodiment means ideal conditions. All their procedure examples used CoCl2 and gave >95% yields. They didn't give any info on what yields one would get with other catalysts though. Will using other catalysts such as NiCl2 or CuCl2 result in lower yield or will it just reduce the reaction rate? Since they are all 1st row metal halides, I assume they all participate in the same kind of catalytic cycle so I would be inclined to assume that the yield will not change, only the rate will change. Is that correct?

[Edited on 8-1-2012 by CrimpJiggler]


That sounds to me like exemplary patent ass covering.
The point of a patent is to claim what you know works but cover anything that may be related or may possibly work.
You may have a process that works with iron salts but you cannot get it to work with or in only low yields with copper or nickel.
You claim your patent with iron only and six months later your competitor gets it to work with catalytic copper in 100% yield and in half the time and it is outside your patent.
Pig sick or wot?!