User talk:Mountainmover55



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 * If you have a question that is not one of the frequently asked questions below, check out Questions, stop by and/or ask a question at the Teahouse, [ ask me on my talk page], or click the button below. Happy editing and again, welcome! Happy Squirrel (talk) 01:14, 19 April 2016 (UTC)

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Some suggestions
NiCl2(dppp) adopts both sq planar and (a tiny bit is my guess) of the tetrahedral geometry. The former is diamagnetic. The sq planar form does the Kumada chem. So it is helpful to acknowledge the geometric equilibrium, but most of the action is with the sq planar form. The orange color is also consistent with closed shell. You might check, but the chlorides tend to favor the planar geometry in this series of Ni(II) complexes. So I wonder if the planar depiction should be shown still.--Smokefoot (talk) 21:40, 24 June 2019 (UTC)

In the reference I placed in the article, the authors observe that dpppNiX2 (Cl, Br, I) is in a rapid equilibrium between tetrahedral and square-planar in solution (Keq = 1-3, which is not a tiny bit, but a 50:50 to 75:25 mixture, which is quite significant). Even in the solid state (which has the red-orange color) they observe a magnetic moment for dpppNiCl2, indicating the solid state structure is a mixture of square-planar and tetrahedral forms. I agree that the square-planar geometry would produce a diamagnetic complex though. As to what geometry "does the Kumada chem" as you say, once the dichloride precatalyst reacts with a Grignard or zinc or boron reagent, it reduces down to dpppNi(0), which then can undergo oxidative addition, transmetallation, etc etc. While I don't disagree that (dppp)Ni(R)X or (dppp)NiR2 would be planar and diamagnetic (many examples of those isolated complexes), but its very difficult to establish which geometry of the precatalyst reacts the organometallic reagent in the cross-coupling. I would argue that the tetrahedral form would react faster with a Grignard or zinc reagent, as the p-orbital electrons on chloride have less overlap with metal d-orbitals in a tetrahedral geometry than in the square-planar form, allowing them to more favorably interact with Mg, Zn, etc. and allow for more rapid transmetallation. But this is just a theory, and is not supported by experiments. Therefore, I think it is important to make readers aware of the equilibrium between the square-planar and tetrahedral geometries in the article for this very useful precatalyst. I tried to upload an image similar to the one in the article for (PPh3)2NiCl2, but wikipedia will not allow me to upload it. If the equilibrium can't be shown, I think no image should be shown.--Mountainmover55 (talk) 10:27, 25 June 2019 (UTC)

Iron(III) chloride solutions
Hi Mountainmover55,

I saw your edit at iron(III) chloride. I'm not sure the previous version was a typo. Do you have a copy of Cotton to hand to check the original wording?

Greenwood & Earnshaw (second edition, pages 1088-1090) says solutions and salts containing [Fe(H2O)6]3+ are typically pale pink or pale violet if hydrolysis is avoided (e.g. by keeping the pH around zero). So the original text was not wrong.

They also note the hydrolytic processes are complicated but discuss it in detail for iron(III) perchlorate. There are equilibria between [Fe(H2O)6]3+ and the yellow charge-transfer species [Fe(H2O)5(OH)]2+, [Fe(H2O)4(OH)2]+, and the hydroxide-bridged dimer [Fe(H2O)4(OH)]24+. So it's not just chloride ligands in [FeCl2(H2O)4]+ and [FeCl4]− that could account for the yellow colour of aqueous iron(III) chloride.

Ben (talk) 20:12, 29 May 2022 (UTC)


 * Thanks Ben! Sorry, I think I understood the text as discussing Fe(II) (which was why I thought the original editor meant Mn(II)).  My bad, thanks for catching this! Mountainmover55 (talk) 14:13, 31 May 2022 (UTC)

No problem, it was interesting to dig into this. I wasn't quite sure myself but had an inkling something subtle was going on. Ben (talk) 22:13, 7 June 2022 (UTC)