Creutz and Taube (1969), Spingler et al. (2001) and Jackson et al. (2004)

Hello all you avid CHM650 readers!

We have three papers to consider for Wednesday which will assist in our introduction to (or remembrance of) inorganic chemistry. We covered oxidation states and d electron configurations in the course on Monday. We assigned oxidation states, coordination geometries and electron configurations to the Creutz-Taube complex. A complex so cool it even has its own wikipedia page.

The other papers discuss what are referred to as Werner complexes, and Werner is a co-author on one of them despite the fact he was dead for over 80 years by that point. You should assign oxidation states, electron configuration on your own (don’t post your answer in the comments) for discussion on Wednesday.

Have a read over these papers (they are all very short) and post your questions.

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13 Responses to “Creutz and Taube (1969), Spingler et al. (2001) and Jackson et al. (2004)”

  1. Hunter Burgin Says:

    While going through the three papers and assigning oxidation states and electron configurations to the various coordination compounds I found myself having trouble with those compounds that had multiple metallic ions such as the Werner Hexols and the Creutz-Taube Complex. I wasn’t sure if I should “break” the compounds into individual complexes or if I should attempt to assign one single electron configuration for the entire complex. My initial thought was to assign individual oxidation states and electron configurations for each central metal ion in the complex but the results seemed to get convoluted in the case of Werner’s First Hexol where so many hydroxyl groups are shared among the various cobalt ions. If any one could shed some light on determining the electron configuration of complexes with multiple metals (without giving specific answers) I would appreciate it!

    • profhurst Says:

      One should definitely start off simple and build from there. But in general either the “divide and conquer” or the “add it all” up should give the same result. You could start with Fremy’s salt (2nd paragraph of the Jackson paper) and progress from there.

      Generally cobalt only comes as the +2 and +3 oxidation states, so that helps us limit things further.

  2. Porter Marsh Says:

    My questions is about the Jackson paper. The Werner hexols all use oxygen atoms or alcohols to bridge the Cobalts. In Werner’s first hexol, the three Cobalts are held together by 6 bridging alcohols. Why are alcohols used to bridge the Cobalts instead of just oxygen? The bridging alcohols are making two bonds to the Cobalts and one bond to the hydrogen which should give the oxygen a positive charge. Why is bridging alcohol preferred to bridging oxygen that would only have to make two bonds?
    Second but related question, if the OH that is bound to one cobalt is also bound to another cobalt does it still have a negative charge? The sheet we were given in class says OH ligands are negative but is that still true if the O in the OH is bound to three things?

    • profhurst Says:

      The hydroxyo and oxo ligands both started off as water in solution. They can lose one hydrogen, and sometimes both, that’s just the way the chemistry worked.

      As for the hydroxo and oxo, even though they are bound to multiple metals shouldn’t change their basic charge. The electrons are shared amongst more bonds, are therefore weaker and therefore longer. Does this agree with the crystal structure in Figure 5?

  3. Adam Settimo Says:

    For the first paper, Spingler et al. (2001), from what I can tell, the group was just confirming the werner complexes through modern techniques applied to Werner’s original crystals. The preservation and stability of these complexes in incredible over the near century that they were sitting idle. I guess the parts that confuse me are in the proceedural. What/where are 1,2? Can we see their structures somewhere? Also, are the current authors just analyzing Werners crystals, or are they also synthesizing their own for spectroscopic comparison?
    For the Jackson et al paper, my questions just have to do with the assigning of oxidation states and therefore the electron configuration. I am assuming that the hydroxy groups are still negative one a piece (even though they seem to have three bonds).
    For the final paper, I have my more main question(s). While checking out the back story for Creutz and Taube paper, I came across information about the ruthenium ion being made by and then named after Carol Creutz and the Nobel prize being given to Henry Taube, her thesis advisor. This made me dig deeper into the story, and brought me to the other work that Taube had done to lead to his Nobel Prize. I bring this up because it brought me to his discovery of inner sphere electron transfer through this reaction:

    [CoCl(NH3)5]2+ + [Cr(H2O)6]2+ → [Co(NH3)5(H2O)]2+ + [CrCl(H2O)5]2+

    Where the transfer of electrons through the chlorine bridge of the intermediate proved these bridges between inner spheres, exist. It is stated that the intermediate exists only for a moment, but the transfer of the chlorine from the Co to the Cr proves the existence of the bridged intermediate. My question is about the Creutz-Taube ion where the charge on the whole ion is 5+ and the charge is split between the two metal centers, giving each a 2.5+ average charge on each metal. What is the stability of the Creutz-Taube ion? Is this an intermediate like the cobalt/chromium reaction above? or is this a stable molecule? If so, is this partially because of the conjugated system of the bridging pyrazine that helps stabilize?

    • profhurst Says:

      There is actually the paper on inner-sphere electron transfer in the packet which is relevant to your point here.

      The reaction is transfer of one electron in the Chromium-cobalt systems, so there is no “in between” state as there is with the Creutz-Taube complex.

  4. Kevin Greenwood Says:

    In the Spingler paper, I am a little unclear about the properties of the molecule regarding the superoxo ligand bridging the two metal centers. Oxygen-oxygen single bonds are around 1.49 angstroms, but table two lists the measured distance at 1.34 angstroms. Comparing the bond lengths between cobalt and the attached amine ligands (all around 1.96) and the cobalt-superoxide ligand (1.88), what accounts for for the increased attraction between the bridging oxygens? Cobalt is pulling harder on the oxygen as compared to adjacent nitrogens. Shouldn’t this weaken the O-O bond as electron density is pulled towards the metal centers? This stability in the superoxide likely explains the stability of the sample over nearly a century, I am just a bit confused as to the how.

  5. Tony Says:

    First thing first, I am having an easy time understanding the oxidation states from the general chemistry approach with the rules (like elementals are 0, monoatomic is the charge to fit the octet rule, simple atoms match their ionic charge, etc.) Can I still think this way or is this academically immature? It seems to work fine when determine the article’s compound’s atom’s oxidation numbers. This especially helped to understand the triple bonded oxygen that some found problematic.

    Ok now for the articles:

    In Spingler’s I would like to note that it is interesting they are revisiting crystals synthesized in 1909. I don’t have much feedback otherwise.

    In jacksons I had a hard time finding out what is meant by C2d, c2h, and sigma symmetry. I only found c2 and Cs online.

    In creutz’s article it was fascinating to read about job’s method to determine the stereochemistry of the compound. The whole premise of this article fascinates me. It is interesting how the uv vis left unattended gave ir data that was unexpected. It is fascinating how they have a 2.5 charge and not an integer charge. And it was mind boggling that the electron jumped with ir light. The only thing I struggled with is comprehending the section with frank codon barrier and how they deciphered it was that process going on and not the energy barrier going from the ground state and hopefully we’ll cover that in class.

  6. Josh Ellsworth Says:

    With all the work that went into the synthesis and resolution of Werner’s first hexol, why is the structure that he proposed for the “2nd” hexol so different? It is counter intuitive that he assigned the complex an overall charge of 3+ when it seems to have been easily separated from other 3+ species in ion exchange chromatography. Were the analytical methods of the time able to distinguish the difference between one 6+ complex and 2 3+ complexes? I was also curious as to whether a similar complex could be formulated using Nitrogen in place of the oxo bridges, and could those Nitrogens assist in an inner shell electron transfer, as in the Creutz Taube complex (or is the aromatic ring of the pyrazine crucial for electron transfer)? Have inner shell electron transfers been observed in complexes containing more than two metal centers, or does one have to limit it to a two body system in order to equalize distribution of the half charge? would it be possible to effect a kind of electron crowd surfing if one were to link a series of Ru atoms together with pyrazines and then slowly oxidize the complex?

    • profhurst Says:

      Well there certainly wasn’t ion-exchange chromatography back then. One had maybe IR, combustion analysis and polarized light and that was about it.

      Nitrogen really won’t fill the role, as it can’t do similar chemistry (although it is not unheard of).

      Perhaps use some spacing and carriage returns to separate out the wall of text for the separate questions.

  7. Daniel Begay Says:

    On the Jackson paper, I was examining the different hexol molecules and was a bit confused. Is the (6+)’s by both Werner’s first and second hexol assumed to be the overall charge of the molecules even after positively-charged Cobalt atoms and negatively-charged ligands are accounted for?

    I also had a question about the Creutz-Taube paper. We discussed that while observing the Ruthenium molecule in the IR range, the authors discovered that there was inner sphere electron transfers occurring. After making this discovery, What significance did this mechanism bring to the scientific/academic/research community? Is this mechanism now being utilized in some type of inorganic synthesis? I feel that being able to move electrons through the metal-pyrazine-metal bridge would become a useful technique. I’m curious, as i was unable to find more information in this area. Maybe I’ve come to a dead end.

  8. Adam Settimo Says:

    In the Jackson et al paper, are the are the bridging ligands in a state of partial bonding? Is that how they maintain their ionic effect on the inner spheres?

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