How Can XPS and ESR Determine Oxidation State in Coordination Compounds?

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Discussion Overview

The discussion revolves around determining the oxidation state of platinum in the coordination compound tetraamminediiodoplatinum tetraiodoplatinate. Participants explore various methods and reasoning for identifying oxidation states, including the use of formal charges and techniques like X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR).

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes that there are multiple possibilities for the oxidation states of platinum in the complex, suggesting combinations like 3 and 3, or 4 and 2.
  • Another participant requests a detailed explanation of how different oxidation states can be determined, asking for the reasoning behind the calculations.
  • A participant outlines their approach to calculating the charges of platinum in the complex, indicating that formal charges alone are insufficient for determining oxidation states.
  • It is noted that Pt(IV) is typically the highest oxidation state encountered without significant effort, while Pt(III) is rare and Pt(I) may require unusual bonding scenarios.
  • One participant cautions against treating oxidation states as absolute, emphasizing that in complex compounds, the assignment of oxidation states can be somewhat arbitrary and primarily serves to ensure the overall charge balance.
  • Another participant mentions that XPS and ESR can be used to infer oxidation states, suggesting these techniques may provide insights into the oxidation state determination process.

Areas of Agreement / Disagreement

Participants express differing views on the reliability and methods for determining oxidation states, with some advocating for a more flexible interpretation of oxidation states in complex compounds. There is no consensus on a definitive method or understanding of the oxidation states involved.

Contextual Notes

Participants highlight limitations in determining oxidation states solely from chemical formulas and emphasize the need for additional knowledge about the behavior of platinum in various oxidation states.

jolly_math
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Homework Statement
Name the following coordination compound:
[Pt(NH3)4I2][PtI4]
Relevant Equations
oxidation state
I know that the compound is tetraamminediiodoplatinum tetraiodoplatinate. To make the compound neutral, I find there are several possibilities of the platinum ion oxidation state in the complex cation and anion(3 and 3, 4 and 2, etc.) How would I be able to determine the oxidation state? Thank you.
 
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How do you work out that there will be different oxidation states? Please show your work so we can follow your reasoning.
 
TeethWhitener said:
How do you work out that there will be different oxidation states? Please show your work so we can follow your reasoning.
I'm representing the charge of Pt as [Pt](1st or 2nd)
[Pt(NH3)4I2]: overall charge is [Pt](1st) - 2
[PtI4]: overall charge is [Pt](2nd) - 4
I want to find charge of Pt so that [Pt] - 2 + [Pt] - 4 = [Pt](1st) + [Pt](2nd) + 6 = 0,
possibilities are 3 + 3, 4 + 2, etc.
 
jolly_math said:
I'm representing the charge of Pt as [Pt](1st or 2nd)
[Pt(NH3)4I2]: overall charge is [Pt](1st) - 2
[PtI4]: overall charge is [Pt](2nd) - 4
I want to find charge of Pt so that [Pt] - 2 + [Pt] - 4 = [Pt](1st) + [Pt](2nd) + 6 = 0,
possibilities are 3 + 3, 4 + 2, etc.
I see. Unfortunately, there’s no way to figure it out by analyzing formal charges alone. You also need to know that Pt(IV) is the highest oxidation state you’ll see without going to heroic efforts, and also that Pt(III) is an incredibly rare oxidation state (I can’t think of a single example, but there might be some in the literature). Also, Pt(I) is a weird oxidation state that likely requires Pt-Pt bonding. All this is knowledge that you wouldn’t be able to glean from the chemical formula, but suffice it to say that if you’re working with platinum, the only oxidation states you’ll likely be dealing with are +2 and +4.
 
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Also: don't treat oxidation states too religiously, especially in more complicated compounds, especially transition metal complexes. Apart from some very simple cases there is no physical property that we can measure to check what the oxidation state of an atom is. In molecules electrons are on molecular orbitals and are not assigned to any particular atom. Actually we can assign these numbers a bit at random, as long they produce decent logic. Your compound is a good example: no matter what oxidation states of both Pt atoms are, the only thing that really matters is that the overall charge is zero. Sure, we do expect them to have "reasonable" values, but it is not worth to dig too deep, as there is no sound logic that can be applied.
 
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