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

[jolly_math]

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.

 

[TeethWhitener]

How do you work out that there will be different oxidation states? Please show your work so we can follow your reasoning.

 

[jolly_math]

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.

 

[TeethWhitener]

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.

 

[Borek]

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.

 

[chemisttree]

Some would argue differently.

XPS is used to infer that as is ESR.