formal charge of Rh in RhCl3(PR3)3

[TwoPaddles]

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RhCl3(PR3)3

How does Rh carry a +3 charge in this compound ?

 

[WhiteWashed]

RhCl3(PR3)3

How does Rh carry a +3 charge in this compound ?

can u give more info into what PR is?

 

[Forthegood]

The MCAT does not usually contain such uncommon elements. They seem to always be concerned that you know your oxygens and hydrogens and alkalis well.

 

[collegestud2013]

RhCl3(PR3)3

How does Rh carry a +3 charge in this compound ?

😛R3 is a neutral ligand (assuming R is a neutral alkyl group), and and the 3 Cl- ligands each have a charge of -1. Because the overall coordination compound is neutral, the Rhodium must have a charge of +3 to balance the three -1 charges from Cl-. So the TM here is Rh(III).

This would be a d6 octahedral compound. It's not easy to say whether its HS or LS since the Cl-s are pi donors while the 😛R3s are pi acceptors, and on the opposite end of the spectrochemical series.

 

[MD Odyssey]

RhCl3(PR3)3

How does Rh carry a +3 charge in this compound ?

This looks really similar to Wilkinson's catalyst - just has two extra chlorine atoms. In Wilkinson's catalyst, the central rhodium atom is bonded to a chlorine (or in this case, 3 chlorines) and then three PPh3 groups. I suspect that the authors of the Berkeley review are using PR3 as a substitute or shorthand for the PPh3 that's used in that catalyst.

Since the PPh3 (or PR3) group isn't charged, then the formal charge of the central rhodium has to be +3, since there are three negatively charged chlorine atoms.

Not at all clear to me when I worked that passage for the first time and even after the fact, it took about 30 minutes of soul-searching to figure it out.