What is the charge on the iron(III) complex ion in [Fe(OH)2(H2O)4]Br?

A. 0
B. 1+
C. 2+
D. 3+
The answer is B, but why?

1 Answer
Dec 6, 2017

There is a #+1# charge on the complex....!

Explanation:

But a FORMAL #+3# charge on the iron centre....

SO we gots #Fe^(3+)# FORMALLY bound to #2xxHO^-# ligands, and to #4xxOH_2# ligands....

We add up the charges....#+3+2xx(-1)=+1#....and so for the coordination complex we gots a formal cation, i.e. #[Fe(OH)_2(OH_2)_4]^+#...this is what we conceive to be the complex ion IN SOLUTION.. Were we to isolate it as its bromide salt, it would likely crystallize from solution as...#[Fe(OH)_2(OH_2)_4]^(+)Br^-#, i.e. a neutral bromide salt of the complex ion.

Are you happy with this?