Inorganic chemistry: d-Metal complexes

[jsundberg]

I need some help, in explaining how to know what kind of d-metal complex a molecule is.

For example, I have:
1. [Cr(H2O)6]2+
2. [Cr(CN)6]4-

I know that #1 is d4, and #2 is d3, but that's just because it says so in my paper. How do I "calculate" it if that information is not given? Many thanks!



(My english sucks, hope you understand what I mean).

 

[gravenewworld]

How many valence electrons are there in each? (Hint-look at the charge)
How do the ligands on each metal effect it?

 

[shrumeo]

It all depends on if you are using the ionic counting system of the covalent counting system.

It looks like the 2 examples are using the ionic system.

Let me try to give a step by step way to tell the d-electron count on your metal.

1. Identify your metal and locate it on the periodic table.
2. Count the number columns on the periodic table starting in the first row, the alkali metals, and ending in the row of your TM. This is the number of valence electrons in the neutral metal atom in a ligand or crystal field. In the case of chromium, this is 6, so it would be d6.
3. Determine its oxidation state [in #1 and #2 it's Cr(II)]
4. Subtract the oxidation state number from the number you got by counting periodic columns and you know the number of d-valence electrons on your central metal atom.

 

[zlidziej]

I need some help, in explaining how to know what kind of d-metal complex a molecule is.

For example, I have:
1. [Cr(H2O)6]2+
2. [Cr(CN)6]4-

I know that #1 is d4, and #2 is d3, but that's just because it says so in my paper. How do I "calculate" it if that information is not given? Many thanks!



(My english sucks, hope you understand what I mean).

Cr is an exception. it has 6 valence electrons, so since water is neutral Cr is 2+ charge, so d = (6-2) = 4
CN has -1 charge so Cr charge is +2 => d=6-2 = 4