What is the formula of manganese oxohydroxide: MnOOH and MnO(OH)2?

I found various formulae of manganese oxohydroxide. Some site says it is $$\ce{MnOOH}$$, other say it is, $$\ce{MnO(OH)2}$$. So, which one is correct?

1. The mineral manganite is considered manganese oxide-hydroxide $$\ce{MnOOH}$$, but yahoo answer claims that it is $$\ce{MnO(OH)2}$$.

2. In Winkler titration, $$\ce{MnO(OH)2}$$ is formed:

$$\ce{2 MnSO4(s) + O2(aq) → 2 MnO(OH)2(s)}$$

There is some uncertainty about whether the oxidised manganese is tetravalent or trivalent. Some sources claim that $$\ce{Mn(OH)3}$$ is the brown precipitate, but hydrated $$\ce{MnO2}$$ may also give the brown colour. So, is $$\ce{MnO(OH)2}$$ hydrated $$\ce{MnO2}$$?

So which one is manganese oxohydroxide- $$\ce{MnOOH}$$ or $$\ce{MnO(OH)2}$$?

• The difference is that one contains $\ce{Mn^{3+}}$ and the other $\ce{Mn^{4+}}$, and they coexist together perfectly fine. – Ivan Neretin Jan 24 '16 at 13:51
• @IvanNeretin Are you sure they contains Manganese ions? Simon's answer says that they are bonded covalently...... – Nilay Ghosh Jan 27 '16 at 12:52
• That's not important. All ionic compounds are in fact partly ionic and partly covalent. You may interpret those +3 and +4 as just the oxidation states. – Ivan Neretin Jan 27 '16 at 12:56

First, the difference the substances is the oxidation number of manganese. In $\ce{MnOOH}$, the oxidation number of manganese is 3+. While in $\ce{MnO(OH)_2}$, the oxidation number for manganese is 4+.

However this doesn't mean $\ce{MnOOH}$ is manganese (III) oxyhydroxide and $\ce{MnO(OH)_2}$ is manganese (IV) oxyhydroxide, not for $\ce{MnO(OH)_2}$ at least. If you move the element around, you will get $\ce{MnO(OH)_2}$ is actually $\ce{H_2MnO_3}$. $\ce{H_2MnO_3}$ is dihydroxy(oxo)manganese which is an acidic substance.

For the question regarding the structure for both substances, I'm sorry that I don't haven't the image but I can describe it (Hope that would do). For $\ce{MnOOH}$, manganese is single bonded with $\ce{OH}$ and manganese is double bonded with oxygen. For $\ce{MnO(OH)_2}$, manganese have two single bonds with both of the $\ce{OH}$ and manganese is double bonded with oxygen.

In conclusion, $\ce{MnOOH}$ is manganese (III) oxyhydroxide and $\ce{MnO(OH)_2}$ is dihydroxy(oxo)manganese. In structure wise, manganese is single bonded with $\ce{OH}$ and manganese is double bonded with oxygen for $\ce{MnOOH}$. For $\ce{MnO(OH)_2}$, it likes $\ce{MnOOH}$ but have one more single bond with $\ce{OH}$.

• I understood your explanation but a picture would have been better. Actually, I need a visualization. – Nilay Ghosh Jan 25 '16 at 8:29
• I will find it for you or draw it – Simon-Nail-It Jan 25 '16 at 8:41
• Are the compounds covalently bonded? Ivan (see comment) says it contains manganese ions..... Also in this site , the empirical formula mentioned is Mn3+OOH – Nilay Ghosh Jan 27 '16 at 12:50
• What I assume is that is the manganese oxidation state instead of ion. But I will hope there is more people more expert in this topic may help you. – Simon-Nail-It Jan 27 '16 at 13:10
• dihydroxy(oxo)manganese or manganous acid is actually a hypothetical compound. – Nilay Ghosh Mar 9 at 15:51