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Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: puru on February 02, 2005, 10:25:53 AM

Title: [Mn(CO)5]-
Post by: puru on February 02, 2005, 10:25:53 AM

Can transition metals show negative oxidation states like the one above?
Is OsO4 Covalent?

Title: Re:[Mn(CO)5]-
Post by: movies on February 02, 2005, 11:21:04 AM

Yes, transition metals can have a formal negative charge.  I'm not certain that your example is actually a real molecule, however.

OsO₄ is often drawn as a covalently bonded molecule, but I have been told that the metal-oxygen bonds are almost certainly ionic.  If you compare the electronegativities (2.2 for Os, 3.44 for O) then it's definitely ionic.

Title: Re:[Mn(CO)5]-
Post by: AWK on February 03, 2005, 09:00:24 AM

But, how you explain a boiling point of OsO4, which is 118 C.

Title: Re:[Mn(CO)5]-
Post by: movies on February 03, 2005, 03:35:54 PM

Quote from: AWK on February 03, 2005, 09:00:24 AM

But, how you explain a boiling point of OsO4, which is 118 C.

I hadn't thought of that, but I would think that in the crystal phase the packing is not that of a typical ionic compound since there is a fairly dense layer of negative charge surrounding the positively charged core of the OsO₄.  This would result in a fairly large electrostatic repulsion between OsO₄ molecules.