# Does the magnesium 2+ ion prefer an octet or more?

In organic chemistry I was told that the magnesium ion which is part of Grignards is coordinated to several ether molecules. The overall structure around the magnesium is tetrahedral, which implies that two ether molecules have coordinated to the magnesium center. The professor said something about fulfilling magnesium ion's octet with this configuration.

In inorganic chemistry and biochemistry however I learned about hexacoordinated magnesium - i.e. $\ce{Mg(H2O)6}$. Magnesium ion tends to form octahedral complexes; this implies a coordination number of 6.

So -

1) Does magnesium ion adopt both these configurations? Can it be found as part of tetrahedral and octahedral complexes?

2) Which is preferred? I suspect this answer depends on a variety of factors.

• Have a look at "ligand-field theory"... Mar 24 '15 at 0:36