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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: vhpk on April 30, 2008, 08:23:04 PM

Title: dimer
Post by: vhpk on April 30, 2008, 08:23:04 PM

Why do aluminium chloride exist at Al2Cl6 (dimer) but BCl3 don't? I'm wondering if there is an effect of delocalized electron in aluminium atom?
So, how can we explain this right? Thanks for help

Title: Re: dimer
Post by: Astrokel on April 30, 2008, 11:31:39 PM

My guess would be due to the availibility of d-orbitals in Al since its in the period 3, and therefore it allows an expansion of valence shell, thereby its able to form a coordinate dative bond with another AlCl3 to dimerize.

Title: Re: dimer
Post by: Dan on May 01, 2008, 06:55:45 PM

I'm not convinced by the d-orbitals argument. I think the 3d will be too high in energy and in any case the Al of AlCl₃ has an empty 2p orbital that is far lower in energy to interact with the lone pairs on a Cl.

I think the answer may be simply that boron is too small to accomodate four chlorines. My inorganic's rusty though.