Chemical Forums
Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: Archer on December 07, 2013, 03:11:33 PM
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This complexation is a relatively well known, reversible, reaction between unsaturated organic compounds and silver nitrate. Some of the products are isolatable solids. It's an old observation but I am unclear as to the process which leads to this complex forming.
My inorganic chemistry is relatively week so I have no idea what interactions are taking place or why the nitrate counterion appears to be essential in this process
Does anyone have any information on this for general interest purposes.
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This complexation is a relatively well known, reversible, reaction between unsaturated organic compounds and silver nitrate. Some of the products are isolatable solids. It's an old observation but I am unclear as to the process which leads to this complex forming.
My inorganic chemistry is relatively week so I have no idea what interactions are taking place or why the nitrate counterion appears to be essential in this process
Does anyone have any information on this for general interest purposes.
From what I recall (a colleague made use of this a while ago) it's thought to be pi donation into empty orbitals from the alkene to the silver which just "bulks it up" a bit and aids separation. I don't recall nitrate per se being essential, it may just be that's what was at hand. I think Lew Mander published a bit on this - try Williams, C. M. and Mander, L. N. (2001) Chromatography with silver nitrate. Tetrahedron, 57 3: 425-447 ( doi:10.1016/S0040-4020(00)00927-3 )
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There is overlap between π-orbitals of ligand and σ-acceptor orbital of central atom and there is back donation from dπ orbitals of central atom to antibonding π-orbitals of ligand.
Each pi-bond donates 2 electrons but they dont affect the oxidation state of central atom so the nitrate probably to balance +1 charge of silver?
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I have been quesioned as to whether or not this thread should be posted as inorganic but I thought that this following X-Ray data would help explain why I have chosen to post it here.
This looks to me like there is a lot more inorganic interaction between the Silver and the nitrate. I would have picked up these N-O-Ag bonds as short contacts but the automated refinement software has suggested bonds.
A cif checker has picked this up as an alert level G Note: Polymeric structures can be legitimate or due to an erroneous structure analysis.
Personally I think this is erroneous but I woud like the opinion of an inorganic chemist.
Note that the structure below has been modified to omit some of the atoms.
The second attachment was taken from:
N. C. Baenziger et al Metal-Olefin Compounds. VIII. The Crystal Structure of a Norbornadiene-Silver Nitrate Complex, C7H8.2AgNO3, Inorg. Chem., 1966, 5 (8), pp 1399–1400
DOI: 10.1021/ic50042a025
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I got an idea - why not try the experiment out with a non-coordination anion (tetrafluoroborate, perchlorate, hexafluorophosphorate) instead of nitrate? This will tilt the equilibrium towards sliver bonding with the carbons.