MadSci Network: Chemistry
Query:

Re: How does mercury bond in C2H3HgN?

Date: Mon Jun 20 17:15:16 2005
Posted By: Dan Patel, Graduate Student, Chemistry
Area of science: Chemistry
ID: 1115792842.Ch
Message:

After searching the chemical literature, there is much information on the spectroscopic characterization of methylmercury(II)cyanide and only two reports of its structure in the solid state. Specifically, X-ray diffraction was used to determine the structure of (and therefore the bonding in) methylmercury(II)cyanide.

J.C. Mills and coworkers in 1968 actually used both X-ray diffraction and neutron diffraction (which, unlike X-ray diffraction can be used to obtain information on the location of protons in a crystal). The crystals used for these experiments were grown from a chloroform solution of methylmercury(II)cyanide. It was found that mercury is bound to the methyl group and to the cyanide group through the carbons atoms, which would give a C-Hg-C-N skeleton. Furthermore, it was found that this molecule, in the single crystal, adopts a linear geometer, which means that the C-Hg-C bond angle is 180 degrees.

Additionally, microwave spectroscopy was used to study the structure and bonding of methylmercury(II)cyanide by Rego and coworkers. These studies also determined that the molecule was linear. Furthermore, the authors mention the idea of hybridization where mixing of the mercury dz and s orbitals is responsible for bonding. However, no firm suggestions are made.

Finally, one could use molecular orbital theory, which is a more complete and accurate way of describing bonding, to describe the bonding in CH3HgCN. In molecular orbital theory, hybridization concepts are not used and instead one only considers overlap between atomic orbitals. This analysis is more complicated than those involving hybridization, but in general it appears as though 6s, 5d, and 6p orbitals on mercury are involved in bonding with the lone pairs from the methyl and cyano ligands (according to DeKock and coworkers).

For more information I would suggest reading the articles cited below. Hope this answers your question and sorry for the late reply.

References:

Mills, J.C., Preston, H.S.; Kennard, C.H.L.  Journal of Organometallic 
Chemistry, 14, 1968, 33-41.

Rego, Christopher A.; Cox, Peter.  Journal of Chemical Physics, 89 (1), 
1988, 124-128.

DeKock, Roger L.; Baerends, Jan Evert, Boerrigter, Paul M.; Hengelmolen, 
Rudy.  Journal of the American Chemical Society, 106 (12), 1984, 3387-3396.


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