Submitted by Anne Bentley / Lewis & Clark College on Fri, 04/08/2011 - 15:10
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Here's a short question to ponder for an April Friday afternoon. 

 

Consider the dimethylthiocarbamate ligand (dtc, structure shown on p. 328 of Miessler & Tarr 4th edition), which can coordinate to metals in a bidentate fashion through both sulfur atoms.  Why, on the other hand, does a ligand like oxalate coordinate through only one oxygen of the carboxylate resonance pair?  (Oxalate is bidentate, but only because it has two carboxylate groups.)

 

Does it come down to atomic size - sulfur is larger so its carbon-sulfur bonds are better able to "stretch" to two binding sites?

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coordination chemistry
Kurt Birdwhistell / Loyola University New Orleans
I believe dtc is a better sigma and pi donor than oxalate.  In Mo(II) and W(II) dtc supports an unusual trigonal prism structure.  I can not put my hands on the articles at the moment, but this was discussed by Templeton, Joe in late 1980s papers. 
Fri, 04/08/2011 - 16:06 Permalink
Nancy Williams / Scripps College, Pitzer College, Claremont McKenna College
In my world, that ligand has a double bond between N and C, and single bonds between C and S. So both sulfurs are anionic. I don't believe in the existance of C-S pi bonding. Or, at least, not much of it, and not when there's a better alternative.
Tue, 04/19/2011 - 22:01 Permalink