Theoretical studies of the mechanism of reduction of N2 by an iron-phosphine complex

INOR 739

Robert B. Yelle, ryelle@uoregon.edu1, Justin L. Crossland, jcrossla@uoregon.edu2, Nathaniel K. Szymczak, szymczak@uoregon.edu2, and David R. Tyler3. (1) Computational Science Institute, University of Oregon, 5294 University of Oregon, 1600 Millrace Drive Suite 105, Eugene, OR 97403, (2) Department of Chemistry, University of Oregon, Eugene, OR 97403, (3) Materials Science Institute, University of Oregon, 1252 Univ of Oregon, Eugene, OR 97403-1252
Electronic structure calculations using DFT were performed on several potential intermediates for the reduction of N2 to ammonia by Fe(DMPE)2(N2) (DMPE = 1,2-bis(dimethylphosphinoethane), or FeP4 for short. Two mechanisms were compared; a Schrock-type monomer mechanism, where FeP4 binds N2 in end-on fashion and involves a stepwise addition of protons and electrons, and a dimer mechanism, where two FeP4 units coordinate the bridging N2. The Schrock-type monomer mechanism was not favorable after the first one-electron reduction, whereas the formation of a dimer was not favorable until after the second protonation step. It was found that all dimers considered prefer to dissociate into different monomer complexes, thus, dimer formation may serve a s a means for inner-sphere electron transfer. An alternate monomer mechanism is proposed in which the first four protonation steps are favorable, and involves a two-electron reduction from another, sacrificial, [FeP4N2]0 complex.

 

Theoretical and Computational Chemistry
7:00 PM-10:00 PM, Tuesday, August 21, 2007 BCEC -- Exhibit Hall - B2, Poster

Sci-Mix
8:00 PM-10:00 PM, Monday, August 20, 2007 BCEC -- Exhibit Hall - B2, Sci-Mix

Division of Inorganic Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007