A comparison of N 2 cleavage in Schrock's Mo[N 3 N] and Laplaza-Cummins' Mo[N(R)Ar] 3 systems
-
Altmetric Citations
Christian, Gemma; Stranger, Robert; Yates, Brian F
Description
The four-coordinate Mo-[N3N] complex, [N3N] = [{RNCH2CH2}3N], R = 3,5-(2,4,6-iPr 3C6H2)2C6H3 (HIPT), which is capable of converting N2 to ammonia catalytically, reacts with N2 in a similar manner to Mo[N(R)Ar]3 (R = tBu, Ar = 3,5-C6H3Me2) to form a dinitrogen-bridged dimer intermediate, but unlike its three-coordinate counterpart, N2 cleavage is not observed. To rationalise these differences, the reaction of N2 with the model Mo[NH 2]3[NH3] and full ligand Mo[N3N] systems was explored using...[Show more]
dc.contributor.author | Christian, Gemma | |
---|---|---|
dc.contributor.author | Stranger, Robert | |
dc.contributor.author | Yates, Brian F | |
dc.date.accessioned | 2015-12-10T22:30:58Z | |
dc.identifier.issn | 0947-6539 | |
dc.identifier.uri | http://hdl.handle.net/1885/55324 | |
dc.description.abstract | The four-coordinate Mo-[N3N] complex, [N3N] = [{RNCH2CH2}3N], R = 3,5-(2,4,6-iPr 3C6H2)2C6H3 (HIPT), which is capable of converting N2 to ammonia catalytically, reacts with N2 in a similar manner to Mo[N(R)Ar]3 (R = tBu, Ar = 3,5-C6H3Me2) to form a dinitrogen-bridged dimer intermediate, but unlike its three-coordinate counterpart, N2 cleavage is not observed. To rationalise these differences, the reaction of N2 with the model Mo[NH 2]3[NH3] and full ligand Mo[N3N] systems was explored using density functional theory and compared with the results of an earlier study involving the model three-coordinate Mo[NH 2]3 system. Although the overall reaction is exothermic, the final N-N cleavage step is calculated to be endothermic by 75 kJ mol -1 for the model system when the Mo-amine cap bond length is fixed to mimic the constraints of the ligand straps, but exothermic by 14 kJ mol -1 for the full ligand system. In the latter case, the slightly exothermic cleavage step can be attributed to the destabilization of the N 2 bridged dimer relative to the nitride product owing to the steric effects of the bulky R groups. The activation barrier for N-N cleavage is estimated at 151 kJ mol-1 for the model system, more than twice the calculated value for Mo[NH2]3, and even greater, 213 kJ mol-1, for the full ligand [N3N]Mo system. A bonding analysis shows that although the binding of the amine cap helps to stabilize the intermediate dimer, at the same time it destabilizes the metal d-orbitals involved in backbonding to the π* orbitais on N2. As a result, backdonation is less efficient and N-N activation reduced compared to the three-coordinate system. Thus, the increased stability of the intermediate dimer on binding of the amine cap combined with the reduced level of N-N activation and higher kinetic barrier, explain why N-N cleavage has not been observed experimentally for the four-coordinate Mo[N3N] system. | |
dc.publisher | Wiley-VCH Verlag GMBH | |
dc.source | Chemistry, A European Journal | |
dc.subject | Keywords: Amines; Biochemistry; Bond length; Density functional theory; Dimerization; Ligands; Nitrides; Nitrogen fixation; Organic compounds; Programming theory; Activation barriers; Bonding analysis; Co-ordinate systems; Cummins (CO); Density functional calculati Density functional calculations; Dimerization; Molybdenum; Nitrogen fixation; Structure-activity relationships | |
dc.title | A comparison of N 2 cleavage in Schrock's Mo[N 3 N] and Laplaza-Cummins' Mo[N(R)Ar] 3 systems | |
dc.type | Journal article | |
local.description.notes | Imported from ARIES | |
local.identifier.citationvolume | 15 | |
dc.date.issued | 2009 | |
local.identifier.absfor | 030701 - Quantum Chemistry | |
local.identifier.ariespublication | u4217927xPUB325 | |
local.type.status | Published Version | |
local.contributor.affiliation | Christian, Gemma, College of Physical and Mathematical Sciences, ANU | |
local.contributor.affiliation | Stranger, Robert, College of Physical and Mathematical Sciences, ANU | |
local.contributor.affiliation | Yates, Brian F, University of Tasmania | |
local.description.embargo | 2037-12-31 | |
local.bibliographicCitation.issue | 3 | |
local.bibliographicCitation.startpage | 646 | |
local.bibliographicCitation.lastpage | 655 | |
local.identifier.doi | 10.1002/chem.200801127 | |
dc.date.updated | 2016-02-24T10:42:31Z | |
local.identifier.scopusID | 2-s2.0-58449098682 | |
local.identifier.thomsonID | 000262661400013 | |
Collections | ANU Research Publications |
Download
File | Description | Size | Format | Image |
---|---|---|---|---|
01_Christian_A_comparison_of_N_2__cleavage_2009.pdf | 445.26 kB | Adobe PDF | Request a copy |
Items in Open Research are protected by copyright, with all rights reserved, unless otherwise indicated.
Updated: 17 November 2022/ Responsible Officer: University Librarian/ Page Contact: Library Systems & Web Coordinator