Alkylation of Dinitrogen in [(HIPTNCH[subscript 2]CH[subscript 2])[subscript 3]N]Mo Complexes (HIPT = 3,5-(2,4,6-i-Pr[subscript 3]C[subscript 6]H[subscript 2])[subscript 2]C[subscript 6]H[subscript 3])
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Author(s)
Kupfer, Thomas
Schrock, Richard Royce
Date Issued
August 2009
Journal
Journal of the American Chemical Society
Publisher
American Chemical Society (ACS)
Citation
Kupfer, Thomas, and Richard R. Schrock. “Alkylation of Dinitrogen in [(HIPTNCH2CH2)3N]Mo Complexes (HIPT = 3,5-(2,4,6-i-Pr3C6H2)2C6H3).” Journal of the American Chemical Society 131, no. 35 (September 9, 2009): 12829-12837.
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Author's final manuscript
Abstract
In this paper we explore the ethylation of dinitrogen (employing [Et[subscript 3]O][BAr[f over 4]]; Ar[superscript f] = 3,5-(CF[subscript 3])[subscript 2]C[subscript 6]H[subscript 3]) in [HIPTN[subscript 3]N]Mo (Mo) complexes ([HIPTN[subscript 3]N][superscript 3−] = [N(CH[subscript 2]CH[subscript 2]NHIPT)[subscript 3]][superscript 3−]; HIPT = 3,5-(2,4,6-i-Pr[subscript 3]C[subscript 6]H[subscript 2])[subscript 2]C[subscript 6]H[subscript 3]) with the objective of developing a catalytic cycle for the conversion of dinitrogen into triethylamine. A number of possible intermediates in a hypothetical catalytic cycle have been isolated and characterized: MoN═NEt, [Mo═NNEt[subscript 2]][BAr[f over 4]], Mo═NNEt[subscript 2], [Mo═NEt][BAr[f over 4]], Mo═NEt, MoNEt[subscript 2], and [Mo(NEt[subscript 3])][BAr[f over 4]]. Except for MoNEt[subscript 2], all compounds were synthesized from other proposed intermediates in a hypothetical catalytic reaction. All alkylated species are significantly more stable than their protonated counterparts, especially the Mo(V) species, Mo═NNEt[subscript 2] and Mo═NEt. The tendency for both Mo═NNEt[subscript 2] and Mo═NEt to be readily oxidized by [Et[subscript 3]O][BAr[f over 4]] (as well as by [H(Et[subscript 2]O)[subscript 2]][BAr[f over 4]], [Mo═NNH[subscript 2]][BAr[f over 4]], and [Mo═NH][BAr[f over 4]]) suggests that their alkylation is unlikely to be part of a catalytic cycle. All efforts to generate NEt[subscript 3] in several stoichiometric or catalytic runs employing MoN[subscript 2] and Mo≡N as starting materials were unsuccessful, in part because of the slow speed of most alkylations relative to protonations. In related chemistry that employs a ligand containing 3,5-(4-t-BuC[subscript 6]H[subscript 4])[subscript 2]C[subscript 6]H[subscript 3] amido substituents alkylations were much faster, but a preliminary exploration revealed no evidence of catalytic formation of triethylamine.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1021/ja904535f
