Alkylation of dinitrogen in [(HIPTNCH(2)CH(2))(3)N]Mo complexes (HIPT = 3,5-(2,4,6-i-Pr(3)C(6)H(2))(2)C(6)H(3)).
In this paper we explore the ethylation of dinitrogen (employing [Et(3)O][BAr(f)(4)]; Ar(f) = 3,5-(CF(3))(2)C(6)H(3)) in [HIPTN(3)N]Mo (Mo) complexes ([HIPTN(3)N](3-) = [N(CH(2)CH(2)NHIPT)(3)](3-); HIPT = 3,5-(2,4,6-i-Pr(3)C(6)H(2))(2)C(6)H(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(2)][BAr(f)(4)], Mo=NNEt(2), [Mo=NEt][BAr(f)(4)], Mo=NEt, MoNEt(2), and [Mo(NEt(3))][BAr(f)(4)]. Except for MoNEt(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 horizontal lineNNEt(2) and Mo=NEt. The tendency for both Mo=NNEt(2) and Mo=NEt to be readily oxidized by [Et(3)O][BAr(f)(4)] (as well as by [H(Et(2)O)(2)][BAr(f)(4)], [Mo =NNH(2)][BAr(f)(4)], and [Mo=NH][BAr(f)(4)]) suggests that their alkylation is unlikely to be part of a catalytic cycle. All efforts to generate NEt(3) in several stoichiometric or catalytic runs employing MoN(2) and Mo[triple bond]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(6)H(4))(2)C(6)H(3) amido substituents alkylations were much faster, but a preliminary exploration revealed no evidence of catalytic formation of triethylamine.
Kupfer
Thomas
T
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Schrock
Richard R
RR
D000478:Alkylation; D002384:Catalysis; D005021:Ethylamines / Q000737:chemistry; D008982:Molybdenum / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction
D005021:Ethylamines; D009942:Organometallic Compounds; D008982:Molybdenum; D009584:Nitrogen; C016162:triethylamine