Terms of Use Detailed Terms Alkylation of Dinitrogen in [(hiptnch 2 Ch 2 ) 3 N]mo Complexes

In this paper we explore the ethylation of dinitrogen (employing [Et3O][BAr4]; Arf = 3,5(CF3)2C6H3) in [HIPTN3N]Mo (Mo) complexes ([HIPTN3N] = [N(CH2CH2NHIPT)3]; HIPT = 3,5-(2,4,6-i-Pr3C6H2)2C6H3) 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; they are MoN=NEt, [Mo=NNEt2][BAr4], Mo=NNEt2, [Mo=NEt][BAr4], Mo=NEt, MoNEt2, and [Mo(NEt3)][BAr4]. Except for MoNEt2, 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=NNEt2 and Mo=NEt. The tendency for both Mo=NNEt2 and Mo=NEt to be readily oxidized by [Et3O][BAr4] (as well as by [H(Et2O)2][BAr4], [Mo=NNH2][BAr4], and [Mo=NH][BAr4]) suggest that their alkylation is unlikely to be part of a catalytic cycle. All efforts to generate NEt3 in several stoichiometric or catalytic runs employing MoN2 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-BuC6H4)2C6H3 amido substituents alkylations were much faster, but a preliminary exploration revealed no evidence of catalytic formation of triethylamine.