title: Reduction of dinitrogen to ammonia at a well-protected reaction site in a molybdenum triamidoamine complex.
abstract: We have synthesized a triamidoamine ligand ([(RNCH2CH2)3N]3-) in which R is 3,5-(2,4,6-i-Pr3C6H2)2C6H3 (HexaIsoPropylTerphenyl or HIPT). The reaction between MoCl4(THF)2 and H3[HIPTN3N] in THF followed by 3.1 equiv of LiN(SiMe3)2 led to formation of orange [HIPTN3N]MoCl. Reduction of [HIPTN3N]MoCl with magnesium in THF under dinitrogen led to formation of salts that contain the {[HIPTN3N]Mo(N2)}- ion. The {[HIPTN3N]Mo(N2)}- ion can be oxidized by zinc chloride to give [HIPTN3N]Mo(N2) or protonated to give [HIPTN3N]Mo-N=N-H. Other relevant compounds that have been prepared include {[HIPTN3N]Mo-N=NH2}+, [HIPTN3N]MoN, {[HIPTN3N]Mo=NH}+, and {[HIPTN3N]Mo(NH3)}+. (The anion is usually {B(3,5-(CF3)2C6H3)4}- = {BAr'4}-.) Reduction of [HIPTN3N]Mo(N2) with CoCp2 in the presence of {2,6-lutidinium}BAr'4 in benzene leads to formation of ammonia and {[HIPTN3N]Mo(NH3)}+. Preliminary X-ray studies suggest that the HIPT substituent creates a deep, three-fold symmetric cavity that protects a variety of dinitrogen reduction products against bimolecular decomposition reactions, while at the same time the metal is left relatively open toward reactions near the equatorial amido ligands.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Dmitry V
authors.initials: DV
authors.lastname: Yandulov
authors.forename: Richard R
authors.initials: RR
authors.lastname: Schrock
mesh_terms: D000588:Amines / Q000138:chemical synthesis / Q000737:chemistry*; D000641:Ammonia / Q000737:chemistry*; D001665:Binding Sites; D008982:Molybdenum / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction; D013730:Terphenyl Compounds / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: D000588:Amines; D009942:Organometallic Compounds; D013730:Terphenyl Compounds; D000641:Ammonia; D008982:Molybdenum; D009584:Nitrogen