Vibrational spectroscopic properties of molybdenum and tungsten N2 and N2Hx complexes with depe coligands: comparison to dppe systems and influence of H-bridges

Energetics and Mechanism of Ammonia Synthesis through the Chatt Cycle: Conditions for a Catalytic Mode and Comparison with the Schrock Cycle

“…This is the counterpiece of our earlier theoretical investigations of the Schrock cycle, applying the same assumptions and quantum-chemical methodology (functional, basis sets, solvent correction etc.). Moreover, the present DFT investigation complements our spectroscopic and theoretical studies on important intermediates of the Chatt cycle, that is, Mo and W bis(dinitrogen complexes), diazenido(À) and hydrazido(2À) complexes, [18,23] hydrazidium complexes [24] and Mo nitrido/imido complexes, [21] all with diphosphine (dppe or depe) ligands. In view of the fact that the electronic structures, spectroscopic properties and chemical reactivities of these (and other) intermediates of the Chatt cycle have been defined and detailed insight into many elemental steps of the Chatt cycle has been achieved, [28] quantum chemistry can now be employed to establish an overall mechanistic picture of this chemistry and help to solve the remaining obstacles to a working catalytic system.…”

“…+ , [20] [ [18] e) [MoN(N 3 )A C H T U N G T R E N N U N G (dppe) 2 ], [21,22] [21] [MoBr(NH)A C H T U N G T R E N N U N G (dppe) 2 ]Br. [22] Bond length [] [24] Moreover, 4 a has a very low N-N-stretching frequency (236.5 cm…”

Octahedral Molybdenum(0) Monodinitrogen Complexes Facially Coordinated by the Tripodal Ligand 1,1,1‐Tris(diphenylphosphanylmethyl)ethane – Influence of Diphosphane Coligands on the Activation of N2

“…This feature appears to be at somewhat higher energy than those observed in Mo-and W-NNH 2 complexes with anionic trans ligands. [34] DFT Investigations Figure 11 shows the highest occupied (HOMO) and lowest unoccupied molecular orbitals (LUMO) of 2 and 3. These schemes conform to the prototypical MO scheme determined for fac-[Mo(N 2 )(PH 3 ) 5 ] by Stephan et al [22] The two LUMOs consist of the antibonding π* orbitals of the dinitrogen ligand, which lie energetically close to each other.…”

A Chatt‐Type Catalyst with One Coordination Site for Dinitrogen Reduction to Ammonia

“…[11] On the basis of the classic Chatt-type bis(dinitrogen) Mo/W complexes containing diphosphine coligands (e.g.,d ppe or depe)t he first mechanism fort he transition-metalm ediated conversion of N 2 to NH 3 was formulated,t he so-called Chatt cycle (Scheme2). [12] This reactive scheme starts with the protonation of the parentN 2 complex, leading to the hydrazido(2-) complex. In the subsequent steps, one additional proton and two electrons are required to cleave the NÀNb ond and generate the first equivalent of ammonia.…”