Topic: Low Coordination Number Heterometallic Complexes with Tungsten or Molybdenum Imido/Amido Metalloligands
Speaker: Professor Robert LaDuca - Michigan State University, Chemistry, Lyman Briggs
Date: Monday, June 1, 2020
Time: 11:20 AM
Location: Via Zoom: https://msu.zoom.us/j/4991612163 see email for password
Metal amide (M–NRR') and imide (M=NR) compounds have shown functional versatility in many types of industrially relevant small molecule activations and organic transformations, such as the conversion of nitrogen to ammonia, hydrocarbons to alcohols, alkenes into pharmaceutically useful amines, and alkenes into polymers tailored for high-end applications. These compounds have also been used as volatile precursors for high-purity protective nitride coatings in the electronics industry. Nevertheless, the chemistry of mixed metal imide/amide complexes remains underexplored.
Preliminary results from our laboratory have shown that the well-known tungsten imide/amide complex [W(–NHtBu)2(=NtBu)2] can react cleanly with a variety of metal amides [M(–NR2)x] (M = Fe, Mn, Co, Zn, R = Si(CH3)3, x = 2; M = Y, Eu, R = Si(CH3)3, x = 3; M = Ti, Zr, R = CH3, x = 4) to afford mixed metal imide/amide complexes with tungsten metalloligands after facile removal of the volatile amine byproduct.
Depending on the ratio of the two reactants and the temperature of the reaction, heterobimetallic or heterotrimetallic complexes can be obtained. These products have been spectroscopically and structurally characterized by single crystal X-ray diffraction. The heterotrimetallic complexes containing two paramagnetic metal ions bridged by a central tungsten imide core show antiferromagnetic coupling in most cases. Molecules with the other type of possible heterotrimetallic arrangement, with a single paramagnetic ion capped by two tungsten imide/amide metalloligands, manifest some enticing reversible oxidation/reduction chemistry. Additionally, ammonolysis of the W/Fe imide/amide bimetallic derivative has yielded the hexagonal FeWN2 nitride ceramic solid.