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FORMATION OF DINITROGEN COMPLEXES OF MOLYBDENUM AND THEIR REACTIONS WITH ACIDS TO GIVE AMMONIA
Abstract
The formation of bis(dinitrogen) complexes of molybdenum, Mo(N(,2))(,2)P(,4), where P = tertiary phosphine, from higher valent molybdenum complexes was studied. It was found that the yield limiting factor in the syntheses was the concentration of dissolved dinitrogen in solution. The concentration of phosphine was also found to affect the yields. The highest yields of dinitrogen complexes were found when the reactions were performed at 0(DEGREES)C and high pressures (> 6 atm) of nitrogen gas were maintained over the reaction solutions. The use of reducing agents of high purity, which had clean surfaces, was necessary for facile reduction reactions to dinitrogen complexes. Use of impure reducing agents gave incomplete reductions. Reduction reactions starting with molybdenum (V), (IV), or (III) compounds were found not to form long-lived molybdenum(II) intermediates. Also studied was the formation of ammonia from the reactions of acids with bis(dinitrogen) complexes of molybdenum. It was found that the presence of at least one monodentate phosphine ligand in the dinitrogen complex was necessary for the production of ammonia. The acids HCl, HBr, HI, and Ph(,3)PHBr gave similar yields of products. The ultimate products in the reactions were MoX(,3)P(,3), NH(,4)X, N(,2), and free phosphine. The reaction of HBr with Mo(N(,2))(,2)(TRI)(Ph(,3)P) in THF was followed by ('31)P NMR spectroscopy. The initial formation of both cis- and trans-{MoBr(NNH(,2))(TRI)(Ph(,3)P)}('+) hydrazido(2-) complexes was observed. A resonance due to free Ph(,3)P was observed to grow in as the reaction proceeded. The resonances due to the cis isomer disappeared over one hour and no additional resonances were seen after two hours. A number of factors indicated that the ammonia-forming reactions proceeded via a dimerization of hydrazido complexes.
Subject Area
Chemistry
Recommended Citation
BOSSARD, GERALD EDWARD, "FORMATION OF DINITROGEN COMPLEXES OF MOLYBDENUM AND THEIR REACTIONS WITH ACIDS TO GIVE AMMONIA" (1983). ETD collection for University of Nebraska-Lincoln. AAI8314900.
https://digitalcommons.unl.edu/dissertations/AAI8314900