Extensive efforts have been made to develop more energy-efficient synthetic paths to ammonia utilizing transition metal complexes capable of coordinating, activating, and cleaving dinitrogen. Towards this goal, we have previously reported a Group 5 cyclopentadienyl amidinate (CpAm) dinitrogen complex, {(?5-C5Me5)Ta[N(iPr)C(Me)N(iPr)]}2(�-?1:?1-N2) (1  ), that undergoes thermal cleavage of the N-N bond at room temperature.  By contrast, the recently reported Group 6 analogues of 1  , {(?5-C5Me5)M[N(iPr)C(Me)N(iPr)]}2(�-?1:?1-N2), where M = Mo (2  ) and W (3  ), are thermally stable up to 100 �C.  To experimentally probe the potential energy landscape for N-N bond cleavage via 2  and 3  ,   the expected dinuclear bis(�-nitrido) complexes, {(?5-C5Me5)M[N(iPr)C(Me)N(iPr)](�-N)}2 for M = Mo (4  ) and W (5  ), were independently synthesized through reduction of the mononuclear terminal nitrido chloride precursors, (?5-C5Me5)M[N(iPr)C(Me)N(iPr)](N)Cl.  Surprisingly, with 4   and 5   serving as   spectroscopic standards, we have unequivocally established the facile and quantitative conversion of 2  to 4  through photolysis at room temperature.  Similar photoconversion of 3  to 5   occurs but at a significantly reduced rate.  Finally, the potential role of formal metal oxidation state on N-N bond cleavage was probed through cyclic voltammetry and synthesis of the thermally-stable dicationic dinuclear complex, {(?5-C5Me5)W[N(iPr)C(Me)N(iPr)]}2(�-?1:?1-N2)}{B[(3,5-CF3)C6H3]4]2 (6  ).

Photolytic N-N bond cleavage within the thermally-stable group 6 metal pentamethylcyclopentadienyl, amidinate dinitrogen complexes, {(η5-C5Me5)M[N(iPr)C(Me)N(iPr)]}2(μ-η1:η1-N2) (M = Mo, W)

244th National Meeting (2012)

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