Direct Access to Parent Amido Complexes of Rhodium and Iridium through N—H Activation of Ammonia

摘要

Ammonia is a low-cost and potentially valuable building block for almost every nitrogen-containing compound required by industry. There is an obvious interest in utilizing this chemical as feedstock in catalytic organic transformations to produce higher-value products, an issue that has began to be explored with some degree of success. However, most of late transition metal catalyzed reactions do not occur with ammonia. Several factors have been invoked to explain this lack of reactivity:1) The high strength of the N—H bond of ammonia (107 kcalmol~(-1)) makes its activation very difficult to achieve by metal centers; 2) the catalyst often deactivates through the formation of stable Werner ammine (M←NH3) adducts; and 3) the low acidity of ammonia prevents its participation in proton exchange reactions that could lead to N—H activation.