It is possible to create a wide variety of chemicals and their intermediates using catalysis, which is fundamentally sustainable. One characteristic of base-metal catalysts (and generally, complexes with nearby spin states) is that they are frequently sensitive to O2; in contrast, precious-metal complexes exhibit slower O2 reactions and greater robustness. The removal of air is a relatively simple process, even though air sensitivity complicates reactions. Using air-stable carboxylate or halide complexes that are catalytically transformed into the active catalyst is one way that this problem has been addressed.