Multiple Mechanisms for the Thermal Decomposition of Metallaisoxazolin-5-ones from Computational Investigations.

The thermal decompositions of metallaisoxazolin-5-ones containing Ir, Rh, or Co are investigated using density functional theory. The experimentally observed decarboxylations of these molecules are found to proceed through retro-(3+2)-cycloaddition reactions, generating the experimentally reported η2 side-bonded nitrile complexes. These intermediates can isomerize in situ to yield a η1 nitrile complex. A competitive alternative pathway is also found where the decarboxylation happens concertedly with an aryl migration process, producing a η1 isonitrile complex. Despite their comparable stability, these η1 bonded species were not detected experimentally. The experimentally detected η2 side bound species are likely involved in the subsequent C-H activation reactions with hydrocarbon solvents reported for some of these metallaisoxazolin-5-ones.