Matrix effects and their role in the low-temperature photochemistry of (η-Aniline)Cr(CO)3

The low-temperature chemistry and photochemistry of (η6-Aniline)Cr(CO)3 was investigated by matrix isolation techniques in frozen CH4 or N2. The spectroscopic properties of the matrix changed both during the deposition process and also following annealing of the matrix to 40 K. These changes are explained by the elimination of lattice defects in the crystalline medium which forces haptotropic changes to (η6-Aniline)Cr(CO)3 producing (η2-N-Aniline)Cr(CO)3 and (η3-N-Aniline)Cr(CO)3 as identified by IR spectroscopy. These assignments are supported by DFT calculations which also provide estimates of the energetics of the haptotropic shift processes. The reduced hapticity species exhibit different photochemical properties compared to (η6-Aniline)Cr(CO)3. They undergo complete decarbonylation following irradiation at 436 nm.