Matrix Photochemistry of Gallium and Indium Atoms (M) in the Presence of Methane: Formation and Characterization of the Divalent Species CH₃MH and Univalent Species CH₃M

Abstract

IR and UV/vis spectroscopic measurements have been used to chart the reactions set in train by irradiating methane-doped argon matrices containing gallium or indium atoms, first with light having λ = 200−400 nm, and subsequently with broad-band UV−visible light. Assignments of the IR absorption bands are made and their carriers characterized on the basis of D and 13C substitution and by comparison either with the vibrational properties of related molecules or with those forecast by DFT calculations. Photoexcitation at λ = 200−400 nm results in insertion of the group 13 metal atom into a C−H bond to form the angular monomethylmetal hydride molecule, CH3MH (M = Ga, In). This product is not photostable but decomposes on exposure to radiation with λ = 200−800 nm to give the first sighting of CH3M, the simplest organic derivative of Ga(I) and In(I) to be characterized to date. The vibrational properties of the species CH3MH and CH3M are compared with those of related molecules and analyzed for the light they shed on the characters of the M−C and M−H bonds.