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

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 13 C 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, CH 3 MH (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 CH 3 M, the simplest organic derivative of Ga(I) and In(I) to be characterized to date. The vibrational properties of the species CH 3 MH and CH 3 M 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.