SPECTROSCOPY AND PHOTODISSOCIATION OF DIMETHYLZINC IN SOLID ARGON - 2- FTIR DETECTION ARF LASER PHOTOLYSIS

The IR spectroscopy of matrix-isolated DMZ is presented as a precursor for the analysis of DMZ photochemistry in the solid rare gases, In ag reement with gas-phase work, the present study reassigns the band obse rved at 1309.2 cm(-1), currently assigned in the matrix literature to the bending mode of the impurity methane, to the nu(10) + nu(14) band combination mode of DMZ. From a combination of IR absorption and UV lu minescence studies, atomic zinc and a pair of methyl radicals (Zn + 2C H(3)) are identified as the photochemical products formed with ArF exc imer laser photolysis. A concerted dissociation pathway of DMZ in soli d Ar is considered to be the only mechanism leading to the production of methyl radicals in the vicinity of ground-state atomic zinc. The la ck of observation of the methylzinc (CH3Zn) and methyl radicals as pro ducts is explained in terms of the rapid geminate recombination of the se radicals in the matrix cage, which in turn explains the poor effici ency of DMZ dissociation in the solid. Evidence exists for the formati on of secondary products with ArF photolysis, namely, the production o f ethylzinc hydride and acetylene. It is proposed that the former aris es from the excited-state insertion of atomic zinc into the C-H bonds of the small amounts of ethane arising from the recombination of the m ethyl radicals, Acetylene is a product of ArF dissociation of ethylene which results from recombination of hot methyl radicals.