Structural determination and gas-phase synthesis of monomeric, unsolvated IZnCH₃ (X̃¹a₁): A model organozinc halide

The first experimental structure of a monomeric organozinc halide, IZnCH₃, has been measured using millimeter-wave direct absorption spectroscopy in the frequency range 256-293 GHz. IZnCH₃ is a model compound for organozinc halides, widely used in cross-coupling reactions. The species was produced in the gas phase by reaction of zinc vapor with iodomethane in the presence of a dc discharge. IZnCH₃ was identified on the basis of its pure rotational spectrum as well as those of the isotopically substituted species I⁶⁶ZnCH₃, I⁶⁴Zn¹³CH₃, and I⁶⁴ZnCD₃. IZnCH₃ is unmistakably a symmetric top molecule (X̃¹A₁) belonging to the C_3v point group, in agreement with DFT calculations, with the following experimentally determined structural parameters: r_IZn = 2.4076(2) A˚, r_ZnC = 1.9201(2) A˚, r_CH = 1.105(9) A˚, and <H-C-H = 108.7(5)°. The basic methyl group geometry is not significantly altered in this molecule. Experimental observations suggest that IZnCH₃ is synthesized in the gas phase by direct insertion of activated atomic zinc into the carbon-iodine bond of iodomethane. (Figure Presented).