| Abstract
| - The most-studied organocopper, methylcopper (CH3Cu), has been synthesized for the first timeas a monomer, free of other ligands or coordinated solvent, and detected using millimeter-wave rotationalspectroscopy. The molecule was created in the gas phase by the reaction of copper vapor and severaldifferent precursors, including CH4 and tetramethylsilane. An obvious symmetric top pattern was observed,indicative of C3v symmetry. For confirmation, rotational spectra of four isotopically substituted species,65Cu12CH3, 63Cu12CD3, 63Cu13CH3, and 65Cu13CH3, were recorded as well, following large-scale synthesesof specifically labeled precursors. From this data set, accurate spectroscopic constants and a structure forCH3Cu were derived. The rm(2) geometry shows the shortest alkyl carbon−copper(I) bond length known(1.8809 Å) and a rather large H−C−H angle in the methyl group (109.88°). The measured rotational anddistortion constants are well reproduced by QCISD calculations. This study should allow further refinementof theoretical calculations on methylcopper and other organocopper derivatives, which are valuable syntheticintermediates in organic chemistry.
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