title: Structural and conformational properties of 2-propenylgermane (allylgermane) studied by microwave and infrared spectroscopy and quantum chemical calculations.
abstract: The structural and conformational properties of allylgermane have been investigated using Stark and Fourier transform microwave spectroscopies, infrared spectroscopy, and high-level quantum chemical calculations. The parent species H2C=CHCH2GeH3 was investigated by microwave spectroscopy and infrared spectroscopy, while three deuterated species, namely, H2C=CDCH2GeH3, H2C=CHCHDGeH3, and H2C=CHCH2GeD3, were studied only by infrared spectroscopy. The microwave spectra of the ground vibrational state as well as of the first excited state of the torsion vibration around the sp2-sp3 carbon-carbon bond were assigned for the 70Ge, 72Ge, and 74Ge isotopomers of one conformer. This rotamer has an anticlinal arrangement for the C=C-C-Ge chain of atoms. The infrared spectrum of the gas in the 500-4000 cm(-1) range has been assigned. No evidence of additional rotameric forms other than anticlinal was seen in the microwave and infrared spectra. Several different high-level ab initio and density functional theory calculations have been performed. These calculations indicate that a less stable form, having a synperiplanar conformation of the C=C-C-Ge link of atoms, may coexist with the anticlinal form. The energy differences between the synperiplanar and anticlinal forms were calculated to be 5.6-9.2 kJ/mol depending on the computational procedure. The best approximation of the equilibrium structure of the anticlinal rotamer was found in the MP2/aug-cc-pVTZ calculations. The barrier to internal rotation of the germyl group was found to be 6.561(17) kJ/mol, from measurements of the splitting of microwave transitions caused by tunneling of the germyl group through its threefold barrier.
authors.affiliation: Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, NO-0315 Oslo, Norway.
authors.forename: Anne
authors.initials: A
authors.lastname: Horn
authors.forename: Harald
authors.initials: H
authors.lastname: Møllendal
authors.forename: Jean
authors.initials: J
authors.lastname: Demaison
authors.forename: Denis
authors.initials: D
authors.lastname: Petitprez
authors.forename: Juan Ramon
authors.initials: JR
authors.lastname: Aviles Moreno
authors.forename: Abdessamad
authors.initials: A
authors.lastname: Benidar
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Guillemin
mesh_terms: D002627:Chemistry, Physical / Q000379:methods*; D005583:Fourier Analysis; D005857:Germanium / Q000737:chemistry; D008872:Microwaves; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D011789:Quantum Theory; D012984:Software; D013055:Spectrophotometry, Infrared / Q000379:methods
chemical_list: C521282:2-propenylgermane; D009942:Organometallic Compounds; D005857:Germanium