Günther Maier

Propargylene: A C3H2 isomer with unusual bonding

Propargylene was identified in a matrix as a product of photolysis of cyclopropenylidene and diazopropyne. The molecule is a triplet. The optimum geometry predicted by ab initio calculations corresponds to a structure HC≡C–CH. The transition structure in the interconversion HC≡C–CH⇄HĊ=C=ĊH⇄HC–C≡CH is very low in energy and close to the energy of the vibrational ground state. Owing to this nonrigidity, computed infrared (IR) frequencies based on a harmonic treatment do not match the experimental spectrum. When this nonrigidity is taken into account by using a nonharmonic approximation calculated UMP2/6‐31G** IR spectra are in good agreement with the observed spectra of HCCCH and DCCCD.

Matrix-isolation infrared investigation of the flash vacuum thermolysis of norbornadienone azine

Abstract The flash vacuum thermolysis of norbornadienone azine over the temperature range 300 to 800°C was investigated by matrixisolation IR methods. The following thermolysis products could be identified: isocyanogen, cyanogen, benzene, benzonitrile and hydrogen cyanide. A tentative assignment of the infrared-active ν 2 stretching vibration of diisocyanogen, CNNC, in an argon matrix is made. The peak positions of four fundamentals (ν 1 to ν 4 ) of isocyanogen, CNCN, and of two stretching fundamentals (ν 1 and ν 2 ) of 13 CNCN, CN 13 CN, C 15 NCN and CNC 15 N in an argon matrix were measured. Combination bands yielded a value for ν 5 of CNCN. A molecular force field for CNCN was determined.

Neue wege zum cyclobutadien und methylencyclopropen

Abstract New routes to cyclobutadiene (2) and methylenecyclopropene (4) are described. Matrix irradiation of cyclopropenylketene (9) gives cyclobutadiene. Flash pyrolysis of 8, 11, 16, 17 and 18 also generates cyclobutadiene, which can be deposited from the gas phase onto a window cooled to 10 K. Methylenecyclopropene is one of the products in the thermal fragmentation of 8 or 14.

1,4-Disilabenzol. - Dimethoxysilylen als idealer synthesebaustein

Abstract Flash pyrolysis of 1,4-disila-2,5-cyclohexadiene (4) yields 1,4-disilabenzene (5), which can be isolated and identified UV spectroscopically in an argon matrix at 10 K.

Photoisomerisierung von tetrachlormethan in einer argon-matrix

Abstract Irradiation of tetrachloromethane (3) in argon at 12 K leads to a new species, which - from a comparison of the calculated and experimental IR spectra - is best described as an iso-tetrachloromethane with structure 5. The reverse reaction 5 → 3 can also be induced photochemically.

Thioformaldehyde S‐sulfide (Thiosulfine)

Matrix isolation spectroscopy allows the direct identification of ylide 1 and its cyclic isomer 2. They were obtained by pyrolysis of 1,2,4-trithiolane under high vacuum; the cyclic compound forms from 1 by thermal ring closure in a kinetically controlled reaction.

Laser Irradiation of Monomeric Acetylene and the T-Shaped Acetylene Dimer in Xenon and Argon Matrices

Irradiation of acetylene (4) in an argon matrix with an ArF laser (λ = 193 nm) yields the ethynyl radical C2H· (5) and C2 (6). If the same wavelength is used to irradiate 4 in a xenon matrix, only the infrared signal of the compound Xe–C2 (7) can be detected. The same band is found on irradiation at λ = 248 nm (KrF laser) in a xenon matrix, despite the fact that acetylene (4) does not absorb light of this wavelength. Irradiation of the T-shaped acetylene dimer 9 in an argon or xenon matrix at λ = 193 nm yields butadiyne (11) and vinylacetylene (12). However, irradiation with a KrF laser (λ = 248 nm) in a xenon matrix additionally yields cyclobutadiene (13). The dependence of the mechanisms of the fragmentation and dimerization of acetylene (4) on the matrix material is discussed.

Reaction of Silicon Atoms with Hydrogen Cyanide: Generation and Matrix-Spectroscopic Identification of CHNSi and CNSi Isomers

Cocondensation of thermally generated silicon atoms with hydrogen cyanide in an argon matrix can be used as an access to compounds of the composition CHNSi and CNSi. Isolation, matrix-spectroscopic identification and photo-chemical behavior of these species are described. Structural assignments are made by the comparison of experimental with calculated IR spectra.

Cyanocarbene, Isocyanocarbene, and Azacyclopropenylidene: A Matrix-Spectroscopic Study

The generation of quasilinear triplet HCCN from cyanoketene and diazoacetonitrile has been confirmed by matrix isolation, and the isomerization to singlet HCNC and singlet azacyclopropenylidene (see scheme) has been established for the first time.

Isolierung und Kristallstrukturanalyse eines Titantetrachlorid-Komplexes eines 1,3-Diketons

Abstract Titanium tetrachloride forms a crystalline adduct with 3,3-dimethyl-2,4-pentanedione ( 2 ). This observation together with the structural data of complex 4 can help to understand the directive force of TiCl4 in stereoselective reductions of diketones.