Gábor Vass

ARENE-TRANSITION METAL COMPLEXES AS PRECURSORS OF HARD COATINGS PREPARED BY THE CHEMICAL VAPOUR DEPOSITION TECHNIQUE

Abstract Chemical aspects of hard coating preparation by chemical vapour deposition were studied in the temperature range 300–600°C using bis(arene)chromium and (cyclopentadienyl)zirconium or hafnium tetrahydroborate compounds as precursors. Chromium carbide was deposited from bis(benzene)chromium (I), bis(toluene)chromium (II) and bis(p-xylene)chromium (III); another set of experiments, thin films of zirconium carbide-boride as well as zirconium and hafnium carbide from (cyclopentadienyl)zirconium tris(tetrahydroborate) (IV) bis(cyclopentadienyl)zirconium bis(tetrahydroborate) (V) and bis(cyclopentadienyl)hafnium bis(tetrahydroborate) (VI) were prepared. In both cases mass spectrometry fragmentation patterns have been invoked to rationalize trends in the deposition temperature and chemical composition of the obtained thin films.

He(I)/He(II) ultraviolet photoelectron spectroscopic studies on organosulfur compounds with emphasis on the sulfur–oxygen interaction

Abstract The electronic structure of compounds having the possibility of exhibiting intramolecular sulfur–oxygen non-bonded interaction of the S(II, IV or VI)⋯O(carbonyl or nitro) type and a hypervalent sulfur atom of the O–S–O type — i.e, R–S–Me, R–SO–Me, R–SO2–Me (R=2-nitrophenyl; 2, 7 and 12), R–S–R, R–SO–R, R–SO2–R (R=2-methoxycarbonylphenyl; 5, 10 and 15) and spirosulfurane (16) — have been investigated by the He(I) and He(II) ultraviolet photoelectron spectroscopic method. Reference compounds with R=phenyl or 4-nitrophenyl group (1, 3, 4, 6, 8, 9, 11, 13 and 14) were also studied for the sake of completeness and uniformity. On the basis of the photoelectron spectra and ab initio Hartree–Fock calculations, the sulfur–oxygen non-bonded interaction in compounds 2, 7, 12 and 5, 10, 15 can be attributed to electrostatic interaction. The sulfur–oxygen bond in the sulfoxides and sulfones, which is usually considered as a polarized double bond, seems to be a single bond with zwitterionic character. The photoelectron spectra of spirosulfurane (16) show no similarity to those of the symmetrical disubstituted sulfide, sulfoxide and sulfone (5, 10 and 15).

HE(I) PHOTOELECTRON SPECTROSCOPIC STUDY OF HALF- AND BENT SANDWICH TETRAHYDROBORATES

Abstract The He(I) ultraviolet photoelectron spectra of CpZr(BH 4 ) 3 , Cp 2 Zr(BH 4 ) 2 , Cp 2 Hf(BH 4 ) 2 , Cp 2 Ta(BH 4 ) and Cp 2 TaH 3 are reported. A tentative assignment is given for the low energy part of the spectra. At higher energies, cyclopentadienide ionizations merge with the borohydride ionizations resulting in a complicated overlapped band structure. As a consequence no photoelectron spectroscopic evidence can be given concerning the ligation of the tetrahydrborate groups.

Generation, spectroscopy, and structure of cyanoformyl chloride and cyanoformyl bromide, XC(O)CN.

Cyanoformyl chloride and cyanoformyl bromide, XC(O)CN (X = Cl and Br), have been investigated in the gas phase by UV photoelectron and mid-infrared spectroscopies. The ground-state geometries of the neutral molecules have been obtained from quantum-chemical calculations at the B3LYP and CCSD(T) levels using the aug-cc-pVTZ basis set. The individual spectroscopies provide a detailed investigation into the vibrational and electronic character of the molecules and are supported by quantum-chemical calculations. The results are compared to data for structurally and chemically related molecules.

Photoelectron spectroscopy of mono and binuclear iron and chromium cyclooctatetraene complexes

Abstract The ultraviolet photoelectron spectra of mono and binuclear cyclooctatetraene (COT) complexes (CO) 3 FeCOT ( I ) [(CO) 3 Fe] 2 COT ( II ), CpCrCOT (Cp: 1,3 cyclopentadienyl) ( III ) and (CpCr) 2 COT ( IV ) are reported. The interpretation of the low energy part of the spectra is followed by a discussion concerning the metal–ligand (COT) and metal–metal interactions. The calculated gas phase structure of CpCrCOT is presented and its main features are discussed.

Structure, spectroscopy, and thermal decomposition of 5-chloro-1,2,3,4-thiatriazole: a He I photoelectron, infrared, and quantum chemical study

Abstract5-Chloro-1,2,3,4-thiatriazole has been investigated in the gas phase for the first time by mid-infrared and He I photoelectron spectroscopy. The ground-state geometry has been obtained from quantum chemical calculations at the CCSD(T) and B3LYP levels using aug-cc-pVTZ basis set. Ionization potentials have been determined and the electronic structure has been discussed within the frame of molecular orbital theory. IR and photoelectron spectroscopies, supported by quantum chemical calculations at the B3LYP and SAC-CI levels, provide a detailed investigation into the vibrational and electronic character of the molecule. Thermal stability of 5-chloro-1,2,3,4-thiatriazole has been studied both experimentally and theoretically. Flash vacuum thermolysis of the molecule produces fast quantitatively N2, ClCN, and sulfur. Theoretical calculations at the CCSD(T)//B3LYP level predict competitive decomposition routes, starting either with a retro-cycloaddition reaction leading to N2S and ClCN or with a ring opening to chlorothiocarbonyl azide intermediate, to produce finally N2, S, and ClCN. Calculations also predict that N2S is reactive and decomposes in bimolecular reactions to N2 and S2.

UPDATED INORGANIC AND ORGANOMETALLIC LABORATORY COURSE FOR JUNIOR CHEMISTRY STUDENTS

An advanced inorganic and organometallic laboratory programme has been worked out for junior students. The laboratory exercises were selected to provide an introduction for the students to the different techniques and compound classes of inorganic and organometallic chemistry. Emphasis was also put on the improvement of the students’ verbal and written communication skills through laboratory reports and short talks. The student responses to the programme consisting of twelve groups of experiments were favourable. [Chem. Educ. Res. Pract. Eur.: 2000, 1, 179-182]