Mario Onyszchuk

Mesitylpseudohalogermanes Mes2Ge(CN)2 and Mes3GeX (X=CN, NCS, N3, NCO and OH; Mes=2,4,6-trimethylphenyl): syntheses, crystal and molecular structures

Abstract The crystal and molecular structures of the mesitylpseudohalogermanes, Mes2Ge(CN)2 (Mes=2,4,6-trimethylphenyl) and Mes3GeX (X=CN, NCS, N3, NCO, or OH), have been determined by X-ray diffraction methods; the isocyanate and hydroxide crystallise as a 1:1 hydrogen-bonded complex. All are covalent monomers free from pseudohalogen bridging, and all except the cyanides and hydroxide are N-bonded to germanium. Each Ge atom is four-coordinate in a distorted tetrahedral geometry, as evident from (mes)Ge(mes) angles between 112 and 120°, which are attributed to the sterically demanding mesityl groups. The greatest distortion is displayed by Mes2Ge(CN)2, for which the NCGeCN angle of 97.8(3)° and (mes)Ge(mes) angle of 119.8(3)° are also consistent with the bulky mesityl groups and the small steric requirements of the cyano groups. The GeNY angles show a distinctive trend, decreasing from 173.3(5)° for the isothiocyanate (Y=CS), through 153.5(5)° for the isocyanate (Y=CO), to 119.0(7)° for the azide (Y=NN), an effect attributed to differences in electronic structure of the pseudohalo ligands. The geometries of the compounds examined here are compared with those of some other tri- and dimesityl-Group 14 metal derivatives as well as related phenylgermanium compounds.

Synthesis, reactivity and crystal structure of trimesitylgermylamine, Mes3GeNH2

Abstract Trimesitylgermylamine, Mes 3 GeNH 2 , prepared in high yield by the coupling of Mes 3 GeCl (Mes  2,4,6-Me 3 C 6 H 2 ) with NaNH 2 or LiNH 2 , has been fully characterized by 1 H and 13 C NMR, IR and mass spectrometry. It is a rare example of a stable primary germylamine, melting at 166°C, which is only slowly cleaved by H 2 O, CH 3 OH, HCl or phenol, indicating that the central Ge atom is protected from attack by the mesityl groups. Unlike other germylamines, Mes 3 GeNH 2 reacts with t BuCOCl to give the N -substituted amide, Mes 3 GeNHCO t Bu, rather than Mes 3 GeCl. Preliminary X-ray crystallographic analyses reveal that the Ge atom has approximate tetrahedral coordination with an average GeC bond length of 1.978(3) A and a GeN bond length of 1.854(3) A, and crowding around the Ge atom so that it is shielded from attack by approaching reactants.

Reactions of cyclotrigermane and germylenes with carbonyl compounds: Cycloadducts and oligomers

Reactions of germylenes, generated by thermolysis of cyclotrigermanes, or of bulky germylenes, with various α-dicarbonyl compounds are described. They proceed through a radical pathway, as confirmed by ESR measurements, to give different types of compounds. In the reaction of (Mes2Ge)3 with fluorenone, formation of the 2:1 ketone/germylene cycloadduct and of the oxadigermetane, resulting from a transient digermene, occurred. In the case of acenaphthene quinone, we observed the first example of cycloaddition between a digermene and an α-diketone. The X-ray crystal structure of the product shows a drastically distorted six-membered ring system. The formation of oligomeric adducts was observed with parabenzoquinone.

The crystal and molecular structures of diphenyldi(isothiocyanato)- bis(hexamethylphosphoramide)-tin(IV) and -lead(IV)

The compound diphenyldi(isothiocyanato)bis(hexamethylphosphoramide)tin(IV) is triclinic, space group P1, a 9.832(3), b 11.401(12), c 16.735(17) A, α 89.46(7), β 76.59(6), γ 85.81(5)° and Z  2. The structure was refined on 3741 nonzero Mo-Kα reflections collected at 173 K to R  0.036. The analogous lead(IV) compound is also triclinic, space group P1, a 10.031(1), b 12.427(2), c 15.292(5) A, α 86.97(2), β 77.78(2), γ 85.66(1)°, Z = 2. This structure was refined on 2886 Mo-Kα reflections collected at room temperature to R  0.031. These two compounds are isomorphous with unit cells containing two symmetry-independent Ph2M(NCS)2 · 2HMPA (M = Sn or Pb; HMPA = hexamethylphosphoramide) molecules occupying crystallographic inversion centers. The two molecules have very similar geometries, with an all-trans arrangement of ligands around the metal.

A fast atom bombardment mass spectrometry study of the hexamethylphosphoramide adducts of phenyltin(IV) and phenyllead(IV) halides

Abstract The fast atom bombardment (FAB) mass spectra of a series of hexamethylphosphoramide (HMPA) adducts of phenyltin(IV) halides [Ph 3 SnX · HMPA (X = Cl, Br, I); Ph 2 SnX 2 · HMPA (X = Br, I); Ph 2 SnX 2 · 2HMPA (X = Br, I)] and phenyllead(IV) halides [Ph 3 PbX · HMPA (X = Cl, Br, I); Ph 2 PbX 2 · HMPA (X = Br, I) and Ph 2 PbX 2 · 2HMPA (X = Cl, Br, I)] in a glycerol/HMPA matrix have been investigated, and compared with their electron impact (EI) spectra. No parent ions are observed in either FAB or EI, but in the FAB spectra there is a much higher proportion of metal-containing ions which also have and HMPA molecule attached. This is the case even in a HMPA-free matrix such as p -nitrophenyloctyl ether (NPOE). The main difference in the FAB spectra is the preferential loss of halide compared to phenyl, the reverse of that observed in the EI spectra. The same trend is observed for the IE and FAB spectra of the uncomplexed organometallics. Diphenyltin dihalide · HMPA adducts in the glycerol/HMPA matrix form Ph 3 Sn species which are absent when NPOE is used as the matrix liquid.

Synthesis and vibrational spectra of some tri- and di-phenylhaloplumbates

Abstract Phenylhaloplumbate salts of the type [Et 4 N][Ph 3 PbXY] (X or Y = Cl, Br, I), [Et 4 N][Ph 6 Pb 2 X 2 Y] (X or Y=Cl, Br), [Et 4 N][Ph 2 PbX 3 ] (X = Cl, Br, I), and [Me 4 N] 2 [Ph 2 PbX 4 ] (X = Cl, Br) have been prepared and characterised in the solid state by infrared and Raman spectroscopy over the range 250–80 cm −1 . Similar vibrational data are reported for [Me 4 N][Ph 3 PbX 2 ] (X = Cl, Br) and [Me 4 N][Ph 2 PbCl 3 ] as well as new data for Ph 3 PbX and Ph 2 PbX 2 (X = Cl, Br, I). These infrared and Raman data are consistent with 5-coordinate, approximately trigonal-bipyramidal structures for triphenyllead systems (except Ph 3 PbI) and 6-coordinate, approximately octahedral structures for diphenyllead systems (except Ph 2 PbI 2 ), the required degree of coordination being achieved by halogen bridges where necessary. Stretching modes associated with halogen bridges are observed as strong, broad infrared bands only weakly Raman active, characteristics which suggest that these bonds have high ionic character.

Synthesis and vibrational spectra of diphenyl-lead di-isothiocyanate adducts with some O- and N-donor ligands

Abstract Diphenyl-lead di-isothiocyanate forms: (a) 1:2 complexes with hexamethylphosphoramide, dimethylsulphoxide, N,N-dimethyl-acetamide, N,N-dimethylformamide, piperidine, and ethylene-diamine; (b) 1:1 complexes with 2,2′-bipyridyl and 1,10-phenanthroline; (c) the condensation product Ph2Pb(NCS) (ox) with 8-hydroxyquinoline. All complexes are solids, insoluble in common polar and nonpolar organic solvents, and most melt with decomposition at about 200°. Only Ph2Pb(NCS)2·2hmpa (m.p. 232°) can be recrystallized from benzene in which it is monomeric. Attempts to isolate complexes of Ph2Pb(NCS)2 with triethylphosphate, tetrahydrofuran, dioxane, pyridine, aniline, acetonitrile, triphenylphosphine, acetylacetone, and tetramethylethylenediamine were unsuccessful. The infrared and Raman spectra of Ph2Pb(NCS)2 and its complexes show: (a) bands near 2100 cm−1 which are attributed to ν(CN) of -NCS- bridging groups; (b) bands near 800 cm−1 which are −1 due to the δ(NCS) vibration. These observations and the physical properties of the compounds suggest that weak Pb-S bonds of the -NCS- bridges in polymeric Ph2Pb(NCS)2 are broken up by ligands to produce complexes containing lead-ligand bonds, Pb-NCS bonds, and -NCS- bridge bonds to a degree which depends upon the donor power of the ligand.

Preparation and spectroscopic studies of some cyclic urea adducts of triphenyl-tin and -lead halides

Abstract 1,3-Dimethyl-2-imidazolidinone (dimethylethylene urea, DMEU) and 1,3-di- methyl-3,4,5,6-tetrahydro-2(I H )-pyrimidinone (dimethylpropylene urea, DMPU) adducts of the type Ph 3 SnX·L (X = Cl, Br and I), Ph 3 PbX·L (X = Br, I), 3Ph 3 PbCl·2DMEU and 2Ph 3 PbCl · DMPU have been prepared and characterized. Assignments are made for ν(CO) and ν(CN) frequencies in the IR, and for skeletal frequencies observed in both the IR and Raman spectra in the range 400 to 100 cm −1 Infrared measurements show that the adducts are bound through the carbonyl oxygen, and are highly dissociated in dichloromethane solution. 1 H and 119 Sn or 207 Pb NMR measurements reveal that ligand exchange, fast on the NMR time scale, occurs in solution. Coordination of the ligand causes a large upfield shift in the 119 Sn or 207 Pb resonances, but Ph 3 MI · L have shifts similar to those for the parent iodides, indicating almost complete dissociation. Thermodynamic parameters are reported for the dissociation of Ph 3 SnX · DMPU (X = Cl, Br) in CH 2 Cl 2 solution.

Trimesitylgermylamine Mes3GeNH2 : syntheses, structure, propriétés

Abstract Sterically hindered trimesitylgermylamine is a rare example of a stable primary germylamine. X-ray structural data show that germanium is shielded from nucleophilic attack by the surrounding mesityl groups. Nitrogen is still accessible, and the only reactions which occur are those in which the first step of the transition state proceeds through an electrophilic attack on nitrogen. With acid chlorides, Mes3GeNH2 reacts mainly as a primary amine forming the corresponding N-germylamides. The primary amine behaviour is also evident in the reaction with aldehydes. However, functional hydrogen cannot be substituted by lithium, probably because of steric hindrance which prevents the approach of an organolithium derivative. Insertion reactions into the Ge‒N bond are difficult. Carbon dioxide and disulfide react only upon heating and yield trimesitylgermyliso- or isothiocyanates (Mes3GeN˭C˭X; X˭O, S) through thermal degradation of the carbamate or dithiocarbamate initially formed. 3,5-di-tert-butylorthoqu...

REACTIONS OF CYCLOTRIGERMANE WITH p-BENZOQUINONES: OLIGOMERS AND A NOVEL 1,3-CYCLOADDUCT

Thermolysis of hexamesitylcyclotrigermane in the presence of various derivatives of pbenzoquinone are described. A surprising 1,3-cycloadduct was isolated in the case of pbenzoquinone; it is the first example of a 1,3-cycloaddition of a digermene to a quinone followed by a 1,4-H shift. The X-ray crystal structure of the adduct reveals a planar configuration of fused fiveand six-membered rings and a deformation of the heterocycle because of the germanium atoms. Two other p-quinones substituted in ortho positions by aromatic cycles (naphthoquinone and anthraquinonej were used to decrease the fraction of the rearranged cycloadduct and thereby to increase the oligomeric forms. Introduction Recently we described the reactions of hexamesitylcyclotrigermane with various adiketones and showed that they proceed by a pathway involving radicals to give cyclic and polymeric compounds. The mechanism of the addition of carbonyl compounds such as aldehydes or ketones to disilene or germasilene (generated by photolysis of the corresponding trimetalla compounds) has been determined. These authors also proposed the formation of biradical intermediates which gave disproportionation or ring closure. On the other hand, it has been reported that the photolysis of cyclic organosilanes with phenantraquinone gave silylene insertion products by a process involving radicals. We now report reactions of cyclotrigermane with pbenzoquinone, p-naphthoquinone and p-anthraquinone with the objective of determining whether or not they proceed by a similar pathway. Results and discussion When 1,4-benzoquinone was allowed to react with hexamesitylcyclotrigermane, we obtained a mixture of a linear oligomer 2 having one organogermylene unit, a cyclic oligomer 3 and a surprising 1,3-cycloadduct 4, the formation of which was mentioned but that w a s no t identified. (Mes2Ge)3· CSH6 100°C — ο Ω Mes^ ι Gei Mes + Mes2Ge (1) m 2 : m = 1 3 : m = 2, η = 2 Compound 4.could be extracted from the reaction mixture after several recrystallizations from hexane, petroleum ether and ether, and was obtained pure in a 17% yield. In its H and 1 C NMR spectra, the two mesityl groups are not equivalent, as expected from the different environments of the germanium atoms, one attached to an oxygen atom and the other to a carbon atom of the aromatic ring. The H NMR spectrum of the aromatic system showed the expected coupling interactions of the three non-equivalent protons. An X-ray crystal structure study of compound 4 confirmed its 1,3-cycloadduct structure as shown by the ORTEP diagram in Figure 1. The two fiveand six-membered rings are in the same plane, but the heterocycle is highly distorted.