Gian Angelo Vaglio

Investigation of the complex reactions of SiH4 and GeH4 in the ion trap using dynamically programmed scanning

Abstract The rate constants of the gas-phase reactions of primary ions in a 1:1 SiH 4 /GeH 4 mixture have been determined by ion trap mass spectrometry and compared with those obtained for SiH 4 and for GeH 4 alone. The main reaction pathways are hydride or hydrogen transfer, formation of ions containing two silicon or two germanium atoms and ions containing silicon and germanium together. Experimental rate constants have been compared with the calculated collision rate constants and efficiencies have been determined. The formation of mixed ions, important in the radiolytical preparation of materials of interest in photovoltaic technology, is more efficient when SiH + m ( m = 0, 1) ions react with GeH 4 than when GeH + reacts with SiH 4 , and occurs at comparable rates to SiH + 2 and GeH + 2 reacting with GeH 4 and SiH 4 , respectively.

Butadienic derivatives and metal carbonyls II. Some rearrangements of butadienic ligands in reactions with dodecacarbonyltriruthenium

Abstract Isomerization and rearrangement of ligands L, such as 1,4-trans,trans-diphenyl-1,3-butadiene, hexadiene isomers, isoprene and 1,3-butadiene, occur in the reactions with Ru3(CO)12 to give trimetallic complexes of molecular formula HRu3(O)9(L-H), in addition to bi- and monometallic complexes of known structure. On the contrary the diene skeleton is always maintained when L is 2,3-dimethyl-1,3-butadiene. Structures of HRu3(CO)9(L-H) complexes are suggested and some novel features in their proton n.m.r. spectra are described.

Isomerisation of pentenes with H4Ru4(CO)12

Abstract Catalytic isomerisation of 1-pentene to 2- cis and 2- trans -pentene with H 4 Ru 4 (CO) 12 in toluene at 70.4 °C is described. Carbon monoxide, hydrogen, weak acids and polar substances, such as ethyl acetate, decrease the isomerisation rate. Reactions of H 4 Ru 4 (CO) 12 with trans -C 2 H 2 D 2 and [1,2-D 2 ] 1-pentene and of D 4 Ru 4 (CO) 12 with 1-pentene suggest the operation of a metal-hydride addition-elimination mechanism involving σ-alkyl intermediates. The active species is supposed to be mainly originated by loss of CO to give H 4 Ru 4 (CO) 11 . Catalytic hydrogenation of the pentene isomers occurs at the approaching of the equilibrium and is largerly enhanced by addition of hydrogen to the reaction system.

Acetylenic derivatives of metal carbonyls XII. Diphenylacetylenic derivatives of dodecacarbonyltriosmium

The reaction of the complex (C6H5C2C6H5)2Os3(CO)8 (I) with CO has been investigated and a structure suggested for the compound, (C6H5C2C6H5)2Os3(CO)9, thus obtained. This consists basically of an Os3 cluster, in which one of the osmium atoms belongs to a osmacyclopentadiene ring, and to which only terminal carbonyl groups are bonded. The formation of this product from (I) and CO was found to be a second-order process. The reactions of complex (I) with halogens have also been investigated, and the resulting binuclear derivatives identified.

Gas phase ion/molecule reactions in monogermane-hydrocarbon mixtures: a comparative Fourier transform mass spectrometry and chemical ionization mass spectrometry study

Abstract The gas phase ion/molecule reactions of GeH 4 with some simple saturated (CH 4 , C 2 H 6 ) and unsaturated hydrocarbons (C 2 H 2 , C 3 H 4 , C 3 H 6 ) have been studied by high pressure mass spectrometry and Fourier transform mass spectrometry. The effects of the nature of the hydrocarbon and of the total pressure and the relative concentrations of the reagent gases on the formation of GeC containing ions are reported. Saturated hydrocarbons give only limited amounts of such species, whereas a variety of GeC containing products are efficiently produced when alkenes or alkynes are added to germane. In these latter cases, GeCH + 3 and GeCH + 5 are among the most abundant products, invariably accompanied by ions containing germanium, carbon and hydrogen in relative yields increasing with the hydrocarbon partial pressure. For all systems, the reaction pattern is presented and discussed in relation to the preparation of amorphous GeC containing materials for photovoltaic applications.

Acetylenic derivatives of metal carbonyls. Part XV. Reaction of dodecacarbonyltriosmium with unsymmetrically substituted alkynes

Abstract Dodecacarbonyltriosmium and phenylacetylene (L) in refluxing benzene give Os 3 (CO) 10 L, Os 3 (CO) 10 L 2 , Os 3 (CO) 9 L and HOs 3 (CO) 9 (LH) as primary products. Reactivity of these complexes is investigated and formation of 1,2,4-triphenylbenzene in a sequence starting from Os 3 (CO) 10 L is described. Corresponding reactions with propyne and 1-butyne exhibit a close analogy with those of phenylacetylene. A partially different behaviour is shown by methylphenylacetylene (L′), which reacts with dodecacarbonyltriosmium to give two isomers of molecular formula HOs 3 (CO) 8 (L′H)L′ as main products. These complexes are suggested to be isostructural with an analogous compound obtained from diphenylacetylene. The main factors affecting the reaction trends are considered.

Effect of phosphorus-donor ligands on the isomerisation of pentenes catalysed by substituted derivatives of H4Ru4(CO)12

Abstract The catalytic activity of H 4 Ru 4 (CO) 11 L (where is PPh 3 , P(OEt) 3 , P(OPh) 3 ), H 4 Ru 4 (CO) 10 [P(OEt) 3 ] 2 and H 4 Ru 4 (CO) 8 [P(OEt) 3 ] 4 in the isomerisation of pentenes in toluene at 70.4 °C is described. The initial conversion rate is proportional to the catalyst concentration, decreases with increasing CO pressure, while the addition of the free ligand causes a decrease of the conversion rate, in the initial steps, ascribed to its preferential coordination on the active sites. For H 4 Ru 4 (CO) 11 L, the isomerisation rate decreases with L in the sequence P(OEt) 3 > (P(OPh) 3 > PPh 3 > CO. The conversion rate, moreover, decreases with n in the series H 4 Ru 4 (CO) 12−n [P(OEt) 3 ] n (n = 1, 2, 4). The results are interpreted by suggesting that the RuCO bonds are mainly involved in the active site formation and that the phosphorus-donor ligands cause a weak increase of the activity of the carbonyl groups. However, the free sites formed by RuCO bond cleavage of Ru(CO) 2 L units are considered to give a little contribution to the isomerisation for the steric hindrance of L.

Gas phase ion-molecule reactions of monogermane with oxygen and ammonia☆

High pressure and Fourier transform mass spectrometry have been used to study the ion-molecule reactions of germanium-containing ions with oxygen, ammonia, and GeH4 itself. The effects of the total pressure and of the ratio between GeH4 and oxygen or ammonia are reported. In self-condensation reactions the most reactive species are Ge+ and GeH2P+, which give dimer ions containing an even number of hydrogen atoms. Formation of GeHnO2+ (n = 0, 1) and GeHnO+ (n = 0−3) ions is observed in GeH4/O2 mixture. The most abundant species is GeHO+, which originates in the reaction of Ge2H2+ with one O2 molecule, as demonstrated by FTMS. High pressure experiments suggest that oxygen-containing ions are also formed by pathways involving monogermanium ions. Analogous behaviour is observed in the GeH4/NH3 mixtures, where GeNHn+ (n = 2, 3, 4, 6) ions are formed in higher abundances than GeHO+ (n = 1−3) ions under similar conditions.

Gas phase ion-molecule reactions of monogermane with carbon oxides and ethylene: Formation of germanium-carbon bonds

Abstract The gas phase ion-molecule reactions of GeH 4 with some carbon-containing compounds (CO, CO 2 , and C 2 H 4 ) have been studied by high pressure mass spectrometry and Fourier transform mass spectrometry. The effects of the total pressure and of the relative concentrations of the reagent gases on the ion pattern are reported. In the presence of CO and CO 2 , GeH n CO + or GeH n CO 2 + , GeH n O + , and GeH n C + ions are observed, all of which show very low abundances. In contrast, condensation processes of GeH 4 with C 2 H 4 give GeC n H m + ( n = 1–4) species, in very high yield for n = 1, 2 but lower for n = 3, 4. For all three systems, reaction mechanisms are suggested and are discussed in relation to the preparation of amorphous materials containing germanium carbides for photovoltaic applications.

Hydrogenation of pentynes catalyzed by substituted derivatives of H4Ru4(CO)12 with phosphorus-donor ligands

The catalytic hydrogenation under mild conditions of 1-pentyne and 2-pentyne in the presence of phosphine and phosphite substituted derivatives of H4Ru4(CO)12 has been investigated. The initial rates of hydrogenation of both 1- and 2-pentyne with the monosubstituted derivatives were found to follow the trend: P(OPh)3 ≅ P(OEt)3 < PPh3 ≅ P(n-Bu)3. The initial rates of hydrogenation of 2-pentyne decrease with increasing substitution of the catalyst, while the opposite trend is observed for 1-pentyne. The specificity of all the catalysts investigated, towards the formation of cis-2-pentene and 1-pentene from 2-pentyne and 1-pentyne respectively, is similar and is improved as compared with that observed in the presence of H4Ru4(CO)12. The experimental results are interpreted on the basis of the stability of the alkyne carbonylmetal intermediates and of the influence which increasing substitution on H4Ru4(CO)12 plays on the formation of active sites. The complexity of this multistep process, however, does not allow a comprehensive rationalisation of the experimental data.