The fragmentation of 5- and 3-substituted thiophene-2-carboxamides under electron impact

The 70 eV electron impact mass spectra of twelve 5- and 3-substituted thiophene-2-carboxamides are discussed with the aid of exact mass measurements and labelling experiments. All mass spectra exhibit pronounced molecular ions. Some isomeric 5- and 3-substituted title compounds can be differentiated by mass spectrometry. The fragmentation is influenced by a strong ‘ortho-effect’ which activates the NH₃ elimination. In the other cases the most important fragmentation is NH₂˙ loss, followed by CO elimination.     

Mass spectrometry of metal compounds: II—mass spectrometric studies of [CF3EMn(CO)4]2, [CF3EFe(CO)3]2 (E = S,Se), CF3SeFe(CO)2C5H5 and CF3SCr(NO)2C5H5

The electron impact induced mass spectra of [CF₃SMn(CO)₄]₂, [CF₃SeMn(CO)₄]₂, [CF₃SFe(CO)₃]₂, [CF₃SeFe(CO)₃]₂, CF₃SeFe(CO)₂C₅H₅ and CF₃SCr(NO)₂C₅H₅ are reported. These compounds exhibit weak molecular ion peaks and undergo preferential loss of CO or NO groups. The CO or NO free fragments suffer typical loss of ECF₂(E = S, Se) with the simultaneous shift of F from carbon to metal. The ions [FFeC₅H₅]⁺ and [FCrC₅H₅]⁺ in the spectra of the cyclopentadienyl compounds prefer expulsion of π-cyclopentadienyls. The pyrolysis effects on the spectra of the compounds have been studied. An increase in temperature eases the expulsion of ECF₂ groups from all the compounds and favors the formation of [Fe(C₅H₅)₂]⁺ and [Cr(C₅H₅)₂]⁺ in the cyclopentadienyl compounds.     

Fast atom bombardment mass spectra of [(diars)Fe(CO)2(C(O)Me)(P-donor)]+ BF4− salts

Characteristic fast atom bombardment (FAB) mass spectra (8 keV, argon, glycerol matrix) have been obtained for an isostructural series of organometallic cations of the form cis,trans[(diars)Fe(CO)₂(C(O)Me)L]⁺ Bf₄ (L = phosphorus donor). The fast atom bombardment mass spectra (FABMS) obtained show relatively abundant fragments corresponding to the cationic portion of the complex [C⁺]. Extensive fragmentation also occurs via successive CO loss, phosphorus donor ligand cleavage, and ligand decomposition. Evidence for a rearrangement fragmentation corresponding to the process [Fe(C(O)Me)]⁺ → [FeMe]⁺ + CO is presented.     

Synthesis and structures of new heteronuclear cluster complexes [PPh4][Fe4Rh3Se2(CO)16] and [PPh4]2[Fe3Rh4Te2(CO)15]

The reaction of the K₂[Fe₃Q(CO)₉] clusters (Q = Se or Te) with Rh₂(CO)₄Cl₂ under mild conditions is accompanied by complicated fragmentation of cores of the starting clusters to form large heteronuclear cluster anions. The [PPh₄][Fe₄Rh₃Se₂(CO)₁₆] and [PPh₄]₂[Fe₃Rh₄Te₂(CO)₁₅] compounds were isolated by treatment of the reaction products with tetraphenylphosphonium bromide. The structures of the products were established by X-ray diffraction. In both compounds, the core of the heteronuclear cluster consists of two octahedra fused via a common Rh₃ face. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 775–778, May, 2006.     

Electronic structure and reactivity of X2Co2(CO)6 (X2  RC2R′, P2, As2) and RxR′ 6-xC6Co2(CO)4 radical anions

Radical anions of the dinuclear species X₂Co₂(CO)₆ (X₂  P₂, As₂, RC₂R′) and R_x,R′_6-xC₆CO₂(CO)₄ have been characterized by electrochemical and ESR methods. The frozen solution spectra could be analysed in unusual detail to evaluate the g and hyperfine tensor components and these data allow definitive statements to be made about the directional nature and orbital character of the unpaired electron density. Most of the RC₂R′Co₂(CO)₆^? radical anions decay to monomeric paramagnetic species.     

Negative ion mass spectra of Os3(CO)12X2 and Os3(CO)10X2 complexes (X = Br,I)

The negative-ion mass spectra at 70 eV of the compounds Os₃(CO)₁₂X₂ and Os₃(CO)₁₀X₂ (X =Br, I) are reported. Negative molecular ions are absent and only Os₃-containing fragments due to the loss of carbonyl groups are observed. [M  CO]^? is the base peak in the spectrum of Os₃(CO)₁₀I₂ and has a very high abundance in that of Os₃(CO)₁₀Br₂, whereas it is very weak in the spectra of Os₃(CO)₁₂X₂, where [M  3 CO]^? is the base peak. This change in the ionic intensities is related to the closed and open structure of the Os₃ unit in Os₃(CO)₁₀X₂ and Os₃(CO)₁₂X₂ respectively.     

Thiocarbonylkomplexe des eisens : II. Darstellung und eigenschaften von[(CO)4FeC(S)NMe2]− und (CO)4FeC(SMe)NMe2

(CO)₄FeCS reacts with the ortho amide of the carbon acid C(NMe₂)₄ to yield the anionic thiocarbamoyl complex I, which with “magic methyl” can be converted into the neutral carbene complex. The spectroscopic properties (IR, NMR and mass spectra) of the new complexes are discussed.     

Electron impact mass spectra of some nickel(II) and palladium(II) complexes of diphenylphosphinoacetone and 3-diphenylphosphinobutan-2-one

The electron impact mass spectral fragmentation of five newly synthesized Ni(II) and Pd(II) complexes of diphenylphosphinoacetone (HL), i.e. trans-[ NiCl₂(HL)₂] and trans-[PdCl₂(HL)₂] and their enolates cis-[NiL₂] and cis-[PdL₂] and the bis-enolate of 3-diphenylphosphinobutan-2-one (HLMe), trans-[Ni(LMe)₂], is discussed. The proposed fragmentation mechanisms and the ion structures were confirmed by high-resolution data for three of the compounds and by Ni and Pd isotope abundances. The results obtained reveal that a mass spectral differentiation is useful in the identification of these types of complexes. Especially with phosphinoenolate bis-chelates molecular ion peaks are observed.     

Mass spectra of polymeric thioformaldehydes (CH2S)3, (CH2S)4, (CH2S)5 and (CH2S)x

The mass spectral fragmentations of various thioformaldehydes, 1,3,5-trithiacyclohexane, 1,3,5,7-tetrathiacyclooctane, 1,3,5,7,9-pentathiacyclodecane and a polymeric form (CH₂S)_x have been examined. The principal features of the spectra are reported. The fragmentation occurred by fracture of the ring in the cyclic compounds with or without rearrangement.     

Massenspektren alicyclischer verbindungen—V : Massenspektrometrische untersuchungen an cyclohexan-(4)-di-carbonsäure-(1,2)-anhydriden

The electron impact mass spectra of 21 4-cyclohexene-1,2-dicarboxylic anhydrides were analysed. It was found that the mass spectrometric fragmentation depends on the constitution, the configuration and the conformation. The intensity of the peak and the abundance of the ratio in cis compounds are greater than in trans isomers. The elemination of CO in the cis compounds is followed by elemination of CO₂H, in the trans isomers by elemination of CO₂.     

The mass spectra of 1,1,1-trichloro-2,4-pentanedione and its Al(III), Cr(III), Fe(III), Mn(II), Co(II) and Cu(II) complexes

The compounds 1,1,1-trichloro-2,4-pentanedione, Cu(II)tca₂, Co(II)tca₂, Mn(II)tca₂, Al(III)tca₃, Cr(III)tca₃ and Fe(III)tca₃ (tca?1,1,1-trichloro-2,4-pentanedionato, [CCl₃COCHCOCH₃]^?) have been prepared and their mass spectra have been obtained. The mass spectral results have been compared with findings for comparable fluorinated and nonhalogenated compounds. Comparisons are made in terms of internal redox reactions and hard and soft acid base theory. Rearrangement of chloride from ligand to metal accompanied by the elimination of CO or other neutral even electron fragments emerges as an important reaction for the ions of these compounds. While the internal redox reactions characteristic of all previous β-diketonate complex mass spectra still occur, their importance appears reduced to some degree by the facility of the chlorine rearrangement.     

Synthesis, Chemical Characterization, and Molecular Structure of Au8{Fe(CO)4}4(dppe)2 and Au6Cu2{Fe(CO)4}4(dppe)2

The new Au₈{Fe(CO)₄}₄(P^P)₂ and Au₆Cu₂{Fe(CO)₄}₄(P^P)₂ (P^P=dppm, dppe) neutral cluster compounds were isolated in good yields by condensation of the [Au₃{Fe(CO)₄}₂(P^P)]^- anions with Au(SEt₂)Cl and CuCl, respectively, and have been characterized by IR, NMR and microanalyses. The molecular structures of Au₈{Fe(CO)₄}₄(dppe)₂ and Au₆Cu₂{Fe(CO)₄}₄(dppe)₂ have been determined by X-ray diffraction studies. Both molecules adopt a stereogeometry of the heavy atoms consisting of a triangulated and corrugated ribbon twisted around the elongation direction. Contrary to the expectations the latter displays the two copper atoms in the sites of highest connectivity. This implies that site exchange between copper and gold occurs during the synthesis.     

C2对称的手性双噁唑啉和双噻唑啉的质谱碎裂机理研究

The electron impact mass spectra of ten new C2-symmetric chiral bis(oxazoline) and bis(thiazoline) have been studied. Bis(thiazoline) and bis(oxazoline) possess the same fragmentation mechanism under EI conditions. An unusual fragmentation pathway has been found in the compounds studied. Due to the presence of phenyl group, compounds 6 and 10 undergo a new fragmentation pathway except for the common way as the other eight compounds.Mass analyzed ion kinetic energy spectra experiments and high resolution accurate mass measurement were conducted to confirm the proposed fragmentation pathways.     

Redistribution reactions in the ion source of a mass spectrometer of complexes of titanium (iv), tin (iv) and germanium (iv) with 8-quinolinolato and halo or ethoxy ligands

The relative intensities of peaks in the mass spectra of the compounds MX_4?nox_n (oxH = 8-quinolinol; n = 2; M = Ti; X = F, Cl, Br or OEt; M = Sn; X = F, Cl, Br or I; M = Ge; X = Cl or Br; n = 1; M = Ti; X = OEt) depend on the insertion temperature and the residence time of the sample in the mass spectrometer. In most cases ions which cannot arise by fragmentation of the respective molecular ions are observed. These ions arise from the ionisation and fragmentation of species which are due to redistribution reactions in the mass spectrometer. The fragmentation pattern of the compounds MX₂ox₂ (X = halogen), mainly involving loss of ligand radicals, is related to the common oxidation states of the metals and reflects the metal-halogen bond strength. The molecular ions of the compounds Ti(OEt)_4?nox_n (n = 0, 1 or 2) fragment by loss of intact ligand radicals.     

Mass spectral fragmentation patterns of 2,5-bis(p-R2-phenyl)-(3,4)-R1-furans

The electron impact mass spectrometric fragmentation pathways for several 2,5-bis(p-R₂-phenyl)-(3,4)-R₁-furans, I, were investigated. Our investigation of the mass spectra of these compounds revealed interesting relationships between substitution pattern in the framework of I and the fragmentation patterns.     

Mass-spectrometric investigation of coordination compounds of nickel(II) with radical anions of S-alkyl-1-phenylisothiosemicarbazides

The electron-impact mass spectra of coordination compounds of nickel(II) with the general formula NiL₂, in which the radical anions [C₆H₅N -N-C(SR)=NR¹]^–, where R=CH₃ and R=H(I), R=CD₃ and R=H(II), R=C₂H₅ and R=H(III), and R=CH₃ and R=C₆H₅(IV), serve as the ligands, have been studied. In the mass spectra of compounds I–IV the peaks of the molecular ions have the highest intensity among the organometallic fragments. The initial stage of the fragmentation of [M]^+. is associated with the formation of the rearrangement ions [NiL + H]⁺, [NiL + C₆H₅]⁺, and [NiL + SR]⁺, ions, whose appearance becomes understood, if it is taken into account that the removal of one ligand is accompanied by the impairing of spins and the mass spectra of compounds I–IV is the presence of lines for the [NiL]⁺ ion in them. The dissociative ionization of compounds I–IV is strongly reminiscent of the behavior of ordinary complexes of metals with ligands of the nonradical type. The fragmentation scheme of the molecular ions under the effects of electron impact has been presented and discussed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 3, pp. 368–371, May–June, 1990.     

Mass spectral fragmentation pattern of 4,4′-bipyridines. Part II. 4,4′-oxybispyridine and 4,4′-thiobispyridine

The mass spectra of 4,4′-oxybispyridine and 4,4′-thiobispyridine are reported. In the former the base peak is due to the molecular ion and the fragmentation routes involve loss of H, CO, HCN, C₂H₂N and C_sHO from the molecular ion as well as rupture of the central bonds. In the latter the base peak is also due to the molecular ion and the fragmentation routes involve loss of H, CS, S, HCN and C₂HS as well as central bond rupture.     

Optical, Electrochemical, and Catalytic Properties of the Unsaturated Host Pd3(dppm)3(CO)2+ and Pd4(dppm)4(H)2+ 2 Clusters: An Overview

This paper presents an overview of the optical, photophysical, and photochemical properties including UV-visible and luminescence spectra in solution at 298 and 77 K, along with electrochemical, and catalytic behavior under reduction conditions (for both thermally and electrochemically assisted systems) of the tri- and tetranuclear Pd₃(dppm)₃(CO)²⁺ and Pd₄(dppm)₄(H)²⁺ ₂ clusters (dppm=bis(diphenylphosphino)methane). This review is also complemented with relevant information about their syntheses, molecular and electronic structures supported from computer modeling, EHMO and DFT calculations, and their host-guest behavior with anions and neutral molecules, in relation with their observed reactivity.     

Negative ion mass spectra of metal complexes: Secondary electron capture and CS2 elimination from nickel (ii) dithiocarbamates

Negative ion mass spectra of series of bis-(N, N-dithiocarbamato)nickel(II) complexes of formula [NiS₂C·NR¹R²]₂ (where·NR¹R² ? ·NEt₂ ·NPr₂, ·NBu₂, pyrrolidinyl, piperidyl, morpholinyl, and ·NEtPh) have been obtained by secondary electron capture. Intense molecular anions are given for all compounds, with most fragments originating from these ions. Metastable data indicate that CS₂ is eliminated from all molecular anions.     

High-spin,five-coordinate complexes of cobalt(II)with 2-substituted imidazoles

Summary A series of new five-coordinate complexes of cobalt(II) of the type, dihalotris-(2-substituted imidazole)cobalt(II), of formulae Co(2-MeIm)₃Cl₂, Co(2-EtIm)₃X₂ (X = Cl, Br, I) and Co(2-i-PrIm)₃I₂, were synthesized and characterized by elemental analyses, electrolytic conductivity, diffuse reflectance as well as by solution spectra, i.r. and far i.r. spectra, x-ray powder pattern and magnetic susceptibility measurements. The mass spectra of the complexes did not exhibit peaks due to the molecular ions, but only showed the ligand fragmentation patterns. The t.g.a. and d.t.a. measurements were also carried out for the complexes.