Mass spectra of organometallic compounds—VII; Organonitrogen derivatives of metal carbonyls

The positive-ion mass spectra of the following organonitrogen derivatives of metal carbonyls are discussed: (i) The compounds NC₅H₄CH₂Fe(CO)₂C₅H₅, NC₅H₄CH₂COMo(CO)₂C₅H₅, NC₅H₄CH₂W(CO)₃C₅H₅, NC₅H₄CH₂COMn(CO)₄, C₅H₁₀NCH₂CH₂Fe(CO)₂C₅H₅, (CH₃)₂NCH₂CH₂COFeCOC₅H₅ and (CH₃)₂NCH₂CH₂COMn(CO)₄ obtained from metal carbonyl anions and haloalkylamines, (ii) The isocyanate derivative C₅H₅Mo(CO)₃CH₂NCO; (iii) The arylazomolybdenum derivatives RN₂Mo(CO)₂C₅H₅ (R ? phenyl, p-tolyl, or p-anisyl); (iv) The compound (C₆H₅N)₂COFe₂(CO)₆ obtained from Fe₃(CO)₁₂ and phenyl isocyanate; (v) The N,N,N′,N′-tetramethylethylenediamine complex (CH₃)₂NCH₂CH₂N(CH₃)₂W(CO)₄. Further examples of eliminations of hydrogen, CO, and C₂H₂ fragments were noted. In addition evidence for the following more unusual processes was obtained: (i) Elimination of HCN fragments from the ions [NC₅H₄CH₂MC₅H₅]⁺ to give the ions [(C₅H₅)₂M]⁺ (M ? Fe, Mo and W); (ii) Conversion of C₅H₅Mo(CO)₃CH₂NCO to C₅H₅Mo(CO)₂CH₂NCO within the mass spectrometer; (iii) Elimination of N₂ from [RN₂MoC₅H₅]⁺ to give [RMoC₅H₅]⁺; (iv) Novel eliminations of HNCO, FeNCO, and C₆H₅NC fragments in the mass spectrum of (C₆H₅N)₂COFe₂(CO)₆; (v) Facile dehydrogenation of the N,N,N′,-N′-tetramethylethylenediamine ligand in the complex (CH₃)₂NCH₂CH₂N(CH₃)₂W(CO)₄.     

Electron-impact studies of organometallic molecules—VIII: Some transition metal derivatives of polyfluorobenzenes

The mass spectra of (π-C₅H₅)₂Ti(C₆F₅)X (X ? Cl and C₆F₅), C₆F₅Re(CO)₅, R_fFe(CO)₂(π-C₅H₅) (R_f ? C₆F₅, 4-HC₆F₄, and three isomeric H₂C₆F₃), and C₆F₅Ru(CO)₂(π-C₅H₅) are compared to those of C₆F₅X (X ? F, Cl, Br, I) and the three isomers of C₆F₄H₂. Significant differences occur, apparently depending on the relative thermodynamic stabilities of the various fragments which may be formed. Comparison of the mass spectra of pentafluorophenyl- and pentafluorobicyclo[2.2.0]hexa-2,5-dien-2-yl-Re(CO)₅ show that similar ions are produced by both complexes, perhaps because of thermal isomerisation before ionisation.     

Mass spectra of organometallic compounds–XII: Tetraphenylcyclobutadiene derivatives

The mass spectra of the tetraphenylcyclobutadiene complexes (C₆H₅)₄C₄Fe(CO)₃, C₅H₅CoC₄(C₆H₅)₄ and C₉H₇CoC₄(C₄H₅)₄ are reported. Evidence is presented for the loss of the tetraphenylcyclobutadiene ring by a two-step sequence involving successive losses of two (C₆H₅)₂C₂ fragments. Significant differences are observed in the fragmentations of the monopositive and dipositive molecular ions of C₉H₇CoC₄(C₆H₅)₄.     

Mass spectra of organometallic compounds—IX: Compounds with metal-metal bonds

The mass spectra of the following compounds have been investigated: (i) The organotin derivatives (CH₃)₃SnMo(CO)₃C₅H₅ and (CH₃)₃SnNCW(CO)₅; (ii) The mercury derivatives Hg[Mn(CO)₅]₂, Hg[Co(CO)₄]₂, Hg[Mo(CO)₃C₅H₅]₂ and ClHgMo(CO)₃C₅H₅; (iii) The polynuclear cyclopentadienyl metal derivatives [C₅H₅Ru(CO)₂]₂, [C₅H₅Cr(CO)₃]₂, [C₅H₅Cr(NO)₂]₂ and [C₅H₅Fe-CO]₄; (iv) The trinuclear cobalt carbonyl derivatives YCCo₃(CO)₉ (Y = Cl and CH₃); (v) The binuclear triene-iron carbonyl derivatives C₄H₄Fe₂(CO)₆ and C₈H₁₀Fe₂(CO)₆. The mass spectra of the trimethyltin derivatives exhibited stepwise loss of methyl groups as well as of carbonyl groups. The mass spectra of the mercury derivatives exhibited the facile loss of mercury. The mass spectrum of [C₅H₅Cr(CO)₃]₂ indicated a very weak chromium-chromium bond since it exhibited no ion containing two chromium atoms. The mass spectrum of the nitrosyl derivative [C₅H₅Cr(NO)₂]₂ exhibited the stepwise loss of its four nitrosyl groups. The mass spectrum of [C₅H₅FeCO]₄ was rather complex and exhibited a variety of unusual processes including eliminations of neutral Fe and C₅H₅Fe fragments. Unusual ions observed in the mass spectrum of CH₃CCo₃(CO)₉ include the bare polymetallic ions [Co_n]⁺ (n = 3 and 2). Many examples of the elimination of neutral CO, C₂H₂ and H₂ fragments were noted in this work.     

Electron-impact studies of organometallic molecules—VI. Some transition metal derivatives of alicyclic fluorocarbons

The mass spectra of a series of alicyclic fluorocarbon complexes of manganese, rhenium, iron and ruthenium are described and discussed. It is shown that the breakdown of these complexes after ionization depends on the nature of the metal, and of the other groups attached to the metal. Effects due to elimination of metal halides, formation of metal fluoride ions, and ligand transfer reactions are found, and result in significant differences in the fragmentation patterns of the complexes from those of the parent fluorocarbons.     

Mass spectra of organometallic compounds: XIV—Some monometallic olefing manganese tricarbonyl derivatives

The metastable ion supported fragmentation process in the mass spectra of the cyclohexadienyl derivative C₆H₇Mn(CO)₃, the cycloheptadienyl derivative C₇H₉Mn(CO)₃, the 1,2,3,4,5-and 1,2,3,5,6-pentahaptocyclootadienyl derivatives C₈H₁₁Mn(CO)₃, the cyclooctatrienyl derivative C₈H₉Mn(CO)₃ and the substituted cyclopentadienyl derivative (CH₃)₂NCH₂C₅H₄Mn(CO)₃, are described. Losses of carbonyl groups, generally stepwise, from the molecular ions to give the corresponding [M – 3CO]⁺· ions are first observed. Further fragmentation of the carbonyl-free [M – 3CO]⁺· ions can involve a variety of processes such as the following: (a) elimination of a neutral manganese atom to give a hydrocarbon fragment; (b) elimination of a neutral hydrocarbon fragment to give an [MnH]⁺· ion; (c) dehydrogenation; (d) elimination of a 2-carbon C₂H₂ or C₂H₄ fragment; (e) elimination of a C₃H₄ or C₃H₆ fragment as a neutral species when it is bridging two carbon atoms bonded to manganese, as in C₈H₉Mn(CO)₃ and 1,2,3,4,5,h⁵-C₈H₁₁Mn(CO)₃, respectively. Fragmentation of the [M – 3CO]⁺· ion in (CH₃)₂NCH₂C₅H₄Mn(CO)₃ presents the following additional features: (a) elimination of C₆H₆ with a nitrogen shift from carbon to manganese; (b) elimination of a neutral dimethylamino fragment to give [C₆H₆Mn]⁺·, which then loses neutral C₆H₆, C₆H₅ or Mn fragments and thus is formulated tentatively as [(fulvene)Mn]⁺· or [C₆H₅MnH]⁺· rather than [(benzene)Mn]⁺·.     

Mass spectra of organometallic compounds–XI: Pyrrolyl,indenyl and fluorenyl derivatives of manganese carbonyl

The positive ion mass spectra of the π-pyrrolyl derivatives C₄H₄NMn(CO)₂L (L = (C₆H₅)₃E or CO; E = P, As, or Sb), the π-indenyl derivatives C₉H₇Mn(CO)₂L (L = (C₆H₅)₃E or CO; E = P, As, or Sb) and the π-fluorenyl derivatives C₁₃H₉Mn(CO)₂L (L = (C₆H₅)₃P or CO) have been investigated. The relative tendencies of ions of the type [QMnE(C₆H₅)₃]⁺ (Q = π-pyrrolyl, π-indenyl, or π-fluorenyl; E = P, As, or Sb) to fragment by losses of the Q ring system and the (C₆H₅)₃E ligand are compared. Phenyl transfers from phosphorus, arsenic, or antimony to manganese to form relatively high abundances of [C₆H₅Mn]⁺ are also observed. Other processes typical of metal carbonyl derivatives (CO losses), aromatic derivatives (C₂H₂ eliminations) and (C₆H₅)₃E derivatives (phenyl losses, conversion of [(C₆H₅)₃E]⁺ directly to [C₆H₅E]⁺, and formation of [C₁₂H₈E]⁺ 9-heterofluorenyl ions) are observed in these mass spectra and are supported in many cases by the presence of appropriate metastable ions.     

Electron-impact studies of organometallic molecules—X. Some simple transition metal fluorocarbon complexes

The mass spectra of several fluoroalkyl, fluoroalkenyl and fluoroacyl complexes of manganese, rhenium, iron and ruthenium carbonyls are described. After loss of carbonyl groups, fluoroalkyl compounds eliminate an olefin, with formation of metal halide species. A trifluorovinyl complex shows a novel elimination of a carbon atom to give an ion postulated to be a difluorocarbene-metal fluoride; the occurrence of difluorocarbene-metal ions in the spectra of some related complexes is also discussed. The spectra of the acyl complexes show little evidence of elimination of the acyl carbonyl group; the major process is fission of the CO? R_f bond with loss of a fluoroalkyl radical and formation of the cationic metal carbonyl, e.g. π-C₅H₅M(CO)₃⁺ (M ? Fe or Ru). The relevance of thermal or photochemical model reactions to processes occurring in the mass spectrometer is discussed.     

Mass spectrometry of onium compounds—II. Carnitine and O-acyl derivatives

Carnitine and its O-acyl derivatives undergo two major pyrolytic reactions in the mass spectrometer. Firstly elimination of water from carnitine or acid from acylcarnitine takes place followed by intramolecular displacement and formation of crotonyl lactone and trimethylamine. Secondly intramolecular displacement occurs with formation of a substituted γ-lactone and trimethylamine. For the lower acid derivatives only the elimination pathway is important. For carnitine and higher derivatives both processes are important. The electron induced fragmentations of the major pyrolysis products are relatively simple. The most important pathways for the major components are discussed. The pyrolytic composition and mode of fragmentation are characteristic and can be used for identification purposes.     

Mass spectrometry of hop compounds—II: Mass spectra of related oxygen heterocyclic compounds

Mass spectra have been determined of a number of phloroglucinol derivatives and closely-related compounds encountered in chemical studies of hop components. Initial fission involving acyl, alkyl or alkenyl side-chains gives predominantly even-electron ions which then fragment their oxygen heterocyclic rings by elimination of neutral molecules, whilst gem-dialkenyl centres show preference for loss of an alkenyl group. The fragment ions induced by electron-impact may be correlated to a useful extent with molecular structure.     

Fragmentation and rearrangement processes in the mass spectra of perhalogenoaromatic compounds—VIII: Fluoroaromatic heterocyclic derivatives of group IV

The metastable ion supported fragmentations and fluorine transfer rearrangements of a series of fluoroaromatic heterocyclic derivatives of silicon, germanium and tin are reported. Of particular interest is the unique loss of neutral SiF₄ from the parent ion of (C₁₂F₈)Si yielding the [C₂₄F₁₂]⁺˙ ion. These and similar rearrangements are discussed and structures are proposed for some of the ions observed. The general case of cyclic rearrangement intermediates prior to the loss of neutral metal fluorides from perfluoroaromatic derivatives is discussed. Losses of neutral metal fluorides from the parent ions appear to involve a species with increased co-ordination number about the central atom as an intermediate. In addition to (C₁₂F₈)₂M, the following compound types were studied: (C₆H₅)₂Ge(C₁₂F₈), (C₁₂F₈S)₂M and R₄Sn₂(C₆F₄)₂ (where M = a Group IV metal and R = CH₃ or C₆H₅).     

Mass spectrometry of hop compounds—III. Mass spectra of substituted 1,3-cyclopentanediones derived from hop constituents

The mass spectra of isohumulones (IV, V), tetrahydroisocohumulones (VI, VII), tetrahydroisohumulones (VIII) neohydroisocohumulones (XI, XII) cohumulinic acid (III), lupuloxinic acid (XV), humulinone (XIV) and related compounds are described. Ions which appear to be diagnostic for particular structures are discussed.     

Mass spectra of liquid crystals. III—phenylpyrimidine derivatives

The 70 eV electron impact mass spectra of 34 1-phenyl-2,5-pyrimidine derivatives are presented. Based on the observed mass shifts by the various substituents, the nature of the main fragment ions is rationalized.     

Electron-impact studies of organometallic molecules—VII. Some transition metal complexes derived from 3,3,3-trifluoroprop-1-yne

The mass spectra of ten complexes derived from 3,3,3-trifluoroprop-1-yne, namely (CF₃C?CH)CO₂(CO)₆, (CF₃C?CH) [π? C₅H₅Ni]₂, (CF₃C?CH)₃Co₂(CO)₄, CF₃CH₂C[Co(CO)₃]₃, are discussed in terms of their structures. The major processes observed can be satisfactorily explained in terms of (i) loss of carbonyl groups, if present; (ii) loss of one fluorine atom from the parention (iii) elimination of neutral metal fluorides, with ligand transfer reactions in the case of the iron complexes; (iv) elimination of neutral fluorocarbon molecules.     

Mass spectrometry of onium compounds—XVII: Anilinium carboxylates. orthoeffect in anthranilic acid derivatives

The N,N,N-trimethylanilinium carboxylates are transmethylated to the isomeric esters before evaporation in the mass spectrometer. Pyroltic reactions and electron-impact fragmentations are elucidated by means of deuterio analogues. The orthoisomer behaves anomalously in that initial expulsion of a methyl radical is important. Deuteration has shown this reaction to take place along two distinct routes, either from the nitrogen or from the ester.     

Mass spectra of organoboron compounds—II: The mass spectra of triphenylboroxine and its precursor phenylboronic acid

The mass spectrometric fragmentation pattern of phenylboronic acid has been determined and that of triphenylboroxine redetermined and extended, and the origin of some high abundance ions, previously unassigned, have been identified.     

Mass spectra of organoarsenic compounds—II: Electron-impact-induced fragmentation of 2-substituted-1,2,2-dioxarsenanes

The electron-impact-induced fragmentation of 2-substituted 1,3,2-dioxarsenanes has been studied. The main fragmentation modes have been determined with the use of high resolution mass measurements and by application of the metastable defocusing technique. The predominant fragmentation for the 2-alkyl-1,3,2-dioxarsenanes proceeds via the loss of the 2-substituent from the molecular ion. In the case of 2-phenyl-1,3,2-dioxarsenanes elimination of the phenyl group competes with the formation of a C₆H₅ As ion as well as loss of aldehyde from the molecular ions.     

Fluorocarbon metal compounds—role models in organotransition metal chemistry

Early studies on organo-transition metal complexes with fluorocarbon ligands are reviewed in a historical context in relation to the renaissance of organometallic chemistry which followed the discovery of ferrocene.     

Fragmentation and rearrangement processes in the mass spectra of perhalogeno-aromatic compounds—VII. Pentafluorophenyl derivatives of nitrogen

The mass spectra of several perfluoroaromatic nitrogen compounds, including primary and secondary amines, diamines, nitriles, hydrazines, azines and azo compounds, are presented. Fragmentation patterns of these compounds are described and the data are discussed in terms of comparisons amongst perfluoroaromatic nitrogen compounds, and with reference to the hydrogen substituted analogs, or to oxygen and sulfur analogs of a particular compound.     

Electron-impact studies of organometallic molecules—XI:. Some polyfluoroaromatic derivatives of ferrocene

The mass spectra of eight ferrocene derivatives containing C₆F₅, C₆F₅CO, C₆F₅CH₂ or p-CH₃OC₆F₄ groups attached to one or both cyclopentadienyl rings are described and discussed. In addition to features normally found in the mass spectra of ferrocene compounds, the migration of fluorine to the iron atom leads to the formation of ions such as [C₅H₄COFeF]⁺. The elimination of neutral FeF₂ or C₅H₅FeF molecules is also found.