Structural analysis of organometallic compounds with soft ionization mass spectrometry

Abstract

The analysis of organometallic compounds with mass spectrometry has some special features in comparison with organic and bioorganic compounds. The first step is the choice of a suitable ionization technique, where the electrospray ionization is certainly the best possibility for most classes of organometallic compounds and metal complexes. Some ionization mechanisms of organometallic compounds are comparable to organic molecules, such as protonation/deprotonation, and adduct formation with sodium or potassium ions; however, in many cases, different mechanisms and their combinations complicate the spectra interpretation. Organometallics frequently undergo various types of adduct and polymerization reactions that result in significantly higher masses observed in the spectra in comparison to molecular weights of studied compounds. Metal elements typically have more natural isotopes than common organic elements, which cause characteristic wide distributions of isotopic peaks; for example, tin has ten natural isotopes. The isotopic pattern can be used for the identification of the type and number of metal elements in particular ions. The ionization and fragmentation behavior also depend on the type of metal atom; therefore, our discussion of mass spectra interpretation is divided according to the different type of organometallic compounds. Among various types of mass spectrometers available on the market, trap-based analyzers (linear or spherical ion-traps, Orbitrap) are suitable to study complex fragmentation pathways of organometallic ions and their adducts, whereas high-resolution and high-mass accuracy analyzers (time-of-flight-based analyzers, or Fourier transform-based analyzers-Orbitrap or ion cyclotron resonance mass spectrometers) provide accurate masses applicable for the determination of the elemental composition of individual ions.

Electrospray Ionization Mass Spectrometry of Palladium(II) Quinolinylaminophosphonate Complexes

“…The most abundant acetonitrile adducts are [(M + Na) + CH 3 CNNaX -HX] + at m/z 516 (for 1) and m/z 572 (for 3) as well as [(M + Na) + CH 3 CN -NaX -HX -PhN=CHX + at m/z 413 (for 2) with relative intensity of 61%, 35% , and 28%, respectively (Table S1) + are probably obtained from clusters formed by addition of one organophosphorus ligand molecule to the sodium adduct of the molecular ion. It is interesting to note that a variety of aggregate ions including dimer and trimer species have been observed in the ESI-MS experiments of some palladium(II) and platinum(II) complexes derived from ethylenediamine, amidine, and azetidinone ligands [21,35,36]. As a general remark, it should be pointed out that by increasing the source collision energy, the cluster ions as well as the molecular ions became less abundant and the intensity of the ions obtained by complex fragmentation increased ( Figure S2) [37].…”

“…This is a soft ionization technique, which has been widely used in the structural analysis of nonvolatile and thermally labile species as large biomolecules and various coordination metal complexes [18][19][20][21][22]. ESI-MS enables detection and mass determination of large biomolecules such as proteins and provides investigation of the metallated biomolecules [18,[23][24][25].…”

The application of electrospray ionization mass spectrometry to homogeneous catalysis

“…These methods contribute significantly to the utility of mass spectrometry as a mechanistic tool in organometallic chemistry, but this review will focus solely on reactions occurring in homogeneous solutions. For an overview of gas-phase studies of organometallic complexes see the excellent reviews by Traeger [25], Plattner [26], Holčapek [27] and Schröder [28]. New advances in the field of ion spectroscopy deserve mention; namely, the detailed structural characterization of reactive intermediates within a mass spectrometer [29].…”

Mass spectrometry for the detection of potential psychiatric biomarkers

“…In this case, ESI is the ionization mode preferred for the characterization of biomolecules, ionic and very labile organic and organometallic compounds though LC-MALDI-MS is also an eventuality [55, 56]. Bottom-up proteomics represents the case where samples are first digested to generate peptides which can then be analyzed by mass spectrometry while top-down proteomics designate a method where the mass of the entire protein is being measured by a mass spectrometer followed by its sequencing.…”