Investigation of metal complex coordination structure using collision-induced dissociation and ion–molecule reactions in a quadrupole ion trap mass spectrometer

Using a modified quadrupole ion trap mass spectrometer, a series of metal complex ions have been reacted with acetonitrile in the gas phase. Careful control of the coordination number and the type of coordinating functionality in diethylenetriamine-substituted ligands enable the effects of the coordination sphere on metal complex reactivity to be examined. The association reaction kinetics of acetonitrile with these pentacoordinate complexes are followed in order to obtain information about the starting complexes and the reaction dynamics. The kinetics and thermodynamics of acetonitrile addition to the metal complex ions are strongly affected by the chemical environment around the metal center such that significant differences in reactivity are observed for Co(II) and Cu(II) complexes with various coordination spheres. When thiophene, furan, or benzene moieties are present in the coordination sphere of the complex, addition of two acetonitrile molecules is readily observed. In contrast, ligands with better donors react mainly to add one acetonitrile molecule. Among the ligands with good donors, a clear trend in reactivity is observed in which complexes with nitrogen-containing ligands are the least reactive, sulfur-containing complexes are more reactive, and oxygen-containing complexes are the most reactive. In general, equilibrium and reaction rate constants seem to be consistent with the hard and soft acid and base (HSAB) principle. Interestingly, the presence of certain groups (e.g., pyridine and imidazole) in the coordination sphere clearly can change the acid character of the metal as seen by their effect on the binding properties of other functional groups in the same ligand. Finally, we conclude that because complexes with different coordination spheres react to noticeably different extents, ion-molecule (I-M) reactions may be potentially useful for obtaining coordination structure information for transition metal complexes. Along with collision-induced dissociation (CID), I-M reactions can also be tools that provide structural information in a mass spectrometric experiment [5][6][7]. I-M reactions are advantageous as structural probes for several reasons. They are highly selective, efficient, and fast. They are also relatively simple, and there are numerous possible combinations of ions and neutrals that can be analytically useful [7][8][9]. Finally, I-M reactions are inherently softer than CID methods, which require "heating up" ions to induce dissociation.CID of metal complexes has been studied by several investigators but mainly in order to determine the binding strengths of ligands to monovalent metals [10]. Studying the dissociation dynamics of metal complex ions from a structural elucidation standpoint, however, has received less attention. Brodbelt and co-workers have studied the dissociation patterns of polyether, crown ether, and polypyridyl complexes of singly- [11,12] and doubly-charged transition metal ions [13,14]. Details about the effect of ligand flexibility and metal type on dissociation...

Section: Metal Complexes That Add Two Acetonitrilesmentioning

confidence: 94%

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confidence: 99%

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confidence: 99%

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Gas-phase oon-molecule reactions of transition metal complexes: The effect of different coordination spheres on complex reactivity

Combariza

Vachet

2002

“…Ion-molecule reactions in the gas-phase have been used extensively to gain information on the chemistry and reactivity of metals in coordination complexes, as well as the structures of these metal-ligand complexes [25][26][27][28][29][30][31][32][33][34]. In our studies, D 2 O and adventitious CD 3 OD were used as neutral reaction partners with several of the more abundant ions in Figure 1c to assess the degree of coordinative unsaturation of the uranyl in each of the selected species.…”

Section: Ion-molecule Reactions In the Gas-phase With D 2 O And Cd 3 mentioning

confidence: 99%

Ions generated from uranyl nitrate solutions by electrospray ionization (ESI) and detected with fourier transform ion-cyclotron resonance (FT-ICR) mass spectrometry

Pasilis

Somogyi

Herrmann

et al. 2006

Electrospray ionization (ESI) of uranyl nitrate solutions generates a wide variety of positively and negatively charged ions, including complex adducts of uranyl ions with methoxy, hydroxy, and nitrate ligands. In the positive ion mode, ions detected by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry are sensitive to instrumental tuning parameters such as quadrupole operating frequency and trapping time. Positive ions correspond to oligomeric uranyl nitrate species that can be characterized as having a general formula of

“…To gain a better understanding of the intrinsic interactions between different uranyl species and solvent, we have begun an investigation of uranyl-anion complexes in the gas phase using ion-trap mass spectrometry (IT-MS). Several recent reports have demonstrated that intrinsic metal and metal complex chemistry can be investigated by the (controlled) addition of reagent gas to an ion trap [12][13][14][15][16][17][18][19][20][21][22], or by way of the presence of H 2 O and other small molecule contaminants within the He bath gas used to collisionally cool ions and improve trapping efficiency [23][24][25]. The reactions of uranium ions in the gas phase have been the subject of several earlier investigations.…”

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Elucidation of the collision induced dissociation pathways of water and alcohol coordinated complexes containing the uranyl cation

Stipdonk

Anbalagan

Chien

et al. 2003

Multiple-stage tandem mass spectrometry was used to characterize the dissociation pathways for complexes composed of (1) the uranyl ion, (2) nitrate or hydroxide, and (3) water or alcohol. The complex ions were derived from electrospray ionization (ESI) ϩ . The abundance of the species was greater than expected based on previous experimental measurements of the (slow) hydration rate for UO 2 ϩ when stored in the ion trap. To account for the production of the hydrated product, a reductive elimination reaction involving reactive collisions with water in the ion trap is proposed. T he speciation and reactivity of uranium is a topic of sustained interest because species-dependent chemistry [1] controls processes ranging from nuclear fuel processing [2] to mobility and fate in the geologic subsurface [3,4]. The solution chemistry of uranium is dominated by the uranyl dication, UO 2 2ϩ , which is known to form complexes with a range of ligands [1]. Specific interaction with solvent will significantly influence the physico-chemical behavior of the uranyl ion and its complexes, and this has motivated investigations of complex composition and stability using infrared spectroscopy and extended X-ray absorption fine structure [5][6][7][8][9][10][11]. Unfortunately, explicit control over the interactions of solvent and nonsolvent ligands with the uranyl ion is difficult, which makes the study of species-dependent uranium behavior complicated. To gain a better understanding of the intrinsic interactions between different uranyl species and solvent, we have begun an investigation of uranyl-anion complexes in the gas phase using ion-trap mass spectrometry (IT-MS). Several recent reports have demonstrated that intrinsic metal and metal complex chemistry can be investigated by the (controlled) addition of reagent gas to an ion trap [12][13][14][15][16][17][18][19][20][21][22], or by way of the presence of H 2 O and other small molecule contaminants within the He bath gas used to collisionally cool ions and improve trapping efficiency [23][24][25]. The reactions of uranium ions in the gas phase have been the subject of several earlier investigations. Studies by , and by Schwarz and coworkers [30] have probed the reactions between U ϩ and UO ϩ and organic compounds such as alkanes and alcohols. Armentrout and Beauchamp [31] investigated the oxidation of U ϩ using small molecules such as O 2 , CO, CO 2 , COS, and