Dinitrogen Activation in the Gas Phase: Spectroscopic Characterization of C-N Coupling in the V3 C+ +N2 Reaction

We report on cluster-mediated C-N bond formation in the gas phase using N₂ as a nitrogen source. The V₃ C⁺ +N₂ reaction is studied by a combination of ion-trap mass spectrometry with infrared photodissociation (IRPD) spectroscopy and complemented by electronic structure calculations. The proposed reaction mechanism is spectroscopically validated by identifying the structures of the reactant and product ions. V₃ C⁺ exhibits a pyramidal structure of C₁ -symmetry. N₂ activation is initiated by adsorption in an end-on fashion at a vanadium site, followed by spontaneous cleavage of the N≡N triple bond and subsequent C-N coupling. The IRPD spectrum of the metal nitride product [NV₃ (C=N)]⁺ exhibits characteristic C=N double bond (1530 cm^-1 ) and V-N single bond (770, 541 and 522 cm^-1 ) stretching bands.

Can an Elusive Platinum(III) Oxidation State be Exposed in an Isolated Complex?

Platinum(IV) complexes are extensively studied for their activity against cancer cells as potential substitutes for the widely used platinum(II) drugs. Pt^IV complexes are kinetically inert and need to be reduced to Pt^II species to play their pharmacological action, thus acting as prodrugs. The mechanism of the reduction step inside the cell is however still largely unknown. Gas-phase activation of deprotonated platinum(IV) prodrugs was found to generate products in which platinum has a formal +3 oxidation state. IR multiple photon dissociation spectroscopy is thus used to obtain structural information helping to define the nature of both the platinum atom and the ligands. In particular, comparison of calculations at DFT, MP2 and CCSD levels with experimental results demonstrates that the localization of the radical is about equally shared between the d_xz orbital of platinum and the p_z of nitrogen on the amino group, the latter acting as a non-innocent ligand.

Structures and bonding properties of CPt2 -/0 and CPt2H-/0: Anion photoelectron spectroscopy and quantum chemical calculations

We present a combined anion photoelectron spectroscopic and quantum chemical investigation on the structures and bonding properties of CPt₂ ^-/0 and CPt₂H^-/0. The experimental vertical detachment energies of CPt₂ ^- and CPt₂H^- are measured to be 1.91 ± 0.08 and 3.54 ± 0.08 eV, respectively. CPt₂ ^- is identified as a C_2v symmetric Pt-C-Pt bent structure, and CPt₂ has a D_∞h symmetric Pt-C-Pt linear structure. Both anionic and neutral CPt₂H adopt a Pt-C-Pt-H chain-shaped structure, in which the ∠PtCPt and ∠CPtH bond angles of CPt₂H^- are larger than those of CPt₂H. The Pt-C bonds in CPt₂ ^-/0 and CPt₂H^-/0 exhibit covalent double bonding characters. The Pt=C bonds are much stronger than the C-H bond that may explain why the C atom CPt₂H^-/0 prefers to form Pt=C bonds rather than C-H bonds. It may also explain why platinum can insert into the C-H bond to activate the C-H bond as reported in the literature.

Elusive Intermediates in the Breakdown Reactivity Patterns of Prodrug Platinum(IV) Complexes

Kinetically inert platinum(IV) complexes are receiving growing attention as promising candidates in the effort to develop safe and valid alternatives to classical square-planar Pt(II) complexes currently used in antineoplastic therapy. Their antiproliferative activity requires intracellular Pt(IV)-Pt(II) reduction (activation by reduction). In the present work, a set of five Pt(IV) complexes has been assayed using mass spectrometry-based techniques, i.e., collision-induced dissociation (CID), and IR multiple photon dissociation (IRMPD) spectroscopy, together with ab initio theoretical investigations. Breakdown and reduction mechanisms are observed that lead to Pt(II) species. Evidence is found for typically transient Pt(III) intermediates along the dissociation paths of isolated, negatively charged (electron-rich) Pt(IV) prodrug complexes.

Liberation of three dihydrogens from two ethene molecules as mediated by the tantalum nitride anion cluster Ta3N2− at room temperature

The full dehydrogenation of C₂H₄ by gas-phase anions Ta₃N₂⁻ as well as the structure and reactivity of the M–N–C cluster is reported for the first time.

Effect of adduct formation with molecular nitrogen on the measured collisional cross sections of transition metal-1,10-phenanthroline complexes in traveling wave ion-mobility spectrometry: N2 is not always an "inert" buffer gas

The number of separations and analyses of molecular species using traveling wave ion-mobility spectrometry-mass spectrometry (TWIMS-MS) is increasing, including those extending the technique to analytes containing metal atoms. A critical aspect of such applications of TWIMS-MS is the validity of the collisional cross sections (CCSs) measured and whether they can be accurately calibrated against other ion-mobility spectrometry (IMS) techniques. Many metal containing species have potential reactivity toward molecular nitrogen, which is present in high concentration in the typical Synapt-G2 TWIMS cell. Here, we analyze the effect of nitrogen on the drift time of a series of cationic 1,10-phenanthroline complexes of the late transition metals, [(phen)M](+), (M = Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, and Hg) in order to understand potential deviations from expected drift time behaviors. These metal complexes were chosen for their metal open-coordination site and lack of rotameric species. The target species were generated via electrospray ionization (ESI), analyzed using TWIMS in N2 drift gas, and the observed drift time trends compared. Theoretically derived CCSs for all species (via both the projection approximation and trajectory method) were also compared. The results show that, indeed, for metal containing species in this size regime, reaction with molecular nitrogen has a dramatic effect on measured drift times and must not be ignored when comparing and interpreting TWIMS arrival time distributions. Density-functional theory (DFT) calculations are employed to analyze the periodic differences due to the metal's interaction with nitrogen (and background water) in detail.