Gas-Phase Unimolecular Reactions of Pallada- and Nickelalactone Anions

Abstract

Electrospray ionization in combination with multistage mass spectrometry experiments in a linear ion trap mass spectrometer was used to generate and study the gasphase ion chemistry of the metallalactones [(CH 3 CO 2 )Ni-(CH 2 CO 2 )] − (m/z 175, 5a) and [(CH 3 CO 2 )Pd(CH 2 CO 2 )] − (m/z 223, 5b). Low-energy collision-induced dissociation (CID) resulted in decarboxylation to produce novel organometallic ions at m/z 131 (Ni) and m/z 179 (Pd). Isotope labeling experiments, bimolecular gas-phase reactions with allyl iodide, and DFT calculations reveal that decarboxylation primarily occurs from the acetato ligand to yield ions of the form [(CH 3 )M(CH 2 CO 2 )] − (M = Pd, Ni). Further CID experiments on [(CH 3 )M(CH 2 CO 2 )] − together with DFT calculations highlight the following. (1) Both palladium and nickel can facilitate C−C bond formation, with elimination of ethylene being observed.(2) The mechanism for formation of ethylene from [(CH 3 )M(CH 2 CO 2 )] − is inherently different for M = Pd versus M = Ni. Elimination of ethylene is competitive with further decarboxylation in the case of nickel, and nickel remains in the 2+ oxidation state throughout. In contrast, the palladium complex is reduced to palladium(0) upon C−C bond formation and undergoes a second decarboxylation before ethylene is released. Finally, the products of the ion−molecule reactions of [(CH 3 )Pd(CH 2 CO 2 )] − (7b) with allyl iodide provide evidence for the formation of the Pd(IV) intermediate [(CH 3 )(I)-(CH 2 CHCH 2 )Pd(CH 2 CO 2 )] − , which decomposes via a range of processes, including losses of iodide, propionate, allyl, and methyl radicals and reductive elimination of butane and methyl iodide.

Gas-Phase Reactions of the Rhenium Oxide Anions, [ReOx]− (x = 2–4) with the Neutral Organic Substrates Methane, Ethene, Methanol and Acetic Acid

“…Gas-phase reactivity of these primary product ions Figure S1). This fragmentation chemistry is related to the extrusion of alkenes or aldehydes from rhenaoxetane cations (Scheme 1), [39][40][41] suggesting a metallalactone structure 67 Figure S3) (9). The bimolecular reactivity observed for m/z 251 is, however, more consistent with the known gas-phase reactivity of transitionmetal complexes containing hydroxide ligands rather than those containing hydride ligands.…”

Anion Recognition by Uranyl–Salophen Derivatives as Probed by Infrared Multiple Photon Dissociation Spectroscopy and Ab Initio Modeling

“…In a recent example, twofold loss of CO 2 from alkali metal and silver oxalates has been discovered and exploited to generate bare metal anions,30, 31 whereas in another very interesting application a decarboxylation reaction promoted by CID resulted in the formation of novel organometallic ions 32. 33…”

Organometallic Gas‐phase Ion Chemistry and Catalysis: Insights Into the Use of Metal Catalysts to Promote Selectivity in the Reactions of Carboxylic Acids and Their Derivatives

“…Reaction of the methyl palladalactone [(Me)Pd(CH 2 CO 2 )] − with allyl iodide proceeds via the formation of an observable Pd (IV) intermediate, [(Me)(I)(CH 2 CHCH 2 )Pd(CH 2 CO 2 )] − (Equation 27) (Vikse et al, 2012) which also decomposes through allylation via RE (forming ions at m/z 291 [(I)Pd(CH 2 CO 2 )] − Equation 28, or m/z 127, I − Equation 29); homocoupling via RE of propionate (Equation 30). Another major side-product is formed via iodide atom abstraction to form m/z 306 [(Me)(I)Pd (CH 2 CO 2 )] − (Equation 31).…”

“…)(I)(CH2CHCH2)Pd(CH2CO2)] − (eq. 27),(Vikse et al, 2012) which also decomposes through: allylation via RE (forming ions at m/z 291 [(I)Pd(CH2CO2)] − eq. 28, or m/z 127, I − eq.…”