Microsolvated and Chelated Butylzinc Cations: Formation, Relative Stability, and Unimolecular Gas‐Phase Chemistry

Abstract

Solutions of butylzinc iodide in tetrahydrofuran, acetonitrile, and N,N-dimethylformamide were analyzed by electrospray ionization mass spectrometry. In all cases, microsolvated butylzinc cations [ZnBu(solvent)(n)](+), n=1-3, were detected. The parallel observation of the butylzincate anion [ZnBuI(2)](-) suggests that these ions result from disproportionation of neutral butylzinc iodide in solution. In the presence of simple bidentate ligands (1,2-dimethoxyethane, N,N-dimethyl-2-methoxyethylamine, and N,N,N',N'-tetramethylethylenediamine), chelate complexes of the type [ZnBu(ligand)](+) form quite readily. The relative stabilities of these complexes were probed by competition experiments and analysis of their unimolecular gas-phase reactivity. Fragmentation of mass-selected [ZnBu(ligand)](+) leads to the elimination of butene and formation of [ZnH(ligand)](+). In marked contrast, the microsolvated cations [ZnBu(solvent)(n)](+) lose the attached solvent molecules upon gas-phase fragmentation to produce bare [ZnBu](+), which subsequently dissociates into [C(4)H(9)](+) and Zn. This difference in reactivity resembles the situation in organozinc solution chemistry, in which chelating ligands are needed to activate dialkylzinc compounds for the nucleophilic addition to aldehydes.

Association and Dissociation of Grignard Reagents RMgCl and Their Turbo Variant RMgCl⋅LiCl

“…As reported previously, the inferred organomagnesium cations have so far eluded detection by ESI mass spectrometry because they apparently undergo extremely fast protolysis reactions with traces of protic solvents remaining in the ionization source . We have, however, previously observed analogous or similar intact organometallic cations in solutions of organozinc and ‐indium halides …”

Gas-phase study of new organozinc reagents by IRMPD-spectroscopy, computational modelling and tandem-MS

“…19 DMF and TMEDA complex ions of alkylzinc compounds obtained from the corresponding alkylzinc iodides prepared in DMF have been detected and characterized in the gas phase using electrospray ionization 21,22 (ESI) tandem-MS experiments. 15,[23][24][25][26] When functionalized alkylzinc iodides are sprayed from DMF solution the derived solvated complex cations are found in the gas phase with significant abundance which can be used as precursor ions for further tandem-MS examinations. Exact ion masses of precursor and product ions were determined using a hybrid linear ion trap/Orbitrap mass spectrometer, [27][28][29] allowing reliable structure assignment and interpretation of the fragmentation pattern generated upon collision induced dissociation (CID).…”

Handling considerations for the mass spectrometry of reactive organometallic compounds

“…55 The Koszinowski group has reported the use of a gas-tight syringe, N 2 as a sheath gas, and a fused-silica tube (0.10 mm inner diameter) to analyze air-sensitive compounds. [56][57][58][59][60][61] The group recommended flushing the inlet system with dry solvent extensively before adding the organometallic sample.…”