36811-90-2Relevant academic research and scientific papers
Determination of Gas-Phase Ligand Binding Energies to Mg+ by FTMS Techniques
Operti, Lorenza,Tews, Edward C.,Freiser, Ben S.
, p. 3847 - 3853 (2007/10/02)
Relative and absolute gas-phase binding energies of 12 organic molecules to Mg+ have been determined by four different methods involving Fourier transform mass spectrometry (FTMS).Mg+ is generated in the FTMS cell by pulsed laser ionization and reacts with the organic compounds to give MgL+ either by direct condensation or by a fast two-step displacememt reaction.The equilibrium constant (Keq) and the absolute rate constants (kf and kr) are obtained for the ligand exchange reaction: MgL+ + L' MgL'+ + L.The equilibrium constants are converted to free-energy differences and relative binding energies are calculated to give the Do(Mg+-L) scale.Entropy changes are assumed to be small and they are discussed in detail.The absolute gas-phase binding energies Do(Mg+-MeOH) and Do(Mg+-Me2CO) are assigned from equilibrium and photodissociation experiments to be 61 +/- 5 and 67 +/- 5 kcal/mol, respectively.The correlation of results from the different methods give a scale of relative and absolute bond energies to Mg+ for the 12 organic molecules examined.The results for Mg+ are compared with previously reported results on H+, CpNi+, Al+, Mn+, and Cu+.These comparisons show for this limited study on oxygen bases that Mg+ is a softer acid than H+ and Al+, very similar in acidity to Mn+ and Cu+, and a harder acid than CpNi+.
