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The gas-phase reactivity of La2+ with Q-Q linear alkanes is investigated and compared to the analogous reactions of La+. La2+ is unreactive with methane and ethane but reacts with propane and butane to give dehydrogenation, alkane loss, and for butane charge-splitting reaction products. Interestingly, charge transfer is not observed in agreement with a simple curve-crossing model. Four ligated species, namely, LaC2H4+, LaC2H42+, LaC3H6+, and LaC3H62+, are photodissociated and the photodissociation thresholds are used directly, or together with information from ligand displacement reactions, to assign thermochemical values for these processes and metal ligand bond energies. The bonding properties of LaC2H2+ and LaC2H22+ are also investigated. A surprising outcome of this study is that the monocation is in some cases more strongly bound to these ligands than the dication. Theoretical calculations by Bauschlicher and co-workers are in good agreement with these results.

Gas-phase thermochemical values £>°(Mg+-OH) = 75 ± 4 kcal/mol, IP(MgOH) = 7.3 ± 0.1 eV, D°(Mg+-0) = 53 ± 3 kcal/mol, and IP(MgO) = 7.9 ±0.1 eV have been experimentally determined by photodissociation measurements and charge-transfer reactions with Fourier transform mass spectrometry. These results, together with previously determined thermochemical data, are used to determine other thermochemical properties of MgOH and MgO. Our value Z)°(Mg-OH) = 67 ± 6 kcal/mol agrees well with previous experimental values. However, £>°(Mg-0) = 59 ± 5 kcal/mol is much lower than previous experimental results, which vary widely, but is in good agreement with a recent ab initio Cl calculation.The thermochemical properties of gas-phase metal monohydroxides have recently been of interest due to the roles these species play in flame chemistry1 and meteor ablation processes.2Most of the bond dissociation energies of the neutral species have come from flame measurements.3 4More recent measurements from Knudsen cell mass spectrometry,4-6 however, have indicated that some of the results reported earlier may be high by as much

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