Ion-molecule reactions in a quadrupole ion trap as a probe of the gas-phase structure of metal complexes

✍ Scribed by Vachet, Richard W.; Hartman, Judith Ann R.; Callahan, John H.

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 380 KB
• Volume: 33
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/(sici)1096-9888(199812)33:12<1209::aid-jms738>3.0.co;2-w

✦ Synopsis

A method is described in which the coordination number in metal complexes can be determined using ion-molecule reactions in a quadrupole ion trap mass spectrometer. Complexes of Ðrst-row transition metals in the + 2 oxidation state, including manganese through zinc, are electrosprayed, isolated in the ion trap and allowed to react with gases. The coordination number is ascertained by observing the reagent ligands that successfully react with the complex. It was generally observed that six-coordinate complexes are unreactive, Ðve-coordinate complexes react with pyridine and ethylamine, four-coordinate complexes react with pyridine, ethylamine and ammonia and threecoordinate complexes react with all the reagent ligands studied, including water and methanol. The order of reactivity for a given complex reacting with the various reagent ligands is found to follow the order of the electrondonating ability of the reagent ligands. In addition, the e †ect of the metal center on the reactivity of the complexes in the gas phase is analogous to solution-phase trends ; electronic structure strongly inÑuences the gas-phase reactions. These results were then used to predict the complexation behavior of novel podand ligands for which condensed phase information is not available. The results indicate that ion-molecule chemistry in the gas phase may be useful in predicting the interactions between novel multidentate ligands and metals in solution.

1998 John Wiley ( & Sons, Ltd.