Notes Coupling an Electrospray Ionization Mass Spectrometer with a Glovebox: A Straightforward, Powerful, and Convenient Combination for Analysis of Air-Sensitive Organometallics Anneke T. Lubben Department of Chemistry, UniVersity of Bath, Bath, BA2 7AY, U.K. J. Scott McIndoe* Department of Chemistry, UniVersity of Victoria, Victoria, BC, BC V8W 3V6, Canada Andrew S. Weller* Department of Inorganic Chemistry, UniVersity of Oxford, UK OX1 3QR, U.K. ReceiVed February 21, 2008 Summary: The study of highly air- and moisture-sensitiVe organometallic complexes by ESI-MS is greatly facilitated by interfacing the instrument to an inert-atmosphere gloVebox, a modification that requires no special precautions beyond proximity. Electrospray ionization mass spectrometry, ESI-MS, has had a checkered history in organometallic chemistry. Subsequent to its commercial introduction in the early 1990s, organometallic chemists took notice of the technique and demonstrated its potential as a tool for analyzing speciation of charged com- pounds in solution. 1–3 Fast, extremely sensitive, and capable of dealing with complex mixtures, ESI-MS occupied a niche that ought to have made it a highly attractive, routine method for analysis. Interpretation of data is not difficult: ESI mass spectra of charged compounds typically provide just [cation] + or [anion] - ions, and the combination of matching experimental isotope patterns with (readily calculated) theoretical isotope patterns, m/z value, and, if necessary, MS/MS studies, provides sufficient information for compositional characterization. 4 Most research institutions offer ready access to the instruments, and even quite reactive compounds can be readily analyzed. 5–7 Why then has ESI-MS been only sporadically adopted by organo- metallic chemists? A major reason is sample decomposition. ESI-MS typically analyzes samples at concentrations sub- stantially lower than millimolar, and standard protocols call for the use of polar solvents such as water, acetonitrile, and methanol. Most charged organometallic compounds can be run with ease in aprotic, relatively nonpolar solvents such as dichloromethane (and even in toluene or hexane if mixed with a lipophilic ionic liquid), 8 but if the injection apparatus has been recently exposed to wet, protic, or oxygenated solvent, the ion of interest may interact with these “impurities” resulting in a degraded compound. This is demonstrated by considering a typical ESI-MS experiment: 0.1 mg of an organometallic compound is dissolved in 1 mL of CH 2 Cl 2 ; a drop of this solution is added to 1 mL of CH 2 Cl 2 (ca. 20× dilution); 0.02 mL (20 μL) of this solution is analyzed to collect the spectrum. Sample consumption in this experiment is 0.05 × 0.02 × 0.1 mg ) 0.01 μg. Assuming a typical molecular weight for the compound of 720 Da, stoichiometric (1:1) reaction of this material requires only 0.25 nanograms of water. Given that most ESI-MS instruments are open-access, trace residual water in the * Corresponding authors. E-mail: mcindoe@uvic.ca; andrew.weller@ chem.ox.ac.uk. (1) Henderson, W.; Nicholson, B. K.; McCaffrey, L. J. Polyhedron 1998, 17, 4291–4313. (2) Colton, R.; Dagostino, A.; Traeger, J. C. Mass Spectrom. ReV. 1995, 14, 79–106. (3) Colton, R.; Traeger, J. C. Inorg. Chim. Acta 1992, 201, 153–155. (4) Henderson, W.; McIndoe, J. S. Mass Spectrometry of Inorganic and Organometallic Compounds: Tools, Techniques, Tips; Wiley: Chichester, 2005. (5) Evans, W. J.; Johnston, M. A.; Fujimoto, C. H.; Greaves, J. Organometallics 2000, 19, 4258–4265. (6) Feichtinger, D.; Plattner, D. A.; Chen, P. J. Am. Chem. Soc. 1998, 120, 7125–7126. (7) Brayshaw, S. K.; Harrison, A.; McIndoe, J. S.; Marken, F.; Raithby, P. R.; Warren, J. E.; Weller, A. S. J. Am. Chem. Soc. 2007, 129, 1793– 1804. (8) Henderson, M. A.; McIndoe, J. S. Chem. Commun. 2006, 2872–4. Figure 1. Inert-atmosphere glovebox situated next to the ESI mass spectrometer. Syringe pump for sample infusion is inside the glovebox; the PEEK tubing passes through a standard glovebox feedthrough sealed with O-rings. See Supporting Information for photographs of the system used herein. Organometallics 2008, 27, 3303–3306 3303 10.1021/om800164e CCC: $40.75  2008 American Chemical Society Publication on Web 05/29/2008