International Journal of Mass Spectrometry 354–355 (2013) 257–262 Contents lists available at ScienceDirect International Journal of Mass Spectrometry journal homepage: www.elsevier.com/locate/ijms Gas phase reactivity of iron pentacarbonyl with anionic metal clusters Matthew A. Henderson, J. Scott McIndoe ∗ Department of Chemistry, University of Victoria, P.O. Box 3065 Victoria, BC, V8W3V6 Canada article info Article history: Received 24 April 2013 Received in revised form 11 June 2013 Accepted 12 June 2013 Available online 24 June 2013 This manuscript is dedicated to the memory of the energetic and inspirational Detlef Schröder. Keywords: Mass spectrometry Electrospray ionization Ion-molecule reactions Carbonyl clusters abstract The anionic transition metal carbonyl cluster [H 3 Ru 4 (CO) 12 ] - may be energized in the gas phase through collision-induced dissociation (CID), which results in sequential loss of hydrogen and carbon monoxide from the cluster. If this experiment is performed in the presence of iron pentacarbonyl gas, up to three equivalents of the iron complex add to the tetranuclear ruthenium complex to give nearly-saturated product clusters with cores containing five, six and seven metal atoms. Further CID reveals that the iron atoms become intimately incorporated into the cluster core, and thus this process represents a method for the gas-phase synthesis of mixed-metal clusters. © 2013 Elsevier B.V. All rights reserved. 1. Introduction A classic example of a hard-to-study reaction is the build-up of transition metal carbonyl cluster compounds, a process which typ- ically occurs at elevated temperature in solution between ligated metal clusters and/or with mononuclear feedstocks [1]. A wide vari- ety of different types of high nuclearity clusters can result [2], and such clusters have a possible role in nanoscience and nanotech- nologies [3] as well as in catalysis [4]. However, the complexity of the reacting mixtures mean that few techniques are equipped to study the intermediate species formed on the way to the final product. Capturing the build-up process spectroscopically is a real challenge: the complex mixture, combined with a lack of truly diag- nostic spectroscopic handles ( 13 C is not sensitive enough and copes poorly with a mixture of similar compounds; CO peaks are broad and not discriminatory enough), means that the final products are usually the most thermodynamically stable species under the given conditions used and are usually isolated by crystallization and char- acterized by single-crystal X-ray diffraction [5]. Mass spectrometry has been sporadically used to examine these mixtures, but not in any systematic way, rather just as a collection of snapshots of solution speciation [6]. Gas-phase ion-molecule reactions provide insight into chem- istry that is not easily studied in solution [7]. The gas phase has the ∗ Corresponding author. Tel.: +1 250 721 7181; fax: +1 250 721 7147. E-mail address: mcindoe@uvic.ca (J.S. McIndoe). virtue of being free from solvent and hence ions are much more reactive as the solvent does not have to be displaced as a prereq- uisite initiation step for subsequent reactions to occur. Ions can be activated through collision-induced dissociation (and/or other acti- vation methods that deposit energy using photons or electrons), which can be carried out in the same chambers in which reac- tive molecules are introduced. Ion-ion reactions can be excluded from consideration (these repel each other in the gas phase) as can molecule–molecule reactions (whose products are neutral and hence invisible to mass spectrometry), so the type of reactivity can be tightly controlled. Others have looked at the reactivity of volatile transition metal organometallic molecules with ions in the gas phase [8], but the field is dominated by self-clustering reactions between ions gener- ated using electron ionization between metal carbonyls in the gas phase and the residual metal carbonyl itself, using ion cyclotron resonance ‘trapped-ion’ techniques [9]. In the negative ion mode, Ridge showed that [Fe(CO) 4 ] - reacts with Fe(CO) 5 in the gas phase to form [Fe 2 (CO) 8 ] - with an efficiency of about 0.01 [10]. Fack- ler illustrated that [Fe(CO) 3 ] - reacted with Fe(CO) 5 to generate [Fe 2 (CO) 6 ] - [11]. The reactions of mononuclear [Fe(CO) n ] + ions with Fe(CO) 5 harvesting a variety of higher nuclearity [Fe x (CO) y ] + clusters up to x = 4 and y = 12 [12]. Other self-clustering studies have included those with Ni(CO) 4 , [13] Co(NO)(CO) 3 , [14] Cr(CO) 6 , [15] Re 2 (CO) 10 , [16] ReMn(CO) 10 [17] and H 2 Os 3 (CO) 10 [18]. Squires detailed the reactivity of an extensive series of anions with Fe(CO) 5 [19]. Freiser used the reaction between laser desorbed M + ions and the volatile organometallic molecules Fe(CO) 5 and Co 2 (CO) 8 to 1387-3806/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ijms.2013.06.006