Results and Discussion - New Synthetic Routes to Polyoxometalate Containing Ionic Liquids - page 71

located at 1998 cm -1 and the observed peak at 1730 nm would actually speak for a
strongly weakened CO-bond and indicate a bridging P 2 - or P 3 -CO complex.
For a complete structural analyses of the product and clarification of the fate of the CO
a crystal structure analyses would be necessary which is nearly not possible to obtain
for ionic liquids (as they are hardly forming crystals). A solution could be to charge
balance the clusters with tetrabutylammonium which also enables phase transfer into
the organic phase but yields solid products that can readily be crystallized by
conventional solvent diffusion methods. Because the thesis at hand deals with ionic
liquids this time consuming procedure was yet not carried out due to the restricted time
schedule of the work. Mass spectrometry was utilized instead in order to obtain some
more clarity of the reaction which the carbon monoxide could undergo with the
investigated ionic liquids.
The used mass spectrometer has an ultra-high resolution (R(FWHM) ca. 4.1 ڄ 10 4 ) with a
mass accuracy error of 1 to 10 ppm depending on the quality of calibration. Detection
was in negative-ion mode and the source voltage was 3.5 kV. The flow rates were 180
μl/hour. The drying gas (N 2 ), to aid solvent removal, was held at 180 ⁰C with a flow rate
of 4.0 l/min. The machine was calibrated prior to the experiment via direct infusion of
the Agilent ESI-TOF low concentration tuning mixture, which provided an m/z range of
singly charged peaks up to 2700 Da in both ion modes. Figure 38 shows the mass
spectrum obtained from (Q 7 ) 6 [SiW 11 O 39 Cu(H 2 O)].