Using Inert Sampling Techniques to Analyze Air-Sensitive Compounds

This article shows the ability of the Advion expression® Compact Mass Spectrometer (CMS) to verify the synthesis of two compounds that are highly sensitive to air, Ag(As4 S3)2[AI(OC(CF3)3 )4] and C18H26CI2 FeP2Si, using the Advion inert Atmospheric Solids Analysis Probe (iASAP).

Introduction

Several of the chemical reactions performed by synthetic chemists entail the use of air-sensitive compounds, for example, organometallics and metal catalysts. They must be performed in a glove box or by utilizing a Schlenk line to mitigate hydrolysis and oxidation.

The sampling and delivery of such samples to a mass spectrometer without exposing them to air can be a challenge.

In this example, the iASAP (Figure 1), a variation of the method produced by Professor Ingo Krossing’s cohort at the Albert-Ludwigs-University of Freiburg, enables transportation and sampling in an environment of inert gas to avoid compound decomposition.

In this article, the ability of the expression CMS to verify the synthesis of two compounds that are highly sensitive to air, Ag(As4 S3)2[AI(OC(CF3)3 )4] and C18H26CI2 FeP2Si, through inert sampling employing the iASAP-enabled APCI ion source of the CMS is described.

This enables the efficient and convenient observation of air-sensitive reactions with no requirement for further sample preparation.

The iASAP — an inert modification of the ASAP protected in an exterior sheath fitted with a three-way valve to allow for a simple flushing of the connected gas line, without the need of an additional vacuum line (Schlenk line connection).

Figure 1. The iASAP — an inert modification of the ASAP® protected in an exterior sheath fitted with a three-way valve to allow for a simple flushing of the connected gas line, without the need of an additional vacuum line (Schlenk line connection). Image Credit: Advion

The air-sensitive reaction was displaced from the Schlenk line to the CMS using iASAP by sampling the reaction mixture, locking in the inert gas, and then placing it directly into the CMS for evaluation (Figure 2).

C18H26CI2 FeP2Si synthesis (Figure 6,7) is especially sensitive to hydrolysis because of the phosphorus silicon bond (Figure 3), but it could still be identified, even when transported to the mass spectrometer using this inert sampling method.

The iASAP with sample sealed in inert gas being inserted directly into the iASAP-enabled APCI ion source of the CMS.

Figure 2. The iASAP with sample sealed in inert gas being inserted directly into the iASAP-enabled APCI ion source of the CMS. Image Credit: Advion

The molecular structures of the two synthesized compounds that represent the target product.

Figure 3. The molecular structures of the two synthesized compounds that represent the target product. Image Credit: Advion

Results

Synthesis of Ag(As4 S3)2[AI(OC(CF3)3 )4]

The mass spectral data confirms the synthesis of [Ag(As4S3)2]+ . The theoretical isotope distributions, compared with data obtained by iASAP analysis on the CMS, identify and confirm all cations involved in the synthesis reaction for: 1. [As3S]+: m/z 256.8, 2. [HAs4S3]+: m/z 396.6, 3. [HAs4 S4 ]+: m/z 428.6, 4. [Ag(As4S3)2]+: m/z 898.1, 5. [Ag(As4S4)(As4S3)]+: m/z 930.2, and 6. [Ag(As4S4)2]+: m/z 962.2.

The mass spectral data confirms the synthesis of [Ag(As4S3)2]+ . The theoretical isotope distributions, compared with data obtained by iASAP analysis on the CMS, identify and confirm all cations involved in the synthesis reaction for: 1. [As3S]+: m/z 256.8, 2. [HAs4S3]+: m/z 396.6, 3. [HAs4 S4 ]+: m/z 428.6, 4. [Ag(As4S3)2]+: m/z 898.1, 5. [Ag(As4S4)(As4S3)]+: m/z 930.2, and 6. [Ag(As4S4)2]+: m/z 962.2.

Figure 4 and 5[1]. The mass spectral data confirms the synthesis of [Ag(As4S3)2]+ . The theoretical isotope distributions, compared with data obtained by iASAP/CMS, identify and confirm all cations involved in the synthesis reaction for: 1. [As3S]+: m/z 256.8, 2. [HAs4S3]+: m/z 396.6, 3. [HAs4 S4 ]+: m/z 428.6, 4. [Ag(As4S3)2]+: m/z 898.1, 5. [Ag(As4S4)(As4S3)]+: m/z 930.2, and 6. [Ag(As4S4)2]+: m/z 962.2. Image Credit: Advion

Synthesis of C18H26CI2 FeP2Si

Mass spectrum confirming the existence of the synthesized P–Si–P ferrocenophane[3]. The intense m/z signal (Figure 6) at 459.0 m/z corresponds to the [M+H]+ . The comparison of the mono-isotopic mass and the isotope distribution with the theoretical distribution (Figure 7) confirms the synthesis of the hydrolysis sensitive compound.

Mass spectrum confirming the existence of the synthesized P–Si–P ferrocenophane[3]. The intense m/z signal (Figure 6) at 459.0 m/z corresponds to the [M+H]+ . The comparison of the mono-isotopic mass and the isotope distribution with the theoretical distribution (Figure 7) confirms the synthesis of the hydrolysis sensitive compound.

Figure 6 and 7[2]. Mass spectrum confirming the existence of the synthesized P–Si–P ferrocenophane[3]. The intense m/z signal (Figure 6) at 459.0 m/z corresponds to the [M+H]+ . The comparison of the mono-isotopic mass and the isotope distribution with the theoretical distribution (Figure 7) confirms the synthesis of the hydrolysis sensitive compound. Image Credit: Advion

Conclusions

The use of the iASAP with the Advion expression CMS enables highly air-sensitive compounds to be studied directly from reactions performed in a Schlenk line or glove box for convenient sampling and more efficient results.

The expression CMS offers high sensitivity with no requirement for sample preparation. Both Ag(As4 S3)2[AI(OC(CF3)3 )4] and C18H26CI2 FeP2Si were simply observed by their theoretical isotope distribution, suggesting an effective compound synthesis.

References and Further Reading

[1] MS Data from Philippe Weis (Group of Prof. Ingo Krossing)

[2] Sample kindly provided by Prof. Rudolf Pietschnig, Denis Kargin; University of Kassel

[3] D. Kargin et al., Dalton Trans. 2016, 45, 2180–2189

Acknowledgments

Produced from materials originally authored by Frank Porbeck1, Prof. Ingo Krossing2, Philippe Weis2, and Anke Hoffmann2 from Advion, Inc.1 and Albert-Ludwigs-University of Freiburg2.

This information has been sourced, reviewed and adapted from materials provided by Advion.

For more information on this source, please visit Advion.

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