Phosphoranide production and decomposition in the gas phase

• The mechanism for the production of phosphoranides is revealed.
• Decomposition mechanism of phosphoranides was also thoroughly studied by DFT.
• Thermodynamic and entropy effects for phosphoranide ion formation were studied.
• Excellent agreement between DFT calculated and experimentally determined geometry parameters of phosphoranides are obtained.

After characterizing the negative ion chemistry of tris(trifluoromethyl)phosphine in a previous work, new insights about the interpretation of the MS/MS mass spectrum of the phosphide anion (CF3)2P−m/z 169 could be revealed and are described in this current work. The phosphide (CF3)2P− anion, m/z 169, was accelerated in a cloud of (CF3)3P neutrals and new product ions could be detected which do not belong to fragmentation channels. Instead, high mass anions m/z 207 and m/z 257 are found, and the reaction mechanism could be revealed by density functional theory (DFT) calculations at B3LYP/6-311 + G(3df)//B3LYP/6-31 + G(2d) level of theory. The formation of the phosphoranide (CF3)3PF−m/z 257 is the result of a fluoride anion transfer from the accelerated phosphide anion (CF3)2P−m/z 169 to the (CF3)3P neutral m = 238. Decomposition of the newly formed phosphoranide (CF3)3PF−m/z 257 leads to the formation of smaller phosphoranides (CF3)2PF2−m/z 207 and CF3PF3−m/z 157 as a result of successive CF2 eliminations. A new rearrangement in the formed phosphoranide (CF3)2PF2− could be revealed, whereby a CC bond formation can take place and the product anion C2F5−m/z 119 could be experimentally obtained.

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