Selenoketene (H2CCSe)+• and selenoketyl cumulene (HCCSe)+ ions and their neutral counterparts: a tandem mass spectrometric and computational study

✍ Scribed by P. Nagi Reddy; R. Srikanth; K. Bhanuprakash; R. Srinivas

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 229 KB
• Volume: 40
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.854

✦ Synopsis

Abstract

Dissociative electron ionization (70eV) of selenophene (C~4~H~4~Se) generates m/z 106 ions of composition [H~2~, C~2~, ^80^Se]^+•^ and m/z 105 ions of [H, C~2~, ^80^Se]^+^. From tandem mass spectrometric experiments, Density Functional Theory (DFT) and ab initio calculations, it is concluded that these ions have the structure of selenoketene H~2~CCSe^+•^ (1a^+•^ )and selenoketyl HCCSe^+^ (2a^+^) ions respectively. The calculations predict that selenoketene ion 1a^+•^ is separated by high energy barriers from its isomers selenirene (H$\catcode@=11 \def\overlsqmatrix#1{\null\vbox{\normalbaselines\m@th \ialign{\hfil$##$\hfil&&\quad\hfil$##$\hfil\crcr \mathstrut\crcr\noalign{\kern-\baselineskip} #1\crcr\mathstrut\crcr\noalign{\kern-\baselineskip}}}} \newdimen\rulwidth \def\downsqbrace#1{\setbox1=\hbox{#1} \rulwidth=\wd1\advance \rulwidth by -6pt \raise3pt\hbox{$\overlsqmatrix{\vrule height5pt\kern-0.5pt\raise5pt\hbox to \rulwidth{\hrulefill}\kern-0.5pt\vrule height5pt\cr\noalign{\vskip-3pt}\hbox{#1}\cr\noalign{\vskip-5pt}}$}} \catcode@=12 \downsqbrace{{\rm CCHS}}$e)^+•^ 1b^+•^, ethyne selenol (HCCSeH)^+•^ 1c^+•^, (CCHSeH)^+•^ 1d^+•^ and (CCSeH~2~)^+•^ 1e^+•^. The selenoketyl ion 2a^+^ is separated by high barriers from its isomers (CCHSe)^+^ 2b^+^, and (CCSeH)^+^ 2c^+^. Neutralization‐reionization mass spectra (NRMS) of these structurally characterized ions confirmed that the corresponding neutral analogues, selenoketene H~2~CCSe 1a and selenoketyl radical HCCSe 2a^•^ are stable in the rarefied gas phase. The relative, dissociation, and isomerization energies for selenoketene and selenoketyl ions and neutrals studied at B3LYP/6–31G(d,p) and G2/G2(MP2) levels are used to support and interpret the experimental results. Copyright © 2005 John Wiley & Sons, Ltd.