<p>Zeise’s salt, [PtCl<sub>3</sub>(H<sub>2</sub>C=CH<sub>2</sub>)]<sup>–</sup><sub>,</sub>
is the oldest known organometallic complex, featuring ethylene strongly bound
to a platinum salt. Many derivatives are known, but none involving dinitrogen,
and indeed dinitrogen complexes are unknown for both platinum and palladium.
Electrospray ionization mass spectrometry of K<sub>2</sub>[PtCl<sub>4</sub>]
solutions generate strong ions corresponding to [PtCl<sub>3</sub>(N<sub>2</sub>)]<sup>–</sup>,
whose identity was confirmed through ion mobility spectroscopy and MS/MS
experiments that proved it to be distinct from its isobaric counterparts [PtCl<sub>3</sub>(C<sub>2</sub>H<sub>4</sub>)]<sup>–</sup>
and [PtCl<sub>3</sub>(CO)]<sup>–</sup>. Computational analysis established a
gas-phase platinum-dinitrogen bond strength of 116 kJ mol<sup>-1</sup>,
substantially weaker than the ethylene and carbon monoxide analogues but stronger
than for polar solvents such as water, methanol and dimethylformamide, and
strong enough that the calculated N-N bond length of 1.119 Å represents weakening
to a degree typical of isolated dinitrogen complexes. </p>
Evaluation of top-down mass spectrometry and ion-mobility spectroscopy as a means of mapping protein-binding motifs within heparin chains