Electrospray ionization mass spectrometric study of mercury complexes of N-heterocyclic carbenes derived from 1,2,4-triazolium salt precursors

摘要

By mixing 1,2,4-triazolium salts(precursors of N-heterocyclic carbenes 1-6)with mercury acetate,a number of complexes have been obtained under electrospray ionization condition.Carbenes 1 and 2 contain one carbene center;therefore,they are able to bond only one mercury cation.Carbenes 3-5 contain two carbene centers;therefore,they can bond two mercury cations.Mercury complexes of 1-5 always contain an acetate anion attached to a mercury cation.Carbene 6 also contains two carbene centers;however,its structure allows formation of a complex containing mercury bonded simultaneously to both centers,therefore,the complex that does not contain an acetate anion.The MS/MS spectra taken for complexes of carbenes 1-5 have shown formation of a cation corresponding to N1 substituent (adamantyl or benzyl),and those of complexes of carbenes 3-5(doubly charged ions)have also shown the respective complementary partner ions.Mercury complex of 2 has yielded some other interesting fragmentation pathways,e.g.a loss of the HHgOOCCH3 molecule.The fragmentation pathway of the mercury complexes of 6 was found to be complicated.