Observation of doubly charged ions in fast atom bombardment mass spectrometry: ruthenium(II) complexes in a nitrobenzyl alcohol matrix

The fast atom bombardment (FAB) mass spectrometric analysis of several series of ruthenium-bidentate ligand complexes such as (RuLL'L'')X/sub 2/, (RuL/sub 2/L')X/sub 2/, and (RuL/sub 2/L')X/sub 2/, and (RuL/sub 3/)X/sub 2/ are discussed, where L, L', and L'' include 2,2'-bipyridine, 1,10-phenanthroline, their derivatives and related compounds. Surprisingly abundant, intact, doubly charged cations (RuL/sub 3/)/sup 2 +/, (RuLL'L'')/sup 2 +/, and (RuL/sub 2/L')/sup 2 +/ are observed for most complexes studied. Structurally significant fragment ions are generally observed for all complexes in addition to singly charged molecular cationic species such as (RuLL'L'')/sup +/ and (RuLL'L'')X/sup +/. The (RuLL'L'')/sup 2 +//(RuLL'L'')/sup +/ ratio, where L = L' = L'', L = L' not equal to L'', or L not equal to L not equal to L'' depending on the series involved, varies from 3.5 to 0.35 over the 22 complexes studied. Reasons for the observation of these unique abundant doubly charged ions in a FAB spectrum, especially in a nitrobenzyl alcohol matrix, are discussed. Ions indicative of ligand exchange reactions between ruthenium centers are not observed for mixed ligand complexes. 23 references, 4 figures, 1 table.