Analysis of transition-metal compounds containing tetrathiafulvalene phosphine ligands by fast atom bombardment mass spectrometry: Limitations and the development of matrix additives for the desorption of multiply charged complexes
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abstract
A series of new complexes incorporating the functionalized tetrathiafulvalene (TTF) ligands ortho-(CH3)2(P(C6H5) 2)2-TTF (o-P2) and (P(C6H5)2)4 TTF (P4) have been prepared and studied by fast atom bombardment mass spectrometry (FABMS). The mononuclear o-P2 complexes [M(o-P2)2](BF4)2 (M = Fe, Pd, Pt) and [Co(o-P2)2(NCCH3)2](BF4)2 were synthesized from reactions of the free ligand with the fully solvated BF4- salts [M(NCCH3)n](BF4)2 (M = Fe, Co, n = 6; M = Pd, Pt, n = 4). The dinuclear P4 complex, [Pt2(P4)(NCCH3](BF4)4, was produced by reacting the free ligand with PtCl2(NC7H5)2followed by abstraction of the chlorides with AgBF4 in acetonitrile. Reaction of [Pd(NCCH3)](BF4)2 with 1 equiv of P4 produces the polynuclear compound formulated as [Pd(P4)]n(BF4)2n which was characterized by infrared, 1H, and 31P{1H} NMR spectroscopies and elemental analysis. The use of FABMS in this study was undertaken in order to elucidate the chemical options of multiply charged cations in the desorption process from the liquid matrix to the gas phase. The use of additives to the FAB matrix (m-nitrobenzyl alcohol) was demonstrated for the P4 complexes which do not give spectra in this medium due to a high positive net charge. The addition of triflic acid (HOTf or CF3SO3H) to the FAB matrix/analyte solution was shown to assist in the MS analysis of cationic complexes with up to six charges and a mass range up to m/z 4000. When HOTf is added, bound OTf- anions are formed and are attached to the cationic complex, lowering the net charge to +1. The method of using matrix additives as opposed to chemically synthesizing the OTf- compounds is a convenient in situ method which produces species that are capable of being analyzed by FABMS.
