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Electrospray ionization mass spectrometry of palladium(II) quinolinylaminophosphonate complexes

The mass spectrometric behaviour of palladium(II) halide complexes of three types of quinolinylaminophosphonates, diethyl and dibutyl esters of [alpha-anilino-(quinolin-2-yl)methyl]phosphonic (L1, L2), [alpha-anilino-(quinolin-3-yl)methyl]phosphonic (L3, L4) and [alpha-(quinolin-3-ylamino)-N-benzyl]phosphonic acid (L5, L6), was investigated under positive ion electrospray ionization conditions. Each type of ligands forms complexes with different metal-ligand interactions. Mononuclear dihalide adducts cis-[Pd(L1/L2)X2] (1-4) and trans-[Pd(L3/L4)2X2] (5-8) as well as dinuclear tetrahalide complexes [Pd2(L5/L6)3X4] (9-12) (X=Cl, Br) are formed by metal bonding either through the quinoline or both the quinoline and amino nitrogen atoms. The sodiated molecule [M+Na]+ is observed in the mass spectra of all the complexes and its abundance as well as the fragmentation pathway depends on the type of the complex. In the cis complexes (1-4) the initial decomposition goes under two fragmentation routes: those in which the sodium molecular adduct sequentially loses halides HX/NaX and those in which this loss is in the competition with the loss of dialkyl phosphite. The predominant pathways for decomposition of trans dihalide (5-8) and tetrahalide (9-12) complexes include three competitive reactions ; the loss of halides, dialkyl phosphites and the intact phosphonate ligand molecule and its fragments formed by ester dissociation or complete loss of the phosphonate ester moiety. A series of acetonitrile adducts and cluster ions derived from dimolecular clusters [2M+Na]+ were also detected. The most important fragmentation patterns are rationalized and supported by the MSn studies.

mass spectrometry ; electrospray ionization ; tandem mass spectrometry ; quinolinylaminophosphonate ; palladium(II) complex

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