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FAB Mass Spectrometry (fab + mass_spectrometry)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

Synthesis of (1,2,4-Oxadiazole)palladium(II) Complexes by [2 + 3] Cycloaddition of Nitrile Oxides to Organonitriles in the Presence of PdCl2

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2005
Nadezhda A. Bokach
Abstract The reaction between the nitrile oxides 2,4,6-R3C6H2CNO (R = Me, OMe) and trans -[PdCl2(RCN)2], or RCN (R = Me, Et, CH2CN, NMe2, Ph) in the presence of PdCl2, proceeded smoothly under mild conditions and allowed the isolation of the 1,2,4-oxadiazole complexes trans -[PdCl2{Na=C(R)-ON=Cb(C6H2R3)(Na,Cb)}2] (1,8) in 40,85,% yields. In CH2Cl2, the reaction between 2,4,6-R3C6H2CNO and [PdCl2(MeCN)2] furnishes [PdCl2(ONCC6H2R3)2] (9 and 10), which are the first representatives of metal compounds where nitrile oxides act as ligands. The 1,2,4-oxadiazole complexes 1,8 were characterized by elemental analysis, FAB mass spectrometry, and IR, 1H and 13C{1H} NMR spectroscopy, while 2, 3, 7, and 8 were additionally characterized by X-ray crystallography. The liberation of the heterocyclic species from 1,8 was successfully performed by substitution reaction either with 1,2-bis(diphenylphosphanyl)ethane or with an excess amount of Na2S·7H2O in MeOH; the liberated 1,2,4-oxadiazoles (11,18) were characterized by positive-ion FAB mass spectrometry and 1H and 13C{1H} NMR spectroscopy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Structural Characterization of N -Methylpyridoxine (MePN; PN = Vitamin B6) and Its Diorganotin Complexes [SnR2(MePN-H)]I (R = Me, Et, Bu and Ph)

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2003
José S. Casas
Abstract For comparison with the corresponding pyridoxine complexes we have prepared dimethyl-, diethyl-, dibutyl- and diphenyltin(IV) complexes of N -methylpyridoxine (MePN). The compounds [SnMe2(MePN,H)]I (1), [SnEt2(MePN,H)]I (2), [SnBu2(MePN,H)]I (3) and [SnPh2(MePN,H)]I·H2O (4) were isolated and characterized by IR, Raman, Mössbauer, 1H, 13C and 119Sn NMR spectroscopy, and by EI and FAB mass spectrometry. The crystal structures of [HMePN]I and of compounds 1, 2·2H2O and 3 were determined by X-ray diffractometry. Their lattices contain dimeric [SnR2(MePN,H)]22+ units (R = Me, Et, Bu) in which two bridging-chelating methylpyridoxinato anions link pentacoordinate Sn atoms with coordination polyhedra closer to square pyramids than to trigonal bipyramids. NMR results show that the dimeric cations persist in (CD3)2SO. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Cyclopolymerization and Copolymerization of Functionalized 1,6-Heptadienes Catalyzed by Pd Complexes: Mechanism and Application to Physical-Gel Formation

CHEMISTRY - A EUROPEAN JOURNAL, Issue 29 2010
Sehoon Park Dr.
Abstract Cationic Pd complexes, prepared from [PdCl(ArNC12H6NAr)(Me)] and Na[B{3,5(CF3)2C6H3}4] (NaBARF), catalyze the cyclopolymerization of 4,4-disubstituted 1,6-heptadienes. The polymers produced contain a trans -fused five-membered ring in each repeating unit. NMR spectroscopy and FAB mass spectrometry of the polymers formed indicated that the initiation end of the chain contains either the cyclopentyl group derived from the preformed Pd,monomer complex or a hydrogen atom left on the Pd center by the chain-transfer reaction. The stable cyclopentylpalladium species are involved in both initiation and propagation steps and undergo isomerization into (cyclopentylmethyl)palladium species followed by the insertion of a CHCH2 bond of a new monomer molecule into the PdCH2 bond. Copolymerization of 1,6-heptadiene derivatives with ethylene, catalyzed by the Pd complexes, yields polymers that contain trans five-membered rings and branched oligoethylene units. Copolymerization of isopropylidene diallylmalonate with 1-hexene affords a polymer with 26,% diene incorporation. The copolymerization consumes 1-hexene more readily than isopropylidene diallylmalonate, although gel permeation chromatography and NMR spectroscopy of the polymers produced show the formation of copolymers rather than of a mixture of homopolymers. Polymerization of 1-hexene initiated with a Pd,barbiturate complex and terminated with 5-allyl-5-hexylpyrimidine-2,4,6(1H,3H,5H)-trione/Et3SiH leads to polyhexene with barbiturate moieties at both terminal ends. Addition of 5-hexyl-2,4,6-triaminopyrimidine to a toluene solution of the telechelic poly(1-hexene) converts the solution into gel. [source]