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This study reports the isolation and characterization of nickel and vanadyl porphyrins in the residue (535 °C+) and asphaltenes from Arabian Heavy crude oil. The residue was obtained by distillation of crude oil, whereas the asphaltenes were precipitated by rc-heptane from the crude oil. Metalloporphyrins were first extracted from the residue and the asphaltenes. The nickel porphyrins were separated from vanadyl porphyrins by means of adsorption chromatography on silica gel and alumina using solvents of increasing polarity. The chromatographic separation process was monitored by ultraviolet-visible spectrophotometry. Both nickel and vanadyl porphyrins were identified and characterized by ultraviolet-visible spectrophotometry and mass spectrometry.been fully or partially established. Types of these porphyrins and their structures are also listed.

Ligand scrambling reactions in cyano(thione)gold(I) complexes ([>C=S-Au-CN]) to form [Au(>C=S)2]+ and [Au(CN)2]– species have been investigated for a series of thiones in DMSO using 13C and 15N NMR spectroscopy. Rapid approach to equilibrium occurred and resulted in distinct signals for the [>C=S-Au-CN] and [Au(CN)2]– complexes, both in 13C and 15N NMR. Equilibrium constants (Keq) were determined for scrambling of all the complexes by integrating the CN resonances in the 13C NMR recorded at 298 K. The influence of various factors (initial concentration, ionic strength, temperature, and solvent polarity) on the Keq value was examined for a representative complex (ImtAuCN (Imt = Imidazolidine-2-thione)).Key words: cyanogold(I) complexes, thiones, ligand scrambling, NMR, Keq.

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SummaryThe structure of a colorless dimer (4a) of puupehenone (l), which was isolated from Pacific marine sponges, has been elucidated from spectral data.Marine sponges are a rich source of secondary metabolites, particularly terpenoids [ 11. Occasionally, compounds of mixed biosynthesis have been encountered, among them the puupehenones 1-3, which are constructed of sesquiterpene and benzene moieties [2]. The yellow encrusting sponge, identified as Heteronenza sp. (family Spongiidue, order Dictyoceratidu, class Demospongiae), from which puupehenone (1) was originally isolated, was first collected by us off the Hawaiian islands of Lanai and Oahu. The halopuupehenones 2 and 3 were minor constituents in a Heteronemu sample from Enewetak in the Marshall islands. In all collections we encountered several dimeric compounds, some of them highly colored. A colorless dimer, bispuupehenone (4a). was subsequently also isolated from a Tahitian sponge, Hjrtios (= Inodes) eubumma (family Thorectidae, order Dictyoceratida), and is the subject of this report.H. eubumma was preserved in EtOH and then further extracted with the same solvent. The aqueous residue was partitioned with cyclohexane. Chromatography of the organic residue on Sephadex, then silica gel, yielded puupehenone (1) and bispuupehenone (4a), m.p. 234-240". A composition of C42H5406 was ascertained by mass spectrometry. The fragmentation pattern, including abundant M + -15 (m/z 639) and M + -151 (see wiggly line in 4) ions, were reminiscent of the puupehenone spectrum [2]. The presence of OH-groups was indicated by IR bands at 3560 and 3420 cm-I.The I3C-NMR spectrum displayed 2 1 signals, thus confirming that bispuupehenone (4a),is a symmetrical dimer of 1. Fifteen upfield signals parallel those of other drimane derivatives, e.g. 1, its methanol adduct 5, or 8-epichromazonarol (6) [3] I )