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Treatment of 2 equiv of Au(THT)Cl (THT = tetrahydrothiophene) with the bis(secondary) phosphines HP(R) approximately PH(R) (linker approximately = (CH(2))(3), R = Mes = 2,4,6-Me(3)C(6)H(2) (1), R = Is = 2,4,6-(i-Pr)(3)C(6)H(2) (2), R = Ph (4); approximately = (CH(2))(2), R = Is (3); HP(R) approximately PH(R) = 1,1'-(eta(5)-C(5)H(4)PHPh)(2)Fe (5)), gave the dinuclear complexes (AuCl)(2)(mu-HP(R) approximately PH(R)) (6-10). Dehydrohalogenation with aqueous ammonia gave the phosphido complexes [(Au)(2)(mu-P(R) approximately P(R))](n) (11-15). Ferrocenyl- and phenylphosphido derivatives 15 and 14 were insoluble; the latter was characterized by solid-state (31)P NMR spectroscopy. Isitylphosphido complexes 12 and 13 gave rise to broad, ill-defined NMR spectra. However, mesitylphosphido complex 11 was formed as a single product, which was characterized by multinuclear solution NMR spectroscopy, solid-state (31)P NMR spectroscopy, and elemental analyses. Mass spectrometry suggested that this material contained eight gold atoms (n = 4). A structure proposed on the basis of the (1)H NMR spectra, containing a distorted cube of phosphorus atoms, was confirmed by X-ray crystallographic structure determination. NMR spectroscopy, including measurement of the hydrodynamic radius of 11 by (1)H NMR DOSY, suggested that this structure was maintained in solution. Density functional theory (DFT) structural calculations on 11 were also in good agreement with the solid-state structure.

For the past 70 yr, researchers in the Soil Science/Renewable Resources Department at the University of Alberta have used isotopes to study topics of ecological importance. This review highlights the soil isotope research conducted within our department over this time, including an historical overview of studies of interest. Analytical techniques and advances in instrumentation are discussed, focusing on the measurement of light stable isotope ratios (i.e., for C, H, N, S, and O) using isotope ratio mass spectrometry (IRMS). Early soil isotope work (1950–2000s) focused on agricultural soils and soil fertility issues. These studies included the use of radioactive isotopes such as 14C and 35S, and (or) artificially enriched stable isotopes including 15N-labelled fertilizers. More recently (2000–present), the scope of research widened to include natural-abundance stable isotope ratio studies as higher-sensitivity IRMS systems became more prevalent. Current isotope research topics include N biogeochemistry in natural and managed ecosystems, land management effects on greenhouse gas emissions, carbon cycling in northern landscapes, paleo-reconstruction in peatlands, carbon sequestration in boreal forests, and biodegradation of petroleum hydrocarbons. Further technological progress also enabled new techniques such as compound-specific IRMS analysis, including δ13C and δ2H measurements of soil n-alkanes and phospholipid fatty acids. In conclusion, current IRMS instrumentation presents unparalleled opportunities for multidisciplinary research to track carbon, plant nutrients, and pollutants as they move through soils.

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