Cold seep formation from salt diapir-controlled deep biosphere oases.

Deep sea cold seeps are sites where hydrogen sulfide, methane, and other hydrocarbon-rich fluids vent from the ocean floor. They are an important component of Earth's carbon cycle in which subsurface hydrocarbons form the energy source for highly diverse benthic micro- and macro-fauna in what is otherwise vast and spartan sea scape. Passive continental margin cold seeps are typically attributed to the migration of hydrocarbons generated from deeply buried source rocks. Many of these seeps occur over salt tectonic provinces, where the movement of salt generates complex fault systems that can enable fluid migration or create seals and traps associated with reservoir formation. The elevated advective heat transport of the salt also produces a chimney effect directly over these structures. Here, we provide geophysical and geochemical evidence that the salt chimney effect in conjunction with diapiric faulting drives a subsurface groundwater circulation system that brings dissolved inorganic carbon, nutrient-rich deep basinal fluids, and potentially overlying seawater onto the crests of deeply buried salt diapirs. The mobilized fluids fuel methanogenic archaea locally enhancing the deep biosphere. The resulting elevated biogenic methane production, alongside the upward heat-driven fluid transport, represents a previously unrecognized mechanism of cold seep formation and regulation.

Ligand-based reactivity of a platinum bisdithiolene: double diene addition yields a new C2-chiral chelate ligand.

The reaction of Pt(tfd)(2) [tfd = S(2)C(2)(CF(3))(2)] with excess 2,3-dimethyl-1,3-butadiene initially yields the expected 1:1 adduct, in which the diene has added across two sulfur atoms on separate tfd ligands. However, within 1 day at 50 degrees C, this kinetic product quantitatively converts into a thermodynamic product where two dienes have added to one tfd ligand via unprecedented addition across the dithiolene CS bonds. The new reaction is highly selective for the C(2)-symmetric diastereomer. A new chiral bisthioether chelate ligand has formed in the product, which has been characterized crystallographically.

Nickel dithiolene chelate rings in a new role as eta5-coordinating ligands: synthesis, structural characterization, and redox reactivity of an "Fe2Ni" bis-double-decker.

A bis-double-decker complex has been assembled from the nickel bisdithiolene complex [Ni(S 2C 2Me 2) 2] (1-/2-) and two [Cp*Fe] (+) units (Cp* = C 5Me 5). The complex, [(eta (5)-Cp*-Fe-mu-eta (5),eta (5)-((S 2C 2Me 2) 2Ni)Fe-eta (5)-Cp*] ( n ) ( 1 ( n )), was isolated in two charge states ( n = 0, 1). The structure of 1 (+) was confirmed by X-ray crystallography for 1 (+)PF 6 (-) and 1 (+)BF 4 (-), and it shows the nickel bisdithiolene units pi-donating to iron centers. Both salts crystallize in a centrosymmetric space group (center of inversion at nickel). Computational (density functional theory) data indicate a highly delocalized spin density for 1 (+). The reaction of 1 with 1 or 2 equiv of HBF 4 leads to oxidation to form 1 (+) or 1 (2+), respectively. On an electrochemical time scale, reversibility is observed for the redox series 1/ 1 (+)/ 1 (2+), with an additional slower step for oxidation of 1 (2+).