Structure-activity relationship of palladium phosphanesulfonates: toward highly active palladium-based polymerization catalysts.

Palladium phosphanesulfonate [R(2)P(C(6)H(4)-o-SO(3))PdMeL] catalysts permit the copolymerization of an exceptional large number of functional olefins with ethylene. However, these catalysts usually have reduced activity. We here have conducted a systematic study on the influence of the phosphane substituent, R, on activity and molecular weight. Phosphanes with strong σ-donating character are shown to lead to the most active catalysts. Thus, the catalyst based on phosphane bis-tert-butyl-phosphanyl-benzenesulfonic acid (R=tBu) exhibits unprecedented high activity, rapidly polymerizing ethylene at room temperature to yield a linear polymer of high molecular weight (M(w)=116,000 g mol(-1)). The influence of the R group on the catalyst ability to incorporate methyl acrylate is also investigated.

Probing the Regiochemistry of Acrylate Catalytic Insertion Polymerization via Cyclocopolymerization of Allyl Acrylate and Ethylene.

When palladium phosphine sulfonate catalysts were used, ethylene and allyl acrylate were copolymerized. The copolymer structure was analyzed by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) and was found to contain both δ-valerolactone and γ-butyrolactones inserted within the chain. These cyclic structures were determined to be the outcome of 1,2 allyl insertions and 2,1 acrylate insertions except when the acrylate was cyclopolymerized: in this case, regiochemistry of the insertion was 1,2. This first example of cyclopolymerization with Pd phosphine sulfonate catalysts outlines the extraordinary versatility of this family of compounds and paves the way to new polyolefins containing complex repeat units built in.

A ruthenium catalyst yielding crosslinked polyethylene.

A ruthenium phosphane aryl sulfonate was found to be an efficient catalyst for the polymerization of ethene. Surprisingly, the resulting polyethylene is crosslinked.

From sea to sea: Canada's three oceans of biodiversity.

Evaluating and understanding biodiversity in marine ecosystems are both necessary and challenging for conservation. This paper compiles and summarizes current knowledge of the diversity of marine taxa in Canada's three oceans while recognizing that this compilation is incomplete and will change in the future. That Canada has the longest coastline in the world and incorporates distinctly different biogeographic provinces and ecoregions (e.g., temperate through ice-covered areas) constrains this analysis. The taxonomic groups presented here include microbes, phytoplankton, macroalgae, zooplankton, benthic infauna, fishes, and marine mammals. The minimum number of species or taxa compiled here is 15,988 for the three Canadian oceans. However, this number clearly underestimates in several ways the total number of taxa present. First, there are significant gaps in the published literature. Second, the diversity of many habitats has not been compiled for all taxonomic groups (e.g., intertidal rocky shores, deep sea), and data compilations are based on short-term, directed research programs or longer-term monitoring activities with limited spatial resolution. Third, the biodiversity of large organisms is well known, but this is not true of smaller organisms. Finally, the greatest constraint on this summary is the willingness and capacity of those who collected the data to make it available to those interested in biodiversity meta-analyses. Confirmation of identities and intercomparison of studies are also constrained by the disturbing rate of decline in the number of taxonomists and systematists specializing on marine taxa in Canada. This decline is mostly the result of retirements of current specialists and to a lack of training and employment opportunities for new ones. Considering the difficulties encountered in compiling an overview of biogeographic data and the diversity of species or taxa in Canada's three oceans, this synthesis is intended to serve as a biodiversity baseline for a new program on marine biodiversity, the Canadian Healthy Ocean Network. A major effort needs to be undertaken to establish a complete baseline of Canadian marine biodiversity of all taxonomic groups, especially if we are to understand and conserve this part of Canada's natural heritage.