No abstract

Dilithium phenylphosphide reacts with 1,3-dichloropropane or 1,2-dichloroethane to give 1-phenylphosphetane (1) or 1-phenylphosphirane (2), respectively, both of which can be isolated by distillation in vacuo. The phosphetane rapidly polymerizes when neat but is stable in benzene wherefrom the polymer can be selectively and quantitatively separated from 1 by the addition of trans-dichlorobis(diethyl sulfide)palladium(II). Four-membered 1 has a remarkably low-field 31P NMR chemical shift (13.9 ppm), and 2, a remarkably high-field shift (−236 ppm). The crystal and molecular structures of the potential cyclotrimerization precursor complexes fac-[Mo(CO)3(1)3] (7), fac-[Mo(CO)3(2)3] (8), and [(η5-C5H5)Fe(2)3]PF6 (9) have been determined. Both molybdenum complexes have C 3 symmetry in the solid state, and the iron complex has C 1 symmetry. An interesting feature of the three structures is that the phenyl groups of the small phosphorus heterocycles in each case are arranged in groups of three syn or anti to the auxiliary ligands.

Ab initio molecular orbital calculations at the G2 level of theory have been used to characterize the potential energy surface for the reactions of phosphirenium or phosphiranium ions with acetylene or ethylene. Comparisons between two competing pathways for π-ligand exchange are discussed along with comparisons between the lower energy exchange pathway and a competing insertion reaction. The lower energy exchange reactions have barriers (4−39 kJ mol-1) much smaller than those of the insertion reactions (215−234 kJ mol-1), despite the fact that the insertion products are strongly preferred thermodynamically. This is consistent with the exclusive observation of exchange experimentally. The transition structures for the preferred exchange reactions contain PH2 + moieties that are rotated so that they are almost parallel to the CC bond of the ring and the CC bond of the incoming hydrocarbon, leading to the prediction that the reactions are stereospecific with respect to the configuration at phosphorus.

No abstract

A us t ra lia 1 -P h enyl p hosp h i ra ne reacts with methyl trif late to give 1 -methyl-1 -p hen yl p hosp h i ra n i u m t riflate, which reacts with acetylenes to give the corresponding phosphirenium salts.

Blue whale songs provide a measure for characterising worldwide blue whale population structure. These songs are divided into nine regional types, which maintain a stable character. Five of the nine song types have been recorded over time spans greater than 30 years showing no significant change in character. The nine song types can be divided into those containing only simple tonal components (high latitude North Pacific, North Atlantic and Southern Ocean song types), those comprised of complex pulsed units in addition to the tonal components (Pacific Ocean margin song types from California, Chile and New Zealand), and those which have the greatest complexity of all and the longest cycling times (Indian Ocean song types from Sri Lanka, Fremantle and Diego Garcia). We suggest that temporally stable differences in song provide another characteristic for comparison with genetic and morphological data when defining blue whale populations. Furthermore, as Mellinger and Barlow (2003) recommend, when there is a lack of other data or lack of clarity in other data sets, evidence of distinct differences in songs between areas should be used as a provisional hypothesis about population structure when making management decisions. Worldwide study is needed to better understand the various populations and subspecies within species like the blue whale that have large geographic distributions and have both migrating and resident populations.

No abstract

No abstract