RESUMO
A new ruthenium pincer complex [RuHCl(CO)(PNP)] (PNP = PhCH2N(CH2CH2PPh2)2) () was synthesized and characterized. The reactivity of complex with electrophilic reagents XOTf (X = H, CH3, and Me3Si; OTf = CF3SO3) was studied by variable temperature NMR spectroscopy with an aim to observe and characterize sigma complexes of type [Ru(η(2)-HX)Cl(CO)(PNP)][OTf] (X = H (), CH3 (), Me3Si ()). Reaction of complex with HOTf resulted in the formation of the dihydrogen complex, [Ru(η(2)-H2)Cl(CO)(PNP)[OTf] (). On the other hand, the reaction between complex and MeOTf and Me3SiOTf resulted in the direct elimination of MeCl and Me3SiCl via a SN2 type of reaction without the intermediacy of the respective sigma complexes and . This contrasting reactivity behaviour has been rationalized taking into consideration the approach of the relatively bulky electrophiles CH3(+) and Me3Si(+) onto the hydride moiety of the ruthenium fragment, which is sterically hindered.
RESUMO
Aphid Lipaphis erysimi (Kaltenbach) infestation on mustard (Brassica juncea L.) account for considerable yield losses in India. Experimental data from six north Indian locations were used to study the role of weather on the incidence and development of mustard aphid. Temperature was found to regulate the aphid appearance and population build-up. In warm humid climate, time to attain peak population was relatively shorter than in cool climates. Aphids appeared mostly when the accumulated thermal time ranged between 810-847 degrees cd. Functional relations proposed in the present investigation between aphid incidence and peak population, using previous weeks weather and pest data for majority of the locations, could be used for taking any prophylactic/control measures.