All the syntheses were carried out under an argon atmosphere with standard Schlenk line and glove box techniques. Compounds, such as, [Cp*TaCl4], [1] S2CPPh3, [2,3] and the external reference for the 11 B{ 1 H} NMR, [Bu4N][B3H8] [4] were synthesized according to the literature methods. Thin-layer chromatography was carried out on 250 mm aluminum supported silica gel TLC plates. NMR spectra were recorded in a 500 MHz Bruker FT-NMR spectrometer. Chemical shifts are referenced to (residual) solvent signals ( 1 H/ 13 C{ 1 H}; CDCl3: δ = 7.26/77.16 ppm) or external [Bu4N][B3H8] ( 11 B: δ = 30.07 ppm). Mass spectra were recorded in a Bruker Micro TOF-II mass spectrometer in ESI ionization mode. I.1 Synthesis and CharacterizationsScheme S1. Synthesis of compound 1. Synthesis of 1:A suspension of [Cp*TaCl4] (0.100 g, 0.22 mmol) in 8 mL toluene at -78 ºC was charged dropwise with lithium borohydride solution 2.0 M in THF (0.7 mL) in toluene (10 mL) over 15 min and kept under constant stirring for 1 hour. Then freshly prepared solution of excess S2CPPh3 (0.075 g of PPh3 dissolved in 6 mL of CS2) was added in the reaction mixture over 5 min and kept under constant stirring for 24h at room temperature.The colour of the reaction mixture changed from yellow to brown. The solvent was evaporated in vacuum; residue was extracted into hexane/CH2Cl2 (60:40 v/v) and passed through Celite. After the removal of the solvent from the filtrate, the residue was subjected to chromatographic workup using silica-gel TLC plates. Elution with hexane/CH2Cl2 (60:40 v/v) yielded orange [(Cp*Ta)2(µ,η 2 :η 2 -B2H5)(μ-H)(κ 2 ,µ-S2CH2)2], 1 (0.0125g, 14.02 %) along with known compound 2 (0.025 g, 33.30 %).

In mosquito control programs, insecticides of botanical origin have the potential to eliminate eggs, larvae, and adults. So, the larvicidal, ovicidal, and oviposition-deterrent activities of petroleum ether and ethyl acetate extracts of the leaves of Eugenia jambolana, Solidago canadensis, Euodia ridleyi, and Spilanthes mauritiana were assayed against the three vector mosquito species, namely Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus. The larval bioassay was conducted following the World Health Organization method. The maximum larval mortality was found with ethyl acetate extract of S. mauritiana against the larvae of A. stephensi, A. aegypti, and C. quinquefasciatus with LC 50 values of 11.51, 28.1, 14.10 ppm, respectively. The mean percent hatchability of the ovicidal activity was observed at 48-h post-treatment. The percent hatchability was found to be inversely proportional to the concentration of the extract and directly proportional to the number of eggs. The flower head extract of S. mauritiana gave 100 % mortality followed by E. ridleyi, S. canadensis, and E. jambolana against the eggs of the three mosquito vectors. For oviposition-deterrent effect, out of the five concentrations tested (20, 40, 60, 80, and 100 ppm), the concentration of 100 ppm showed a significant egg laying-deterrent capacity. The oviposition activity index value of E. jambolana, E. ridleyi, S. canadensis, and S. mauritiana against A. aegypti, A. stephensi, C. quinquefasciatus at 100 ppm were −0.71, −0.71, −0.90, −0.93, −0.85, −0.91, −1, −1, −0.71, −0.85, −1, and −1, respectively. These results suggest that the leaf/flower extracts of certain local plants have the potential to be developed as possible eco-friendly means for the control of mosquitoes.

No abstract

A series of amidinate-based N,O-chelated magnesium complexes [(L 1 )2(THF)2Mg] (1), [(L 2 )2(THF)2Mg] (2), [(L 3 )2(THF)2Mg] (3), and [(L 4 )2Mg] (4) were prepared by treating N-benzoyl-N′-arylbenzamidines (L 1–4 H) with 0.5 equiv of di-n-butylmagnesium in THF. Analogous CH3CN-coordinated complexes [(L 1 )2(CH3CN)2Mg] (5) and [(L 3 )2(CH3CN)2Mg] (6) were prepared in a similar way using CH3CN as solvent. All of the compounds were characterized by 1H/13C NMR spectroscopy, and the molecular structures of 1, 2, and 4–6 were further confirmed by single-crystal X-ray diffraction studies. Complexes 1, 2, 5, and 6 displayed good catalytic activity toward the ring-opening polymerization (ROP) of ε-caprolactone. In addition, 1, 5, and 6 were also found to be excellent catalysts for making cyclic carbonates from CO2 and epoxides in the presence of a cocatalyst, n-Bu4NBr.

Syntheses, structures, and electronic properties of group 5 metal–thiolate complexes that exhibit unusual coordination modes of thiolate ligands have been established. Room-temperature reaction of [Cp*VCl2]3 (Cp* = η5-C5Me5) with Na5[B­(SCH2S)4] led to the formation of [Cp*VO­{(SCH2)2S}] (1). The solid-state X-ray structure of 1 shows the formation of six-membered l,3,5-trithia-2-vanada­cyclo­hexane that adopted a chair conformation. In a similar fashion, reactions of heavier group 5 precursors [Cp*MCl4] (M = Nb or Ta) with Na5[B­(SCH2S)4] yielded bimetallic thiolate complexes [(Cp*M)2(μ-S)­{μ-C­(H)­S3-κ2 S:κ2 S′,S″}­{μ-SC­(H)­S-κ2 C:κ2 S‴,S′′′′}] (3a: M = Nb and 3b: M = Ta). One of the key features of molecules 3a and 3b is the presence of square-pyramidal carbon, which is quite unusual. The reactions also yielded bimetallic methanedithiolate complexes [(Cp*Nb)2(μ-S)­(μ-SCH2S-κ2 S,S′)­(μ,η2:η2-BH3S)] (2) and [(Cp*Ta)2(μ-O)­(μ-SCH2S-κ2 S,S′)­(μ-H)­{μ-S2C­(H)­SCH2S-κ2 S″:κ2 S‴,S′′′′}] (4). Complex 2 contains a methanedithiolate ligand that stabilizes the unsaturated niobaborane species. On the other hand, one ((mercapto­methyl)­thio)­methane­di­thiolate ligand {C2H4S3} is present in 4, which is coordinated to metal centers and exhibits the {μ-κ2 S″:κ2 S‴,S′′′′} bonding mode. Along with the formation of 3b and 4, the reaction of [Cp*TaCl4] with Na5[B­(SCH2S)4] yielded [(Cp*Ta)2(μ-S)­{μ-(SBS)­S­(CH2S)2(BH2S)-κ2 B:κ2 S:κ4 S′,S″,S‴,S′′′′}] (5) containing a trithiaborate unit (BS3). Complex 5 consists of pentacoordinate boron that resides in a square-pyramidal environment. All the complexes have been characterized by multinuclear NMR, UV–vis spectroscopy, mass spectrometry, and single-crystal X-ray diffraction studies.