Synthesis, structure and reactivity study of magnesium amidinato complexes derived from carbodiimides and N,N′-bis(2,6-diisopropylphenyl)-1,4-diaza-butadiene ligands

We report an amidinato ligand-supported series of magnesium complexes obtained from the insertion of a magnesium–carbon bond into a carbon–nitrogen double bond of different carbodiimides and α-diimine ligands. The magnesium complexes [Mg(CH2Ph){CyN[double bond, length as m-dash]C(CH2Ph)NCy}]2 (1), [Mg(CH2Ph){iPrN[double bond, length as m-dash]C(CH2Ph)NiPr}]2 (2) and the homoleptic [Mg{tBuN[double bond, length as m-dash]C(CH2Ph)NtBu}2] (3) (Cy = cyclohexyl, iPr = isopropyl, tBu = tert-butyl) were prepared by the reaction of dibenzyl magnesium [Mg(CH2Ph)2(Et2O)2] with the respective carbodiimides either in 1 : 1 or 1 : 2 molar ratio in toluene. The analogous reaction of [Mg(CH2Ph)2(Et2O)2] with the N,N′-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene (Dipp2DAD) ligand afforded the corresponding homoleptic magnesium complex [Mg{DippN[double bond, length as m-dash]C(CH2Ph)CH2NDipp}2] (4) (Dipp = 2,6 diisopropylphenyl) in good yield. The solid-state structures of magnesium complexes 1–4 were confirmed by single-crystal X-ray diffraction analysis. It was observed that in each case, a magnesium–carbon bond was inserted into the carbon–nitrogen double bond of either carbodiimides or Dipp2DAD resulting in a monoanionic amido–imino ligand. In a further reaction between 1 and N-aryliminopyrrolyl ligand 2-(2,6-iPr2C6H3N[double bond, length as m-dash]CH)C4H3NH (ImpDipp-H) in 1 : 2 molar ratio, a new magnesium complex [Mg(ImpDipp)2{CyN[double bond, length as m-dash]C(CH2Ph)NHCy}] (5), with one amidinato and two aryliminopyrrolyl ligands in the coordination sphere, was obtained in good yield. In contrast, the homoleptic magnesium complex 4 reacted with one equivalent of N-aryliminopyrrolyl ligand (ImpDipp-H) to produce another mixed ligated magnesium complex [Mg{DippN[double bond, length as m-dash]C(CH2Ph)CH2NDipp}(ImpDipp)] (6), with a benzylated DAD ligand and aryliminopyrrolyl ligands in the coordination sphere. Further reaction of complex 4 with benzyl alcohol (PhCH2OH) afforded the third mixed ligated magnesium complex [Mg{DippN[double bond, length as m-dash]C(CH2Ph)CH2NDipp}(OCH2Ph)2] (7) in very good yield. The magnesium complexes 5–7 were characterised using standard analytical/spectroscopic techniques and their solid-state structures were established by single-crystal X-ray diffraction analysis

Interaction of Nitric Oxide with Phytohormones under Drought Stress

Plants are often exposed to a plethora of stress conditions such as salinity, extreme temperatures, drought, and heavy metals that can greatly impact farmer’s income. Nitric oxide (NO) has been implicated in resistance to various plant stresses and hence gaining increasing attention from plant researchers. NO mediate various abiotic and biotic stresses in plants including drought stress. However, it is still unclear about the actual involvement of NO in drought stress responses at a whole plant level. Whether NO act alone or in coherence with other phytohormones and signaling molecules is an open question till now. Here we summarized the interaction of NO with the well-known phytohormones in coping with the drought stress

Insights Into the Nitric Oxide Mediated Stress Tolerance in Plants

During the last two decades, several studies have established nitric oxide (NO) as a crucial signaling molecule during plant stress responses. NO protect plants from stressful conditions mostly through the activation of antioxidant defense, by maintaining metabolic homeostasis, by altering the gene transcription and posttranslational protein modifications. So far, most of the NO functions have been explored based on manipulation of endogenous NO levels by exogenous donors/scavengers or through mutants and transgenics. However, it is hard to draw any clear conclusions, since most of these studies are not uniform, being rather superficial without exploring the underlying signaling pathways. Indeed, the integration of the crosstalk events between NO and other signaling molecules under stress responses is also very critical. Importantly, lack of complete understanding of its production and signaling cascade is a serious setback for further elucidation by genetic and molecular approaches. Therefore, a step forward now will be to explore more NO responsive genes, proteins, and their networks under stress to serve as a key resource for further NO research

Titanium and zirconium complexes of the N,N′-bis(2,6-diisopropylphenyl)-1,4-diaza-butadiene ligand: syntheses, structures and uses in catalytic hydrosilylation reactions

We report here a number of dianionic 1,4-diaza-1,3-butadiene complexes of titanium and zirconium synthesised by a salt metathesis reaction. The reaction of either CpTiCl3 or Cp2TiCl2 with the dilithium salt of N,N′-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene [1; abbreviated (Dipp)2DADLi2] afforded the mono-cyclopentadienyl titanium complex [η5-CpTi((Dipp)2DAD)Cl] (2) bearing a dianionic ene-diamide ligand, while the analogous reaction of zirconocene dichloride (Cp2ZrCl2) with the dilithium salt 1 gave the bis-cyclopentadienyl zirconium complex [Cp2Zr{(Dipp)2DAD}] (3). The metal dichloride complexes [Ti((Dipp)2DAD)Cl2] (4) and [{(Dipp)2DADZrCl(μ-Cl)}2(κ3-Cl)(Li)(OEt2)2] (5) were obtained by the reaction of 1 and anhydrous metal tetrachloride in a 1 : 1 molar ratio in diethyl ether at room temperature. Meanwhile, the homoleptic titanium complex [Ti{((Dipp)2DAD)}2] (6) was isolated in good yield by the treatment of 1 with TiCl4 in a 1 : 2 molar ratio in diethyl ether. The complexes 2 and 5 were further reacted with neosilyl lithium to afford mono- and bis-alkyl complexes of titanium [η5-CpTi{(Dipp)2DAD}(CH2SiMe3)] (7) and zirconium [Zr{(Dipp)2DAD}(CH2SiMe3)2] (8) respectively. Molecular structures of the complexes 2, 3, and 5–8 in the solid states were confirmed by single crystal X-ray diffraction analysis. The solid state structures of all the complexes reveal that the metal ions are chelated through the amido-nitrogen atoms and the olefinic carbons of the [(Dipp)2DAD]2− moiety, satisfying the σ2,π coordination mode. Compound 8 was used as a catalyst for the intermolecular hydrosilylation reaction of a number of olefins, and moderate activity of catalyst 8 was observed

Plant Responses to Ozone Stress: Actions and Adaptations

Ozone (O3) is a blue-colored gaseous molecule naturally present in the Earth’s stratosphere region at about 20-30 km above the Earth’s surface. O3 was naturally formed in the stratosphere about 200 billion years ago by photolysis of molecular oxygen by UV radiations from the Sun and chemical recombination with oxygen molecules. O3 sensitivity is often linked to low leaf mass per area and low leaf area-based antioxidant levels or stomatal conductance. The damaging effects of O3 on plant health were reported as early as 1905 when there was severe vegetable crop damage in Los Angeles. The entry of O3 into the leaf through the stomata triggers a cellular response and ultimately results in damage to crop productivity. O3-induced oxidative stress often leads to general redox-dependent alterations in ion conductance in many plant species. Under natural conditions, plants constitute a significant part of the ecosystem. Practically any change in a plant can have a great impact on associated ecosystems

Synthesis and Structure of Unprecedented Samarium Complex with Bulky Bis-iminopyrrolyl Ligand via Intramolecular C=N Bond Activation

An unprecedentate samarium complex of the molecular composition [{κ3-{(Ph2CH)N=CH}2C4H2N)}{κ3-{(Ph2CHN=CH)(Ph2CHNCH)C4H2N}Sm}2] (2), which was isolated by the reaction of a potassium salt of 2,5-bis{N-(diphenylmethyl)-iminomethyl}pyrrolyl ligand [K(THF)2{(Ph2CH)N=CH}2C4H2N)] (1) with anhydrous samarium diiodide in THF at 60 °C through the in situ reduction of imine bond is presented. The homoleptic samarium complex [[κ3-{(Ph2CH)–N=CH}2C4H2N)]3Sm] (3) can also be obtained from the reaction of compound 1 with anhydrous samarium triiodide (SmI3) in THF at 60 °C. The molecular structures of complexes 2 and 3 were established by single-crystal X-ray diffraction analysis. The molecular structure of complex 2 reveals the formation of a C–C bond in the 2,5-bis{N-(diphenylmethyl)iminomethyl}pyrrole ligand moiety (Ph2Py–). However, complex 3 is a homoleptic samarium complex of three bis-iminopyrrolyl ligands. In complex 2, the samarium ion adopts an octahedral arrangement, whereas in complex 3, a distorted three face-centered trigonal prismatic mode of nine coordination is observed around the metal ion