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Monocationic bis(hydrocarbyl)yttriumcomplexes [YR2(THF)2][A] (R = CH2SiMe3, CH2C6H4-o-NMe2; A = weakly coordinating anion)underwent hydrogenolysis using dihydrogen or phenylsilane to givea mixture of polynuclear solvent-stabilized dihydride cations [YH2(THF)2]n[A]n. The mixture composition as well as the nuclearity ndepended on the starting material, solvent, and reactionconditions. NMR spectroscopic data in solution and X-ray diffractiondata suggested that the main product was tetranuclear, although conclusivestructural data were not obtained. DFT calculations supported a closo-type tetrahedral [YH2(THF)2]44+core. The hydridic character of these cationswas revealed by their reaction with benzophenone to give the bis(diphenylmethoxy)cation [Y(OCHPh2)2(THF)4][AlR4]. The reaction of this cluster with the (NNNN)-type macrocycleMe4TACD under dihydrogen gave the dinuclear tetrahydridedication with quadruply bridging hydride ligands, [Y2(μ-H)4(Me4TACD)2][A]2, analogousto the previously characterized lutetium derivative. NH-acidic (Me3TACD)H gave the dinuclear dihydride dication [Y2(μ-H)2(Me3TACD)2(THF)2][A]2. [ABSTRACT FROM AUTHOR]

We have prepared tungsten bispyrrolyl (Pyr) or bis-2,5-dimethylpyrrolyl (Me2Pyr) complexes W(NAr)(CHCMe2Ph)(1-Pyr)2(DME) (1), W(NAr)(CHCMe2Ph)(1-Me2Pyr)(5-Me2Pyr) (2), W(NArCl)(CHCMe3)(1-Pyr)2(DME) (3b), and W(NArCl)(CHCMe3)(1-Me2Pyr)(5-Me2Pyr) (4) (Ar 2,6-diisopropylphenyl, ArCl2,6-dichlorophenyl) in excellent yields by treating the appropriate W(NR)(CHCMe2R‘)(OTf)2(DME) species with LiPyr or LiMe2Pyr. Compounds 2and 4react with ethylene slowly to yield stable methylene complexes, W(NAr)(CH2)(1-Me2Pyr)(5-Me2Pyr) (5) and W(NArCl)(CH2)(1-Me2Pyr)(5-Me2Pyr) (6). In contrast, treatment of what is believed to be a fortuitous 1:1 mixture of 3band W(NArCl)(CHCMe3)(1-Pyr)2W(NArCl)(CHCMe3)(1-Pyr)(5-Pyr) with ethylene leads to formation of W(-NArCl)(1-Pyr)22(7) in moderate (54%) yield. Compounds 2and 4react with HNMe2PhB(ArF)4(ArF3,5-(CF3)2C6H3) in dichloromethane to yield cationic species that contain one 5-Me2Pyr ligand and one 2,5-dimethylpyrrolenine ligand formed through addition of a proton to C(2) of a dimethylpyrrolyl ligand, e.g., W(NArCl)(CHCMe3)(Me2Pyr)NC4(H3-2,3,4)(Me2-2,5)B(ArF)4-(9). X-ray studies were carried out on 1, 2, 6, 7, and 9. [ABSTRACT FROM AUTHOR]

Tungsten alkylidene complexes that contain the 2,6-dichlorophenylimido ligand (NArCl), W(NArCl)(CHCMe3)(ORF6)2and W(NArCl)(CHCMe3)(Biphen)(THP) (ORF6OCMe(CF3)2; Biphen2-3,3‘-di-t-Bu-5,5‘,6,6‘-tetramethyl-1,1‘-biphenyl-2,2‘-diolate; THP tetrahydropyran), have been prepared from W(NArCl)(CHCMe3)(OSO2CF3)2(dme). Reaction of W(NArCl)(CHCMe3)(ORF6)2with excess ethylene gave the tungstacyclobutane complex W(NArCl)(ORF6)2(C3H6), while reaction of W(NArCl)(CHCMe3)(ORF6)2with internal olefins gave the dimer, W(-NArCl)(ORF6)22. W(NArCl)(CHCMe3)(Biphen)(THP) reacted with excess ethylene to give W(NArCl)(Biphen)(C3H6), which yielded W(NArCl)(Biphen)(C2H4)(THF) upon addition of THF. The tungstacyclopentane complex, W(NArCl)(Biphen)(C4H8), was formed upon treatment of W(NArCl)(Biphen)(C2H4)(THF) with ethylene. W(NArCl)(Biphen)(C3H6) decomposed to yield (interalia) the dimeric, heterochiral methylidene complex, W(NArCl)(Biphen)(-CH2)2, which decomposed further to yield homochiral W(NArCl)(Biphen)2(-CH2CH2). Finally, W(NArCl)(Biphen)2(-CH2CH2) loses ethylene reversibly to yield W(NArCl)(Biphen)2, which could not be isolated in pure form. W(-NArCl)OC(CF3)2Me22, W(NArCl)(Biphen)(C3H6), W(NArCl)(Biphen)(C2H4)(THF), W(NArCl)(Biphen)(C4H6), W(NArCl)(Biphen)(-CH2)2, and W(NArCl)(Biphen)2(-CH2CH2) were characterized through X-ray studies. [ABSTRACT FROM AUTHOR]

Background and Aims The genus Eucalyptus occupies a broad ecological range, forming the dominant canopy in many Australian ecosystems. Many Eucalyptus species are renowned for tolerance to aridity, yet inter-specific variation in physiological traits, particularly water relations parameters, contributing to this tolerance is weakly characterized only in a limited taxonomic range. The study tests the hypothesis that differences in the distribution of Eucalyptus species is related to cellular water relations. Methods Six eucalypt species originating from (1) contrasting environments for aridity and (2) diverse taxonomic groups were grown in pots and subjected to the effects of water deficit over a 10-week period. Water potential, relative water content and osmotic parameters were analysed by using pressure–volume curves and related to gas exchange, photosynthesis and biomass. Key Results The six eucalypt species differed in response to water deficit. Most significantly, species from high rainfall environments (E. obliqua, E. rubida) and the phreatophyte (E. camaldulensis) had lower osmotic potential under water deficit via accumulation of cellular osmotica (osmotic adjustment). In contrast, species from low rainfall environments (E. cladocalyx, E. polyanthemos and E. tricarpa) had lower osmotic potential through a combination of both constitutive solutes and osmotic adjustment, combined with reductions in leaf water content. Conclusions It is demonstrated that osmotic adjustment is a common response to water deficit in six eucalypt species. In addition, significant inter-specific variation in osmotic potential correlates with species distribution in environments where water is scarce. This provides a physiological explanation for aridity tolerance and emphasizes the need to identify osmolytes that accumulate under stress in the genus Eucalyptus. [ABSTRACT FROM AUTHOR]