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The dependency of soil particle wettability on soil water content implies that soils subjected to drying-wetting cycles become wettable with wetting and water repellent with drying. While this has been demonstrated widely, the results are contradictory when water repellent soils are subjected to a sequence of cycles. Added to this, past wettability measurements were seldom done in batches of samples collected from the field at natural or dry water contents, with little appreciation that slight particle size variations, different drying-wetting histories and fabric (as required by different wettability measurement methods) may alter the results. This note presents soil particle wettability—soil water content relations by means of an index test following staged drying and wetting paths over a period of 8 months for an untreated, oil-contaminated anthropogenic soil (a mixture of slag, coal particles, fly ash and mineral particles) from Barry Docks (UK), a site formally used for oil storage, which is to be remediated and redeveloped for housing. The results revealed a decrease in the water repellency and increasing mineralization and bacterial activity with the wetting and drying cycles.

In previous studies, extracts from water-repellent soils have been applied to wettable substrates to examine the role of organic matter in causing water repellency, but the effects of individual compounds found in water-repellent soils have not been examined. To address this research gap, acid-washed sand (AWS) and wettable sandy soil were coated with a range of hydrophobic organic compounds that had been identified by gas chromatography-mass spectrometry (GC-MS) analysis of extracts from a range of water-repellent soils in previous published work. Saturated and unsaturated long chain acids, alkanes, amides, esters, cholesterol and β-sitosterol were applied at various loadings to investigate the effects of chain length, molecular shape, functional group, heating, particle size and packing efficiency on soil wettability. No single compound induced repellency on AWS at loadings equivalent to the level of detection of individual compounds in water-repellent soils by GC-MS. The extent of water repellency induced on AWS varied considerably with compound type, suggesting that it depends more on the presence of specific compounds rather than their quantity. A combination of long chain acid and alkane was found to be the most effective at inducing water repellency. Heating at 105°C for 24 hours caused a marked increase in repellency. Particle size had no effect on degree of induced repellency across the approximately 2.5 times variation in diameter examined.

Cocondensation of tungsten vapour with 1,2,3,4,5-pentamethylcyclopentadiene gives bis(η-pentamethylcyclopentadienyl)tungsten dihydride, (η-C5Me5)2WH2; photolysis of the dihydride yields, sequentially, the ‘tucked-in’ compounds (η-C5Me5)W(η-C5Me4CH2)H and (η-C5Me5)W(η-C5Me3CH2CH2).

The silver(I) and mercury(II) complexes of 1,5-diselena[5]ferrocenophane (L) have been synthesized. The X-ray crystal structures of L, [AgL2]PF6 and [HgI2L] are reported. The small cavity of the macrocyclic ligand means that the ring must undergo a conformational change to allow coordination, and there is no significant through-space interaction M⋯Fe in any of the complexes. Electrochemical studies showed that no electronic communication between ferrocenylene groups was observed in the silver complex where the through-bond Fe···Fe distances are in the range 13.10 (3)–13.27(3) A.

We describe the photochemical characteristics of two phosphorescent palladium diselenolenes [Pd(2)(Se(2)C(8)H(12))(2)(PBu(3))(2)] (1) and [Pd(2)(Se(2)C(8)H(12))(2)(PPh(3))(2)] (2) which, to the best of our knowledge, are the first reported examples of luminescent Pd-Se compounds. Both compounds exhibit broadband near-infrared phosphorescence in the solid state, with lambda(max) of 717 nm for 1 and 792 nm for 2 at 298 K, and 752 nm for 1 and 785 nm for 2 at 77 K. No phosphorescence was detected for either compound when they were dissolved in nitrogen-purged acetonitrile or toluene solution at 298 K but they do phosphoresce at 77 K in organic glasses with emission quantum yields of 0.12 (+/-0.01) for 1 and 0.13 (+/-0.01) for 2 in an ethanol/diethylether/toluene (1:2:1) (EDT) glass. Emission lifetimes at 77 K are the same whether in the solid state or in an organic glass with first order fit lifetimes of tau = 18.8 (+/-0.7) micros and 11.5 (+/-0.3) micros for 1 and 2, respectively. Combination of these lifetimes with quantum yields gives radiative lifetimes of 151 (+/-13) micros and 86 (+/-7) micros for compounds 1 and 2, respectively, at 77 K in EDT glass. At 77 K solid state quantum yields are estimated to be of the same order of magnitude as those in glasses, and these decrease by a factor of about 3-5 in going from 77 to 298 K. In the solid state at 298 K emission lifetimes are 1.83 (+/-0.02) micros and 7.0 (+/-0.3) micros for 1 and 2, respectively. We could detect no transients by nanosecond flash photolysis which could be assigned to the triplet state in room temperature solution, and no emission assignable to singlet oxygen across the wavelength range 1200-1350 nm upon 550 nm excitation of either 1 or 2 in acetonitrile solution. We estimate the quantum yield of singlet oxygen formation to be less than about 5 x 10(-4), which is also an upper limit for the yield of triplet states of any significant lifetime in fluid solution. Density functional theory (DFT) calculations of the S(0) to S(1) and T(1) transitions show a shift in molecular orbital character from one with significant -ene pi involvement but very little P involvement in the ground-state to one with less -ene pi but greater P involvement in the excited states; there is also a significant shift in the distribution of involvement of atomic orbitals on the four Se atoms.

A series of linear tridentate ligands, FcE(CH2)3E′(CH2)3EFc (E, E′ = Se or Te), was synthesised. Their chloropalladium(II) and chloroplatinum(II) complexes were also prepared. The new compounds were characterised by a range of spectroscopic and analytical techniques, including multinuclear NMR spectrometry and X-ray crystallography. In an electrochemistry study of the complexes no communication between the ferrocenyl centres was observed, regardless of the through-bond Fe···Fe distance.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

The Group 6 metal tetracarbonyl complexes [Cr(CO) 4 {FcTe(CH 2 ) 3 TeFc}], [Mo(CO) 4 {FcE(CH 2 ) 3 E′Fc}] (E = E′ = Se; E = Se, E′ = Te; E = E′ = Te), and [W(CO) 4 {FcTe(CH 2 ) 3 TeFc}] (Fc = [Fe(η 5 -C 5 H 5 )(η 5 -C 5 H 4 )]) have been prepared and fully characterised. Electronic communication between the ferrocenyl groups is observed in the case of [Mo(CO) 4 {FcSe(CH 2 ) 3 SeFc}], where the through-bond Fe⋯Fe distance is 13.17 A, but in the other four complexes the longer through-bond Fe⋯Fe distances (⩾13.56 A) preclude it.

Room temperature reaction of [Pd2(dba)3]/PR3 or [Pt(C2H4)(PR3)2] (dba = dibenzylideneacetone; R = Et, Bu) with the diselenides (R′Se)2 (R′ = Ph, Fc) yielded the oxidative addition products trans-[M(SeR′)2(PR3)2] (M = Pd, Pt). These have been characterised by multinuclear NMR and UV–Vis spectroscopy, mass spectrometry, and, in the cases of trans-[Pt(SePh)2(PR3)2] (R = Et, Bu) and trans-[Pt(SeFc)2(PBu3)2], also by X-ray crystallography.

1,3-Bis(ferrocenylchalcogeno)propanes, FcE(CH2)3E′Fc (E, E′ = Se, Te), and 1,2-bis(ferrocenylseleno)ethane, FcSe(CH2)2SeFc have been prepared, characterised, and included in a spectroscopic and electrochemical study of a series of compounds containing two ferrocenes linked by a chalcogen-containing bridge. Cyclic and differential pulse voltammetry show that there is electronic communication between the two ferrocene units when the bridge is short (as in Fc2E), but that the interaction rapidly becomes weaker with increasing Fe⋯Fe distance, and is undetectable for the ethane and propane derivatives. 77Se and 125Te NMR spectroscopic measurements reveal that the 77Se chemical shift of Fc2Se2 is anomalously high, which correlates with the long wavelength of its lowest energy electronic absorption.

Reaction of a 1,3-bis(ferrocenylchalcogeno)propane, FcE(CH2)3E′Fc (L: E, E′ = Se or Te; Fc = [Fe(η5-C5H5)(η5-C5H4)]), with a palladium(II) or platinum(II) precursor [M(NCMe)4](PF6)2 (M = Pd or Pt) in acetonitrile at room temperature led in good yield to the bis-chelate complexes [ML2](PF6)2. The structures of FcSe(CH2)3SeFc and all six complexes have been determined by X-ray crystallography. Electrochemical studies showed that electronic communication between ferrocenyl groups, absent in all three bis(ferrocenylchalcogeno)propanes, is established on complexation only for E = Se and E′ = Se or Te, when the through-bond Fe⋯Fe distance is reduced to 13.17 A or less.

The novel mono(cyclopentadienyl)selenium derivatives, Se(C5Me4R)Fc (Fc = ferrocenyl, [Fe(η5-C5H5)(η5-C5H4)]; R = H or Me) have been prepared by treatment of diferrocenyl diselenide with LiC5Me4R, and characterised by NMR spectroscopy and mass spectrometry. The structure of Se(C5Me5)Fc has been confirmed by X-ray crystallography, and its redox properties have been examined by cyclic voltammetry. It reacts with [W(CO)5(THF)] to form [W2(μ-SeFc)2(CO)8] via C–Se bond cleavage.

The condensation of bis(o-formylphenyl) selenide with 1,2-diaminoethane or 1,3-diaminopropane yielded the new macrocyclic ligands 1 and 2 in very good yields. Crystals of 1 are monoclinic, space group P2(1)/c with a = 10.0648(10) angstrom, b = 37.390(4) angstrom, c = 8.0073(11) angstrom, Z = 4 and those of 2 are triclinic, space group P (1) over bar with a 7.200(3), b = 9.137(3), C = 12.780(6) angstrom, Z = 1. The coordination chemistry of 1 and 2 has been studied with the "soft" metal ion Pd-II and "hard" metal ions Ni-II and Co-II. Reaction of [PdCl2(COD)] with 1 mol-equiv. of 1 or 2 in refluxing methanol and addition of NH4PF6 afforded the PdII complexes 5 and 6, respectively. Compound 5 is an unexpected partially hydrolyzed complex. It crystallizes in the tetragonal space group P4(1)2(1)2 with a = 10.7737(10) angstrom, b = 10.7737(10) angstrom, c = 28.190(5) angstrom, Z = 4. The structure shows the Pd-II ion coordinated to a square-planar arrangement of two selenium and two nitrogen atoms. Reaction of NiCl(2)(.)6H(2)O with I or 2 and NH4PF6 yielded complexes 7 and 8, respectively. The assignment of octahedral geometries to [Ni(L)](PF6)(2)] (7: L = 1; 8: L = 2) follows from their paramagnetism [mu(eff) = 3.23 (7), 1.81 (8) B.M.] and their UV/Vis spectra. This was also confirmed by single-crystal Xray studies. The crystal structures of 7 and 8 showed a distorted octahedral nickel center coordinated by two selenium and four nitrogen atoms. 7: Monoclinic, space group P21/c; a 9.979(2) angstrom, b = 18.901(4) angstrom, c = 19.333(4) angstrom; Z = 4. 8:Orthorhombic, space group Pna2(1); a = 20.277(5), b = 20.865(5), c = 9.416(2) angstrom; Z = 4. The cyclic voltammograms of 7 and 8 in MeCN solution show well-behaved quasi-reversible Ni-III/Ni-II couples. The analogous Co-II complex, [Co(1)](PF6)(2)] (9) also shows a quasi-reversible Co-III/Co-II couple. (c) Wiley-VCH Verlag GmbH T Co. KGaA, 69451 Weinheim, Germany, 2005.

The dinuclear palladium diselenolenes [Pd2(Se2CnH2n−4)2(PR3)2] react with haloalkanes, via electrophilic attack at the bridging selenium atoms, to yield the neutral mononuclear square plan...

After an initial evaluation of several solvents, the efficiency of Soxhlet extractions with isopropanol/ammonia (s.g. 0.88) (70 : 30 v : v; 24 h) in extracting compounds associated with water repellency in sandy soils was examined using a range of repellent and wettable control soils (n = 15 and 4) from Australia, Greece, Portugal, The Netherlands, and the UK. Extraction efficiency and the role of the extracts in causing soil water repellency was examined by determining extract mass, sample organic carbon content and water repellency (after drying at 20°C and 105°C) pre- and post-extraction, and amounts of aliphatic C–H removed using DRIFT, and by assessing the ability of extracts to cause repellency in acid-washed sand (AWS). Key findings are: (i) none of organic carbon content, amount of aliphatic C–H, or amount of material extracted give any significant correlation with repellency for this diverse range of soils; (ii) sample drying at 105°C is not necessarily useful before extraction, but may provide additional information on extraction effectiveness when used after extraction; (iii) the extraction removed repellency completely from 13 of the 15 repellent samples; (iv) extracts from all repellent and wettable control soils were capable of inducing repellency in AWS. The findings suggest that compounds responsible for repellency represent only a fraction of the extract composition and that their presence does not necessarily always cause repellency.

Cycloalkeno-1,2,3-selenadiazoles react with a mixture of [Pd2(dba)3] (dba = dibenzylideneacetone) and a trialkylphosphine, in toluene under reflux, to yield the complexes [PdL(PR3)] (L = SeC(R1) C(R2)N NC(R1) C(R2)Se; R1–R2 = (CH2)n−2; n = 6, 7, 8; R = Et, Bu), which contain a novel Se, N, Se tridentate ligand formed by the coupling of two 1,2,3-selenadiazole molecules; the structures of cyclohexeno-1,2,3-selenadiazole and the product with R = Bu and n = 6 have been determined by X-ray crystallography.

The reaction between [Pd(2)(dba)(3)] (dba = dibenzylideneacetone), tributylphosphine, and a bis(cycloalkeno)-1,4-diselenin leads to either a mononuclear diselenolene [Pd[SeC(R(1))=C(R(2))Se](PBu(3))(2)] or a dinuclear diselenolene [Pd(2)[SeC(R(1))=C(R(2))Se](2)(PBu(3))(2)] [R(1), R(2) = (CH(2))(n), n = 4, 5, 6] depending on the stoichiometry employed. Treatment of the dinuclear diselenolenes with 1,2-bis(diphenylphosphino)ethane (dppe) provides a high-yielding route to the mononuclear species [Pd[SeC(R(1))=C(R(2))Se](dppe)]. All new compounds have been characterized by standard spectroscopic and analytical techniques, in particular by multinuclear NMR spectroscopy; the structure of each of the mononuclear tributylphosphine complexes has been determined by X-ray crystallography. Computational studies show that the observed asymmetry of the diselenolenes in the solid state is a result primarily of intramolecular repulsive interactions between the ligands.

The study of compounds associated with soil water repellency usually involves removing organic material from a sample by some extraction procedure. An evaluation of the kinetics and efficiency of Soxhlet extraction using an isopropanol-aqueous ammonia mixture is given here. Increasing extraction time caused an increase in the mass of material extracted and a decrease in soil water repellency. The same compound types were detected by gas chromatography-mass spectrometry in all extracts, but their proportions varied with extraction time. In particular, the removal of alkanes from the soil sample was less rapid than that of more polar compounds.

Separation and chemical characterisation of specific compounds responsible for soil water repellency has not previously been achieved. Here we describe the extraction, separation and analysis by gas chromatography-mass spectrometry of organic compounds found in wettable and water repellent sandy soils from the Netherlands and United Kingdom. Fatty acids (C16–C24), amides (C14–C24), alkanes (C25–C33), aldehydes/ketones (C23–C31) and complex ring-containing structures were detected in all samples. We found a greater abundance of high molecular mass polar compounds in the water repellent samples.

Substituted μ3-carbido-capped tricobalt carbonyl clusters have been synthesised by reaction of [Co3(μ3-C(O)OCH2CHCH2)(CO)9] with a range of monodentate and chelating phosphane ligands. The products have been characterised by microanalysis, IR and NMR spectroscopy, mass spectrometry and, in the case of [Co3(μ3-CR)(CO)7(dppe)], [Co3(μ3-CR)(CO)7(dppm)], [Co3(μ3-CR)(CO)7(PPh3)2], [Co3(μ3-CR)(CO)7(PMe3)2] and [Co3(μ3-CR)(CO)6(PEt3)3] (R=C(O)OCH2CHCH2), single crystal X-ray diffraction.

A series of 22 ferrocenyl alkyl selenides and tellurides has been prepared from the diferrocenyl dichalcogenides. The compounds have been characterised by mass spectrometry, multinuclear NMR spectroscopy, cyclic and differential pulse voltammetry. There is a close correlation between the 77 Se and 125 Te chemical shifts of analogous compounds, with δ ( 125 Te)/ δ ( 77 Se)=1.60. Other trends in the NMR data are also apparent. All the compounds studied undergo a one electron reversible oxidation at slightly more positive potentials than ferrocene itself. In addition, the tellurides exhibit a second quasi-reversible process at higher potentials, which appears to be chalcogen-based. There is no obvious correlation between the electrochemical results and the NMR spectroscopic data.

The tetrachalcogenides [ME4(dppe)] (M = Pd, E = S; M = Pt, E = S, Se) react with the activated alkynes RO2CC≡CCO2R (R = Me, Et) to form the dithiolenes and diselenolenes [M{E2C2(CO2R)2}(dppe)]; the structures of the compounds with E = S, R = Et have been determined by X-ray crystallography; [PdS4(dppe)] also reacts with the carbene complex [W(CO)5{C(OEt)C≡CPh}] to yield the bimetallic dithiolene [Pd{S2C2[C(OEt)W(CO)5]Ph}(dppe)].

Reaction of [Pt(dppe)2] (dppe=1,2-bis(diphenylphosphino)ethane) with elemental selenium in toluene under reflux, or of [PtCl2(dppe)] with lithium polyselenide in tetrahydrofuran, leads in good yield to the complex [PtSe4(dppe)] whose structure has been determined by X-ray crystallography. Reaction of [Pt(dppe)2] with elemental tellurium, followed by treatment with dichloromethane, leads to isolation of the salt [Pt3(μ3-Te)2(dppe)3]Cl2. [Pd(dppe)2] reacts with elemental selenium to give [Pd2(μ-Se)2(dppe)2] or [Pd3(μ3-Se)2(dppe)3]Cl2, depending on the conditions.

Reaction of [Pd(PPh3)4] with cycloalkeno-1,2,3-selenadiazoles or bis(cycloalkeno)-1,4-diselenines in toluene under reflux led in good yield to the dinuclear diselenolenes [Pd2{SeC(R1)C(R2)Se}2(PPh3)2] [R1,R2 = (CH2)n; n = 4, 5, 6] which have been characterised by microanalysis, multinuclear NMR, IR, and mass spectroscopy; the molecular structure of the compound with n = 6 has been determined by X-ray cystallography.

Treatment of LiC 5 Me 5 with either Se 2 Cl 2 or elemental Se followed by oxidation leads to the formation of a mixture of the polyselenides Se n (C 5 Me 5 ) 2 ( n = 2, 3 and 4). The 77 Se- 77 Se coupling constants measured by NMR spectrosopy for these compounds are the largest yet reported for acyclic systems.

The novel alkyl(pentamethylcyclopentadienyl)selenium derivative Se(C 5 Me 5 )Me has been prepared by treatment of LiC 5 Me 5 sequentially with Se and MeI. It reacts with [W(CO) 5 THF] to form [W(CO) 5 {Se(C 5 Me 5 )Me}]. Spectroscopic characterisation of the new compounds includes the measurement of the first reported value for the coupling constant 1 J ( 77 Se- 183 W).

Treatment of tetrakis(triphenylphosphine)platinum with elemental selenium (red or vitreous) in toluene solution under reflux yields an insoluble solid. This dissolves in dichloromethane with reaction, eventually to form a 1 : 1 mixture of [PtCl2(PPh3)2] and the new compound [Pt(Se2CH2)(PPh3)2], which has been characterized by multinuclear NMR spectroscopy and X-ray crystallography. Under the same conditions, tetrakis(triphenylphosphine)-palladium yields only decomposition products. © John Wiley & Sons, Inc.

The synthesis of the 2-bromocyclooctenyl selenides, C8H12(Br)SeR (3a: R  Me; 3b: R  Et; 3c: R  CH2Ph), and the 2-bromocyclohexenyl selenides, C6H8(Br)SeR (4a: R  Me; 4b: R  Et; 4c: R  CH2Ph), is described. Compounds 3a–e and 4a, b react with K2PtCl4 to yield square planar platinum (II) complexes of the form trans-PtL2Cl2 (5a: L = 3a; 5b: L = 3b; 5c: L = 3c; 6a: L = 4a; 6b: L = 4b). The analogous palladium(II) complex trans-PdL2Cl2 (7c: L = 4c) has been prepared from Pd(C6H5CN)2Cl2. All new compounds have been characterised by NMR, infrared and mass spectroscope and microanalysts. Complexes 5a–c, 6a, b and 7c exist as a racemic mixture of two diastereoisomers related by inversion at selenium. NMR spectroscope shows that interconversion between these two isomers is slow for 5a–e, but faster for 6a, b and 7c.

The reactions of a range of cyclopentadienylcobalt diselenolenes with cycloocteno-1,2,3-selenadiazole involve ligand exchange and formation of cyclopentadienyl(1,2-cyclooctenediselenolato)cobalt. An example of a proposed intermediate in this process, the novel Se3-chelate cyclopentadienyl[bis(2-selenolatocyclooct-1-enyl)-selenide]cobalt, has been prepared and characterised.

The reactions of a range of cyclopentadienylcobalt diselenolenes with cycloocteno-1,2,3-selenadiazole involve ligand exchange and formation of cyclopentadienyl(1,2-cyclooctenediselenolato)cobalt. An example of a proposed intermediate in this process, the novel Se3-chelate cyclopentadienyl[bis(2-selenolatocyclooct-1-enyl)-selenide]cobalt, has been prepared and characterised.

Cyclopentadienyldicarbonylcobalt reacts with dimethylacetylene dicarboxylate in the presence of selenium to yield cyclopentadienyl[1,2-bis(methoxycarbonyl)-1,2-diselenolato]cobalt (1), cyclopentadienyl[1-cyclopentadienyl-2,3,4,5-tetrakis(methoxycarbonyl)cobaltacyclopenta-2,4-diene]cobalt (2) and tetrakis(methoxycarbonyl)selenophene (3). These compounds have been characterized by spectroscopic and analytical techniques, and in the case of 3, by a single crystal X-ray diffraction study.

Cycloocteno-1,2,3-selenadiazole (1) and cyclopenta-dienyldicarbonylcobalt (2) react in the presence of an excess of elemental sulfur to yield the dithiolene cyclopentadienyl(1,2-cyclooctenedithiolato)cobalt (3). Available evidence indicates that this reaction involves the intermediacy of a cobalt–alkyne complex. Compound 3 is the first example of a cyclopentadienylcobalt dithiolene bearing aliphatic substituents. Analogous reactions performed using only catalytic quantities of 2 provide high-yield syntheses of bis(cycloocteno)-1,4-dithiin (6) and bis(cycloocteno)-1,4-diselenin (7), whose structures have been determined by X-ray diffraction.

Magnesocene ( 1 ) reacts with polyfunctional alcohols ( 2a , N,N -dimethylethanolamine; 2b , 2-ethoxyethanol; 2c , 2-(2-ethoxyethoxy)ethanol; 2d , 2-{[(2-dimethylamino)ethyl]methylamino}ethanol) to yield polymeric cyclopentadienylmagnesium alkoxides ( 3a–d ). Compounds 3a–d dissolve in pyridine to yield solutions containing pyridine adducts ( 4a–d ) of the corresponding monomers, which may be isolated in the cases of 4a,b . These compounds all appear to contain formally 12-electron, pseudo-6-coordinate magnesium. Compound 1 reacts with 2,4-dimethyl-6-t-butylphenol ( 5 ) to form cyclopentadienyl (2,4-dimethyl-6-t-butylphenoxy)magnesium ( 6 ), in which the steric bulk of the phenoxide ligand stabilizes the monomeric, 8-electron configuration.

Co-condensation of molybdenum or tungsten atoms with 1,2,3,4,5-pentamethylcyclopenta-1,3-diene (C5HMe5) affords the decamethylmetallocene dihydrides [M(η-C5Me5)2H2](M = Mo or W). UV photolysis of the latter results in the sequential formation of the ‘tucked-in’ compounds [M(η-C5Me5)(η6-C5Me4CH2)H] and [M(η-C5Me5){η7-C5Me3(CH2)2}](M = Mo or W). For the tungsten analogue, deuterium labelling studies show that the latter reaction proceeds via the decamethylmetallocene followed by intramolecular oxidative addition to a ring methyl group. Treatment of [W(η-C5Me5)2H2] with CCl4 yields [W(η-C5Me5)2Cl2], which reacts with ZnMe2 to afford [W(η-C5Me5)2Me2] and with LiCH2But to afford [W(η-C5Me5)(η6-C5Me4CH2)Cl]. Reduction of [W(η-C5Me5)2Cl2] with sodium amalgam gives [W(η-C5Me5)(η6-C5Me4CH2)H]; reduction of the latter with potassium affords an intermediate anion, which reacts with water or iodomethane to give [W(η-C5Me5)2H2] or [W(η-C5Me5)2Me2] respectively. [Mo(η-C5Me5)2H2] reacts with 1,2-diiodoethane to give [Mo(η-C5Me5)2I2], which is reduced by sodium amalgam to [Mo(η-C5Me5)(η6-C5Me4CH2)H]; there is no evidence for the formation of [{Mo(η-C5Me5)2}2]. Co-condensation of rhenium atoms with C5HMe5 yields [Re(η-C5Me5)2H] and [Re(η-C5Me5)(η6-C5Me4CH2)], both of which can be reversibly protonated to give [Re(η-C5Me5)2H2]+ and [Re(η-C5Me5)(η6-C5Me4CH2)H]+ respectively. UV photolysis of [Re(η-C5Me5)2H] gives the stable 17-electron metallocene [Re(η-C5Me5)2], which reacts with nitric oxide to afford the bent nitrosyl derivative, [Re(η-C5Me5)2(NO)]. [Re(η-C5Me5)2] may be reduced to the diamagnetic anion [Re(η-C5Me5)2]– with potassium; the latter reacts with iodomethane to afford [Re(η-C5Me5)2CH3], but the analogous reaction with chloro- or iodo-methyl ether results in the unexpected formation of [Re(η-C5Me5){η-C5Me4(CH2OMe)}Me]. Oxidation of [Re(η-C5Me5)2] with AgBF4 gives the ‘tucked-in’ cation [Re(η-C5Me5)(η6-C5Me4CH2)H]+, which is also obtained from the reaction of [Re(η-C5Me5)2H] with chlorocarbons. UV photolysis of [Re(η-C5Me5)(η6-C5Me4CH2)H]+ gives the double ‘tucked-in’ cation [Re(η-C5Me5){η7-C5Me3(CH2)2}]+; photolysis of [Re(η-C5Me5)2H2]+ also results in the stepwise formation of [Re(η-C5Me5)(η6-C5Me4CH2)H]+ and [Re(η-C5Me5){η7-C5Me3(CH2)2}]+.

The reaction between [Pd2(dba)3] (dba=dibenzylideneacetone), tributylphosphine, and a bis(cycloalkeno)-1,4-diseleninleads to either a mononuclear [Pd{SeC(R1)2 C(R2)Se}(PBu3)2], or a dinuclear [Pd2{SeC(R1)2 C(R2)Se}2(PBu3)2] diselenolene (R1–R2=(CH2) n ; n =4, 5,6) depending on the stoichiometry employed; the structure of the monomeric product with n =5 has been determined by X-ray crystallography.

Soil water retention curves (SWRCs) are usually obtained on the assumption small water menisci spread in the surface of particles yielding contact angles near zero degrees. While this is true at high water contents, where pores are filled by water or a film of water covers the particles, it is less likely for drier states, where the adhesion of water menisci to the surface of the particles is controlled by the nature of the particle surface (chemistry and surface roughness) and the presence of organic matter. Here, we investigate hysteretic effects in the relation between water content and soil particle wettability versus suction for model samples following drying and wetting paths. A comparison is done for a model material (mixture of sand and clay) with and without water repellent substances, being the samples with water repellent substances in a subcritical water repellent state (contact angles

The causes of soil water repellency are still only poorly understood. It is generally assumed that hydrophobic organic compounds are responsible, but those concerned have not previously been identified by comparison between samples taken from a water repellent topsoil and the wettable subsoil. In this study we separated, characterised, and compared the organic compounds present at 4 different depths in a sandy soil under permanent grass cover that is water repellent in the upper 0.30 m but wettable below this. Soil samples were extracted using a mixture of isopropanol and aqueous ammonia (7 : 3 v : v). Samples were wettable after extraction and re-application of the extract from each sample onto wettable sand induced water repellency. The chloroform-soluble portions of the extracts were analysed by gas chromatography and gas chromatography-mass spectrometry. The compounds identified at all soil depths included long-chain carboxylic acids (C16–C24), amides (C14–C24), alkanes (C25–C31), aldehydes or ketones (C25–C29), and more complex ring-containing structures. 1H and 13C nuclear magnetic resonance spectroscopy, and the carbon/hydrogen ratio as determined by microanalysis, confirmed the predominantly aliphatic character of the extracts. Both wettable and water repellent samples contained hydrophobic compounds. The 3 water repellent samples contained far more organic material, although the amount extracted was not related to the degree of water repellency. Perhaps more importantly, they contained polar compounds of high relative molecular mass, which were almost absent from the wettable subsoil. It may be speculated that these are the compounds in this soil whose presence in significant amounts is necessary for water repellency to be exhibited.

The effects of variation in heating temperature T (50–300°C), heating duration (20–60 min), and post-heating equilibration times (24–168 h at 20°C and 50% relative humidity) on the wettability, as measured by the Critical Surface Tension (CST) method, of 4 initially water repellent soils from Canada, Portugal, and the UK are reported. All soils show an increase in water repellency following heating at temperatures in the range of 50 to 150°C, followed by a considerable decline after heating to 200–250°C, and, except for one soil, the eradication of repellency after heating to 300°C. For two soils with a comparatively high organic carbon content and fine texture, water repellency levels were also affected by the length of the post-heating equilibration period. The results demonstrate that (i) the common practice of heating samples to 105°C does not provide a viable standard procedure for the measurement of water repellency as it may alter repellency to different degrees, and (ii) where heat treatment is required, a post-heating equilibration time of 24 h is not necessarily sufficient for sample repellency levels to adjust to atmospheric laboratory conditions; therefore it is advisable to prolong equilibration to at least one week prior to measurement.

The compounds (C5H5)2MH2 (M  MO, W) do not react with (C5H5)2Mg or (C5Me5)2Mg. The reaction of (C5H5)2MoH2 with (CH3)2Mg in the presence of tmeda, (CH3)2NCH2CH2N(CH3)2, has been monitored by 1H NMR spectroscopy and yields Mg[Mo(H)(C5H5)2)2]2(tmeda). A similar compound, Mg[Mo(H)(C5H5)2]2(Et2O)2, is formed from (C5H5)2MoH2 and (CH3)2Mg or [C5H5MgCH3(Et2O)]2 in diethyl ether solution when no tmeda is present. These results are discussed in terms of ligand redistribution equilibria. (C5H5)2WH2 reacts too slowly with (CH3)2Mg for products to be isolated.

The reaction between [Pt(PPh(3))(4)] and cycloocteno-1,2,3-selenadiazole or bis-cycloocteno-1,4-diselenin in toluene under reflux yielded the poorly soluble mononuclear platinum diselenolene [Pt(Se(2)C(8)H(12))(PPh(3))(2)], 1c. Treatment of [Pt(C(2)H(4))(PR(3))(2)] with a bis-cycloalkeno-1,4-diselenin in a mixture of 1,4-dioxane, THF and toluene under reflux led in good yield to the platinum diselenolenes [Pt(Se(2)C(n+4)H(2n+4))(PR(3))(2)] (R = Et (2), Bu (3); n = 3 (b), 4 (c)). The analogous complexes [Pt(Se(2)C(8)H(12))(L)] (L = dppm: 4c; L = dppe: 5c; L = dppp: 6c) were prepared from 1c via ligand exchange with chelating phosphines. All new compounds have been characterised by multinuclear NMR, IR and UV-visible spectroscopy and mass spectrometry, and their luminescence properties have been examined. The molecular structures of [Pt(Se(2)C(7)H(10))(PEt(3))(2)] (2b), [Pt(Se(2)C(8)H(12))(PEt(3))(2)] (2c) and [Pt(Se(2)C(8)H(12))(dppm)] (4c) have been determined by X-ray crystallography.

A novel macrocyclic ferrocenophane, 1,5,9,13-tetraselena[13]ferrocenophane (L), was synthesized. Reaction of L with [M(NCMe)(4)](PF(6))(2) (M = Pd and Pt) or [Cu(NCMe)(4)](PF(6)) led to complexes [ML](PF(6))(2) (M = Pd and Pt) or [CuL](PF(6)). The Ag(i) cation induced the formation of a one-dimensional polymer {[AgL](PF(6))}(n) due to its large ionic radius. The structures of L and its four complexes have been determined by X-ray crystallography. Electrochemical studies showed that, in [ML](PF(6))(2) (M = Pd and Pt), the half-wave potential of the 1,1'-ferrocenediyl group shifts to much more positive potentials due to the strong through-space interaction between the two metals (M...Fe).

The reaction of [Li(TMEDA) 2 ][1,2,4-SbP 2 C 2 Bu t 2 ] 1 with E(S 2 CNEt 2 ) 2 (E = Se or Te) leads to the chalcogen substituted diphospholes [1,2,4-EP 2 C 2 Bu t 2 ] (E = Se 2 , E = Te 3 ). Compound 3 represents the first example of a tellurium substituted diphosphole.

The reaction between [Pd2(dba)3] (dba = dibenzylideneacetone), a trialkylphosphine, and a cycloalkeno-1,2,3-selenadiazole in toluene under reflux leads in good yield to the complexes [PdL(PR3)] [L = SeC(R1)C(R2)N NC(R1)C(R2)Se; R1–R2 = (CH2)n; R = Et, Bun] containing a novel Se,N,Se tridentate ligand formed by the coupling of two 1,2,3-selenadiazole molecules; the structure of the product with R = Bun and n = 4 has been determined by X-ray crystallography.

The reaction of cyclohepteno-1,4-diselenin 1 with [PtCl 2 (PhCN) 2 ] proceeds via unprecedented oxidative addition of a C–Se bond to yield a platinum(IV) product, whose novel dimeric structure has been determined by X-ray crystallography; by contrast, 1 reacts with [PdCl 2 (PhCN) 2 ] to form trans-[PdCl 2 L 2 ] (L = 1).

Bis(pentamethylcyclopentadienyl)selenium reacts with sources of M(CO)5(M = Cr, W) fragments, to yield complexes of the diselenide Se2(σ-C5H5)2, which are characterised spectroscopically and by X-ray crystallography: these are the first examples of selenide to diselenide reduction within the coordination sphere of a transition metal, and the first structures of complexes containing a terminal diselenide ligand to be reported.

Reaction of [Co(C5R15)(CO)2](R1= H or Me) with 1,2,3-selenadiazoles in toluene under reflux in the presence of an excess of elemental selenium leads in moderate yield to the diselenolenes [Co(C5R15){SeC(R2)C(R3)Se}][R2–R3=(CH2)6, CHCH(CH2)4 or CHCH(CH2)2CHCH; R2= Ph, R3= H; R2= R3= Ph]. In particular this procedure provides access to novel compounds without electron-withdrawing substituents. The products have been characterised by 1H NMR, IR, UV/VIS and mass spectroscopy, microanalysis and cyclic voltammetry. Each diselenolene undergoes a fully reversible one-electron reduction, and exhibits a low-energy electronic transition at ca. 800 nm. Of the substituents (R1,R2,R3), R1 has the greatest influence on the spectroscopic and electrochemical properties. For structurally similar compounds there is a linear correlation between the half-wave potential for the reduction and the energy of the first electronic absorption band.

The pentamethylcyclopentadienyl–sulphur compounds S(C5Me5)2(1) and S2(C5Me5)2(2) have been prepared by the reaction of Li(C5Me5) with SCL2 and S2Cl2, respectively. Compounds (1) and (2) were characterised by n.m.r. and mass spectroscopy. The X-ray crystal structure of (1) has been determined. Compound (1) crystallises in the monoclinic space group P21/c(no. 14), with a= 10.375(2), b= 11.274(2), c= 16.132(9)A, β= 91.92(3)°, and Z= 4. The reaction of (1) with [Fe2(CO)9] results in the known cluster compound, [Fe3S2(CO)9](3), the identity of which was confirmed by X-ray crystallography. Unsuccessful attempts were made to prepare cations of the type [S(C5Me5)2]n+ by (i) oxidation of (1) and (2), or (ii) the reaction of S(C5Me5)Cl (prepared in situ) with Al2Cl6. Cyclic voltammetric experiments on (1) and C5Me5H suggest that oxidation occurs at the carbocyclic ring rather than at the sulphur atom.

Thermolysis of cyclooctaselenadiazole (2) yields only selenium-containing products. Compound 2 reacts with CpCo sources to give [(η5-C5H5)CO]2(μ2η3,η2-C8H6Se), a fluxional compound whose structure has been determined by X-Ray crystallography.

The reaction of selected bicyclic 1,2,3-selenadiazoles with (η 5 -C 5 H 5 )Co(PPh 3 ) 2 in the presence of an excess of elemental selenium leads to cyclopentadienylcobalt 1,2-diselenolene complexes. These bright blue compounds are the first to contain diselenolene ligands without electron-withdrawing substituents. They may be reversibly reduced electrochemically.

Co-condensation of hexamethylcyclopentadiene with molybdenum atoms forms bis(η-pentamethylcyclopentadienyl)dimethylmolybdenum via a carboncarbon bond addition reaction to the metal. The dimethyl compound is readily oxidised to the paramagnetic cation [Mo(η-C 5 Me 5 ) 2 Me 2 ] + .