Christopher P. Morley

Extraction of compounds associated with water repellency in sandy soils of different origin

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 ◦ Ci s 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.

Organic compounds at different depths in a sandy soil and their role in water repellency

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.

Effects of heating and post-heating equilibration times on soil water repellency

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.

Bis(η-pentamethylcyclopentadienyl) complexes of molybdenum, tungsten and rhenium via metal vapour synthesis

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}]+.

Electrochemical and NMR spectroscopic studies of selenium- and tellurium-substituted ferrocenes I: ferrocenyl alkyl chalcogenides [Fe(η-C5H5)(η-C5H4ER)]

Abstract 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.

Synthesis and characterisation of new 2-bromovinyl selenides and their platinum group metal complexes

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.

Synthesis and characterization of Pd and Pt complexes of 1,3-bis(ferrocenylchalcogeno)propanes: crystal structures of FcSe(CH2)3SeFc and [M{FcE(CH2)3E'Fc}2](PF6)2 (M = Pd, Pt; E, E′ = Se, Te; Fc = [Fe(η5-C5H5)(η5-C5H4)])

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.

Reaction of the Tetrachalcogenides [ME4(dppe)] (M = Pd, E = S; M = Pt, E = S, Se) with Activated Alkynes to Form Dithiolenes and Diselenolenes

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)].

The reactions of [M(dppe)2] (M=Pd, Pt) with elemental selenium or tellurium: preparation and structure of the platinum polyselenide [PtSe4(dppe)]

Abstract Reaction of [Pt(dppe) 2 ] (dppe=1,2-bis(diphenylphosphino)ethane) with elemental selenium in toluene under reflux, or of [PtCl 2 (dppe)] with lithium polyselenide in tetrahydrofuran, leads in good yield to the complex [PtSe 4 (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 [Pt 3 (μ 3 -Te) 2 (dppe) 3 ]Cl 2 . [Pd(dppe) 2 ] reacts with elemental selenium to give [Pd 2 (μ-Se) 2 (dppe) 2 ] or [Pd 3 (μ 3 -Se) 2 (dppe) 3 ]Cl 2 , depending on the conditions.

A novel synthetic route to chalcogen substituted diphospholes

Abstract 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.