The synthesis of a range of diphosphines R,PCH,CH,PR, from CI,PCH,CH,PCI, is described. The properties of a series of complexes [ReCI( N, ) (R,PCH,CH,PR,),] derived from them are discussed. The relationship between the values of €+Ox and v( N,) for the complexes suggests that electronwithdrawing substituents on the diphosphine upset the usual balance of CJ and n: effects in rhenium-clinitrogen bonding.We have recently described ' 7 , the synthesis of the diphosphine Cl,PCH,CH,PCl, which is the precursor of a range of tetraalkyl-and tetra-aryl-diphosphines. These diphosphines enabled us to prepare a range of bis(dinitrogen) complexes of molybdenum and tungsten,, and we were able to show that E,"" for these complexes is affected by phosphine substituents principally inductively, whereas v(N,) shows the N, to be conjugated with the phosphine substituents. We also showed how metaldinitrogen bond-breaking was facilitated by electron-withdrawing diphosphines. In this paper we describe the extension of this work to rhenium complexes of general formula [ReCl(N,)(diphosphine),l, as well as the detailed preparation of the diphosphines themselves. Results and DiscussionPreparation of the Diphosphinex-We have developed a synthesis of Cl,PCH2CH,PC121 based on a method originally described in a patent., The variant described here is an improvement on that described l v 2 by us elsewhere.This route (1) avoids biologically active phosphorus-sulphur PCl, + P + C2H4-C12PCH2CH2PC12(1)derivatives, but has the drawback that it is apparently ironcatalysed, and does not proceed in a glass-lined autoclave unless considerable areas of metal are exposed to the reaction mixture.The autoclave is then attacked, yielding iron phosphide. The autoclave begins to deteriorate after several runs, showing surface cracks. This requires careful checking to ensure that the autoclave is always able to withstand the reaction pressure (ca. 140 atm at maximum). We have not investigated in detail alternative possibilities, such as catalysis by iron powder in a glass-lined autoclave.The 1,2-bis(dichlorophosphino)ethane was treated with a variety of alkyl-lithium and Grignard reagents to yield the following diphosphines, as detailed in the Experimental section:
A transmission electron microscope study has shown that an unstained layer, thought to contain covalently bound fatty acids, completely surrounds the cuticle cells of wool fibers. Alcoholic alkali and chlorine treatments, which both release covalently bound fatty acids, result in the disappearance of the unstained layer. This layer is thought to be an integral part of the cuticle cell membrane. Similar unstained layers between cortical cells are different from the unstained cuticle membrane, because they remain unmodified by alcoholic alkali treatments.Recent studies have provided evidence that wool fibers contain a layer of fatty acids covalently bound to the surface of the cuticle cells, probably by a thioester linkage [ 2,7,13,15,16,21 ] . These acids are orientated to produce a &dquo;polyethylene-like&dquo; hydrophobic layer at the fiber surface [20]. A feature of the fatty acid distributions of the surface lipids of wool and many other keratinous fibers is the presence of a large amount of an unusual, branched chain fatty acid, 18-methyleicosanoic acid [ 13,16 ] .Keratin fibers such as wool and human hair consist of elongated spindle-shaped cortical cells packed into the cylindrical. core of the fiber (known as the cortex), which is surrounded by an overlapping sheath of flattened cuticle cells [ 10 ] . The intercellular spaces have been termed the cell membrane complex, which under the transmission electron microscope appears as an intensely stained region (the 6-layer) sandwiched between a pair of unstained layers (the @-layers) [4]. The @-layers are thought to largely contain lipids and to originate from the follicle cell plasma membranes, whereas the 5-layer is believed to consist primarily of protein, deposited in the intercellular spaces during keratinization [4,10].In this study, we have examined the unstained fjlayers in wool fibers, and in particular those associated with the cuticle cells using transmission electron microscopy, following a variety of alcoholic alkali and chlorine treatments. These treatments are known to release various levels of covakntly bound fatty acids from the fiber, depending on the treatment conditions [ 13,15 ] . Changes observed in the unstained layers of cuticle cells after treatment indicate that oovakntly bound fatty acids are an integral part of the /3-layer surrounding cuticle cells. Materials and MethodIn this study, we used Merino woois ( 16 or 22 cm diameter), obtained by cutting butt portions (about two-thirds of the length) from fleece staples and cleaned by two alternative procedures. The 16 11m Merino wool was cleaned by drying in a vacuum oven for 24 hours at 50*C, Soxhlet extracted with t-butanol for 5 hours, followed by isooctane for 3 hours, then rinsing in distilled water for 6 hours [ 15 ] . The 22 11m Merino wool was cleaned after the method of Leeder and Marshal[6], in which vacuum dried wool was sequentially extracted with dry t-butanol, heptane, rinsed extensively with distilled water, rodried, and then sonicated for 3 hours with dry heptane. Both pr...
The heterogeneity of intermediate filament proteins (IFP) from wool has been investigated using two-dimensional polyacrylamide gel electrophoresis with immobilised pH gradients in the first dimension. The charge heterogeneity has been confirmed with some of the IFP separated as a string of spots with similar molecular weight, but markedly different in isoelectric point (pI). The molecular weight and pI distribution of the string of IFP changed after treatment with alkaline phosphatase, indicating that some of the heterogeneity is caused by phosphorylation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.