Owen J. Curnow

A critical review of all-cellulose composites

Cellulose is a fascinating biopolymer of almost inexhaustible quantity. While being a lightweight material, it shows outstanding values of strength and stiffness when present in its native form. Unsurprisingly, cellulose fibre has been rigorously investigated as a reinforcing component in biocomposites. In recent years, however, a new class of monocomponent composites based on cellulosic materials, so-called all-cellulose composites (ACCs) have emerged. These new materials promise to overcome the critical problem of fibre–matrix adhesion in biocomposites by using chemically similar or identical cellulosic materials for both matrix and reinforcement. A number of papers scattered throughout the polymer, composites and biomolecular science literature have been published describing non-derivatized and derivatized ACCs. Exceptional mechanical properties of ACCs have been reported that easily exceed those of traditional biocomposites. Several different processing routes have been applied to the manufacture of ACCs using a broad range of different solvent systems and raw materials. This article aims to provide a comprehensive review of the background chemistry and various cellulosic sources investigated, various synthesis routes, phase transformations of the cellulose, and mechanical, viscoelastic and optical properties of ACCs. The current difficulties and challenges of ACCs are clearly outlined, pointing the way forward for further exploration of this interesting subcategory of biocomposites.

Development of Aqueous Metathesis Catalysts

Recent developments (and some historical aspects) of protic solvent metathesis using ill-defined catalysts [e.g., RuCl3·H2O and Ru(H2O)6(tos)2] and also the more easily handled, well-defined ruthenium-based alkylidene complexes (based on 15, 16, and 17) are highlighted. Modification of these catalysts has been achieved for applications in protic solvents with the introduction of water-solubilizing ligands and by immobilization onto a suitable support. The introduction of water-solubilizing cationic and anionic phosphines is synthetically straightforward with various catalysts having been prepared in this way (see 18, 19, 29–32, 36). Immobilzation methods include tethering to a water-soluble polymeric support (see 39, 40) and modification of the benzylidene group (see 43–46). Ionic tags have also been attached to the benzylidene group (see 48–50, 52, 53). Several other approaches have also been reported as discussed here to prepare modified catalysts that display good activity in protic media (see 54–59).

Triaminocyclopropenium salts as ionic liquids.

Salts of the charge-delocalised cations of the triaminocyclopropenium (tac) family bearing alkyl substituents have been prepared and shown to be air- and water-stable ionic liquids.

Synthesis and coordination chemistry of the tethered bis(cyclopentadienyl)-phosphine ligand precursor PPh(CH2CH2C5H5)2: X-ray structure oftrans-PdCl2[PPh(CH2CH2-η5-C5H4)2Fe]2

Abstract The preparation of the tethered bis(cyclopentadienyl)-phosphine compound bis(2-cyclopentadienylethyl)phenylphosphne1 from phenylphosphine,n-butyllithium and spiro[2,4]hepta-4,6-diene is described. The synthesis of the ferrocene complexPPh(CH2CH2-η5-C5H4)2Fe2 from1 and the synthesis of the heterobimetallic Pd Fe complextrans-PdCl2[PPh(CH2CH2-η5-C5H4)2Fe]2, 3 from2, along with its X-ray structure, is also described.

Synthesis and electrochemistry of complexes containing the ferrocenyl–phosphine ligand PPh(CH2CH2-η5-C5H4)2Fe

Abstract Treatment of the tethered bis(cyclopentadienyl)-phosphine compound bis(2-cyclopentadienylethyl)phenylphosphine (1) produces moderate yields (40–50%) of the ferrocene complex PPh(CH2CH2-η5-C5H4)2Fe (2). Reaction of 2 with Me3NO in tetrahydrofuran gives the phosphine oxide OPPh(CH2CH2-η5-C5H4)2Fe (3) whereas treatment with the metal complexes trans-PdCl2(PhCN)2, cis-PtCl2(PhCN)2, Fe2(CO)9, and Mo(CO)5(THF) give the corresponding di- or tri-metallic complexes trans-PdCl2[PPh(CH2CH2-η5-C5H4)2Fe]2 (4), cis-PtCl2[PPh(CH2CH2-η5-C5H4)2Fe]2 (5), (OC)4FePPh(CH2CH2-η5-C5H4)2Fe (7), and (OC)5MoPPh(CH2CH2-η5-C5H4)2Fe (8), respectively, in which 2 is acting as a neutral two-electron-donor phosphine ligand. The electrochemistry of complexes 2, 3, 4, 5 and 7 have been investigated and complexes 3, 4 and 7 have been characterised further by X-ray crystallography.

A facile route to functionalised, protic and chiral ionic liquids based on the triaminocyclopropenium cation

Readily prepared alkoxydiaminocyclopropenium salts provide an easy access to triaminocyclopropenium (tac) ionic liquids containing functionalised, protic and chiral cations.

Synthesis and X-ray structures of the five-coordinate zirconocene complexes PhP(CH2CH2-η5-C5H4)2ZrCl2, [PhP(CH2CH2-η5-C5H4) 2ZrCl(H2O)]Cl and PhP(CH2CH2-η5-C5H4)2Zr(NCS)2

Abstract The five-coordinate zirconocene dichloride PhP(CH2CH2-η5-C5H4)2ZrCl2 (3), containing a tethered bis(cyclopentadienyl)-phosphine ligand, was prepared by treating a tetrahydrofuran solution of ZrCl4(thf)2 with Li2[PhP(CH2CH2C5H4)2]. An X-ray crystal structure analysis confirmed the phosphorus atom to be coordinated to the zirconium metal center. Dissolution of 3 in wet methanol followed by evaporation of the solvent yielded the crystallographically characterized cationic chloroaqua complex [PhP(CH2CH2-η5-C5H4)2ZrCl(H2O)]+ as the chloride salt (4). Treatment of an aqueous solution of 3 with excess thiocyanate gave a good yield of the bis(isothiocyanato) complex PhP(CH2CH2-η5-C5H4)2Zr(NCS)2 (7), the structure of which was confirmed by X-ray crystallography.

Cyclopropenium Cations Break the Rules of Attraction to Form Closely Bound Dimers.

The crystal structures of tris(ethylmethylamino)-cyclopropenium chloride and tris(diethylamino)-cyclopropenium iodide reveal the presence of closely bound dicationic dimers formed from two closed-shell monomer units. The distances between the C3 centroids of the staggered monomers are at the short end of those normally found in π-stacked neutral arenes, let alone charged aromatic rings. Computational analysis reveals that short-range interactions are dominated by strong dispersion forces, enabling metastable dicationic dimers to form without covalent intermolecular bonding. Surrounding counterions then provide a background source of charge balance, imparting strong thermodynamic stability to the system. Additionally, these counterions form a weak but attractive electrostatic bridge between the monomer units, contributing to the surprisingly short observed intermolecular C3-C3 centroid distance.

A C2-symmetric analogue of dppf: synthesis and structures of the indenyl-diphosphine complex 1,3-(Ph2PSe)2(C9H6) and the racemic and meso isomers of the heterobimetallic complex Mo(CO)4(1-PPh2-η5-C9H6)2Fe

Abstract The preparation, isolation and characterisation of 1,3-bis(diphenylphosphino)indene (1) from indene and chlorodiphenylphosphine is described. The reaction of 1 with selenium gives the diselenide adduct 1,3-bis(diphenylselenophosphino)indene (2) which was characterised crystallographically. Deprotonation of 1 and treatment with ferrous chloride gives the unstable tetraphosphine complex bis(1,3-bis(diphenylphosphino)indenyl)iron(II) (3). Complex 3 decomposes to the diphosphine complex bis(1-diphenylphosphinoindenyl)iron(II) (4) via replacement of one diphenylphosphine substituent per indenyl ligand by a hydrogen atom. Complex 4 was also prepared by treatment of two equivalents of 1-diphenylphosphinoindenide with ferrous chloride. The heterobimetallic complex tetracarbonyl(bis(1-diphenylphosphinoindenyl)iron(II))molybdenum(0) (5) was also prepared and crystal structures of both the meso (5a) and C2-symmetric racemic (5b) isomers are reported.

“Iniden”-Komplexe: Ausweitung einer isoelektronischen Reihe auf die dritte Hauptgruppe

Abstract The reaction of K2[Cr(CO)5] with InCl3, followed by addition of [Bu4N]Br, gives {[(CO)5Cr]2InBr}2- (1), that can be isolated in good yield as its tetrabutylammonium salt. Similarly, the reaction of K2[Cr(CO)5] with TlCl3, after metathesis with [Bu4N]Hal, gives {[(CO)5Cr]2TlHal}2- (Hal  Cl, Br, I; 2a-c) in yields of around 60%. X-ray analyses show trigonal planar coordination of the bridging elements, In (1) and Tl (2), in all products. Short InCr (266 pm, 1) and TlCR (268 pm, 2) bond distances indicate substantial shortening by π- interactions. Compounds 1 and 2 thus extend the series of “inidene” complexes to compounds with third main group bridging elements.