Single crystals of five very low-melting ionic liquids, [emim]BF4 (mp -1.3 degrees C), [bmim]PF6 (+1.9 degrees C), [bmim]OTf (+6.7 degrees C), [hexpy]NTf2 (-3.6 degrees C), and [bmpyr]NTf2 (-10.8 degrees C), have been grown using a combined calorimetric and zone-melting approach and their crystal structures determined by X-ray diffraction.

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A series of composites, some with permanent porosity, comprising polymers and ionic liquids have been prepared by in-situ polymerization. The characteristics of both composites and isolated polymers have been investigated. Slow mass and phase transfer characterize the interaction with a range of polymers (1-17) in the N,N′-dialkylimidazolium ionic liquids, [emim]BF 4, [bmim]PF6, or [omim]N(SO2CF3)2. Freeradical homopolymerization of 1-vinyl-2-pyrrolidinone in [bmim]PF6 or of 4-vinylpyridine in [omim]N-(SO2CF3)2 gave viscous solutions from which polymer (Mw ) 162 500 and 71 500 g mol -1 , respectively) could be isolated. Detectable ionic liquid residues were retained in the isolated polymers despite five reprecipitations from methanol. Copolymerization of 4-vinylpyridine (VP) with >5% divinylbenzene (DVB) or trimethylolpropane trimethacrylate (TRIM) in [omim]N(SO2CF3)2, and homopolymerizations of the cross-linking monomers on their own, led with 90-100% monomer conversion to a series of gel-like composite materials, B-H, from which cross-linked polymers, B′-H′, could be isolated by Soxhlet extraction of the ionic liquid. Copolymers of VP with 5-30% DVB (E′, F′) showed a low degree of permanent porosity in the dry state. However, poly(DVB) (G′) and poly(TRIM) (H′) have bulk densities (<0.6 g cm -3 ), intrusion volumes (>0.9 cm 3 g -1 ), BET surface areas (70-320 m 2 g -1 ), and morphology (from SEM studies) which demonstrate the porogenic character of the ionic liquids used. Comparisons with the related products I and J obtained in toluene reveal the sensitivity of these systems both to the properties of the porogen solvent and to the monomer used.

The salts [C6H11N2][AuCl4] (1) and [C8H15N2][AuCl4] (2) ([C6H11N2]+ = 1-ethyl-3-methylimidazolium; [C8H15N2]+ = 1-butyl-3-methylimidazolium), prepared by a solvent-free method, display similar crystal structures. 1 crystallizes in the monoclinic P21/c space group (a = 11.1915(15) Å, b = 12.380(2) Å, c = 9.2883(13) Å; β = 98.810(16)°; Z = 4) and 2 in the triclinic P1̄ space group (a = 7.9354(14) Å, b = 8.3930(15) Å, c = 11.397(2) Å; α = 83.94(2)°, β = 87.93(2)°, γ = 78.04(2)°; Z = 2). In both cases, a unique motif is seen consisting of linear chains of alternating corner-to-face arranged [AuCl4]- ions at Au···Cl separations of 3.356(3) Å (1) and 3.452(3) Å (2). Ionic liquid behavior is observed from 58 to 220 °C for 1 and 50 to 250 °C for 2.

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The first imidazole-type carbene complex of platinum(II), cis-(C2H4)(1-ethyl-3-methylimidazol-2-ylidene)PtCl2, has been obtained by reacting PtCl2 and PtCl4 with ethylene in the basic [EMIM]Cl/AlCl3 (1.3:1) ionic liquid (where [EMIM]+ = 1-ethyl-3-methylimidazolium) at 200 degrees C and structurally characterized (monoclinic P21/c space group, a = 10.416(2) A, b = 7.3421(9) A, c = 15.613(2) A, beta = 101.53(2) degrees, Z = 4). This complex can be regarded as a stable analogue of the pi-alkene-Pd(II)-carbene intermediate in the Heck reaction. In addition, a series of new N,N'-dialkylimidazolium salts of platinum group metals of the type [RMIM]2[MCln], where [RMIM+] = 1-alkyl-3-methylimidazolium and M = Pt(II), Pt(IV), or Ir(IV), have been prepared and characterized. The salts [EMIM]2[PtCl6] (1) and [EMIM]2[PtCl4] (2) were prepared in the ionic liquid [EMIM]Cl/AlCl3 and the salts [BMIM]2[PtCl4] (3) and [BMIM]2[PtCl6] (4) (where [BMIM]+ = 1-n-butyl-3-methylimidazolium) and [EMIM]2-[IrCl6] (5) in aqueous or acetonitrile media. From TGA measurements, salts 1-5 decompose in air in several steps eventually to form the corresponding metal, the onset of decomposition being observed at (degree C) 260 (1), 220 (2), 200 (3), 215 (4), and 210 (5). The structures of 1, 2, and 5 were determined by single-crystal X-ray analysis. The three salts crystallize in the monoclinic P21/n space group (1, a = 7.6433(9) A, b = 16.353(2) A, c = 9.213(1) A, beta = 113.56(1) degrees, Z = 2; 2, a = 8.601(1) A, b = 8.095(2) A, c = 13.977(2) A, beta = 91.75(2) degrees, Z = 2; 5, a = 10.353(2) A, b = 9.759(2) A, c = 10.371(2) A, beta = 92.98(3) degrees, Z = 2).

Solvents are important in most industrial and domestic applications. The impact of solvent losses and emissions drives efforts to minimise them or to avoid them completely. Since the 1990s, this has become a major focus of green chemistry, giving rise to the idea of the ‘green’ solvent. This concept has generated a substantial chemical literature and has led to the development of so-called neoteric solvents. A critical overview of published material establishes that few new materials have yet found widespread use as solvents. The search for less-impacting solvents is inefficient if carried out without due regard, even at the research stage, to the particular circumstances under which solvents are to be used on the industrial scale. Wider sustainability questions, particularly the use of non-fossil sources of organic carbon in solvent manufacture, are more important than intrinsic ‘greenness’. While solvency is universal, a universal solvent, an alkahest, is an unattainable ideal.