Negishi coupling is a valuable synthetic protocol for the formation of C-C bonds. However, the use of highly reactive alkyl- or arylzinc reagents in these reactions usually requires them to be performed under strictly anhydrous conditions using Schlenk techniques. It has recently been demonstrated that using deep eutectic solvents (DES) as reaction media allows Negishi reactions to be performed without any protection from air or moisture. This paper explores pre-catalyst scope and regioselectivity in these reactions. This has led to new protocols using cheap and readily available Pd pre-catalysts, e.g. Pd3(OAc)6, whilst allowing coupling of some ortho-functionalised aryl iodides without the need for a supporting phosphine ligand. Unusual solvent-induced selectivity is demonstrated, which allows highly regioselective C-C bond formation to take place, even when multiple C-I bonds are present on the aryl iodide precursor. To further understand this, the activity and selectivity of a range of Pd pre-catalysts towards different iodoarenes has been explored, with the results helping inform the choice of catalyst for specific substrates and desired regioselectivity. The use of DES in these reactions promises to simplify their use, especially in environments where strict exclusion of air and moisture is not possible, whilst simultaneously providing access to regioselectivity that does not occur in conventional solvents under the same conditions.

The species present in a laser-ablated Al plume have been characterized and their reactivity with the surface of the ionic liquid, 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)-imide ([C2mim]-[Tf2N]), has been investigated. Al atoms were confirmed to be present and their kinetic-energy distributions determined by laser-induced fluorescence time-of-flight measurements, over a wider range of ablation fluences than reported previously. Cations were detected directly using an in-line microchannel-plate-detector assembly. Corroboratory measurements of the ions entrained in a He buffer gas confirmed Al+ to be the only cation present in measurable concentrations. The Al+ kinetic energies were determined by time-of-flight and found to be much hotter than anticipated based on previous independent reports; under the highest-fluence conditions examined (30 mJ pulse-1, nominal fluence of 42 J cm-2), the mean kinetic energies of Al and Al+ were 17 and 450 eV, respectively. Using an electrostatic deflector, it was shown that both Al and Al+ projectiles produce AlF through reaction at the surface of the ionic liquid [C2mim]-[Tf2N] containing a fluorinated anion. The AlF yield from Al+ is mildly dominant under our conditions. AlF leaves the surface with near-thermal kinetic energy and rotational distributions. There is a minor component of vibrationally excited AlF which is confined to the fastest products. The observation of near-complete thermalization of the AlF products is consistent with significant penetration of the projectiles into the liquid, as would be anticipated from the high incident kinetic energies, particularly for Al+. The results provide new insights into reactive-atom scattering (RAS) from fluorine-containing liquid surfaces.

Reactive-atom scattering (RAS) using laser-ablated aluminum projectiles has been applied to probe the exposure of fluorinated anions at ionic-liquid (IL) surfaces. Gas-phase AlF was detected by laser-induced fluorescence (LIF) following interaction of the Al plume with ILs containing bis-(trifluoromethylsulfonyl)-imide ([Tf2N]-), trifluoromethanesulfonate ([OTf]-), and tetrafluoroborate ([BF4]-) anions, paired with 1-ethyl-3-methylimidazolium ([C2mim]+) or 1-octyl-3-methylimidazolium ([C8mim]+) cations. Clear AlF signals were observed for all three fluorinated anions, though yields varied markedly, with relative intensities following the sequence [BF4]- > [Tf2N]- ≫ [OTf]-. Molecular dynamics (MD) simulations employing solvent-accessible surface area and a ball-drop algorithm provided quantitative predictions of F-atom outer-surface exposure, defined as the combined surface area of atoms directly accessible to a probe particle of specified radius, which were compared with experimental AlF yields. The reduction in F-atom exposure, qualitatively expected with an increase in cation alkyl-chain length, was predicted by MD for all three anions and observed in the AlF yields from salts with [BF4]- and [Tf2N]-. However, even for these salts, there were a number of quantitative differences between the predictions of outer-surface exposure and AlF yields, which may partially be explained by penetration of the incident projectiles below the alkyl-chain layer present at the extreme outer surface of the liquids. Discrepancies for [OTf]- salts were much larger and are most likely evidence for anion-specific competing primary reactions that suppress AlF production, or for secondary processes that prevent it from surviving and escaping into the gas phase. These results provide new insight into the subtlety of the reactions of the species in the Al plume with fluorinated anions and point to the further understanding that is needed to establish Al-ablation RAS-LIF as a quantitative probe of fluorinated species at IL interfaces.

The (im)miscibility of hydrocarbons and perfluorocarbons is well known, depends on the chain lengths involved and has been exploited widely in many different areas of chemistry. One area where mixing hydrocarbon- and fluorocarbon-containing moieties is of current interest is in ionic liquids (ILs), where physicochemical properties may be tuned via the preparation of mixtures. Recent work has shown that mixtures of the methylimidazolium ILs [CnMIM][Tf2N] and [CnMIM-F2m+1][Tf2N] (m = n-2) are miscible when a perfluorooctyl chain is used (n = 10), which is unexpected at this chain length. In order to explore the influence of electrostatic attraction between ions in this observed miscibility, related, neutral N-substituted imidazoles CnIm and CnIm-F2m+1 employing hydrocarbon and semiperfluorocarbon chains, and their mixtures, were prepared. The mixtures were miscible at room temperature for n = 8 and immiscible for n = 10. The miscible mixtures were investigated by surface tension, small-angle X-ray and neutron scattering methods and by atomistic molecular dynamics simulations. The data show that while the mixtures [C8Im]1-x[C8Im-F13]x are continuously miscible, some preferential aggregation of alkyl and fluoroalkyl chains is nonetheless present, mirroring the behaviour observed for the IL mixtures [C10MIM]1-x[C10MIM-F17]x[Tf2N], yet in contrast to the shorter-chain mixtures [C8MIM]1-x[C8MIM-F13]x[Tf2N] where no aggregates are seen. As such, it has been possible to draw some conclusions concerning the ability of electrostatic interactions between the ions to suppress the otherwise expected immiscibility of the alkyl and fluoroalkyl chains.

The transition metal-mediated activation of element-hydrogen bonds is an important goal for the preparation of commodity chemical compounds and novel materials. Here a facile route to the activation of germanium-hydrogen bonds, based on the spontaneous elimination of dihydrogen, is reported. This represents a mechanistic divergence from the established methods for Ge─H bond cleavage. The novel complexes [Ru(η5-C5H5)(OTf)(PPh3)2] and [{Ru(η5-C5H5)(dppe)}2(μ-N2)]OTf2 are central to the success of this route. These crystalline species may be prepared in high yield and are highly effective sources of the 16-electron [Ru(η5-C5H5)(P)2]+ fragment. Both complexes react with GeH2Ph2 to eliminate H2 and afford [Ru(η5-C5H5)(GePh2OTf)(P)2] [(P)2 = 2 PPh3, dppe], which is best described as a triflate-stabilized metallogermylenium complex. Different species are observed on initial treatment of [Ru(η5-C5H5)(OTf)(PPh3)2] or [{Ru(η5-C5H5)(dppe)}2(μ-N2)]OTf2 with GeH2Ph2. In the dppe case, a σ-germane complex is identified, which is proposed to undergo spontaneous elimination of H2: a key step in the double Ge─H bond activation, promoted by the sterically demanding half-sandwich ruthenium complexes. This represents a distinct pathway for Ge─H bond activation when compared to the established routes, such as deprotonation by a basic hydrocarbyl ligand or oxidative addition, leading the way to new pathways to functionalize organogermanium compounds.

Polarity reversal, or "umpolung", is a widely acknowledged strategy to allow organic functional groups amenable to react in alternative ways to the usual preference set by their electronic features. In this article, we demonstrate that cyclohexyne umpolung, realized through complexation to zirconocene, makes the small strained cycloalkyne amenable to C-F bond functionalisation. Such strong bond activation chemistry is unprecedented in "free" aryne and strained alkyne chemistry. Our study also reveals that the reactivity of the Zr-cyclohexyne complex is highly sensitive to the degree of fluorination of the heteroarene. In addition, parasitic reactions of the ancillary ligand PMe3 were observed when pentafluoropyridine was the substrate.

Catalytic asymmetric hydrogenation of ketones is an important approach to prepare valuable chiral alcohols. Understanding how transition metals promote these reactions is key to the rational design of more active, selective and sustainable catalysts. A highly unusual mechanism for asymmetric hydrogenation of acetophenone catalysed by an anionic IrIII hydride system, including a strong counterion dependence on catalyst activity, is explored and rationalised here. The active catalyst, generated in situ from [IrCl(COD)]2 and a bidentate ligand (P,SR) under H2 in the presence of a strong base (M+iPrO- in isopropanol, M = Li, Na, K), is the solvated M+[Ir(H)4(P,SR)] salt (P,SR = CpFe[1,2-C5H3(PPh2)(CH2SR)], with R = iPr, Ph, Bz and Cy). Catalyst activity increases, for all R derivatives, significantly as the counterion is varied in the order Li < Na < K. For the most active K system, the addition of 18-crown-6 drastically reduces the activity. While the cation strongly affects catalyst activity, it does not significantly affect enantioselectivity. DFT calculations explored these effects in detail and showed that the solvation model used in the calculations is critical. Only a hybrid implicit/explicit solvent model including sufficient explicit solvent molecules to properly describe the first solvation shell of the cation is able to reproduce the experimental observations. This model revealed the fundamental importance of the alkali-metal cation coordination sphere in understanding the counterion effects. The turnover-determining states in the catalytic cycle are those involved in outer-sphere hydride transfer to the substrate. This step leads to coordination of the alkoxide product to the alkali-metal cation, with a significant rearrangement of the coordination sphere of M, whereas there is little change in the geometrical parameters around Ir or the alkoxide. The DFT calculations also pinpointed the major enantio-discriminating interactions and rationalised the insensitivity of the enantioselectivity on the alkali metal cation placement.

As part of an ongoing study of the structure and properties of mixtures of ionic liquids in which one component has a hydrocarbon chain and the other a semiperfluorocarbon chain, we now report a study of the mixtures [C8MIM]1-x[C10MIM-F17]x[Tf2N], [C10MIM]1-x[C8MIM-F13]x[Tf2N] and [C10MIM]1-x[C10MIM-F17]x[Tf2N], where [C8MIM][Tf2N] is 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide, [C10MIM][Tf2N] is 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C8MIM-F13][Tf2N] is 1-(1H,1H,2H,2H-perfluorooctyl)-3-methylimidizolium bis(trifluoromethylsulfonyl)imide and [C10MIM-F17][Tf2N] is 1-(1H,1H,2H,2H-perfluorodecyl)-3-methylimidizolium bis(trifluoromethylsulfonyl)imide. The mixtures were investigated using small-angle X-ray (SAXS) and neutron (SANS) scattering complemented by molecular dynamics simulations (with viscosity and surface tension measurements also possible for the mixtures [C10MIM]1-x[C8MIM-F13]x[Tf2N]). Unlike previous studies of [C8MIM]1-x[C8MIM-F13]x[Tf2N], where no strong evidence of alkyl/fluoroalkyl chain segregation or triphilic behaviour was seen (Elstone et al., J. Phys. Chem. B, 2023, 127, 7394-7407), these new mixtures show the formation of small aggregates of varying sizes of each component, even though all were co-miscible across the full range of compositions. Thus, while a clear polar non-polar peak (PNPP) was observed at large or small values of x, at intermediate compositions the small-angle neutron scattering at low q was dominated by scattering from these small aggregates, while at other compositions, there was little or no evidence of the PNPP. The origins of this behaviour are discussed in terms of inter-chain interactions. The ionic liquids [C10MIM][Tf2N] and [C10MIM-F17][Tf2N] are miscible in all proportions, but scattering studies and MD calculations show the formation of small aggregates. These data are discussed relative to hydrocarbon/fluorocarbon miscibility.

Understanding complex reaction systems and networks is critical in chemistry. While synthetic methods for the selective formation of products are highly sought after, oftentimes it is the full signature of a specific reaction, i.e. the complete profile of products/side-products, that informs mechanistic rationale and acceler-ates discovery chemistry. Moreover, understanding the triggers and sensitivities, under different reaction conditions, that can lead to different products assists with enhanced robustness and safety understanding. In this study we report a methodology using high-throughput experimentation methods and multivariate data analysis that can be used to take the full signature of a chemical reaction, to accelerate an understand-ing of the most complex reaction chemistries. To exemplify our approach, we selected a model Pd-catalyzed reaction system which forms many products – the reaction of two molecules of 2-bromo-N-phenylbenzamide, which affords primarily N-phenyl phenanthridinone. The reaction is a standout bench-mark model for gaining insight on a plethora of side-products. Principal component analysis, correspond-ence analysis and heatmaps with hierarchical clustering have allowed us to examine the factors contrib-uting to the variance in product distributions and show associations between solvents and reaction prod-ucts. Using robust data from experiments performed with eight solvents for four different reaction times at five different temperatures, we have been able to correlate side-products to the major dominant N-phenyl phenanthridinone product, and the post-chemical modification of other side products. Complementary stoichiometric organopalladium studies allowed examination of the Pd precatalyst activation pathway, gaining insight into likely Pd reaction intermediates, particularly an oxidative addition intermediate and downstream PdII intermediates. Automated reaction screening and advanced data analysis tools are transforming the way we examine cata-lytic and synthetic processes. Our study offers a unique and complementary approach to revealing im-portant reaction data on what is arguably one of the most complicated Pd catalyzed transformations known in the chemical literature.

Delivering metallomimetic reactivity from simple p-block compounds is highly desirable in the search to replace expensive, scarce precious-metals by cheap and abundant elements in catalysis. This contribution demonstrates that metallomimetic catalysis, involving facile redox cycling between the P(III) and P(V) oxidation states, is possible using only simple, cheap and readily available trialkylphosphines with no need for complex ligand architectures or external oxidising/reducing agents. Hydrodefluorination and aminodefluorination of a range of fluoroarenes was realised with good to very good yields under mild conditions. Experimental and computational mechanistic studies show that the phosphines undergo oxidative addition of the fluoroaromatic substrate, via a Meisenheimer-like transition state, to form a fluorophosphorane. This undergoes a pseudo-transmetallation step with a silane, via initial fluoride transfer from P to Si, to give experimentally observed phosphonium ions. Hydride transfer from a hydridosilicate counterion then leads to a hydridophosphorane, which undergoes reductive elimination of the product to re-form the phosphine catalyst. This behaviour is analogous to many classical transition-metal catalysed reactions and so is a rare example of both functional and mechanistically metallomimetic behaviour in catalysis by a main-group element system. Crucially, the reagents used are cheap, readily available commercially and easy to handle, making these reactions a realistic prospect in a wide range of academic and industrial settings.

A combined synthetic, mechanistic, and computational study is reported, which provides unique insight into the role of sigma-silane complexes in the catalytic hydrosilylation of nitriles. A novel, highly efficient, highly active, and regioselective catalytic monohydrosilylation of aromatic nitriles with secondary silanes using a ruthenium dihydrogen catalyst is reported along with a novel mechanism for hydrosilylation of nitriles. Investigations into the mechanism of this transformation have revealed the influence of sigma-Si-H complexes in fine-tuning the selectivity of this hydrosilylation reaction. Displacement of the dihydrogen ligand on the ruthenium precatalyst, ruthenium bis-(dihydrogen) complex [RuH2(eta(2)-H-2)(2)(PCy3)(2)], 1, by diphenylsilane leads to the formation of new ruthenium sigma-Si-H complexes, [RuH2(eta(2)-H-2)(eta(2)-HSiHPh2)(PCy3)(2)], 2, and [RuH2(eta(3)-H2SiPh2)(PCy3)(2)], 3. Complex 3 reacts readily with benzonitrile leading to hydrosilylation of the nitrile and coordination of the silylimine formed to the ruthenium as a sigma-H-Si-N-silylimine complex, [RuH2(eta(2)-HSiPh2NCHPh)(PCy3)(2)] (4). This systematic investigation of this reactivity led to the discovery of the first direct evidence of an N-silylimine-coordinated ruthenium complex and its involvement in a catalytic hydrosilylation reaction. This led to the discovery of a catalytic protocol for the efficient and selective coupling of secondary silanes with a range of nitriles using 1 as the catalyst. It is proposed that complexes 3 and 4 are key intermediates on the catalytic reaction coordinate, which leads to hydrosilylation of the nitrile. This is supported by DFT calculations along with the observation that 3 and 4 are catalytically active. The Si-N bond formation was found to proceed via direct attack of the nitrile at the silicon atom in 3. Through carefully chosen structural studies and tests of the new ruthenium complexes, along with DFT calculations, the mechanism of the catalytic hydrosilylation of nitriles has been successfully explained.

The reaction between [IrCl(COD)]2 and dppe in a 1 : 2 ratio was investigated in detail under three different conditions. [IrCl(COD)(dppe)], 1, is formed at room temperature in the absence of base. In the presence of a strong base at room temperature, hydride complexes that retain the carbocyclic ligand in the coordination sphere are generated. In isopropanol, 1 is converted into [IrH(1,2,5,6-η2:η2-COD)(dppe)] (2) on addition of KOtBu, with k12 = (1.11 ± 0.02) × 10-4 s-1, followed by reversible isomerisation to [IrH(1-κ-4,5,6-η3-C8H12)(dppe)] (3) with k23 = (3.4 ± 0.2) × 10-4 s-1 and k32 = (1.1 ± 0.3) × 10-5 s-1 to yield an equilibrium 5 : 95 mixture of 2 and 3. However, when no hydride source is present in the strong base (KOtBu in benzene or toluene), the COD ligand in 1 is deprotonated, followed by β-H elimination of an IrI-C8H11 intermediate, which leads to complex [IrH(1-κ-4,5,6-η3-C8H10)(dppe)] (4) selectively. This is followed by its reversible isomerisation to 5, which features a different relative orientation of the same ligands (k45 = (3.92 ± 0.11) × 10-4 s-1; k5-4 = (1.39 ± 0.12) × 10-4 s-1 in C6D6), to yield an equilibrated 32 : 68 mixture of 4 and 5. DFT calculations assisted in the full rationalization of the selectivity and mechanism of the reactions, yielding thermodynamic (equilibrium) and kinetic (isomerization barriers) parameters in excellent agreement with the experimental values. Finally, in the presence of KOtBu and isopropanol at 80 °C, 1 is transformed selectively to K[IrH4(dppe)] (6), a salt of an anionic tetrahydride complex of IrIII. This product is also selectively generated from 2, 3, 4 and 5 and H2 at room temperature, but only when a strong base is present. These results provide an insight into the catalytic action of [IrCl(COD)(LL)] complexes in the hydrogenation of polar substrates in the presence of a base.

By mixing ionic liquids (ILs), it is possible to fine-tune their bulk and interfacial structure. This alters their physical properties and solvation behavior and is a simple way to prepare a collection of ILs whose properties can be tuned to optimize a specific application. In this study, mixtures of perfluorinated and alkylated ILs have been prepared, and links between composition, properties, and nanostructure have been investigated. These different classes of ILs vary substantially in the flexibility and polarizability of their chains. Thus, a range of useful structural and physical property variations are accessible through mixing that will expand the library of IL mixtures available in an area that to this point has received relatively little attention. In the experiments presented herein, the physical properties and bulk structure of mixtures of 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide [C8MIM][Tf2N] and 1-(1H,1H,2H,2H-perfluorooctyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C8MIM-F13][Tf2N] have been prepared. The bulk liquid structure was investigated using a combination of small-angle X-ray and neutron scattering (SAXS and SANS, respectively) experiments in combination with atomistic molecular dynamics simulations and the measurement of density and viscosity. We observed that the addition of [C8MIM-F13][Tf2N] to [C8MIM][Tf2N] causes changes in the nanostructure of the IL mixtures that are dependent on composition so that variation in the characteristic short-range correlations is observed as a function of composition. Thus, while the length scales associated with the apolar regions (polar non-polar peak─PNPP) increase with the proportion of [C8MIM-F13][Tf2N] in the mixtures, perhaps surprisingly given the greater volume of the fluorocarbon chains, the length scale of the charge-ordering peak decreases. Interestingly, consideration of the contact peak shows that its origins are both in the direct anion···cation contact length scale and the nature (and hence volume) of the chains appended to the imidazolium cation.

We demonstrate a proof-of-concept of a new analytical technique to measure relative F atom exposure at the surfaces of fluorinated materials. The method is based on reactive-atom scattering (RAS) of Al atoms, produced by pulsed laser ablation of solid Al at 532 nm. The properties of the incident ground-state Al were characterized by laser-induced fluorescence (LIF); at typical ablation fluences, the speed distribution is approximately Maxwellian at ∼45000 K, with a most-probable kinetic energy of 187 kJ mol-1 and a mean of 560 kJ mol-1 When these Al atoms impact the surfaces of perfluorinated solids (poly(tetrafluorethylene), PTFE) or liquids (perfluoropolyether, PFPE), gas-phase AlF products are clearly detectable by LIF on the AlF A-X band. Quantitative AlF yields were compared for a small representative set of a widely studied family of ionic liquids based on the common 1-alkyl-3-methylimidazolium ([Cnmim]+) cation. Yields of (1.9 ± 0.2):1 were found from [C2mim][Tf2N] and [C8mim][Tf2N], containing the common fluorinated bis(trifluoromethylsulfonyl)imide anion ([Tf2N]-). This is in quantitative agreement with previous independent low-energy ion scattering (LEIS) measurements and consistent with other independent results indicating that the longer cationic alkyl chains cover a larger fraction of the liquid surface and hence reduce anion exposure. The expected null result was obtained for the ionic liquid [C2mim][EtSO4] which contains no fluorine. These results open the way for further characterization and the potential application of this new variant of the RAS-LIF method.

The gas-liquid interface of ionic liquids (ILs) is critically important in many applications, for example, in supported IL phase (SILP) catalysis. Methods to investigate the interfacial structure in these systems will allow their performance to be improved in a rational way. In this study, reactive-atom scattering (RAS), surface tension measurements, and molecular dynamics (MD) simulations were used to study the vacuum interface of mixtures of partially fluorinated and normal alkyl ILs. The underlying aim was to understand whether fluorinated IL ions could be used as additives to modify the surface structure of one of the most widely used families of alkyl ILs. The series of ILs 1-alkyl-3-methylimidazolium bis (trifluoromethylsulfonyl)imide ([C(n)mim][Tf2N]) with n = 4-12 were mixed with a fixed-length, semiperfluorinated analogue (1H,1H,2H, 2H-perfluorooctyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(8)mimF(13)][Tf2N]), forming [C(n)mim]((1-x))[C(8)mimF(13)](x)[Tf2N] mixtures, where x is the bulk mole fraction of the fluorinated component. The RAS-LIF method combined O-atom projectiles with laser-induced fluorescence (LIF) detection of the product OH as a measure of surface exposure of the alkyl chains. For [C(8)mim]((1-x))[C(8)mimF(13)](x)[Tf2N] mixtures, RAS-LIF OH yields are below those expected from stoichiometry. There are quantitatively consistent negative deviations from linearity of the surface tension. Both results imply that the lower-surface-tension fluoroalkyl material dominates the surface. A similar deficit is found for alkyl chain lengths n = 4, 6, 8, and 12 and for all (nonzero) x investigated by RAS-LIF. Accessible-surface-area (ASA) analyses of the MD simulations for [C(n)mim]((1-x))[C(8)mimF(13)](x)[Tf2N] mixtures qualitatively reproduce the same primary effect of fluoro-chain predominance of the surface over most of the range of n. However, there are significant quantitative discrepancies between MD ASA predictions and experiment relating to the strength of any n-dependence of the relative alkyl coverage at fixed x, and on the x-dependence at fixed n. These discrepancies are discussed in the context of detailed examinations of the surface structures predicted in the MD simulations. Potential explanations, beyond experimental artifacts, include inadequacies in the classical force fields used in the MD simulations or the inability of simple ASA algorithms to capture dynamical factors that influence RAS-LIF yields.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The preparation of mixtures of ionic liquids (ILs) represents an attractive strategy to tune their properties, an important aspect of which is to understand how the structure of the bulk varies with composition. In this study, small-angle neutron scattering (SANS) was used to probe mixtures of methylimidazolium-based ionic liquids [Cnmim][Tf2N] with [C2mim][Tf2N]) (n = 4, 6, 8 and 10) and of [Cmmim][Tf2N] with [C12mim][Tf2N] (m = 2, 4, 6 and 8). Mixtures were prepared in both contrasts, which is to say that one component would be fully hydrogenated while the other was fully deuterated, and vice versa. Data were fitted using a range of appropriate models, of which the Teubner-Strey model provided most useful information and the pure materials showed a nascent Polar Non-polar Peak (PNPP) for n = 6, which became more evident as n increased. In the mixtures [Cnmim]x[C2mim]1-x[Tf2N], the PNPP was evident for n = 10 and 8, nascent for n = 6 and absent for n = 4, with percolation showing a very strong dependence on the chain length of the added IL, [Cnmim][Tf2N]. In contrast, while the ability of [C12mim][Tf2N] to form percolated structures was damped when mixed with [Cmmim][Tf2N], as m increased from 2 to 6, this effect was less strong. However, data obtained for mixtures of [C12mim][Tf2N] and [C8mim][Tf2N], both of which percolate as pure materials, did not fit easily in any of the models applied to the previous systems and gave results that depended on the contrast used. Complementary small-angle X-ray scattering (SAXS) data, however, showed the expected evolution and behaviour of the PNPP, COP and CP, revealing that the unexpected observations were due to an adventitious matching out of isotopic contrasts. As well as revealing details of the structures of these IL mixtures, the results also point to complementary strategies for generating bulk percolated structures as a function of cation chain length.