The impact of a reactant from the gas phase on the surface of a liquid and its transfer through this gas/liquid interface are crucial for various concepts applying ionic liquids (ILs) in catalysis. We investigated the first step of the adsorption dynamics of n‐butane on a series of 1‐alkyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide ILs ([CnC1Im][Tf2N]; n=1, 2, 3, 8). Using a supersonic molecular beam in ultra‐high vacuum, the trapping of n‐butane on the frozen ILs was determined as a function of surface temperature, between 90 and 125 K. On the C8‐ and C3‐ILs, n‐butane adsorbs at 90 K with an initial trapping probability of ≈0.89. The adsorption energy increases with increasing length of the IL alkyl chain, whereas the ionic headgroups seem to interact only weakly with n‐butane. The absence of adsorption on the C1‐ and C2‐ILs is attributed to a too short residence time on the IL surface to form nuclei for condensation even at 90 K.

The adsorption of reactants is an elementary step in the interaction of molecules with liquid or solid surfaces. We recently reported on the trapping of n-butane on the frozen surfaces of ionic liquids (ILs), namely, 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ILs ([CnC 1 Im][Tf 2 N]; n = 1, 2, 3, and 8). To study the influence of the anion, we now present results concerning the trapping of n-butane on 1-alkyl-3-methylimidazolium hexafluorophosphate ILs ([CnC 1 Im][PF 6 ]; n = 2, 4, and 8), that is, ILs with a smaller anion. The adsorption energies close to zero coverage are determined from the temperature dependence of the initial trapping probability using a novel approach. For both groups of ILs, the binding energy is dominated by the interaction of n-butane with the alkyl chain of the cation, whereas the ionic headgroups contribute only weakly. Comparing ILs with different alkyl chains at the IL cation, we find that the adsorption strength of n-butane increases with increasing length of the alkyl chain. In addition, detailed information on the new setup and the data analysis is provided.

The solid catalyst with ionic liquid layer (SCILL) concept is a promising approach to enhance the selectivity of hydrogenation reactions, like the selective hydrogenation of 1,3-butadiene to 1-butene using transition-metal catalysts. In this context, the adsorption dynamics of 1,3-butadiene and 1-butene were studied on Pt(111) modified with ultrathin layers of the ionic liquid (IL) 1,3-dimethylimidazolium bis­(trifluoromethanesulfonyl)­imide ([C1C1Im]­[Tf2N]). The sticking coefficients of the two hydrocarbons are measured using the direct method of King and Wells. Both olefins show pronounced precursor-mediated dynamics on clean Pt(111) and on the IL-modified surface. Increasing the IL coverage leads to an increased blocking of adsorption sites for the incoming olefins. Coadsorbed hydrogen does not significantly affect the precursor and site-blocking effects for 1,3-butadiene. Interestingly, a smaller IL amount is needed to prevent 1-butene adsorption compared to 1,3-butadiene adsorption, which is proposed to be directly related to the IL’s influence on selective hydrogenation in SCILL catalysis. Indeed, molecular dynamics simulations show IL film densification/relaxation as the key mechanism to allowing/excluding olefin adsorption on the metal. Being a function of IL coverage, the energy of film penetration is used to control the effective olefin adsorption energy and thus creates an operation regime for suppressing 1-butene while permitting 1,3-butadiene adsorption.

monosilanes), it has been found that by interrupting the synthesis so as to execute it in two stages, this fission may be largely eliminated.2. In this way (CeH^sSL, (CeHsLSiaO and CeHsSiCL, hitherto obtainable from SizCU, SijO-Br6 and SiCl4, respectively, only by means of the Grignard reaction, have been prepared.3. Hexabenzyldisilane, m. p. 194°, has been synthesized from Si2Cl6 and benzylsodium, as well as by the Grignard reaction between Si2Cl6 and benzylmagnesium chloride.Cambridge, Mass.

The interaction of molecules, especially hydrocarbons, at the gas/ionic liquid (IL) surface plays a crucial role in supported IL catalysis. The dynamics of this process is investigated by measuring the trapping probabilities of nbutane, iso-butane and 1-butene on a set of frozen 1-alkyl-3methylimidazolium-based ILs [C n C 1 Im]X, where n = 4, 8 and X À =Cl À , Br À , [PF 6 ] À and [Tf 2 N] À . The decrease of the initial trapping probability with increasing surface temperature is used to determine the desorption energy of the hydrocarbons at the IL surfaces. It increases with increasing alkyl chain length n and decreasing anion size for the ILs studied. We attribute these effects to different degrees of alkyl chain surface enrichment, while interactions between the adsorbate and the anion do not play a significant role. The adsorption energy also depends on the adsorbing molecule: It decreases in the order n-butane > 1-butene > iso-butane, which can be explained by different dispersion interactions.