Silver–Ethene Complexes [Ag(η²‐C₂H₄)_n][Al(OR^F)₄] with n=1, 2, 3 (R^F=Fluorine‐Substituted Group)

Abstract

Compounds including the free or coordinated gas-phase cations [Ag(eta(2)-C(2)H(4))(n)](+) (n = 1-3) were stabilized with very weakly coordinating anions [A](-) (A = Al{OC(CH(3))(CF(3))(2)}(4), n = 1 (1); Al{OC(H)(CF(3))(2)}(4), n = 2 (3); Al{OC(CF(3))(3)}(4), n = 3 (5); {(F(3)C)(3)CO}(3)Al-F-Al{OC(CF(3))(3)}(3), n = 3 (6)). They were prepared by reaction of the respective silver(I) salts with stoichiometric amounts of ethene in CH(2)Cl(2) solution. As a reference we also prepared the isobutene complex [(Me(2)C=CH(2))Ag(Al{OC(CH(3))(CF(3))(2)}(4))] (2). The compounds were characterized by multinuclear solution-NMR, solid-state MAS-NMR, IR and Raman spectroscopy as well as by their single crystal X-ray structures. MAS-NMR spectroscopy shows that the [Ag(eta(2)-C(2)H(4))(3)](+) cation in its [Al{OC(CF(3))(3)}(4)](-) salt exhibits time-averaged D(3h)-symmetry and freely rotates around its principal z-axis in the solid state. All routine X-ray structures (2theta(max.) < 55 degrees) converged within the 3sigma limit at C=C double bond lengths that were shorter or similar to that of free ethene. In contrast, the respective Raman active C=C stretching modes indicated red-shifts of 38 to 45 cm(-1), suggesting a slight C=C bond elongation. This mismatch is owed to residual librational motion at 100 K, the temperature of the data collection, as well as the lack of high angular data owing to the anisotropic electron distribution in the ethene molecule. Therefore, a method for the extraction of the C=C distance in [M(C(2)H(4))] complexes from experimental Raman data was developed and meaningful C=C distances were obtained. These spectroscopic C=C distances compare well to newly collected X-ray data obtained at high resolution (2theta(max.) = 100 degrees) and low temperature (100 K). To complement the experimental data as well as to obtain further insight into bond formation, the complexes with up to three ligands were studied theoretically. The calculations were performed with DFT (BP86/TZVPP, PBE0/TZVPP), MP2/TZVPP and partly CCSD(T)/AUG-cc-pVTZ methods. In most cases several isomers were considered. Additionally, [M(C(2)H(4))(3)] (M = Cu(+), Ag(+), Au(+), Ni(0), Pd(0), Pt(0), Na(+)) were investigated with AIM theory to substantiate the preference for a planar conformation and to estimate the importance of sigma donation and pi back donation. Comparing the group 10 and 11 analogues, we find that the lack of pi back bonding in the group 11 cations is almost compensated by increased sigma donation.

Tetraalkylammonium Salts of Weakly Coordinating Aluminates: Ionic Liquids, Materials for Electrochemical Applications and Useful Compounds for Anion Investigation

“…A figure of 2 is deposited with the Supporting Information. For the [hfip] À and the [hftp] À anions, the tetraalkylammonium salts are the second examples of really ionic solid-state structures with isolated anions and cations, [41] while all the other species containing these anions, contain molecular structures with coordinated anions, for example, [(P 4 S 3 )AgA], [31,32] [(P 4 )AgA], [45] [(L) 2 AgA], [35,46] or [(L)AgA] [35,46] ( [47] and later in more detail by Glasser and Jenkins. [43,48] This concept allows thermodynamic predictions for condensed phases principally via formula unit volumes.…”

“…This also holds for a series of silver and copper(I) complexes with very weakly basic ligands, for example, P 4 , [29,30] P 4 S 3 , [31,32] S 8 , [33] P 3 N 3 Cl 6 , [34] or C 2 H 4 . [35,36] Since the starting materials to prepare compounds of the fluorinated aluminates are commercially available (best at P&M Invest Russia; http:// www.fluorine.ru) and the synthesis of the lithium aluminate salts [37][38][39] is a simple high yield procedure that we have performed in scales up to 250 g per batch, [40] it only appeared logical to extend the available substance classes to [NR 4 ] + salts. During the preparation of this manuscript, an independent communication of the electrochemical windows of related compounds appeared.…”

On the nature of spin- and orbital-resolved Cu+–NO charge transfer in the gas phase and at Cu(I) sites in zeolites

“…On the other hand, it was suggested, after analyzing atomic population changes upon ligand adsorption on a bare cation versus the cation embedded in a model environment that the unusual catalytic activity of transition-metal exchanged zeolites should be due to the activation of the transition-metal ion by the zeolite framework which functions as a specific ligand. Theoretical studies devoted to the interaction of small ligands with multiple bonds bound by zeolitic sites clearly indicated that the charge flow upon adsorption involves several transfer channels, strongly dependent on a zeolite framework type and a cation position [23,[26][27][28][29][30]. Populations within orbital resolution and devised selection schemes, frequently supported by topological analyses of electron density, were able to discriminate distinct electron transfers for a model metal-ligand bond [23,26,27].…”

“…Theoretical studies devoted to the interaction of small ligands with multiple bonds bound by zeolitic sites clearly indicated that the charge flow upon adsorption involves several transfer channels, strongly dependent on a zeolite framework type and a cation position [23,[26][27][28][29][30]. Populations within orbital resolution and devised selection schemes, frequently supported by topological analyses of electron density, were able to discriminate distinct electron transfers for a model metal-ligand bond [23,26,27]. Nevertheless, modern tools serving this purpose are still desirable to get better insight into individual chargetransfer processes between fragments constituting the complex system, within general partition schemes into preselected fragments with arbitrary symmetry.…”

Silver-free Gold(I) Catalysts for Organic Transformations

“…The non-coordinating or at least extremely weakly coordinating anions X meanwhile have included not only a) fully fluorinated groups BF 4 [36].…”