Weakly Coordinating Anions HA₂^-Generated from Oxoanions A^-and Their Conjugate Acids. Coordination Equilibria, Ionic Conductivities, and the Structures of {Cu₂(H(CH₃SO₃)₂)₄}_nand [Cu(CO)(H(CF₃CO₂)₂)]₂

Abstract

The coordination or ion pairing of the hydrogen-bonded anions H(CF3CO2)2- and H(CH3SO3)2- to NEt4+, Li+, Cu+, and/or Cu2+ was investigated. The structure of [Cu2(H(CH3SO3)2)4]n consists of centrosymmetric dimeric moieties that contain two homoconjugated (CH3SO2O-H...OSO2CH3)- anions per Cu2+ ion, forming typical Jahn-Teller tetragonally elongated CuO6 coordination spheres. The oxygen atoms involved in the nearly linear O-H...O hydrogen bonds (O...O approximately 2.62 A) are not coordinated to the Cu2+ ions. The structure of Cu2(CO)2(H(CF3-CO2)2)2 consists of pseudo-C2-symmetric dimers that contain one homoconjugated (CF3COO-H...OCOCF3)- anion per Cu+ ion, forming highly distorted tetrahedral Cu(CO)O3 coordination spheres. Three of the four oxygen atoms in each hydrogen-bonded H(CF3CO2)2- anion are coordinated to the Cu+ ions, including one of the oxygen atoms in each O-H...O hydrogen bond (O...O approximately 2.62 A). Infrared spectra (v(CO) values) of Cu(CO)(CF3CO2) or Cu(CO)(CH3SO3) dissolved in acetonitrile or benzene, with and without added CF3COOH or CH3SO3H, respectively, demonstrate that HA2- anions involving carboxylates or sulfonates are more weakly coordinating than the parent anions RCO2- and RSO3-. Direct current conductivities of THF solutions of Li(CF3CO2) containing varying concentrations of added CF3COOH further demonstrate that Li+ and NEt4+ ion pair much more weakly with H(CF3CO2)2- than with CF3CO2-.

In situ synthesis and crystal growth of copper(I) carbonyl trifluoroacetate: a dinuclear [Cu2(O2CCF3)2(CO)2] core structure confirmed

“…CO p-backbonding. The measured IR absorptions are in agreement with the data previously reported for a compound of the [Cu(O 2 CCF 3 )(CO)] composition by Rodesiler and Amma (2120 cm -1 in an unspecified medium [3a]), Pampaloni (2130 cm -1 in nujol mulls [5a]), and Strauss (2136 cm -1 in fluorolube mulls [4]). …”

“…The structure of 1 consists of dicopper(I,I) units cis-bridged by two trifluoroacetate groups and also containing one carbonyl ligand at each copper(I) center, [Cu 2 (m 2 -O 2 CCF 3 ) 2 (CO) 2 ]. This contrasts to the previously suggested tetranuclear structure assigned to 1 in [5a] but is consistent with the dinuclear core found in the trifluoroacetic acid bisadduct, [Cu 2 (O 2 CCF 3 ) 2 (CO) 2 (HO 2 CCF 3 ) 2 ] (2) [4].…”

“…In 1969, it was reported that [Cu(O 2 CCF 3 )] undergoes carbonylation at atmospheric pressure to afford [Cu(O 2 CCF 3 )(CO)] [3], which dimerizes to form [Cu 2 (O 2 CCF 3 ) 2 (CO) 2 (HO 2 CCF 3 ) 2 ] in the presence of excess trifluoroacetic acid [4]. Rodesiler 4 ] Á 4 CO in 1977 [3a] but the results of its structural analysis have never appeared in the literature. Another attempt to solve the structure of [Cu(O 2 CCF 3 )(CO)] from powder X-ray diffraction data of a microcrystalline sample was made by Pampaloni and co-workers in 2000 [5a].…”

“…Another attempt to solve the structure of [Cu(O 2 CCF 3 )(CO)] from powder X-ray diffraction data of a microcrystalline sample was made by Pampaloni and co-workers in 2000 [5a]. While no reasonable solution was found, it was hypothesized that the title compound has the tetranuclear [Cu 4 (O 2 CCF 3 ) 4 4 ] Á (C 6 H 6 ) 2 [7]. The latter two compounds have a planar core formed by four copper(I) atoms alternately bridged by carboxylate ligands above and below the Cu 4 -plane.…”

On the Use of a Protic Ionic Liquid with a Novel Cation To Study Anion Basicity

“…The relationship between acidity and mole fraction of the acids (for the regime where the dominant factor is the anion combination with free acid,0 .5 < c < 1, to form hydrogen bondedd ianions and clusters [A(HA) x ] À ) [54,61] needs more explanation. This association of the free acid and the anion lowers the basicity of the counterion as explained by Polyakov et al [62] It was shown in ar ecent communication [53] that H 0 values of ah ydrogen sulfate ionic liquid's mixtures with H 2 SO 4 changes linearly with mole ratio of the acid over almost the full range of compositions. The same behavior can be assumed for DMI hydrogen sulfate and methanesulfonate PILs so it can be concludedt hat 13 Cc hemical shift of DMI after protonation changes linearly with acidity.T he similar slopes of the fitted lines (À11.5 for H 2 SO 4 and À11.0 for HOMs), seen in Figure 5, show as imilare ffect of anion combination with free acids on their basicities for the two cases.…”