Bimetallic Anions Research Articles

Comprehensive analysis of chloroaluminate and composite ionic liquids using direct analysis in real time mass spectrometry

<p indent=0mm>A composite chloroaluminate ionic liquid (IL) modified with copper(I) chloride has attracted considerable attention due to its high catalytic activity and selectivity for isobutane alkylation, where the bimetallic anions of Cu(I)-Al(III) have been proposed to play important roles. Characterization of chloroaluminate and composite ionic liquids (CIL) is crucial for a better understanding of alkylation mechanism and catalysts design. In this work, a plasma-based ion source, direct analysis in real time (DART), was introduced to achieve soft but effective ionization of chloroaluminate IL and CIL with minimized hydrolysis, fragmentation and salt effects. Combined with the isotope patterns strategy and high-energy collision dissociation (HCD) technology, this developed high resolution mass spectrometry (HRMS) method, DART-Orbitrap-HRMS, was not only able to identify the accurate chemical composition of chloroaluminate IL and CIL, but also capable of structure analysis. Based on the comparison of chloroaluminate IL and CIL, it showed that similar acidic anions in both ILs were [AlCl₄]⁻, [Al₂Cl₇]⁻ and [Al₃Cl₁₀]⁻. The remarkable difference was the verification of Cu(I)-Al(III) bimetallic anions as [CuAlCl₅]⁻ and [CuAl₂Cl₈]⁻ merely in CIL, which were proposed to count for the high catalytic activity. Moreover, Cu(I) cation ion that might be related to the alkylation selectivity was characterized as [(Et₃NH)₂CuCl₂]⁺ in CIL. Structure analysis of the two bimetallic anions were then achieved by HCD technology. All the results have provided substantial support for the structure-activity study of CIL, setting the stage for in-depth research on IL-catalyzed isobutane alkylation.

Synthesis and characterization of cobalt(II) and manganese(II) xylaratogermanates: The molecular and crystal structures of the [M(H2O)6][Ge(μ3-L)2{M(H2O)2}2] · 4H2O · nCH3CN Complexes (M = Co, n = 0; M = Mn, n = 1)

A synthetic procedure was developed, and heteropolynuclear coordination compounds—the products of the interaction of germanium tetrachloride with xylaric (trihydroxyglutaric) acid HOOC-CH(OH)-CH(OH)-CH(OH)-COOH (H5L) and the acetates of the 3d metals Mn(II) and Co(II)—were prepared. The compounds were characterized by elemental analysis, thermogravimetry, and IR spectroscopy. The X-ray diffraction analysis of the [M(H2O)6][Ge(μ3-L)2{M(H2O)2}2] · 4H2O · nCH3CN complexes, where M = Co, n = 0 (I) and M = Mn, n = 1 (II), was performed. The crystals of I are monoclinic, a = 10.752(2) A, b = 11.830(2) A, and c = 10.772(2) A, β = 94.741(3)°, V = 1365.4(5) A3, Z = 2, space group P21/n, R1 = 0.0309 for 3200 reflections with I > 2σ(I). The crystals of II are triclinic, a = 9.5330(17) A, b = 9.7415(17) A, and c = 10.3935(18) A, α = 115.024(2)°, β = 97.580(3)°, γ = 111.535(3)°, V = 764.9(2)A3, Z = 1, space group $$P\bar 1$$ , R1 = 0.0621 for 3028 reflections with I > 2σ(I). The bimetallic anions [Ge(μ3-L)2{M(H2O)2}2]2−, the cations [M(H2O)6]2+, and crystal water molecules form the basis of compounds I and II (the acetonitrile molecule is also a constituent of compound II). In the centrally symmetrical trinuclear complex anion, the Ge(1) atom is bound to two M(1) atoms through two completely deprotonated bridging ligands. The Ge(1) atom is coordinated to the six alcohol oxygen atoms of two ligands L5− at the apexes of a distorted octahedron (the average Ge(1)-O distances in I and II are 1.8858(14) and 1.892(3)A, respectively). The coordination polyhedron of the M(1) atom in the complex anion is a strongly distorted octahedron. The base of the coordination polyhedron is formed by the two bridging alcohol oxygen atoms (the average M(1)-O distances in I and II are 2.1756(14) and 2.255(3) A, respectively) of two L5− ligands and by the oxygen atoms of two water molecules (the average M(1)-O distances in I and II are 2.0693(17) and 2.175(4) A, respectively). In the centrally symmetrical complex cation, the coordination polyhedron of the M(2) atom is a somewhat distorted octahedron. The M(2)-O(H2O) bond lengths in I and II vary in the ranges of 2.0137(17)-2.1555(17) and 2.140(5)-2.172(4) A, respectively (the average lengths are 2.0375(17) and 2.166(4) A, respectively). The cations and anions are joined by a branched system of hydrogen bonds.

An unprecedented mode of ligation for a bridged amido-cyclopentadienide (constrained geometry) ligand; pi-olefinic interactions with gallium and indium.

The surprising reaction of GaCl3 or InBr3 with the di-Grignard reagent [Me2Si(C5Me4)(N-t-Bu)](MgCl)2 x THF results in salts of the bimetallic anions of composition [X3M[C5Me4(N-t-Bu)]MX2]- (M = Ga, X = Cl; M = In; X = Br) in which the MX2 moiety undergoes an eta2-interaction with one of the double bonds of the localized cyclopentadienide ring.

Synthesis, characterization, and solution redox properties of (trimpsi)M(CO)(2)(NO) complexes [M = V, Nb, Ta; trimpsi = (t)BuSi(CH(2)PMe(2))(3)

Treatment of [Et(4)N][M(CO)(6)] (M = Nb, Ta) with I(2) in DME at -78 degrees C produces solutions of the bimetallic anions [M(2micro-I)(3)(CO)(8)](-). Addition of the tripodal phosphine (t)BuSi(CH(2)PMe(2))(3) (trimpsi) followed by refluxing affords (trimpsi)M(CO)(3)I [M = Nb (1), Ta (2)], which are isolable in good yields as air-stable, orange-red microcrystalline solids. Reduction of these complexes with 2 equiv of Na/Hg, followed by treatment with Diazald in THF, results in the formation of (trimpsi)M(CO)(2)(NO) [M = Nb (3), Ta (4)] in high isolated yields. The congeneric vanadium complex, (trimpsi)V(CO)(2)(NO) (5), can be prepared by reacting [Et(4)N][V(CO)(6)] with [NO][BF(4)] in CH(2)Cl(2) to form V(CO)(5)(NO). These solutions are treated with 1 equiv of trimpsi to obtain (eta(2)-trimpsi)V(CO)(3)(NO). Refluxing orange THF solutions of this material affords 5 in moderate yields. Reaction of (trimpsi)VCl(3)(THF) (6) with 4 equiv of sodium naphthalenide in THF in the presence of excess CO provides [Et(4)N][(trimpsi)V(CO)(3)] (7), (trimpsi)V(CO)(3)H, and [(trimpsi)V(micro-Cl)(3)V(trimpsi)][(eta(2)-trimpsi)V(CO)(4)].3THF ([8][9].3THF). All new complexes have been characterized by conventional spectroscopic methods, and the solid-state molecular structures of 2.(1)/(2)THF, 3-5, and [8][9].3THF have been established by X-ray diffraction analyses. The solution redox properties of 3-5 have also been investigated by cyclic voltammetry. Cyclic voltammograms of 3 and 4 both exhibit an irreversible oxidation feature in CH(2)Cl(2) (E(p,a) = -0.71 V at 0.5 V/s for 3, while E(p,a) = -0.55 V at 0.5 V/s for 4), while cyclic voltammograms of 5 in CH(2)Cl(2) show a reversible oxidation feature (E(1/2) = -0.74 V) followed by an irreversible feature (0.61 V at 0.5 V/s). The reversible feature corresponds to the formation of the 17e cation [(trimpsi)V(CO)(2)(NO)](+) ([5](+)()), and the irreversible feature likely involves the oxidation of [5](+)() to an unstable 16e dication. Treatment of 5 with [Cp(2)Fe][BF(4)] in CH(2)Cl(2) generates [5][BF(4)], which slowly decomposes once formed. Nevertheless, [5][BF(4)] has been characterized by IR and ESR spectroscopies.