Bismuth-rich bimetallic clusters (CuBi8)3+ and [MBi10]4+ (M = Pd, Pt) from ionothermal synthesis

The reaction of Bi, BiBr3, and CuBr in the Lewis-acidic ionic liquid [BMIm]Br·4AlBr3 (BMIm = 1-n-butyl-3-limidazolium) at 180 °C yielded air-sensitive, shiny black crystals of (CuBi8)[AlBr4]2[Al2Br7]. Crystals of [MBi10][AlCl4]4 (M = Pd, Pt) were obtained by reacting Bi, BiCl3, and MCl2 under similar conditions. The structures have been determined by X-ray diffraction on single-crystals and were found to be very similar to that of the known analogues with other halogens, although not isostructural. In crystals of the complex salts, polyhedral bimetallic clusters (CuBi8)3+ or [MBi10]4+ are embedded in matrices of halogenidoaluminate anions. The heteroatomic nido-cluster (CuBi8)3+ consists of a (Bi8)2+ square antiprism η4-coordinating a copper(I) cation. In the cluster cation [MBi10]4+, the metal atoms M center a pentagonal antiprism of bismuth atoms.

Hexaaquadodeca-μ2-chlorido-octahedro-hexaniobium diiodide

The title compound, [Nb6Cl12(H2O)6]I2, consists of the niobium cluster cation [Nb6Cl12(H2O)6]2+ and two non-coordinating, charge-balancing iodide ions. The edges of the Nb6 octahedron are bridged by chlorido ligands. Each Nb atom is further coordinated by a water ligand. The cluster cation has a charge of +2, which is balanced by that of two iodide anions.

Cation-anion pairs of niobium clusters of the type [Nb6Cl12(RCN)6][Nb6Cl18] (R=Et, nPr, iPr) with nitrile ligands RCN forming stabilizing inter-ionic contacts

Three new niobium cluster compounds with edge bridged, octahedral hexanuclear metal cores have been synthesised. They consist of cluster pairs with [Nb6Cl12(RCN)6]2+ cations, [Nb6Cl18]2− anions, and co-crystallised nitrile molecules, with R = C2H5 (propionitrile), nC3H7 (butyronitrile), iC3H7 (isobutyronitrile). The synthesis is based on the dehydration of [Nb6Cl14(H2O)4] · 4(H2O) with carboxylic acid anhydrides in the presences of an excess of the respective nitrile. An interesting aspect of these compounds is that the metal atoms of the cluster cation have an average oxidation state different from that of the cluster anion, the former being oxidized losing two electrons. In crystals of all three compounds layers of cluster cations are separated by layers of cluster anions. Perpendicular to these layers of the same cluster types, every cation is surrounded by four anions and vice versa. Between the cations and anions short distances are found between the halogenido ligands and the positively charged C atoms of the nitrile ligands (N–C · · · Cl angles of ~90°). These contacts indicate relatively strong dipole-dipole interactions, which presumably contribute to the arrangement of the cluster ions in the crystals.

The sensitivity of benzene cluster cation chemical ionization mass spectrometry to select biogenic terpenes

Benzene cluster cations are a sensitive and selective reagent ion for chemical ionization of select biogenic volatile organic compounds. We have previously reported the sensitivity of a field deployable chemical ionization time-of-flight mass spectrometer (CI-ToFMS), using benzene cluster cation ion chemistry, for detection of dimethyl sulfide, isoprene and α-pinene. Here, we present laboratory measurements of the sensitivity of the same instrument to a series of terpenes, including isoprene, α-pinene, β-pinene, D-limonene, ocimene, β-myrcene, farnesene, α-humulene, β-caryophyllene, and isolongifolene at atmospherically relevant mixing ratios (< 100 pptv). In addition, we determine the dependence of CI-ToFMS sensitivity on the reagent ion neutral delivery concentration and water vapor concentration. We show that isoprene is primarily detected as an adduct (C5H8 ⋅ C6H6+) with a sensitivity ranging between 4 and 10 ncps ppt−1, which depends strongly on the reagent ion precursor concentration, de-clustering voltages, and specific humidity (SH). Monoterpenes are detected primarily as the molecular ion (C10H16+) with an average sensitivity, across the five measured compounds, of 14 ± 3 ncps ppt−1 for SH between 7 and 14 g kg−1, typical of the boreal forest during summer. Sesquiterpenes are detected primarily as the molecular ion (C15H24+) with an average sensitivity, across the four measured compounds, of 9.6 ± 2.3 ncps ppt−1, that is also independent of specific humidity. Comparable sensitivities across broad classes of terpenes (e.g., monoterpenes and sesquiterpenes), coupled to the limited dependence on specific humidity, suggest that benzene cluster cation CI-ToFMS is suitable for field studies of biosphere–atmosphere interactions.

The sensitivity of benzene cluster cation chemical ionization mass spectrometry to select biogenic terpenes

Benzene cluster cations are a sensitive and selective reagent ion for chemical ionization of select biogenic volatile organic compounds. We have previously reported the sensitivity of a field deployable chemical ionization time-of-flight mass spectrometer (CI-ToFMS), using benzene cluster cation ion chemistry, for detection of dimethyl sulfide, isoprene and alpha pinene. Here, we present laboratory measurements of the sensitivity of the same instrument to a series of terpenes, including isoprene, α-pinene, β-pinene, D-limonene, ocimene, β-myrcene, farnesene, α-humulene, β-caryophyllene and isolongifolene at atmospherically relevant mixing ratios (