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In an attempt to build up borane-based multicluster assemblies, thermolysis of [6,9-(SMe2)2-arachno-B10H12] 1in inert hydrocarbon solution, followed by chromatographic separation, has resulted in the isolation not only of the previously established single-cluster product from this reaction, [5-(SMe2)-nido-B10H12] 2(30%), but also the two two-cluster species [6,9-(SMe2)2-arachno-B10H11-1-(6′-nido-B10H13)] 3(20%) and [1,6′-(nido-B10H13)2] 6(ca.0.5%) and the two three-cluster species [6,9-(SMe2)2-arachno-B10H10-1,5-(6′-nido-B10H13)2] 4(5%), characterized crystallographically, and [6,9-(SMe2)2-arachno-B10H10-1,3-(6′-nido-B10H13)2] 5(<1%), identified by NMR spectroscopy. An improved crystallographic investigation of [5-(SMe2)-nido-B10H12] 2is also presented. The feasibility of the stability of species resulting from multiple adjacent substitution of nido-decaboranyl units on the [6,9-(SMe2)2-arachno-B10H12] skeleton is tested by DFT calculations. In an extension, to attempt the use of pre-σ-linked two-cluster compounds as starting substrates, two-cluster [5-(SMe2)-4-(2′-nido-B10H13)-nido-B10H11] 7(0.6%) has been isolated from the reaction of SMe2with [1,5′-(nido-B10H13)2], other identified products being compound 1(39%) and compound 3(10.5%).

Reaction of CuX₂ (X− = Cl− or Br−) with 2 molar equivalents of 3{5}-(2,4,6-trimethylphenyl)pyrazole (HpzMes) in MeOH in the presence of NaOH yields [Cu₃X(HpzMes)₂(μ-pzMes)₃(μ₃-OMe)]X (X− = Cl− or Br−). Crystal structures of these compounds show almost identical triangles of Cu(ii) ions, centred by a triply bridging methoxide ligand and with three edge-bridging pyrazolide groups. The mesityl substituents on the bridging pyrazolide ligands are arranged in HT, HH, TT fashion. χ_MT for both compounds decreases steadily with decreasing temperature, reaching 0.40 cm3 mol−1 K at 70 K before decreasing further below 40 K. This low temperature behaviour could not be interpreted using conventional superexchange Hamiltonians, but was reproduced by an alternative model that incorporated an additional antisymmetric exchange term. This interpretation was confirmed by the Q-band EPR spectra of the two compounds. NMR experiments show that the structures of these compounds are not retained in solution, in contrast to other closely related tricopper compounds. These are the first examples of triangular Cu(ii) compounds bearing a [Cu₃(μ₃-OR)]5+ (R ≠ H) core motif, and the first triangular compounds showing antisymmetric exchange to have been analysed by both susceptibility and EPR measurements.

Reaction of CuX2X− Cl−or Br− with 2 molar equivalents of 35-2,4,6-trimethylphenylpyrazole HpzMes in MeOH in the presence of NaOH yields Cu3XHpzMes2μ-pzMes3μ3-OMeX X− Cl−or Br−. Crystal structures of these compounds show almost identical triangles of Cuii ions, centred by a triply bridging methoxide ligand and with three edge-bridging pyrazolide groups. The mesityl substituents on the bridging pyrazolide ligands are arranged in HT, HH, TT fashion. χMTfor both compounds decreases steadily with decreasing temperature, reaching 0.40 cm3mol−1K at 70 K before decreasing further below 40 K. This low temperature behaviour could not be interpreted using conventional superexchange Hamiltonians, but was reproduced by an alternative model that incorporated an additional antisymmetric exchange term. This interpretation was confirmed by the Q-band EPR spectra of the two compounds. NMR experiments show that the structures of these compounds are not retained in solution, in contrast to other closely related tricopper compounds. These are the first examples of triangular Cuii compounds bearing a Cu3μ3-OR5R ≠ H core motif, and the first triangular compounds showing antisymmetric exchange to have been analysed by both susceptibility and EPR measurements.

Reaction of ZnCl₂ with three molar equivalents of 3{5}-tert-butylpyrazole (HpztBu) yields [ZnCl(HpztBu)₃]Cl (1). Treatment of 1 with an appropriate Ag(i) or Tl(i) salt gives [ZnCl(HpztBu)₃]X (X− = BF₄−, 4; X− = ClO₄−, 5; X− = NO₃−, 6; X− = CF₃SO₃−, 7; X− = PF₆−, 8). Crystal structures of all of the complexes show a [ZnCl(HpztBu)₃]+ cation, with (for 1 and 4-7) only small deviations from C_3v symmetry, with the tert-butyl groups forming a bowl-shaped cavity on one face of the complex. The X− anion binds within this cavity, via hydrogen bonding to the three pyrazole N–H groups. For 8, the PF₆− guest only interacts with two N–H donors, the third pyrazole ring being twisted away from the anion. We attribute this to steric repulsions between the third ligand and the PF₆− anion, which is larger than the other guests used in this study. 1H, 13C and 19F NMR, ESMS and IR studies provide good circumstantial evidence for these structures being retained in solution, although the guest anions undergo rapid intermolecular exchange by NMR that cannot be frozen out above 190 K.

The cations in [ZnCl(HpztBu)₃]Y (Y− = [Co(C₂B₉H₁₁)₂]− or [1-Ph-closo-1-CB₉H₉]−) associate into dimers in the crystal, presenting a bowl-shaped face into which the carbaborane anions can pack. In contrast, the cations in [ZnCl(HpztBu)₃][6,7,8,9,10-Br₅-closo-1-CB₉H₅]·H₂O associate with each other into a 1-D hydrogen-bonded polymer.

The syntheses of [Fe(L1H)₂]X₂ (L1H = 2,6-di(pyrazol-1-yl)pyridine [L1H]; X− = BF₄−, PF₆−) are described. Solvent-free [Fe(L1H)₂][BF₄]₂ shows an approximately D_2d-symmetric metal centre in the crystal, and undergoes an unusual abrupt spin-state transition centered at 261 K in the solid, or at 248 K in acetone solution. A solvated phase [Fe(L1H)₂][BF₄]₂·2.9CH₃NO₂·0.25H₂O can be grown at 240 K, which undergoes an irreversible spin-state transition between 260 and 265 K. In contrast, solid [Fe(L1H)₂][PF₆]₂ adopts an unusual C₂-symmetric coordination geometry, reflecting a ca. 28° twist of one L1H ligand with respect to each other. This salt is high-spin in the range 10–330 K. DFT calculations have rationalised this unusual structure as a Jahn–Teller distortion of the 5E ground state of the six-coordinate Fe(ii) ion. This distortion is favoured by the restricted bite-angle of the L1H ligands.

Reaction of hydrated CuCl₂ with equimolar amounts of Na[L¹]·H₂O (HL¹ = 2-hydroxy-5-methyl-1,4-benzoquinone) and K[Tp^Ph2] ([Tp^Ph2]⁻ = tris-[3,5-diphenylpyrazol-1-yl]hydridoborate) in CH₂Cl₂ at room temperature afforded [Cu(L¹)(Tp^Ph2)] 1 in moderate yields. A similar complexation employing hydrated Zn(BF₄)₂, Na[L¹]·H₂O and K[Tp^Ph2] in refluxing CH₂Cl₂ affords [Zn(L¹)(Tp^Ph2)] 2. The single crystal structure of 1·0.8CH₂Cl₂ reveals a near-regular square pyramidal copper(II) centre, with a chelating [L¹]⁻ ligand. In contrast, the structure of 2 shows a distorted trigonal bipyramidal geometry, with a long interaction to the chelating carbonyl O donor. IR, UV/vis, NMR and/or EPR data demonstrate that 1 and 2 adopt the same molecular structures in CH₂Cl₂ solution as in the solid state. The cyclic voltammogram of 2 in CH₂Cl₂–0.5 M NBuⁿ₄BF₄ at 293 K exhibits chemically reversible 1-electron [L¹]⁻–[L²]²⁻ and [L²]²⁻–[L³]³⁻ (H₂L² = 2-hydroxy-5-methyl-1,4-semiquinone; H₃L³ = 2,4,5-trihydroxytoluene) couples. The CV of 1 under these conditions is more complex, showing an irreversible Cu^II–Cu^I couple, with daughter waves that suggest that reduction of the Cu in 1 results in decomplexation of [L¹]⁻. These results imply that a previously proposed stepwise mechanism for the oxidative half-reaction of copper-containing amine oxidase may only take place if the enzyme’s hydroquinone cofactor is coordinated to the active site copper ion.

Microwave assisted indirect functionalization of alcohols with 1,3-dimethylbarbituric acid followed by spirocyclisation employing a sequential one-pot Ir(iii)/Pd(0) catalysed process, involving the formation of three new C–C bonds, one spirocyclic ring and one di- or tri-substituted exocyclic alkene, is described.

The title ligand (‘L’) in crystalline [CuBrL2]Br·CH3OH and [Cu(OH2)L2]SO4·H2O·CH3OH chelates to both the copper(ii) cations and the charge-balancing anions.

A novel short synthetic route to annelated benzazepines, using additive enhanced palladium–indium catalytic 3-component cascade methodology is described.

No Abstract

Reaction of B₁₀H₁₄ with para-(OHC)C₆H₄(COOH) in aqueous KOH gives the [nido-6-CB₉H₁₁-6-(C₆H₄-para-COOH)]− anion 1 which upon cluster closure with iodine in alkali solution gives the [closo-2-CB₉H₉-2-(C₆H₄-para-COOH)]− anion 2; an analogous procedure with B₁₀H₁₄ and glyoxalic acid OHCCOOH gives the [closo-2-CB₉H₉-2-(COOH)]− anion 4 via the [arachno-6-CB₉H₁₃-6-(COOH)]− anion 3.

Solutions of CuCl2LOH, and other reaction mixtures containing LOHand Cuii or Cui salts, degrade to yield dark green or brown residues containing the LHligand. In contrast, MCl2LOH M Zn, Ni, Co are indefinitely stable in solution and the solid state.

Solutions of [CuCl₂LOH], and other reaction mixtures containing LOH and Cu(ii) or Cu(i) salts, degrade to yield dark green or brown residues containing the LH ligand. In contrast, [MCl₂LOH] (M = Zn, Ni, Co) are indefinitely stable in solution and the solid state.

Single-crystal synchrotron X-ray diffraction analysis of the [NEt₄]+ salt of the [2-Ph-closo-2-CB₆H₆]− anion, obtained from [4-Ph-arachno-4-CB₈H₁₃] and NEt₃ in refluxing toluene, substantiates the anion as the first structurally characterised seven-vertex monocarbaborane.

The title compound, [Fe2Cl4O(C7H12N2)4], contains vertex‐sharing distorted tetrahedral [FeOCl3]−and octahedral [FeOCl(HpztBu)4]+moieties (HpztBu is 5‐tert‐­butyl­pyrazole), linked by a bent oxo bridging ligand. The two FeIIIcentres are also bridged by intramolecular hydrogen bonds between the pyrazole N—H groups and the O2−and Cl−ligands.

The title compound, 5‐methoxy­spiro­[tetra­cyclo­[8.8.1.03,8.012,17]­nonadeca‐3,5,7,12,14,16‐hexene‐19,2′‐[1,3]­dioxolane], C22H24O3, exhibits a twin‐chair conformation with the aromatic rings overlying each other. Comparison of the dihedral angle between these two rings with those from previously reported [3.3]­ortho­cyclo­phanes of this type suggests the presence of a weak attractive charge‐transfer interaction between the two, different, stacked arenes.

The title compound, [Cu(C9H7N2O)2]·2CH3OH, contains a crystallographically centrosymmetric near‐regular square planar CuIIcentre with trans‐disposed chelating ligands. The complex mol­ecules associate into a one‐dimensional polymeric chain viahydrogen bonding to the solvent mol­ecules.

B₁₀H₁₄ and PhCHO yield [6-Ph-nido-6-CB₉H₁₁]− (94%), from which the nine-vertex C-phenyl monocarbaborane anion [4-Ph-closo-4-CB₈H₈]− (68%) can be obtained by heating at 200 °C, and from which the twelve- and ten-vertex analogues [1-Ph-closo-1-CB₁₁H₁₁]− (50%) and [4-Ph-closo-4-CB₉H₉]− (25%) can be obtained by heating at 210 °C with BH₃(NEt₃).

Thermolysis in the solid state of Cs+[arachno-CB₉H₁₄]−, or of Cs+[nido-CB₉H₁₂]−, or the oxidation of nido-1-CB₈H₁₂ with I₂ in THF at −78 °C in the presence of NEt₃, gives the first nine-vertex closo monocarbaborane, the stable [closo-4-CB₈H₉]− anion, in yields of 56, 61 and 75%, respectively.

The lifetimes of electrochemically generated [Cu(L^1.+)(Tp^Ph)]²⁺ and [Cu(L^1.+)(Tp^Cy)]²⁺ are identical to within experimental error.

In the title compound, [Cu(C20H24N2)2]BF4, the complex cation adopts a distorted tetrahedral structure, the dihedral angle between the least‐squares planes of the chelating ligand backbones being 51.1 (2)°. This flattening of the tetrahedral coordination sphere may be driven by the presence of intramolecular π–π stacking interactions between mesityl groups on adjacent ligands.