Borane-Mediated Highly Secondary Selective Deoxyfluorination of Alcohols.

Organofluorine compounds are vital across multiple sectors, hence highly selective methods to install fluorine are of considerable importance. The deoxyfluorination of alcohols is a key approach to prepare organofluorine compounds, however, a highly secondary (2°)-selective deoxyfluorination of alcohols has not been realized to date. Herein, we report that borane-mediated deoxyfluorination results in high 2°-selectivity in inter- and intra-molecular competition reactions versus primary (1°), tertiary (3°) and even benzylic (Bn) alcohols.

Ring-opening polymerization of ε-caprolactone with a macrocyclic tetracarbene indium complex.

The first chiral tetracarbene indium(III) complexes have been synthesized by employing a rigid dianionic macrocyclic tetra-NHC ligand. The macrocyclic indium tetra-NHC bromide and ethoxide complexes are structurally similar to analagous salen complexes. The indium ethoxide complex effectively promotes living ring-opening polymerization of ε-caprolactone at room temperature.

A Base-Free Two-Coordinate Oxoborane.

Oxoboranes (R-BO) are transient species that rapidly trimerise to form boroxines. To date, the only method used to stabilise oxoboranes is to add a Lewis base, but this forms a three-coordinate at boron oxoborane that has a different bonding/reactivity profile. Herein we report a base-free, two-coordinate oxoborane that is isolated as a Lewis adduct with AlCl.

Magnetocaloric effect in a high-spin ferromagnetic molecular cluster.

The reaction of MnCl·4HO with HL ((1-methyl-1H-imidazol-2-yl)methanol) and pdH (1, 3 propanediol) in a basic MeCN solution results in the formation of a mixed-valence [Mn] cationic cluster and two [MnCl] counter anions. The metallic skeleton of the cluster describes two geometrically equivalent mixed-valent, linked [Mn Mn ] supertetrahedra in which nearest-neighbor metal ions have a different oxidation state. Magnetic susceptibility, magnetization data and heat capacity measurements support evidence of predominant ferromagnetic correlations, leading to a = 22 spin ground state for the [Mn Mn ] supertetrahedra, which are pair-linked by a weak antiferromagnetic coupling.

Porous Molecular Crystals Derived from Cofacial Porphyrin/Phthalocyanine Heterodimers.

Porphyrin-based porous materials are of growing interest as heterogeneous catalysts especially for reactions that are of importance to sustainability. Here we demonstrate that porous molecular crystals can be prepared by the simple co-crystallisation of tetraphenylporphyrin (TPP) with octa(2',6'-di-iso-propylphenoxy)phthalocyanine or some of its metal complexes [(dipPhO)PcM; M=H, Al-OH, Ti=O, Mn-Cl, Fe-Cl, Co, Ni, Cu, Zn, Ga-Cl, Ag, In-Cl or Au-Cl]. This process is facilitated by the efficient formation of the supramolecular heterodimer between TPP and (dipPhO)PcM, which is driven by the complementary shape and symmetry of the two macrocycles.

Kinetics and Mechanism of PPh/Ni-Catalyzed, Zn-Mediated, Aryl Chloride Homocoupling: Antagonistic Effects of ZnCl/Cl.

The Ni/PPh-catalyzed homocoupling of aryl chlorides in DMF using Zn as the stochiometric reducing agent is one of a general class of Ni-catalyzed processes, where the mechanism has been a matter of long-standing debate. This study re-evaluates prior conclusions and insights. NMR spectroscopy is used to identify [(PPh)Ni(Ar)Cl] as a key intermediate and to explore the indirect roles of using Zn as the reductant.

A Delocalized Mixed-Valence Dinuclear Ytterbium Complex That Displays Intervalence Charge Transfer.

The analysis of intervalence charge transfer (IVCT) in mixed-valence compounds can help understand electron transfer processes that are important in diverse applications such as molecular electronics and artificial photosynthesis. While mixed-valence complexes of the lanthanides are more difficult to access than their transition metal analogues, they have shown IVCT phenomena derived from Robin-Day Class II localized valency or even electronic transitions due to - metal-metal bonding. In contrast, we report here the synthesis, characterization, and computational analysis of a rare, Robin-Day Class III, singly reduced dinuclear Yb complex, which is best viewed as having delocalized oxidation states.

Controlled and sequential single-electron reduction of the uranyl dication.

A flexible tripodal pyrrole-imine ligand (HL) has been used to facilitate the controlled and sequential single-electron reductions of the uranyl dication from the U(VI) oxidation state to U(V) and further to U(IV), processes that are important to understanding the reduction of uranyl and its environmental remediation. The uranyl(VI) complexes UO(HL)(sol) (sol = THF, py) were straightforwardly accessed by the transamination reaction of HL with UO{N(SiMe)}(THF) and adopt 'hangman' structures in which one of the pyrrole-imine arms is pendant. While deprotonation of this arm by LiN(SiMe) causes no change in uranyl oxidation state, single-electron reduction of uranyl(VI) to uranyl(V) occurred on addition of two equivalents of KN(SiMe) to UO(HL)(sol).

Borane-catalysed C2-selective indole reductive functionalisation.

Indolines are common motifs within pharamceuticals and natural products. Boron catalysis enables the chemoselective allylation of indoles to give allylic indolines in excellent diastereoselectivity. Mechanistic studies revealed formation of the allylic borane, allylation of the imine tautomer of the indole and B-N/B-H transborylation for catalytic turnover.

Triptycene-like naphthopleiadene as a readily accessible scaffold for supramolecular and materials chemistry.

Triptycene derivatives are used extensively in supramolecular and materials chemistry, however, most are prepared using a multi-step synthesis involving the generation of a benzyne intermediate, which hinders production on a large scale. Inspired by the ease of the synthesis of resorcinarenes, we report the rapid and efficient preparation of triptycene-like 1,6,2',7'-tetrahydroxynaphthopleiadene directly from 2,7-dihydroxynaphthalene and phthalaldehyde. Structural characterisation confirms the novel bridged bicyclic framework, within which the planes of the single benzene ring and two naphthalene units are fixed at an angle of ∼120° relative to each other.

Heavy Heterodendralenes: Structure and Reactivity of Phosphabora[3]dendralenes.

The incorporation of phosphorus and boron into [3]dendralenes provides access to heavy heterodendralenes, a new class of main-group precursor to "doped" polycyclic hydrocarbons. []Dendralenes are a core class of unsaturated hydrocarbons built from geminally connected polyenes; the resulting arrangement of conjugated C═C bonds enables []dendralenes to undergo reactions that allow rapid access to complex polycyclic compounds. The increasing technological and synthetic importance of main-group-containing polycyclic hydrocarbons and their analogues makes new routes to access such systems highly attractive.

The Sensitivity of Structure to Ionic Radius and Reaction Stoichiometry: A Crystallographic Study of Metal Coordination and Hydrogen Bonding in Barbiturate Complexes of All Five Alkali Metals Li-Cs.

A systematic study has been conducted on barbiturate complexes of all five alkali metals, Li-Cs, prepared from metal carbonates or hydroxides in an aqueous solution without other potential ligands present, varying the stoichiometric ratio of metal ion to barbituric acid (BAH). Eight polymeric coordination compounds (two each for Na, K, and Rb and one each for Li and Cs) have been characterised by single-crystal X-ray diffraction. All contain some combination of barbiturate anion BA (necessarily in a 1:1 ratio with the metal cation M), barbituric acid, and water.

Catalytic Access to Diastereometrically Pure Four- and Five-Membered Silyl-Heterocycles Using Transborylation.

Silyl-heterocycles offer a unique handle to expand and explore chemical space, reactivity, and functionality. The shortage of catalytic methods for the preparation of diverse and functionalized silyl-heterocycles however limits widespread exploration and exploitation. Herein the borane-catalyzed intramolecular 1,1-carboboration of silyl-alkynes has been developed for the synthesis of 2,3-dihydrosilolyl and silylcyclobut-2-enyl boronic esters.

Transition Metal-Free Catalytic C-H Zincation and Alumination.

C-H metalation is the most efficient method to prepare aryl-zinc and -aluminium complexes that are ubiquitous nucleophiles. Virtually all C-H metalation routes to form Al/Zn organometallics require stoichiometric, strong Brønsted bases with no base-catalyzed reactions reported. Herein we present a catalytic in amine/ammonium salt (EtN/[(EtN)H]) C-H metalation process to form aryl-zinc and aryl-aluminium complexes.

Structure-Property Relationships for Potential Inversion From Electron Acceptors Based on Thiophene-Fused Triptycene Quinones, 1,4-Diketones and Their Malononitrile Adducts.

The synthesis and properties of a series of 11,11,12,12-tetracyano-9,10-anthraquinodimethane (TCAQ) inspired electron acceptors based on thiophene-fused quinone and triptycene motifs is presented. This has yielded insights into structure-property relationships for establishing and modulating simultaneous two-electron reduction processes in TCAQ analogues. These new compounds were synthesised using a Friedel-Crafts acylation between triptycene and thiophene-3,4-dicarbonyl chloride.

Shape-Selective Supramolecular Capsules for Actinide Precipitation and Separation.

Improving actinide separations is key to reducing barriers to medical and industrial actinide isotope production and to addressing the challenges associated with the reprocessing of spent nuclear fuel. Here, we report the first example of a supramolecular anion recognition process that can achieve this goal. We have designed a preorganized triamidoarene receptor that induces quantitative precipitation of the early actinides Th(IV), Np(IV), and Pu(IV) from industrially relevant conditions through the formation of self-assembled hydrogen-bonded capsules.

NacNac-zinc-pyridonate mediated ε-caprolactone ROP.

Herein we report the synthesis, isolation and polymerisation activity of two new zinc compounds based on a 2,6-diisopropylphenyl (Dipp) β-diiminate (NacNac) ligand framework with zinc also ligated by an amidate (2-pyridonate or 6-methyl-2-pyridonate) unit. The compounds crystallised as either monomeric (6-Me-2-pyridonate derivative) or dimeric (2-pyridonate) species, although both were found to be monomeric in solution H DOSY NMR spectroscopy, which was supported by DFT calculations. These observations suggest that both complexes initiate ring-opening polymerisation (ROP) through a single-site monometallic mechanism.

Odd and Even Numbered Ferric Wheels.

The structurally related odd and even numbered wheels [Fe Zn (tea) (teaH) (OMe)Cl ] (1) and [Fe Zn (tea) Cl ] (2) can be synthesized under ambient conditions by reacting Fe and Zn salts with triethanolamine (teaH ), the change in nuclearity being dictated by the solvents employed. An antiferromagnetic exchange between nearest neighbors, J = -10.0 cm for 1 and J = -12.

Experimental Quantification of Halogen⋅⋅⋅Arene van der Waals Contacts.

Crystallographic and computational studies suggest the occurrence of favourable interactions between polarizable arenes and halogen atoms. However, the systematic experimental quantification of halogen⋅⋅⋅arene interactions in solution has been hindered by the large variance in the steric demands of the halogens. Here we have synthesized molecular balances to quantify halogen⋅⋅⋅arene contacts in 17 solvents and solvent mixtures using H NMR spectroscopy.

Tetra-, tetradeca- and octadecametallic clusters of Mn.

Reaction of equimolar amounts of MnBr·4HO and HL ((3,5-dimethyl-1-pyrazol-1-yl)methanol) in a basic MeCN solution leads to the formation of [MnII4(L)Br(HO)] (1), whose metallic skeleton is a [MnII4] tetrahedron and cluster core a [MnII4(μ-O)] cubane. Replacing MnBr·4HO with Mn(OCMe)·4HO affords [MnIII2MnII12O(L)(OAc)] (2) which is best described as a series of edge-sharing [Mn] tetrahedra that have self-assembled into a linear array in which each [Mn] pair is 'twisted' with respect to its neighbours in a corkscrew-like manner. Employment of the triangle [MnIII3O(OAc)(py)](ClO) as a reactant instead of a Mn salt results in the formation of [MnIII14MnII4O(L)(HL)(OAc)(HO)] (3) whose core is comprised of three vertex-sharing [MnIII4] butterflies flanked on either side by one [MnIII4] cubane and one [MnIII2MnII2] tetrahedron.

Amides as modifiable directing groups in electrophilic borylation.

Amide directed C-H borylation using ≥two equiv. of BBr forms borenium cations containing a RN(R')C[double bond, length as m-dash]O→B(Ar)Br unit which has significant Lewis acidity at the carbonyl carbon. This enables reduction of the amide unit to an amine using hydrosilanes.

Influence of alkali metal cations on the formation of the heterobimetallic actinide -butoxides [AnM(OBu)] and [AnM(OBu)] (An = Th, U; M = Li, Na, K, Rb, Cs).

Heterobimetallic -butoxides of alkali metal cations with tetravalent actinide centers exhibit two distinctive structural motifs, [AnM(OBu)] and [AnM(OBu)] (An = Th, U and M = Li, Na, K, Rb, Cs), evidently governed by the size of the alkali metal ions. Both [AnM(OBu)] AnM3 (An = U, M = Li; An = Th, M = Li, Na) and [AnM(OBu)] AnM2 (An = U, M = Na-Cs; An = Th, M = K-Cs) compounds are obtained in nearly quantitative yields by reacting actinide and alkali metal silyl amides with an excess of -butyl alcohol. The AnM3 complexes form a cubane-type coordination motif, whereas the AnM2 complexes display a geometry resembling two face-shared bipyramids.

Iron-catalysed alkene and heteroarene H/D exchange by reversible protonation of iron-hydride intermediates.

C-H functionalisation reactions offer a sustainable method for molecular construction and diversification. These reactions however remain dominated by precious metal catalysis. While significant interest in iron-catalysed C-H activation reactions has emerged, the isolation, characterisation and mechanistic understanding of these processes remain lacking.

Synthesis of Electrophiles Derived from Dimeric Aminoboranes and Assessing Their Utility in the Borylation of π Nucleophiles.

Dimeric aminoboranes, [HBNR] (R = Me or CHCH) containing BN cores, can be activated by I, HNTf (NTf = [N(SOCF)]), or [PhC][B(CF)] to form isolable HB(μ-NR)BHX (for X = I or NTf). For X = [B(CF)] further reactivity, presumably between [HB(μ-NMe)BH][B(CF)] and aminoborane, forms a BN-based monocation containing a three-center two electron B-(μ-H)-B moiety. The structures of HB(μ-NMe)BH(I) and [(μ-NMe)BH(NTf)] indicated a sterically crowded environment around boron, and this leads to the less common O-bound mode of NTf binding.

Boron-Catalyzed, Diastereo- and Enantioselective Allylation of Ketones with Allenes.

The diastereo- and enantioselective allylation of ketones remains a synthetic challenge, with transition metal catalysis offering the most applied methods. Here, a boron-catalyzed allylation of ketones with allenes is presented. Excellent yield, regioselectivity, and diastereoselectivity were found across functionalized substrates.