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Boron tribromide and aryldihaloboranes were found to undergo 1,3-haloboration across one W-N≡N moiety of a group 6 end-on dinitrogen complex (i.e. trans-[W(N2 )2 (dppe)2 ]). The N-borylated products consist of a reduced diazenido unit sandwiched between a WII center and a trivalent boron substituent (W-N=N-BXAr), and have all been fully characterized by NMR and IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Both the terminal N atom and boron center in the W-N=N-BXAr unit can be further derivatized using electrophiles and nucleophiles/Lewis bases, respectively. This mild reduction and functionalization of a weakly activated N2 ligand with boron halides is unprecedented, and hints at the possibility of generating value-added nitrogen compounds directly from molecular dinitrogen.

The chemistry of aluminacyclopentadienes, also known as alumoles, has experienced a resurgence in recent years, resulting in the preparation of a number of new entries in this class of compound. In contrast, their reactivity remains relatively unexplored. Thus far, their Lewis acid–base chemistry has been studied, as well as various ring-insertion reactions with unsaturated species such as alkynes and azides. Herein we present a range of new ring expansion reactions of an alumole with heteroatom-containing unsaturated species, providing novel six-, seven- and eight-membered cyclic products with high heteroatom content. Additionally, an unusual reaction was observed when the alumole was treated with morpholine-N-oxide, involving a stepwise insertion of two oxygen atoms, first into the exocyclic Al–C bond and then the endocyclic Al–C bond.

The reaction of aryl- and amino(dihydro)boranes with dibora[2]ferrocenophane 1 leads to the formation 1,3-trans-dihydrotriboranes by formal hydrogenation and insertion of a borylene unit into the B=B bond. The aryltriborane derivatives undergo reversible photoisomerization to the cis-1,2-μ-H-3-hydrotriboranes, while hydride abstraction affords cationic triboranes, which represent the first doubly base-stabilized B3 H4+ analogues.

A series of 22 new bis(phosphine), bis(carbene), and bis(isonitrile) tetrahalodiborane adducts has been synthesized, either by direct adduct formation with highly sensitive B2 X4 precursors (X=Cl, Br, I) or by ligand exchange at stable B2 X4 (SMe2 )2 precursors (X=Cl, Br) with labile dimethylsulfide ligands. The isolated compounds have been fully characterized using NMR spectroscopy, elemental analysis, and, for 20 of these compounds, single-crystal X-ray diffraction, revealing an unexpected variation in the bonding motifs. In addition to the classical B2 X4 L2 diborane(4) bis-adducts, certain more sterically demanding carbene ligands induce a halide displacement which led to the first halide-bridged monocationic diboron species, [B2 X3 L2 ]A (A=BCl4 , Br, I). Furthermore, low-temperature 1:1 reactions of B2 Cl4 with sterically demanding N-heterocyclic carbenes led to the formation of kinetically unstable mono-adducts, one of which was structurally characterized. A comparison of the NMR spectra and structural data of new and literature-known bis-adducts shows several trends pertaining to the nature of the halides and the stereoelectronic properties of the Lewis bases employed.

The combination of electron-rich diaminoalkynes and ditopic Lewis acids diboranes(4) leads to unusual uncatalysed diboration reactions involving internal Lewis adduct, zwitterion, and C-C bond formation. The products are novel multicyclic, charge-separated compounds with intramolecular dative bonds.

Convenient, solution-phase syntheses of tetrahalodiboranes(4) B\(_2\)F\(_4\), B\(_2\)Cl\(_4\) and B\(_2\)I\(_4\) are presented herein from common precursor B\(_2\)Br\(_4\). In addition, the dimethylsulfide adducts B\(_2\)Cl\(_4\)(SMe\(_2\))\(_2\) and B\(_2\)Br\(_4\)(SMe\(_2\))\(_2\) are conveniently prepared in one-step syntheses from the commercially-available starting material B\(_2\)(NMe\(_2\))\(_4\). The results provide simple access to the full range of tetrahalodiboranes(4) for the exploration of their untapped synthetic potential.

A new structural class of boron-based diradicals is prepared by Lewis base addition to and reduction of singly cyclic (alkyl)(amino)carbene (CAAC) stabilised diborylalkenes. The diradicals feature a perpendicular olefinic bridge preventing delocalization between the B(CAAC) π systems, making the coupling between the spin centres very weak. DFT calculations indicate that the compounds are ground-state (open-shell) singlets, with triplet states negligibly higher in energy, thus making the triplet states easily populated thermally.

A novel thiophene-bridged donor-acceptor system was synthesized with a carbazole as donor and a borole as acceptor unit. The borole group was successfully installed via the tin-boron exchange reaction of 1,1-dimethyl-2,3,4,5-tetraphenylstannole with 9-(5-(dibromoboryl)thiophen-2-yl)carbazole. The effect of the borole on the optoelectronic properties of the donor-acceptor system was explored by spectroscopic (UV/Vis and fluorescence spectroscopy), electrochemical (cyclic voltammetry) and theoretical (TD-DFT) methods as well as by modifying its structure. The corresponding donor-acceptor compound bearing the widely employed dimesitylboryl acceptor group was also synthesized for comparison.

The reaction of the tetrahalodiboranes(4) B2F4, B2Cl4, and B2Br4 with a Lewis basic platinum(0) complex led to the isolation of the cis-bis(difluoroboryl) complex cis-[(Cy3P)2Pt(BF2)2] (1) and the novel borylborato complexes trans-[(Cy3P)2Pt{B(X)–BX3}] (2, X = Cl; 3, X = Br), respectively. The trans influence of the borylborato group was found to be one of the strongest ever observed experimentally. Furthermore, the reactivity of little-explored diaryldifluorodiboranes(4) F2B–BMes2 and the new derivative F2B–BAn2 (An = 9-anthryl) toward a range of platinum(0) complexes was investigated. Reactions with relatively nonbulky platinum(0) complexes led to the formation of unsymmetrical cis-bis(boryl) complexes cis-[(R3P)2Pt(BF2)(BMes2)] (6, R = Me; 7, R = Et) as well as the first example of a fourfold-unsymmetrical bis(boryl) complex, [(Me3P)(Cy3P)Pt(BF2)(BMes2)] (12). The use of a more bulky Pt complex provided access to the unprecedented dinuclear bis(boryl) complexes [{(iPr3P)Pt}2(μ-BF2)(μ-BAr2)] (8, Ar = Me...

Dihalodiboranes(4) react with a N-heterocyclic silylene (NHSi) to generate NHSi adducts of 1-aryl-2-silyl-1,2-diboraindanes, as was confirmed by X-ray crystallography, featuring the functionalization of both B-X (X=halogen) bonds and a sp3 - or sp2 -C-H bond under mild conditions. Coordination of a third NHSi to the proposed 1,1-diaryl-2,2-disilyldiborane(4) intermediates, generated by a twofold B-X insertion, may be crucial for the C-H borylation that leads to the final products. Notably, our results demonstrate the first C-H borylation with a strong B-F bond activated by silylene insertion.

Although the metathesis of metal-boron double bonds with elemental chalcogenides is an established process, no similar reactivity has been observed with element-nitrogen bonds. Such a reaction would provide a new route to iminoborane compounds (RB≡NR'), which have recently experienced renewed synthetic interest. Herein, we present the first observation of M=B/C=N metathesis reactions, which led to the isolation of a stable iminoborane in addition to further iminoborane cycloaddition products.

A zinc-catalyzed combined C[BOND]X and C[BOND]H borylation of aryl halides using B2pin2 (pin=OCMe2CMe2O) to produce the corresponding 1,2-diborylarenes under mild conditions was developed. Catalytic C[BOND]H bond activation occurs ortho to the halide groups if such a site is available or meta to the halide if the ortho position is already substituted. This method thus represents a novel use of a group XII catalyst for C[BOND]H borylation. This transformation does not proceed via a free aryne intermediate, but a radical process seems to be involved.

Herein we report a facile and selective synthetic route to monocyclic NHC-stabilized boriranes. We have succeeded in obtaining two highly stable new boriranes through salt elimination of NHC-stabilized dichloroboranes with the dianion of trans-stilbene, Na2[C14H12]. One borirane was observed to undergo reaction with [Pt(PEt3)3], in which the Pt(0) center oxidatively adds a backbone C-H bond of the NHC, leading to the isolation of the Pt(II) complex trans-[(Et3P)2PtH{C=CH(NMe)2C·BPh(C14H12)}]. The remarkable inertness of the NHC-boriranes suggests a strong stabilising effect of quaternization of the boron atom.

Resonance ionization mass spectroscopic (RIMS) measurements for trace analysis and spectroscopy of 237Np, the ecologically most important isotope of neptunium, are described. The chemical procedure for the separation of neptunium from aqueous samples as well as the preparation of filaments for RIMS are outlined. Several two- and three-step excitation schemes have been investigated in order to find suitable conditions for the sensitive detection of 237Np. Using a three-step, three-color excitation and ionization scheme an overall detection efficiency of 3×10−8 was obtained, resulting in a detection limit of 4×108 atoms (160 fg) of 237Np. The hyperfine structure splittings of the levels under investigation, which influence the detection limit, were measured. A new method to determine the first ionization potential (IP) was applied to neptunium yielding a value of IP=6.2655(2) eV.

Due to its high sensitivity, RIMS enables the precise determination of the first ionization potential of actinide elements with a sample size of ⩽1012 atoms. The actinide atoms under investigation are ionized in the presence of an electric field by multiple resonant laser excitation, and the ions are mass-selectively detected in a time-of-flight spectrometer. The first ionization potential is obtained by scanning the wavelength of the laser used for the last excitation step across the ionization threshold Wth—indicated by a sudden increase of the ion count rate—at various electric field strengths. Extrapolation of Wth to zero electric field strength leads directly to the first ionization potential. The first ionization potentials (IP) of Am, Cm, Bk, Cf and Es were determined for the first time as IPAm=5.9736(3) eV, IPCm=5.9914(2) eV, IPBk=6.1979(2) eV, IPCf=6.2817(2) eV, IPEs=6.3676(5) eV with samples of 1012 atoms. Furthermore, the ionization potentials of Th, U, Np and Pu were remeasured.