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Combination of borane and diaminoferrocene monomers by Si/B exchange condensation reactions afforded either diazabora-[3]ferrocenophanes or, via stepwise processes, larger macrocycles and a series of linear oligomers. Additional incorporation of p-phenylene moieties in the backbone yielded alternating concatenation. [ABSTRACT FROM AUTHOR]

Substituting CC with the isoelectronic BN units is a promising approach to modify the optoelectronic properties of polycyclic aromatic hydrocarbons. While computational studies have already addressed trends in the electronic structure of the various isosteres, experimental data are still scarce. Here, the excited state spectroscopy and dynamics of 4a,8a-azaboranaphthalene were studied by picosecond time-resolved photoionization in a supersonic jet and analyzed with the aid of XMS-CASPT2 and time-dependent DFT calculations. A resonance-enhanced multiphoton ionization spectrum (REMPI) reveals the S1 origin at v = 33 830 ± 12 cm−1. Several vibrational bands were resolved and assigned by comparison with the computations. A [1+1] photoelectron spectrum via the S1 origin yielded an adiabatic ionization energy of 8.27 eV. Selected vibrational bands were subsequently investigated by pump–probe photoionization. While the origin as well as several low-lying vibronic states exhibit lifetimes in the ns-range, a monoexponential decay is observed at higher excitation energies, ranging from 400 ps at +1710 cm−1 to 13 ps at +3360 cm−1. The deactivation is attributed to an internal conversion of the optically excited S1 state via a barrier that gives access to a conical intersection (CI) to the S0 state. The doping significantly changes the energetic ordering of CIs and lowers the corresponding energy barrier for the associated deactivation pathway, as revealed by nudged elastic band (NEB) calculations. [ABSTRACT FROM AUTHOR]

The first poly(ferrocenylene iminoborane), that is, a polyferrocene-based metallopolymer featuring C＝C-isoelectronic/-isosteric B＝N linking units, and a series of monodisperse ferrocenylene iminoborane oligomers are presented. Our studies provide important insight into the structural and electronic nature of this novel class of hybrid materials. [ABSTRACT FROM AUTHOR]

A series of linear oligo(p-phenylene iminoboranes), which are BN-modified congeners of oligo(p-phenylene vinylenes), featuring pendent ferrocene groups have been prepared. Stoichiometric reaction of a bis-silylamine with a bisborane led to selective formation of an unprecedented macrocycle, without the use of a template. [ABSTRACT FROM AUTHOR]

A series of bifuran-bridged bis(triarylboranes) have been synthesized via classical metathesis or catalytic silicon/boron exchange reactions, respectively. The products obtained are strongly luminescent, with quantum yields up to 85%, and reversibly twofold reduced via successive one-electron processes. [ABSTRACT FROM AUTHOR]

Fully aromatic, luminescent, and highly robust BNB-doped phenalenyls have been prepared, which are isoelectronic to the phenalenyl cation. B-Fluoromesityl-substitution leads to fluorescence in an extremely narrow range and significant increase in the reduction potential. Detailed theoretical investigations revealed an intramolecular aromaticity switch upon one-electron reduction. [ABSTRACT FROM AUTHOR]

Direct functionalization and Pd-catalyzed cross-coupling of difuryl(supermesityl)borane (1) led to highly emissive organoborane compounds 3 and 4. Photophysical and TD-DFT studies reveal an increase of the HOMO levels with higher hetarene content and stabilization of the HOMO and LUMO levels through B-doping, leading to very robust, air-stable electron-accepting materials. [ABSTRACT FROM AUTHOR]

Stereospecific access to the unprecedented P–B–P bridged [3]ferrocenophane Fe(C5H4PtBu)2BMes is presented. In contrast to acyclic ferrocenylphosphanes, we find evidence for a shift of spin-density from Fe to P upon pyramidal inversion of the P centers in the mono-cation; the latter has a lifetime of τ = 0.31(4) s. [ABSTRACT FROM AUTHOR]

Thienyl substituted 2H-1,4,2-diazaphosphole complexes 3a,bwere prepared viahighly selective ring-expansion reactions of 2H-azaphosphirene complex 1and nitriles with our new synthetic protocol using triflic acid and NEt3. The single-crystal X-ray structures of 3a,bshow that the 3,5-substituents adopt a coplanar arrangement with the diazaphosphole ring resulting in extended π-conjugation, thus giving rise to absorptions at long wavelengths in their UV/Vis spectra. On the basis of Time-Dependent DFT (TD-DFT) calculations the longest-wavelength absorption could be assigned to a metal–ligand charge transfer (MLCT) process and another low-energy band was interpreted as a superposition of π–π* and n–π* transitions. Protonation of the ring nitrogen yields a pronounced bathochromic shift of all bands along with an increase in their intensity. These effects can be explained by the different extent to which the orbital energies are affected by protonation. [ABSTRACT FROM AUTHOR]

O-Protonation and ring cleavage of oxaphosphirane complexes 1a,benabled the synthesis of novel compounds such as the bicyclic 1,3-oxaphospholane complex 5and the η2-Wittig ylide complex 7, which demonstrate the emerging chemistry of this new reactive intermediate. Whereas P–O bond cleavage occurred, in the first case, thus revealing the superior ability of the P-bonded Cp* group to stabilize cationic charge, in the second case competing C–O and P–O bond cleavages occurred, thus leading to a mixture of complexes 3, 4and 7. [ABSTRACT FROM AUTHOR]

1,3,4,6-Tetraphenylpentalene (Ph 4 Pn) has been synthesised by chemical oxidation of the corresponding pentalenide complex Mg[Ph 4 Pn] with iodine. Ph 4 Pn is a rare example of a room-temperature stable hydrocarbon that is antiaromatic by Hückel's rule and has been fully characterised by NMR and UV-vis spectroscopy, mass spectrometry as well as single-crystal X-ray diffraction. Quantum chemical studies including nucleus-independent chemical shift (NICS) and anisotropy of the induced current density (ACID) calculations showed the existence of an 8π antiaromatic core decorated with four independent 6π aromatic substituents. The formation of Ph 4 Pn is reversible and it can be reduced back to the 10π aromatic Ph 4 Pn 2- with potassium., Competing Interests: The authors declare no conflicts of interest., (This journal is © The Royal Society of Chemistry.)

A series of linear oligo( p -phenylene iminoboranes), which are BN-modified congeners of oligo( p -phenylene vinylenes), featuring pendent ferrocene groups have been prepared. Stoichiometric reaction of a bis-silylamine with a bisborane led to selective formation of an unprecedented macrocycle, without the use of a template.

Treatment of an N -silyl- B -chloro-aminoborane with substoichio-metric quantities of Me 3 SiOTf afforded B-N coupling, whereas activation with 5 mol% of Ag[Al{OC(CF 3 ) 3 } 4 ] led to Cl/Me exchange between the boron and the silicon center. Combined experimental and computational studies of the latter process support a chain reaction that is initiated by nucleation-limited chloride abstraction.

Direct functionalization and Pd-catalyzed cross-coupling of difuryl(supermesityl)borane (1) led to highly emissive organoborane compounds 3 and 4. Photophysical and TD-DFT studies reveal an increase of the HOMO levels with higher hetarene content and stabilization of the HOMO and LUMO levels through B-doping, leading to very robust, air-stable electron-accepting materials.

Atom efficient reactions of 3-ferrocenyl-2H-azaphosphirene complex 1 using a newly developed acid/base ring expansion protocol are presented. Consecutive reaction of 1 in the presence of dimethyl cyanamide with triflic acid and triethylamine yielded the selective formation of 2H-1,4,2-diazaphosphole complex 3. The same protocol using acetone, benzaldehyde and ferrocenyl aldehyde afforded 1,3,5-oxazaphosphol-3-ene complexes 4, 5a,b and 6a,b, the latter as mixtures of diastereomers, which could be separated. Apart from NMR, IR and UV/vis spectroscopic data, the single-crystal X-ray structures of complexes 3, 4 and 6a are discussed.

Synthesis of azaphosphiridine complexes 3a-e was achieved via thermal group transfer reaction using 2H-azaphosphirene complex 1 and N-methyl C-aryl imines 2a-e (i) or via reaction of transient Li/Cl phosphinidenoid complex 5 (prepared from dichloro(organo)phosphane complex 4) using 2a-c (ii), respectively. Reaction of complexes 3a,d and trifluoromethane sulfonic acid in the presence of dimethyl cyanamide led to a highly bond- and regioselective ring expansion yielding 1,3,4sigma3lambda3-diazaphosphol-2-ene complexes 8a,d after deprotonation with NEt3. 31P NMR reaction monitoring revealed that protonation of complex 3a yields the azaphosphiridinium complex 6a, unambiguously identified by NMR spectroscopy at low temperature. All isolated products were characterized by multinuclear NMR spectroscopy, IR and UV/Vis (for 3a,d, 6a, 8a,d), MS and single-crystal X-ray crystallography in the cases of complexes 3b-d, 8a and 8d. DFT studies on the reaction mechanism and compliance constants of the model complex of 6a are presented.