Optical absorption in boron clusters B6_{6} and B6+_{6}^{+} : A first principles configuration interaction approach

The linear optical absorption spectra in neutral boron cluster B$_{6}$ and cationic B$_{6}^{+}$ are calculated using a first principles correlated electron approach. The geometries of several low-lying isomers of these clusters were optimized at the coupled-cluster singles doubles (CCSD) level of theory. With these optimized ground-state geometries, excited states of different isomers were computed using the singles configuration-interaction (SCI) approach. The many body wavefunctions of various excited states have been analysed and the nature of optical excitation involved are found to be of collective, plasmonic type.Comment: 22 pages, 38 figures. An invited article submitted to European Physical Journal D. This work was presented in the International Symposium on Small Particles and Inorganic Clusters - XVI, held in Leuven, Belgiu

Catalytic Tuning of a Phosphinoethane Ligand for Enhanced C-H Activation

Article discussing research on the catalytic tuning of a phosphinoethane ligand for enhanced C-H activation

Towards dual‐metal catalyzed hydroalkoxylation of alkynes

Poly (vinyl ethers) are compounds with great value in the coating industry due to exhib-iting properties such as high viscosity, soft adhesiveness, resistance to saponification and solubility in water and organic solvents. However, the main challenge in this field is the synthesis of vinyl ether monomers that can be synthetized by methodologies such as vinyl transfer, reduction of vinyl phosphate ether, isomerization, hydrogenation of acetylenic ethers, elimination, addition of alcohols to alkyne species etc. Nevertheless, the most successful strategy to access to vinyl ether deriv-atives is the addition of alcohols to alkynes catalyzed by transition metals such as molybdenum, tungsten, ruthenium, palladium, platinum, gold, silver, iridium and rhodium, where gold‐NHC catalysts have shown the best results in vinyl ether synthesis. Recently, the hydrophenoxylation reaction was found to proceed through a digold‐assisted process where the species that determine the rate of the reaction are PhO‐[Au(IPr)] and alkyne‐[Au(IPr)]. Later, the improvement of the hy-drophenoxylation reaction by using a mixed combination of Cu‐NHC and Au‐NHC catalysts was also reported. DFT studies confirmed a cost‐effective method for the hydrophenoxylation reaction and located the rate‐determining step, which turned out to be quite sensitive to the sterical hin-drance due to the NHC ligands

Reactivity of Boryl Complexes: Synthesis and Structure of New Neutral and Cationic Platinum Boryls and Borylenes

A reactivity study on a series of platinum boryl complexes was performed. The first stable base adducts of cationic haloboryl complexes of the form <i>trans</i>-[Pt­{B­(Br)­(NMe₂)}­(NCMe)­(PCy₃)₂]⁺ were isolated and fully characterized. The dianion [B₁₂Cl₁₂]^2– was introduced as a weakly coordinating anion to complex chemistry forming a A₂X salt. Through the reaction of <i>trans</i>-[Pt­{B­(Br)­(<i>t</i>Bu)}­Br­(PCy₃)₂] with BBr₂<i>t</i>Bu, the first highly soluble dinuclear platinum boryl complex, [Pt­{B­(Br)­(<i>t</i>Bu)}­(μ-Br)­(PCy₃)]₂, could be synthesized with concomitant buildup of the corresponding phosphine-borane adduct. In contrast to this observation, reaction of <i>trans</i>-[Pt­{B­(Br)­(Mes)}­Br­(PCy₃)₂] with BBr₃ leads to the formation of the cationic borylene complex <i>trans</i>-[Pt­(BMes)­Br­(PCy₃)₂]⁺ by abstraction of the bromo ligand bound mutually <i>trans</i> to the boryl ligand in the precursor and concomitant buildup of [BBr₄]⁻. Reaction of [Pt­(PCy₃)₂] with BCl₃ and subsequent abstraction of the platinum-bound chloro ligand enabled the structural characterization of <i>trans</i>-[Pt­(BCl₂)­(PCy₃)₂]⁺, which is isoelectronic with the metal-only Lewis pair <i>trans</i>-[Pt­(BeCl₂)­(PCy₃)₂]. The bonding situation in both systems was investigated in detail using quantum chemical calculations. A T-shaped cationic complex, <i>trans</i>-[Pt­{B­(Br)­(Fc)}­(P<i>i</i>Pr₃)₂]⁺, and its precursor <i>trans</i>-[Pt­{B­(Br)­(Fc)}­Br­(P<i>i</i>Pr₃)₂], both with reduced steric bulk at the phosphine ligands compared with their PCy₃ derivatives, were fully characterized

Reactivity of Boryl Complexes: Synthesis and Structure of New Neutral and Cationic Platinum Boryls and Borylenes

A reactivity study on a series of platinum boryl complexes was performed. The first stable base adducts of cationic haloboryl complexes of the form <i>trans</i>-[Pt­{B­(Br)­(NMe₂)}­(NCMe)­(PCy₃)₂]⁺ were isolated and fully characterized. The dianion [B₁₂Cl₁₂]^2– was introduced as a weakly coordinating anion to complex chemistry forming a A₂X salt. Through the reaction of <i>trans</i>-[Pt­{B­(Br)­(<i>t</i>Bu)}­Br­(PCy₃)₂] with BBr₂<i>t</i>Bu, the first highly soluble dinuclear platinum boryl complex, [Pt­{B­(Br)­(<i>t</i>Bu)}­(μ-Br)­(PCy₃)]₂, could be synthesized with concomitant buildup of the corresponding phosphine-borane adduct. In contrast to this observation, reaction of <i>trans</i>-[Pt­{B­(Br)­(Mes)}­Br­(PCy₃)₂] with BBr₃ leads to the formation of the cationic borylene complex <i>trans</i>-[Pt­(BMes)­Br­(PCy₃)₂]⁺ by abstraction of the bromo ligand bound mutually <i>trans</i> to the boryl ligand in the precursor and concomitant buildup of [BBr₄]⁻. Reaction of [Pt­(PCy₃)₂] with BCl₃ and subsequent abstraction of the platinum-bound chloro ligand enabled the structural characterization of <i>trans</i>-[Pt­(BCl₂)­(PCy₃)₂]⁺, which is isoelectronic with the metal-only Lewis pair <i>trans</i>-[Pt­(BeCl₂)­(PCy₃)₂]. The bonding situation in both systems was investigated in detail using quantum chemical calculations. A T-shaped cationic complex, <i>trans</i>-[Pt­{B­(Br)­(Fc)}­(P<i>i</i>Pr₃)₂]⁺, and its precursor <i>trans</i>-[Pt­{B­(Br)­(Fc)}­Br­(P<i>i</i>Pr₃)₂], both with reduced steric bulk at the phosphine ligands compared with their PCy₃ derivatives, were fully characterized

Neutral Hexacoordinate Tin(IV) Halide Complexes with 4,4'‐Dimethy‐2,2'‐bipyridine

A series of three neutral, hexacoordinate tin(IV) complexes were synthesized by the reaction of 4,4'‐dimethyl‐2,2'‐bipyridine (DMB) with SnX4, X = Cl, Br, and I, as starting materials. The complexes (DMB)SnX4 were characterized in solution by 1H, 13C, and 119Sn NMR spectroscopy, and in the solid‐state by 119Sn MAS NMR spectroscopy. In addition, single‐crystal X‐ray diffraction and elemental analysis were used to confirm the molecular structures. In these complexes, the tin atom adopts a distorted octahedral arrangement and the DMB acts as a bidentate N,N'‐chelate ligand. Computational DFT methods were also employed to gain more insight into the nature of the bonding in these complexes, including the hypothetical complexes (DMB)SnX4 (X = F, At). Additionally, the validity and reliability of the 119Sn NMR chemical shifts were examined. The calculated values were compared with the experimental signals and the effects of structure and solvent are discussed. Finally, all of the complexes (DMB)SnX4 were successfully tested for the ring‐opening polymerization (ROP) of bulk ε‐caprolactone under non‐dried and aerobic conditions as precatalyst

1‑Heteroaromatic-Substituted Tetraphenylboroles: π–π Interactions Between Aromatic and Antiaromatic Rings Through a B–C Bond

A series of 2,3,4,5-tetraphenylboroles substituted with different aromatic heterocycles (thiophene, furan, pyrrole, and dithiophene) in the 1-position were synthesized and characterized by means of NMR, elemental analysis, and X-ray crystallography. In contrast to known 2,3,4,5-tetraphenylboroles, X-ray diffraction revealed a nearly coplanar arrangement of the aromatic heterocycles and the antiaromatic borole scaffold as a result of π-conjugation, which could be substantiated by DFT calculations. Furthermore, the 2,2′-dithiophene-bridged bisborole (<b>14</b>) exhibits a large bathochromic shift in the absorption spectrum, demonstrating the exceptional Lewis acidity of the nonannulated borolyl moiety

1‑Heteroaromatic-Substituted Tetraphenylboroles: π–π Interactions Between Aromatic and Antiaromatic Rings Through a B–C Bond

A series of 2,3,4,5-tetraphenylboroles substituted with different aromatic heterocycles (thiophene, furan, pyrrole, and dithiophene) in the 1-position were synthesized and characterized by means of NMR, elemental analysis, and X-ray crystallography. In contrast to known 2,3,4,5-tetraphenylboroles, X-ray diffraction revealed a nearly coplanar arrangement of the aromatic heterocycles and the antiaromatic borole scaffold as a result of π-conjugation, which could be substantiated by DFT calculations. Furthermore, the 2,2′-dithiophene-bridged bisborole (<b>14</b>) exhibits a large bathochromic shift in the absorption spectrum, demonstrating the exceptional Lewis acidity of the nonannulated borolyl moiety