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

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

Metal-free binding and coupling of carbon monoxide at a boron-boron triple bond

Many metal-containing compounds, and some metal-free compounds, will bind carbon monoxide. However, only a handful of metal-containing compounds have been shown to induce the coupling of two or more CO molecules, potentially a method for use of CO as a one-carbon-atom building block for the synthesis of organic molecules. In this work, CO was added to a boron-boron triple bond at room temperature and atmospheric pressure, resulting in a compound into which four equivalent of CO are incorporated: a flat, bicyclic, bis(boralactone). By the controlled addition of one CO to the diboryne compound, an intermediate in the CO coupling reaction was isolated and structurally characterized. Electrochemical measurements confirm the strongly reducing nature of the diboryne compound