Nickel Complexes in C‒P Bond Formation

Bulky, electron-rich, renewable: analogues of Beller's phosphine for cross-couplings

In recent years, considerable progress has been made in the conversion of biomass into renewable chemicals, yet the range of value-added products that can be formed from biomass remains relatively small. Herein, we demonstrate that molecules available from biomass serve as viable starting materials for the synthesis of phosphine ligands, which can be used in homogeneous catalysis. Specifically, we prepared renewable analogues of Beller's ligand (di(1-adamantyl)-n-butylphosphine, cataCXium® A), which is widely used in homogeneous catalysis. Our new renewable phosphine ligands facilitate Pd-catalysed Suzuki-Miyaura, Stille, and Buchwald-Hartwig coupling reactions with high yields, and our catalytic results can be rationalized based on the stereoelectronic properties of the ligands. The new phosphine ligands generate catalytic systems that can be applied for the late-stage functionalization of commercial drugs.

Cross-Electrophile C-PIII Coupling of Chlorophosphines with Organic Halides: Photoinduced PIII and Aminoalkyl Radical Generation Enabled by Pnictogen Bonding

Pnictogen bonding (PnB) has gained recognition as an appealing strategy for constructing novel architectures and unlocking new properties. Within the synthetic community, the development of a straightforward and much simpler protocol for cross-electrophile C-PIII coupling remains an ongoing challenge with organic halides. In this study, we present a simple strategy for photoinduced PnB-enabled cross-electrophile C-PIII couplings using readily available chlorophosphines and organic halides via merging single electron transfer (SET) and halogen atom transfer (XAT) processes. In this photomediated transformation, the PnB formed between chlorophosphines and alkyl amines facilitates the photogeneration of PIII radicals and α-aminoalkyl radicals through SET. Subsequently, the resulting α-aminoalkyl radicals activate C-X bonds via XAT, leading to the formation of carbon radicals. This methodology offers operational simplicity and compatibility with both aliphatic and aromatic chlorophosphines and organic halides.

C- and N-Phosphorylated Enamines-An Avenue to Heterocycles: NMR Spectroscopy

The review presents extensive data (from the works of the author and literature) on the structure of C- and N-chlorophosphorylated enamines and the related heterocycles obtained by multipulse multinuclear ¹H, ¹³C, and ³¹P NMR spectroscopy. The use of phosphorus pentachloride as a phosphorylating agent for functional enamines enables the synthesis of various C- and N-phosphorylated products that are heterocyclized to form various promising nitrogen- and phosphorus-containing heterocyclic systems. ³¹P NMR spectroscopy is the most convenient, reliable and unambiguous method for the study and identification of organophosphorus compounds with different coordination numbers of the phosphorus atom, as well as for the determination of their Z- and E-isomeric forms. An alteration of the coordination number of the phosphorus atom in the phosphorylated compounds from 3 to 6 leads to a drastic screening of the ³¹P nucleus from about +200 to -300 ppm. The unique structural features of nitrogen-phosphorus-containing heterocyclic compounds are discussed.

Stille type P-C coupling polycondensation towards phosphorus-crosslinked polythiophenes with P-regulated photocatalytic hydrogen evolution

Recently, exploring new type polymerization protocols has been a major driving force in advancing organic polymers into highly functional materials. Herein we report a new polycondensation protocol to implant the phosphorus (P) atom in the main backbone of crosslinked polythiophenes. The polycondensation harnesses a Stille phosphorus-carbon (P-C) coupling reaction between phosphorus halides and aryl stannanes that has not been reported previously. Mechanistic studies uncovered that the P-electrophile makes the reactivity of a catalytic Pd-center highly sensitive towards the chemical structures of aryl stannanes, which is distinct from the typical Stille carbon-carbon coupling reaction. The efficient P-C polycondensation afforded a series of P-crosslinked polythiophenes (PC-PTs). Leveraging on the direct P-crosslinking polymerization, solid-state ³¹P NMR studies revealed highly uniform crosslinking environments. Efficient post-polymerization P-chemistry was also applied to the PC-PTs, which readily yielded the polymers with various P-environments. As a proof of concept, new PC-PTs were applied as the photocatalysts for H₂ evolution under visible light irradiation. PC-PTs with an ionic P(Me)-center exhibit a H₂ evolution rate up to 2050 μmol h^-1 g^-1, which is much higher than those of PC-PTs with a P(O)-center (900 μmol h^-1 g^-1) and P(iii)-center (155 μmol h^-1 g^-1). For the first time, the studies reveal that regulating P-center environments can be an effective strategy for fine tuning the photocatalytic H₂ evolution performance of organic polymers.

Organophosphorus Azoles Incorporating a Tetra-, Penta-, and Hexacoordinated Phosphorus Atom: NMR Spectroscopy and Quantum Chemistry

The review presents extensive data (from the author's work and the literature) on the stereochemical structure of functionalized organophosphorus azoles (pyrroles, pyrazoles, imidazoles and benzazoles) and related compounds, using multinuclear ¹H, ¹³C, ³¹P NMR spectroscopy and quantum chemistry. ³¹P NMR spectroscopy, combined with high-level quantum-chemical calculations, is the most convenient and reliable approach to studying tetra-, penta-, and hexacoordinated phosphorus atoms of phosphorylated N-vinylazoles and evaluating their Z/E isomerization.

Nickel-Catalyzed 1,1-Dihydrophosphinylation of Nitriles with Phosphine Oxides

Treatment of phosphine oxides with nitriles usually furnishes 1,2-dihydrophosphinylation products. Herein, we developed a nickel-catalyzed 1,1-dihydrophosphinylation of nitriles with phosphine oxides to access primary amines. This reaction proceeded smoothly under very mild conditions. A series of nitriles and phosphine oxides were compatible with this conversion, and the desired products were obtained in moderate to good yields.

Influence of N- and P-substituents in N-aryl-phosphinoglycine ligands on the selectivity of Ni-catalysed ethylene oligomerization

Quantum-chemical calculations were performed to rationalize the experimental molecular weight distribution of α-olefin products, revealing the main mechanistic models of the process.