Hans_Bauer96

A general palladium-catalyzed hydroaminocarbonylation of acetylene towards important acrylamide derivatives is presented. The novel synthetic protocol shows high functional group-compatibility, high atom efficiency and good chemoselectivity to obtain a variety of bio-active compounds including several actual drugs.

Abstract

The development of all kinds of covalent drugs had a major impact on the improvement of the human health system. Covalent binding to target proteins is achieved by so-called electrophilic warheads, which are incorporated in the respective drug molecule. In the last decade, specifically acrylamides emerged as attractive warheads in covalent drug design. Herein, a straightforward palladium-catalyzed hydroaminocarbonylation of acetylene has been developed, allowing a modular and diverse synthesis of bio-active acrylamides. This general protocol features high atom efficiency, wide functional group compatibility, high chemoselectivity and proceeds additive free under mild reaction conditions. The synthetic utility of this protocol is showcased in the synthesis of ibrutinib, osimertinib, and other bio-active compound derivatives.

The isolation of a four-coordinate triphosphine nickel carbene complex challenges the generally accepted idea that low coordination numbers are required to stabilize M=C double bonds at late transition metal centers. The isolated compound displays nucleophilic and carbene-transfer reactivity. Computational analyses shed light on the unexpected role of the third phosphine in stabilizing the Ni=C fragment.

Abstract

Nickel carbenes are key reactive intermediates in the catalytic cyclopropanation of olefins and other reactions, but isolated examples are scarce and generally rely on low coordination numbers (≤3) to stabilize the metal−ligand multiple bond. Here we report the isolation and characterization of a stable tetracoordinated nickel carbene bearing a triphosphine pincer ligand. Its nucleophilic character is evidenced by reaction with acids, and it can transfer the carbene fragment to CO to form a ketene. A computational study of the Ni=C chemical bond sheds light on the role of the third phosphine in the pincer framework to the stabilization of the nickel carbene fragment.

A zinc complex of a frustrated Lewis pair (FLP)-supported P(−1) ligand is presented. This Zn complex allows access to various other P(−1)-ligated species through transmetallation. Additionally, the reaction of an FLP-chelated P(+1) compound with Na[Co(CO)₄] leads to an η²-phosphaborene complex which is isoelectronic to η²-olefin complexes.

Abstract

Several complexes of the intramolecular frustrated Lewis pair (FLP)-supported P(−1) ligand [ⁱPr₂P(C₆H₄)BCy₂{P}]⁻ are presented (Cy=cyclohexyl). Chief among these is the first example of a monomeric zinc bis(phosphido) complex, which was synthesized as a potential precursor for the solution-phase deposition of Zn₃P₂. While this goal was ultimately unsuccessful, the Zn(II) complex acts as a convenient springboard to other metal phosphide species via transmetallation: affording a tellurium bis(phosphido) complex and a formal adduct of the phosphorus subhalide PPCl₂. Trapping experiments show that the PPCl₂ adduct can also be prepared directly through the in situ reduction of PCl₃ in the presence of an intramolecular FLP ligand. Lastly, we report a formal η²-phosphaborene complex of cobalt(−1) which is isoelectronic to olefin complexes, and explore its bonding via density functional theory (DFT) computations.

Systematic access to anionic silylamine-substituted silicon-based cubanes with unsubstituted atoms was achieved upon cleavage of amido ligands from a bicyclic silicon(I) ring compound with KC₈. A possible intermediate that dimerizes to the products was trapped with SiMe₃Cl. With KOtBu selective SiMe₃ group abstraction form the bicyclic silicon(I) ring compound results in anionic tetrahedral silanide that is coordinated by a bridging imido substituent.

Abstract

The reaction of the bicyclic silicon(I) ring compound Si₄{N(SiMe₃)Mes}₄ 1 with strong zwitterionic character and moderate sterical demand of the amido substituents with two equivalents of KC₈ was investigated. This resulted in the unexpected abstraction of two amido substituents from 1 and additionally in dimerization to a dianionic Si₈ cluster compound 2 with four unsubstituted silicon atoms and two [K([18]crown-6)]⁺ counter cations. Performing this reaction in the absence of [18]crown-6 results in release of only one amido substituent from 1 and dimerization to a dianionic Si₈ cluster 3 with only two unsubstituted silicon atoms. This reaction with KC₈ was repeated and trapping agents such as SiMe₃Cl and tBuCl were added in-situ whereupon the second isolated homocyclic silylene 4 and a monoanionic hydride and tBu substituted Si₈ cluster 5 with one unsubstituted silicon atom were isolated. Furthermore, 1 was reacted with KOtBu which resulted in the selective abstraction of one SiMe₃ group and formation of the tetrahedral silanide 6 with one imido substituent bridging an edge of the tetrahedron.

Die erste Synthese eines vollständig charakterisierten Dicyanketenimins, Me₃Si−NC−C(CN)₂, wurde durch Einführung einer sperrigen Me₃Si-Gruppe erreicht, während die protonierte Spezies zum Tricyanmethan-Isomer HC(CN)₃ führt. Eine weitere Silylierung mit [Me₃Si−H−SiMe₃][B(C₆F₅)₄] führte zur Bildung eines ungewöhnlichen, persilylierten Dikations [C(CN−SiMe₃)₃]²⁺, das durch ein schwach koordinierendes Anion stabilisiert wird.

Abstract

Pseudohalogenide wie Tricyanmethanid, [C(CN)₃]⁻, sind in der Chemie sowie Biochemie weit verbreitet. Die protonierte Spezies HC(CN)₃, eine klassische Pseudohalogen-Wasserstoff-Brønsted-Säure, ist eine sehr starke Säure mit einem pK _S-Wert von −5. HC(CN)₃ ist jedoch schwer zu handhaben, da es dazu neigt, sich schnell zu zersetzen oder – genauer gesagt – zu oligo- und polymerisieren. Daher sind silylierte Pseudohalogenid-Verbindungen mit dem [Me₃Si]⁺ als „großem metallorganischen Proton“ von Interesse, die ähnliche chemische Eigenschaften, aber eine bessere kinetische Stabilisierung aufweisen. Hier wird von der schrittweisen Silylierung des Pseudohalogenid-Anions [C(CN)₃]⁻ berichtet, wobei das schwerere Homolog von HC(CN)₃, nämlich [Me₃Si][C(CN)₃], und in Gegenwart von zwei zusätzlichen [Me₃Si]⁺-Kationen sogar die dikationische Spezies [(Me₃Si−NC)₃C]²⁺ als stabiles [B(C₆F₅)₄]-Salz gebildet wird. Überraschenderweise erfolgt im Gegensatz zur protonierten Spezies HC(CN)₃, bei der das Proton an das zentrale C-Atom von [C(CN)₃]⁻ gebunden ist, die Silylierung des [C(CN)₃]⁻-Anions an einem der drei terminalen N-Atome, wodurch das lange gesuchte Dicyanketenimin [Me₃Si−NC−C(CN)₂] gebildet wird. Alle weiteren Silylierungsschritte finden ausschließlich an den terminalen N-Atomen der drei CN-Gruppen und nicht am zentralen C-Atom statt, bis schließlich das bis dato unbekannte, hochsymmetrische Dikation, [(Me₃Si−NC)₃C]²⁺, gebildet wird. Die experimentellen Daten werden durch quantenchemische Berechnungen in Bezug auf Thermodynamik und chemische Bindungen unterstützt.

Insertion of SO₃ molecules into the N−H bonds of hydrazine, N₂H₄ lead to the hydrazine disulfonate [(SO₃)HNNH(SO₃)]²⁻ and the hydrazine iso-disulfonate, [H₂NN(SO₃)₂]²⁻ anion, respectively. The salts of these new anions have been characterized comprehensively, including thermal analyses, Raman spectroscopy and DFT calculations.

Abstract

The reaction of hydrazinium sulfate and chlorosulfonic acid in pyridine leads to the pyridinium salt of the hydrazine disulfonate anion, [(SO₃)HNNH(SO₃)]²⁻. The salt is the starting material for the preparation of further hydrazine disulfonates, for example of alkaline metals and barium. In all compounds, the [(SO₃)HNNH(SO₃)]²⁻ anion adopts the gauche conformation. The conformer is chiral but all of the investigated compounds crystallize as racemates. The disulfonate anion can occur in another constitution with the two sulfonate groups attached to only one nitrogen atom. This so-called hydrazine iso-disulfonate, [H₂NN(SO₃)₂]²⁻, has been prepared through a substitution reaction between potassium imidodisulfonate, K₂[HN(SO₃)₂], and hydroxylamine-O-sulfonic acid, H₂NOSO₃H. The hydrazine iso-disulfonate anion has been crystallized as potassium and barium compound, respectively. The compounds were characterized by XRD, vibrational spectroscopy, DFT calculations and thermal analyses.

Publication date: 9 January 2025

Source: Chem, Volume 11, Issue 1

Author(s): Zhongtao Feng, Rei Kinjo

Reaktionen von stabilen Diazoalkenen mit Phosphaalkin (tBuCP) und weißem Phosphor (P₄) führen zu Diazamono- und Diazadiphospholen. Diese neuen Organophosphorverbindungen finden Anwendung in der Übergangsmetall- und Hauptgruppenchemie.

Abstract

Reaktionen von Diazoalkenen mit tert-Butylphosphaalkin (tBuCP) und weißem Phosphor (P₄) führen zu neuen Phosphorheterocyclen, 3H-1,2,4-Diazamonophospholen und 1,2,3,4-Diazadiphospholen. Die erhaltenen Verbindungen sind seltene Beispiele für neutrale Heterophosphole. Der Bildungsmechanismus der formalen (3+2)-Cycloadditionsprodukte wurde quantenchemisch berechnet und die elektronischen Strukturen analysiert. Die neuen Phosphole bilden strukturell vielfältige Koordinationsverbindungen mit Übergangsmetallen und Hauptgruppenelementen. Angesichts der wachsenden Anzahl stabiler Diazoalkene bietet diese Arbeit einen unmittelbaren Zugang zu neutralen Aza(di-)phospholen als neue Ligandenklasse.

The green crystals formed in the reduction of Ar^iPr8AlI₂ (Ar^iPr8=C₆H-2,6-(C₆H₂-2,4,6-ⁱPr₃)₂-3,5-ⁱPr₂) with Na on NaCl were shown to contain the free dialuminene Ar^iPr8AlAlAr^iPr8 that forms alongside the previously characterized yellow crystals of the alanediyl :AlAr^iPr8. The interplay between :AlAr^iPr8 and Ar^iPr8AlAlAr^iPr8 in solution was examined in detail with small molecule activation studies and computational methods.

Abstract

Careful analysis of the crystals formed in the reduction of Ar^iPr8AlI₂ (Ar^iPr8=C₆H-2,6-(C₆H₂-2,4,6-ⁱPr₃)₂-3,5-ⁱPr₂) with sodium on sodium chloride showed them to contain the long sought-after dialuminene Ar^iPr8AlAlAr^iPr8 (1) that forms alongside the previously characterized alanediyl :AlAr^iPr8. The single crystal X-ray structure of 1 revealed a nearly planar, trans-bent C(ipso)AlAlC(ipso) core with an Al−Al distance of 2.648(2) Å. The molecular and electronic structure of 1 are consistent with an Al−Al double dative interaction augmented with diradical character and stabilized by dispersion interactions. Density functional theory calculations showed that the reactivity of :AlAr^iPr8 with dihydrogen involves 1, not :AlAr^iPr8, as the reactive species. In contrast, the reaction of :AlAr^iPr8 with ethylene gave two products, the 1,4-dialuminacyclohexane Ar^iPr8Al(C₂H₄)₂AlAr^iPr8 (2) and the aluminacyclopentane Ar^iPr8Al(C₄H₈) (3), that can both form from the aluminacyclopropane intermediate Ar^iPr8Al(C₂H₄). Although the [2+2+2] cycloaddition of 1 with two equivalents of ethylene was also calculated to be exergonic, it is likely to be kinetically blocked by the numerous isopropyl substituents surrounding the Al−Al bond. Attempts to fine-tune the steric bulk of the terphenyl ligand to allow stronger Al−Al bonding were unsuccessful, leading to the isolation of the sodium salt of a cyclotrialuminene, Na₂[AlAr^iPr6]₃ (4), instead of Ar^iPr6AlAlAr^iPr6.

Merging low-valent Mg^I and Be^I chemistry, a unique complex with a Mg−Be bond was isolated and structurally characterized. Formally a Mg^II−Be⁰ complex, the bond is significantly polarized Mg^δ+−Be^δ−. Despite this polarity, the complex is thermally stable and only reacts with polar unsaturated C=O, C=S or N=N bonds.

Abstract

Attempts to create a novel Mg−Be bond by reaction of [(^DIPePBDI*)MgNa]₂ with Be[N(SiMe₃)₂]₂ failed; ^DIPePBDI*=HC[(tBu)C=N(DIPeP)]₂, DIPeP=2,6-Et₂C-phenyl. Even at elevated temperatures, no conversion was observed. This is likely caused by strong steric shielding of the Be center. A similar reaction with the more open Cp*BeCl gave in quantitative yield (^DIPePBDI*)MgBeCp* (1). The crystal structure shows a Mg−Be bond of 2.469(4) Å. Homolytic cleavage of the Mg−Be bond requires ΔH=69.6 kcal mol⁻¹ (cf. CpBe−BeCp 69.0 kcal mol⁻¹ and (^DIPPBDI)Mg−Mg(^DIPPBDI) 55.8 kcal mol⁻¹). Natural-Population-Analysis (NPA) shows fragment charges: (^DIPePBDI*)Mg +0.27/BeCp* −0.27. The very low NPA charge on Be (+0.62) compared to Mg (+1.21) and the strongly upfield ⁹Be NMR signal at −23.7 ppm are in line with considerable electron density on Be and the formal oxidation state assignment of Mg^II−Be⁰. Despite this Mg^δ+−Be^δ− polarity, 1 is extremely thermally stable and unreactive towards H₂, CO, N₂, cyclohexene and carbodiimide. It reacted with benzophenone, azobenzene, phenyl acetylene, CO₂ and CS₂. Reaction with 1-adamantyl azide led to reductive coupling and formation of an N₆-chain. The azide reagent also inserted in the Cp*−Be bond. The inertness of 1 is likely due to bulky ligands protecting the Mg−Be unit.

A mixed Arduengo-Fischer carbodicarbene ligand was synthesized through reaction of a Fischer carbene complex with an N-heterocyclic diazoolefin. Subsequent transmetallations allow ligand transfer to different metal complexes, including RhCl(CO)₂ (see graphic).

Abstract

Carbodicarbenes are strong C-donor ligands, which have found numerous applications in organometallic and main group element chemistry. Herein, we report a structurally distinct carbodicarbene ligand, which is formed by dinitrogenative coupling of a Fischer carbene complex with an N-heterocyclic diazoolefin. The resulting carbonyl complex serves as a stable source for the mixed Arduengo-Fischer carbodicarbene ligand. Facile ligand transfer reactions were demonstrated to occur with gold(I), copper(I), palladium(II), and rhodium(I) complexes.