A Phosphanyl-Phosphagallene that Functions as a Frustrated Lewis Pair

Phosphagallenes ( 1 a / 1 b ) featuring double bonds between phosphorus and gallium were synthesized by reaction of (phosphanyl)phosphaketenes with the gallium carbenoid Ga(Nacnac) (Nacnac=HC[C(Me)N(2,6-i-Pr₂C₆H₃)]₂). The stability of these species is dependent on the saturation of the phosphanyl moiety. 1 a , which bears an unsaturated phosphanyl ring, rearranges in solution to yield a spirocyclic compound ( 2 ) which contains a P=P bond. The saturated variant 1 b is stable even at elevated temperatures. 1 b behaves as a frustrated Lewis pair capable of activation of H₂ and forms a 1:1 adduct with CO₂.     

Novel Synthesis and Structure of Phosphanyl Sugar Derivatives 1

Abstract

Some phosphanyl sugar derivatives, which are analogs of sugars having a phosphorus atom in place of the ring oxygen, were synthesized from 2- and 3-phospholenes as starting materials. Catalytic cis-dihydroxylation of 2-phospholene or 3-phospholene 1-oxide derivatives with osmium(VIII) oxide in the presence of a cooxidant afforded 3-deoxy- or 1-deoxy-tetrofuranose-type phosphanyl sugar derivatives, respectively. cis- Dihydroxylation of 4-acyloxy-2-phospholene 1-oxide derivatives gave tetrofuranose type phosphanyl sugar derivatives. Some of these derivatives of phosphanyl sugars were subjected to structural analyses using ¹H NMR and X-ray crystallography.

     

Hydroalumination of silylacetylenes: a novel and highly stereoselective synthesis of (E)-telluro(silyl)ketene acetals and their applications in Sonogashira cross-coupling reactions

The hydroalumination of silylacetylenes with DIBAL-H followed by the addition of n-butyllithium generated in situ the (Z)-β-vinylorganosilane alanates intermediates, which were trapped with butyltellurenyl bromide (C₄H₉TeBr), furnishing exclusively the (E)-1-butyltelluro-1-tri(organyl)silyl-2-organyl-1-alkenes in 45-70% yields. These telluro(silyl)ketene acetals were utilized as substrates in Sonogashira cross-coupling Pd-catalyzed reactions, furnishing the (Z)-1,4-diorganyl-2-tri(organyl)silyl-1-buten-3-ynes with total control of regio- and stereochemistry in 62-80% yield.     

Synthetic Utility of Stable Phosphanylcarbenes: Synthesis and Crystal Structure of an α‐(Lithiomethylene)phosphorane

The first crystallographically characterized phosphonium yldiide 2 was obtained in a simple reaction by addition of n‐butyllithium to the stable phosphanyl(silyl)carbene 1 . R=cHex₂N.     

β-Carbonylsilanes with a silacyclohexane skeleton and additional C-functionalized organyl groups at the silicon atom: synthesis, reactivity, and NMR-spectroscopic characterization

A series of novel β-carbonylsilanes, with a silacyclohexane skeleton and additional C-functionalized organyl groups at the silicon atom, were synthesized, their reactivity was explored, and they were structurally characterized by multinuclear NMR spectroscopy. The aim of these investigations was to provide the basis for the development of novel silicon-based drugs containing a silacyclohexane skeleton, with a CH₂C(O)R substituent and an additional C-functionalized organyl group at the silicon atom.     

Frustrated Lewis-Pair Neighbors at the Xanthene Framework: Epimerization at Phosphorus and Cooperative Formation of Macrocyclic Adduct Structures

Attachment of a pair of P-stereogenic mesityl(alkynyl)phosphanyl groups at the 4- and 5-positions of a 9,9-dimethylxanthene framework gave mixtures of the respective rac- and meso-bisphosphanyl diastereoisomers. They slowly epimerized in a thermally induced reaction with Gibbs activation barriers of about 25 kcal mol⁻¹ at room temperature (measured and DFT calculated). The reaction of the meso-mesityl(tert-butylethynyl)phosphanyl derivative with two molar equivalents of Piers′ borane [HB(C₆F₅)₂] led to the formation of the alkylidene-bridged geminal bisphosphane/borane-frustrated Lewis pair system. The compound was obtained enriched (>85 %) in the rac diastereoisomer. With a variety of bifunctional donor substrates, the rac-bis-P/B FLP formed macrocyclic compounds. They were all formally derived from meso-configurated diastereoisomers of the bisphosphanylxanthene backbone.     

Phosphanstabilisierte organyltellurenylkationen, [RTe(PR′3)]+

Diorganyl ditellurides, RTeTeR (R = CH₃, p-FC₆H₄) are oxidized by nitrosyl salts, NO⁺X⁻ (X⁻ = BF₄⁻, ClO₄⁻) with formation of the respective organyl tellurenyl cations, RTe⁺ which can be stabilized with tri(n-butyl)phosphine as organyl tellurophosphonium cations, [RTe(P(n-C₄H₉)₃)]⁺.     

ORGANYL (CHLOROETHYNYL) SULPHIDES,ORGANYL (CHLOROVINYL) SULPHIDES AND RELATED PROBLEMS

Abstract

Organyl(β,β-dichlorovinyl)- and organyl(α,β,β-trichlorovinyl) sulphides, CCl₂=CHSR, CCl₂=CClSR, (CCl₂=CHS)₂R, have been obtained by dechlorination and dehydrochlorination of α,β,β,β-tetrachloroethylorganylsulphides and by reactions of tri- and tetrachloroethylenes with mono- and dithiols of the aliphatic and aromatic series in the presence of radical initiators.     

Die ersten CF3-substituierten organyl(chlor)silane

The three component reaction (Et₂N) ₃P/CF₃Br/ R_nSiCl_4-n (n = 1,2,3; RCH₃,Ph) gives CF₃-substituted organyl(chloro)silanes for the first time. Their genesis will be elucidated.     

1,3-Diphosphacyclobutane-2,4-diyl-2-ylidenide: A Unique Carbene and Its Trimethylalane Complex

A unique bonding situation is displayed by the lithium 1,3-diphosphacyclobutane-2,4-diyl-2-ylidenide 2 ⋅[Li(thf)_n]⁺ (Ar=2,4,6-tBu₃C₆H₂) obtained by deprotonation of 1 . According to ab initio calculations, the anion 2 can viewed as a cyclic bis(phosphanyl)carbene. Reaction with trimethylaluminum gives the complex 3 ⋅[Li(thf)₄]⁺ , whose crystal structure is presented.     

Microscopic Reactivity of Phenylferrate Ions toward Organyl Halides

Despite its practical importance, organoiron chemistry remains poorly understood due to its mechanistic complexity. Here, we focus on the oxidative addition of organyl halides to phenylferrate anions in the gas phase. By mass-selecting individual phenylferrate anions, we can determine the effect of the oxidation state, the ligation, and the nuclearity of the iron complex on its reactions with a series of organyl halides RX. We find that Ph₂Fe(I)⁻ and other low-valent ferrates are more reactive than Ph₃Fe(II)⁻; Ph₄Fe(III)⁻ is inert. The coordination of a PPh₃ ligand or the presence of a second iron center lower the reactivity. Besides direct cross-coupling reactions resulting in the formation of RPh, we also observe the abstraction of halogen atoms. This reaction channel shows the readiness of organoiron species to undergo radical-type processes. Complementary DFT calculations afford further insight and rationalize the high reactivity of the Ph₂Fe(I)⁻ complex by the exothermicity of the oxidative addition and the low barriers associated with this reaction step. At the same time, they point to the importance of changes of the spin state in the reactions of Ph₃Fe(II)⁻.     

Synthesis of 1,2-disubstitued benzimidazoles using SiO2/ZnCl2

A general and easy method for the synthesis of several 1,2-disubstituted benzimidazoles using SiO₂/ZnCl₂ and solvent-free conditions is described. This efficient and improved method furnishes selectively and in good yields the corresponding 1,2-bis(organyl)-benzimidazoles starting from o-phenylenediamine and aromatic or aliphatic aldehydes. The catalytic system was re-used up three times and the use of focused microwaves accelerates the reaction.     

Bindungsabstände zwischen organylsubstituierten zinnatomen: II. Cyclo-tetrastannane

The crystal structures of octa-t-butyl-cyclo-tetrastannane (t-Bu₂Sn)₄ and octa-t-amyl-cyclo-tetrastannane (t-Am₂Sn)₄ have been determined by X-ray analysis. The four-membered tin ring of (t-Bu₂Sn)₄ is planar and the molecules are highly ordered in the crystal; the ring of (t-Am₂Sn)₄ is puckered.In both compounds the tintin bonds are longer than in other cyclostannanes which is probably caused by the size requirements of the organyl groups.     

Bis(diisopropylamino)phosphanyldiazomethane: A building block for the synthesis of stable carbene and nitrilimines

Thermolysis of [bis(diisopropylamino)phosphanyl](trimethylsilyl)diazomethane 1 affords the corresponding carbene 2 , which is stable enough to be spectroscopically characterized. This species possesses a phosphorus–carbon multiple-bond character as shown by the 2 + 3 and 2 + 2 cycloaddition reactions observed with trimethylsilyl azide or N₂O and ethyl cyanoformate, respectively. On the other hand, 2 undergoes all the classical reactions of a carbene: cyclopropanation reaction with electron-poor alkenes, carbon–hydrogen bond insertion, and carbene–carbene coupling with isonitriles. Compound 2 reacts with trimethylsilyl triflate affording a stable methylenephosphonium salt 15 . Treatment of the lithium salt of the [bis(diisopropylamino)thiophosphoranyl]diazomethane 18 with the bis(diisopropylamino)phosphanyl chloride leads to a stable nitrilimine 3 . Thermolysis of 3 affords the isomeric diazo derivative 20 , while photolysis gives rise to thiophophoranylnitrile 21 and cyclodiphosphazene 23 . Regioselective 2 + 3 cycloadditions are observed with electron-poor dipolarophiles. Addition of trimethylsilyl triflate to 3 leads to a stable electrophilic nitrilimine 29 .     

Binuclear CpV,Cp*V,and Cp*Ta Complexes containing Organochalcogenolato Bridges, μ‐ER (E = Sulfur,Selenium, Tellurium; R = Methyl,Phenyl, and Ferrocenyl)

Photolysis of the halfsandwich tetracarbonylmetal complexes CpV(CO)₄, Cp*V(CO)₄ and Cp*Ta(CO)₄ in solution in the presence of di(organyl)dichalcogenides E₂R₂ (E = S, Se, Te; R = Me, Ph, Fc) leads to diamagnetic doubly organochalcogenolato‐bridged compounds, [Cp⁽⁾M(CO)₂(μ‐ER)]₂. According to the X‐ray structure determinations carried out for [CpV(CO)₂(μ‐TeMe)]₂, [Cp*V(CO)₂(μ‐TePh)]₂ and [Cp*Ta(CO)₂(μ‐SPh)]₂, the molecular framework consists of a folded M₂(μ‐ER)₂ ring with the cyclopentadienyl ligands in cis‐configuration and the organyl substituents R in a syn‐equatorial arrangement, thus forming a bowl‐shaped molecule with the four terminal CO ligands protruding into the inner sphere. The M…M distances (in the range between 305 and 330 pm) are not considered to indicate direct bonding interactions. The vanadium complexes [Cp⁽⁾V(CO)₂(μ‐ER)]₂ are completely decarbonylated in the presence of an excess of E₂R₂ in boiling toluene, and in many cases the paramagnetic quadruply‐bridged products, [CpV(μ‐ER)₂]₂, can be isolated.     

Fluoraustauschreaktionen an Metalltrifluorphosphan-Komplexen. X [1]. Zum Reaktionsverhalten von Tetrakis(trifluorphosphan)-nickel(0) mit Metallorganylen [2]

Ni(PF₃)₄ ( 1 ) tauscht mit Lithiumorganylen und Grignard-Reagentien Fluor gegen Organyl-Gruppen aus, wobei die Komplexe ( 10–32 ) Ni(PF₃)_4?n(PF₂R)_n (n = 1, 2 und 3), Ni(PF₃)₃(PFR₂), Ni(PF₃)₂(PF₂R)(PFR₂) und Ni(PF₃)₃(PR₃) (R = organ. Rest) gebildet werden. Für den Reaktionsablauf wird ein Vierzentren-Synchron-Mechanismus vorgeschlagen. Fluorine Exchange in Trifluorophosphane Metal Complexes. X. Reactions of Tetrakis(trifluorophosphane)nickel(0) with Metal Organyls The fluorine atoms in Ni(PF₃)₄ ( 1 ) can be partially substituted by organyl groups yielding the complexes ( 10–32 ) Ni(PF₃)_4?n(PF₂R)_n (n = 1, 2 and 3), Ni(PF₃)₃(PFR₂), Ni(PF₃)₂(PF₂R)(PFR₂) and Ni(PF₃)₃(PR₃) (R = organyl group). The mechanism of these peripheric reactions is discussed by assuming a four centered type intermediate.     

Synthesis and Reactivity of Fluoro(Organyl)Phosphanes

Abstract

A new method for producing fluoro(organyl) phosphanes is presented. They are prepared by Cl/F-exchange from the corresponding chloro compounds using Et₃N.nHF as a fluorinating agent. Phosphanyl fluorophospharanes, R₂P-PR₂F₂, are found to be intermediates of the disproportionation of Fluoro (diorganyl) phosphanes. R₂PF react with aldehydes to form phosphinito phosphoranes, R₂PF₂-CHR'-OPR₂. Oxaphospholenes are formed in their reaction with α, β- unsaturated aldehydes. Furthermore, the reactions with 1.2-diketones, carboxylic acid derivatives, and covalent azides are described.     

Novel Synthesis and Structures of Amines and Triazole-Derived Glycoside and Nucleoside Derivatives of Phosphanyl Sugar Analogs

ABSTRACT

3-Methyl-1-phenyl-2-phospholene and 1-phenyl-2-phospholene 1-oxides were converted into 2-bromo-3-hydroxy-3-methyl-1-phenylphospholane and 2-bromo-3-hydroxy-1-phenylphospholane 1-oxide (1-bromo-1,3,4-trideoxy-1,4-C-[(R, S)-phenylphosphinylidene]-glycero-tetrofuranose) by the action of bromine in aqueous medium. The bromo substituent of the phospholane was substituted by treatment with amines or an azide anion to afford novel glycoside derivatives of phosphanyl sugar analogs such as 2-amino-3-hydroxy-1-phenylphospholane (3,4-dideoxy-1,4-C-[(R, S)-phenylphosphinylidene]-glycero-tetrofuranosylamine) and 2-azido-3-hydroxy-3-methyl-1-phenylphospholane 1-oxides with retention of the configuration. The 1,3-dipolar cycloaddition of the 2-azido derivative of the phospholane with alkynes gave 3-hydroxy-3-methyl-1-phenyl-2-(triazol-1′-y1)phospholane 1-oxides as a novel triazole-derived nucleoside of phosphanyl sugar analogs. The structure of the glycoside and nucleoside derivatives of the phosphanyl sugar analogs prepared was deterimined from IR, NMR, and X-ray crystallography analysis.     

Phosphanyl Cyanophosphide Salts: Versatile PCN Building Blocks

The facile preparation of alkali salts of phosphanyl cyanophosphides [NHP‐PCN]^? (NHP=N‐heterocyclic phosphenium) is reported. Their formation is achieved by isoelectronic replacement of O for [N]^? in the phosphaketenes NHP‐PCO using alkaline hexamethyldisilazide M[N(SiMe₃)₂] (M=Na, K) as reagent. The new anionic entities are versatile PCN building blocks which allow the formation of a diversity of new cyanophosphine derivates including the first example of a PCNB hetero‐cumulene and a PCN‐ligated transition metal complex.     

Arylvanadium(III)-Verbindungen. VII. Organovanadium(III)-Verbindungen vom Typ LiVMes3(ERn) und ihr Oxydationsverhalten

Arylvanadium(III) Compounds. VII. Organyl Vanadates of the Type LiVMes₃(ER_n) and their Oxidation Trimesityl vanadium yields with carbyl ligands lithium trimesityl organyl vanadates. It reacts also with LiER_n (E ? Si, Sn, N, P, O) forming complexes of the type LiVMes₃(ER_n). The oxidation behaviour of the amido compounds are investigated, and VMes₃(NPh₂) is synthesized. The compounds are characterized by their magnetical, spectral, and thermal properties.