(Phosphanyl)phosphaketenes as building blocks for novel phosphorus heterocycles

Hydrazone Phosphaketene as a Synthetic Platform To Obtain Three Classes of 1,2,4-Diazaphosphol Derivatives by Switchable Chemoselectivity Strategies

We introduce switchable chemoselectivity strategies based on the hydrazone phosphaketene intermediate to synthesize three classes of 1,2,4-diazaphosphol derivatives. First, the five-membered heterocyclic P and O anion intermediates acted as nucleophilic agents in the selective construction of C-P and C-O bonds. Second, the phosphinidene served as a phosphorus synthon, allowing for the formation of C-P and C-N bonds. Finally, a stepwise mechanism, supported by DFT calculations, was invoked to explain the reaction selectivity.

Phosphinidenes: Fundamental Properties and Reactivity

Phosphinidenes are heavy congeners of nitrenes that have been broadly used as in situ reagents in synthetic phosphorus chemistry and also serve as versatile ligands in coordination with transition metals. However, the detection of free phosphinidenes is largely challenged by their high reactivity and also the lack of suitable synthetic methods, rendering the knowledge about the fundamental properties of this class of low-valent phosphorus compounds limited. Recently, an increasing number of free phosphinidenes bearing prototype structural and bonding properties have been prepared for the first time, thus enabling the exploration of their distinct reactivity from the nitrene analogues. This Concept article will discuss the experimental approaches for the generation of the highly unstable phosphinidenes and highlight their distinct reactivity from the nitrogen analogues so as to stimuate future studies about their potential applications in phosphorus chemistry.

Photolysis of Phosphaketenyltetrylenes with a Carbazolyl Substituent

Phosphaketenes of divalent group 14 compounds can potentially serve as precursors for the synthesis of heavy multiple-bond systems. We have employed the dtbp Cbz substituent (dtbp Cbz=1,8-bis(3,5-ditertbutylphenyl)-3,6-ditertbutylcarbazolyl) to prepare such phosphaketenyltetrylenes [(dtbp Cbz)EPCO] (E=Ge, Sn, Pb). While the phosphaketenyltetrylenes are stable at ambient conditions, they can be readily decarbonylated photolytically. For the germylene and stannylene derivatives, dimeric diphosphene-type products [(dtbp Cbz)EP]2 (E=Ge, Sn) were obtained. In contrast, photolysis of the phosphaketenylplumbylene, via isomerisation of the [(dtbp Cbz)PbP] intermediate to [(dtbp Cbz)PPb], afforded an unsymmetric and incompletely decarbonylated product [(dtbp Cbz)2 Pb2 P2 CO] formally comprising a [(dtbp Cbz)PPb] and a [(dtbp Cbz)PbPCO] moiety.

Stannyl phosphaketene as a synthon for phosphorus analogues of β-lactams

The reaction of the stannyl phosphaketene (Nacnac)SnPCO 1 (Nacnac = CH{(CMe)(2,6-iPr2C6H3N)}2) with B(C6F5)3 produced the 1,4-addition product of (Nacnac)SnPCO(B(C6F5)3). However, the corresponding reactions in the presence of dimethyl maleate, diisopropyl fumarate or diethyl-but-2-ynedioate gave [2+2] addition yielding four-membered phosphacycles, ((Nacnac)Sn(MeO2C))CHPC(OB(C6F5)3)CH(CO2Me), [(C6F5)3B)PC(OSn)C(CO2Me)CH(CO2Me)]2, (Nacnac)Sn(iPrO2C)CC(OAl(C6F5)3)P[CH(CO2iPr)CH2(CO2iPr)]CH(CO2iPr), and (Nacnac)SnP (EtO2CCC(CO2Et))CO(B(C6F5)3), respectively. In contrast, the corresponding reaction of phenylacetylene gave the FLP-addition product (Nacnac)SnOC(P)C(Ph)CH(B(C6F5)3). Collectively, this reactivity demonstrates that the stannyl phosphaketene 1 can act as a synthon for P-analogues of β-lactam derivatives.

Understanding the Mechanism of Diels-Alder Reactions with Anionic Dienophiles: A Systematic Comparison of [ECX]- (E = P, As; X = O, S, Se) Anions

While Diels–Alder (DA) reactions involving neutral or cationic dienophiles are well-known, the characteristics of the analogous reactions with anionic dienophiles are practically unexplored. Herein we present the first comparative computational investigations on the characteristics of DA cycloadditions with anionic dienophiles on the basis of the reactions of [ECX]⁻ anions (E = P, As; X = O, S, Se) with 2H-pyran-2-one. All of these reactions were found to be both kinetically and thermodynamically feasible, enabling synthetic access toward 2-phosphaphenolate and arsaphenolate derivatives in the future. This study also reveals that the [ECO]⁻ anions show clear regioselectivity, while for [ECS]⁻ and [ECSe]⁻ anions, the two possible reaction channels have very similar energetics. Additionally, the activation barriers for the [ECO]⁻ anions are lower than those of the heavier analogues. The observed differences can be traced back to the starkly differing nucleophilic character of the pnictogen center in the anions, leading to a barrier-lowering effect in the case of the [ECO]⁻ anions. Furthermore, analysis of the geometries and electron distributions of the corresponding transition states revealed structure–property relationships, and thus a direct comparison of the cycloaddition reactivity of these anions was achieved. Along one of the two pathways, a good correlation was found between the activation barriers and suitable nucleophilicity descriptors (nucleophilic Parr function and global nucleophilicity). Additionally, the tendency of the reaction energies can be explained by the changing aromaticity of the products.

In contrast to the phosphaethynolate [PCO]⁻ anion, the cycloaddition reactivity of the heavier congeners ([ECX]⁻, where E = P, As and X = O, S, Se) is unexplored. In this computational study, the Diels−Alder reaction between the known [ECX]⁻ anions and 2-pyrone was employed to compare the reactivity patterns. The first activation barrier of these reactions correlates with the nucleophilicity of the anions, indicating a barrier-lowering effect. The feasibility of the studied reactions, leading to P and As heterocycles, was also explored.

Bis‐Phosphaketenes LM(PCO) 2 (M=Ga, In): A New Class of Reactive Group 13 Metal‐Phosphorus Compounds

Phosphaketenes are versatile reagents in organophosphorus chemistry. We herein report on the synthesis of novel bis‐phosphaketenes, LM(PCO)₂ (M=Ga 2 a, In 2 b; L=HC[C(Me)N(Ar)]₂; Ar=2,6‐i‐Pr₂C₆H₃) by salt metathesis reactions and their reactions with LGa to metallaphosphenes LGa(OCP)PML (M=Ga 3 a, In 3 b). 3 b represents the first compound with significant In−P π‐bonding contribution as was confirmed by DFT calculations. Compounds 3 a and 3 b selectively activate the N−H and O−H bonds of aniline and phenol at the Ga−P bond and both reactions proceed with a rearrangement of the phosphaethynolate group from Ga−OCP to M−PCO bonding. Compounds 2–5 are fully characterized by heteronuclear (¹H, ¹³C{¹H}, ³¹P{¹H}) NMR and IR spectroscopy, elemental analysis, and single crystal X‐ray diffraction (sc‐XRD).

Synthesis, electronic nature, and reactivity of selected silylene carbonyl complexes

Room-temperature stable main group element carbonyl complexes are rare. Here we report on the synthesis of two such complexes, namely gallium-substituted silylene-carbonyl complexes [L(X)Ga]2SiCO (X = I 2, Me 3;...

π- delocalization in phosphaphthalimide and its ambident reactivity (O/P) toward main-group electrophiles

The report on phosphaphthalimide (1), the phosphorus analogue of the phthalimide anion, dates back to forty years ago. However, the presence of π-delocalization between two-coordinated phosphorus centre and neighbouring carbonyl...

Phosphorus-Atom Transfer from Phosphaethynolate to an Alkylidyne

A low-spin and mononuclear vanadium complex, (Me nacnac)V(CO)(η2 -P≡Ct Bu) (2) (Me nacnac- =[ArNC(CH3 )]2 CH, Ar=2,6-i Pr2 C6 H3 ), was prepared upon treatment of the vanadium neopentylidyne complex (Me nacnac)V≡Ct Bu(OTf) (1) with Na(OCP)(diox)2.5 (diox=1,4-dioxane), while the isoelectronic ate-complex [Na(15-crown-5)]{([ArNC(CH2 )]CH[C(CH3 )NAr])V(CO)(η2 -P≡Ct Bu)} (4), was obtained via the reaction of Na(OCP)(diox)2.5 and ([ArNC(CH2 )]CH[C(CH3 )NAr])V≡Ct Bu(OEt2 ) (3) in the presence of crown-ether. Computational studies suggest that the P-atom transfer proceeds by [2+2]-cycloaddition of the P≡C bond across the V≡Ct Bu moiety, followed by a reductive decarbonylation to form the V-C≡O linkage. The nature of the electronic ground state in diamagnetic complexes, 2 and 4, was further investigated both theoretically and experimentally, using a combination of density functional theory (DFT) calculations, UV/Vis and NMR spectroscopies, cyclic voltammetry, X-ray absorption spectroscopy (XAS) measurements, and comparison of salient bond metrics derived from X-ray single-crystal structural characterization. In combination, these data are consistent with a low-valent vanadium ion in complexes 2 and 4. This study represents the first example of a metathesis reaction between the P-atom of [PCO]- and an alkylidyne ligand.

A comparative appraisal of three important oil yielding plants for their biodiesel potential

In the present scenario, alternative energy sources are required to achieve the future economic prosperity where shortage of fossil fuels will be a limiting factor and hamper the global economic growth. Therefore, interest in biofuel is increasing continuously. The best way of sustainable development is fossil fuel supplementation with biodiesel to reduce the fossil fuel demand. Biodiesel is a clean burning, ester-based, oxygenated fuel derived from natural and renewable sources. Till now, majority of the people have worked on the biodiesel derived from edible oil. Instead of using edible oil, non-edible oil needs to be explored as feedstock for biofuel because half of the world's population is unable to afford the food oil as feedstock for fuel production. Looking at the significance of biodiesel and the resources of biofuel, in this paper, a comparative exhaustive study has been reported with for three important plants, namely Jatropha curcas, Pongemia pinnata and Balanites aegyptiaca. These plants were selected based on their biodiesel potential, availability, cultivation practices and general information available. The present study involves scientometric publications, comparison of fatty acid composition and biodiesel parameters. We have also compared climatic conditions for the growth of the plants, economic feasibility of biodiesel production and other ecological services. The study paves a way for sustainable solution to policy makers and foresters looking for selection of plant species as bioenergy resource.

Vibrational spectrum and photochemistry of phosphaketene HPCO

The vibrational spectra of the simplest phosphaketene HPCO and its isotopologue DPCO in solid Ar-matrices at 12.0 K have been analyzed with the aid of the computations at the CCSD(T)-F12a/cc-pVTZ-F12 level using configuration-selective vibrational configuration interaction (VCI). In addition to the four IR fundamentals, four overtone and ten combination bands have been unambiguously identified. Furthermore, the photochemistry of HPCO in the matrix has been investigated for the first time. Upon UV-light irradiation (365 or 266 nm), CO-elimination occurs by forming the parent phosphinidene HP that can be trapped by ˙NO to yield the elusive phosphinimine-N-oxyl radical HPNO˙. In contrast, an excimer laser (193 nm) irradiation of HPCO causes additional decomposition to H˙ and ˙PCO with concomitant formation of the long-sought phosphaethyne HOCP.

Heavier element-containing aromatics of [4n+2]-electron systems

While the implication of the aromaticity concept has been dramatically expanded to date since its emergence in 1865, the classical [4n+2]/4n-electron counting protocol still plays an essential role in evaluating the aromatic nature of compounds. Over the last few decades, a variety of heavier heterocycles featuring the formal [4n+2] π-electron arrangements have been developed, which allows for assessing their aromatic nature. In this review, we present recent developments of the [4n+2]-electron systems of heavier heterocycles involving group 13-15 elements. The synthesis, spectroscopic data, structural parameters, computational data, and reactivity are introduced.

On 1,3-phosphaazaallenes and their diverse reactivity

1,3-Phosphaazaallenes are heteroallenes of the type RP Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CNR′ and little is known about their reactivity. In here we describe the straightforward synthesis of ArPCNR (Ar = Mes*, 2,4,6-tBu-C₆H₂; ^MesTer, 2.6-(2,4,6-Me₃C₆H₂)–C₆H₃; ^DipTer, 2.6-(2,6-iPr₂C₆H₂)–C₆H₃; R = tBu; Xyl, 2,6-Me₂C₆H₃) starting from phospha-Wittig reagents ArPPMe₃ and isonitriles CNR. It is further shown that ArPCNtBu are thermally labile with respect to the loss of iso-butene and it is shown that the cyanophosphines ArP(H)CN are synthetically feasible and form the corresponding phosphanitrilium borates with B(C₆F₅)₃, whereas deprotonation of ^DipTerP(H)CN was shown to give an isolable cyanidophosphide. Lastly, the reactivity of ArPCNR towards Pier's borane was investigated, showing hydroboration of the CN bond in Mes*PCNtBu to give a hetero-butadiene, while with ^DipTerPCNXyl the formation of the Lewis acid–base adduct with a B–P linkage was observed.

The combination of phospha-Wittig reagents with isonitriles affords 1,3-phosphaazaallenes and their diverse reactivity has been studied in detail.

η3 -Coordination and Functionalization of the 2-Phosphaethynthiolate Anion at Lanthanum(III)*

We present the η3 -coordination of the 2-phosphaethynthiolate anion in the complex (PN)2 La(SCP) (2) [PN=N-(2-(diisopropylphosphanyl)-4-methylphenyl)-2,4,6-trimethylanilide)]. Structural comparison with dinuclear thiocyanate-bridged (PN)2 La(μ-1,3-SCN)2 La(PN)2 (3) and azide-bridged (PN)2 La(μ-1,3-N3 )2 La(PN)2 (4) complexes indicates that the [SCP]- coordination mode is mainly governed by electronic, rather than steric factors. Quantum mechanical investigations reveal large contributions of the antibonding π*-orbital of the [SCP]- ligand to the LUMO of complex 2, rendering it the ideal precursor for the first functionalization of the [SCP]- anion. Complex 2 was therefore reacted with CAACs which induced a selective rearrangement of the [SCP]- ligand to form the first CAAC stabilized group 15-group 16 fulminate-type complexes (PN)2 La{SPC(R CAAC)} (5 a,b, R=Ad, Me). A detailed reaction mechanism for the SCP-to-SPC isomerization is proposed based on DFT calculations.

Multi-Talented Gallaphosphene for Ga-P-Ga Heteroallyl Cation Generation, CO2 Storage, and C(sp3 )-H Bond Activation

Gallaphosphene L(Cl)GaPGaL (2; L=HC[C(Me)N(2,6-i-Pr2 C6 H3 )]2 ), which is synthesized by reaction of LGa(Cl)PCO (1) with LGa, reacts with [Na(OCP)(dioxane)2.5 ] to LGa(OCP)PGaL (3), whereas chloride abstraction with LiBArF 4 yields [LGaPGaL][BArF 4 ] (4; BArF 4 =B(C6 F5 )4 ). 4 represents a heteronuclear analog of the allyl cation according to quantum chemical calculations. Remarkably, 2 reversibly reacts with CO2 to yield L(Cl)Ga-P[μ-C(O)O]2 GaL (5), while reactions with acetophenone and acetone selectively give compounds 6 and 7 by C(sp3 )-H bond activation.

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-Pr2 C6 H3 )]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 .

Synthesis and decarbonylation chemistry of gallium phosphaketenes

A series of gallium phosphaketenyl complexes supported by a 1,2-bis(aryl-imino)acenaphthene ligand (Dipp-Bian) are reported. Photolysis of one such species induced decarbonylation to afford a gallium substituted diphosphene. Addition of Lewis bases, specifically trimethylphosphine and the gallium carbenoid Ga(Nacnac) (Nacnac = HC[C(Me)N-(C6H3)-2,6-iPr2]2), resulted in displacement of the phosphaketene carbonyl to yield base-stabilised phosphinidenes. In several of these transformations, the redox non-innocence of the Dipp-Bian ligand was found to give rise to radical intermediates and/or side-products.

Synthesis of compounds with C-P-P and C[double bond, length as m-dash]P-P bond systems based on the phospha-Wittig reaction

A reactivity study of a β-diketiminate titanium(iii) phosphanylphosphido complex [^MeNacNacTi(Cl){η²-P(SiMe₃)-PtBu₂}] (1) towards ketones such as benzophenone, 9-fluorenone, acetophenone, cyclopentanone, cyclohexanone and cycloheptanone is reported. The reactions of 1 with aromatic ketones (without α-protons) directly lead to the Ti(iii) complex [^MeNacNacTi(μ²-Cl)(OSiMe₃)] (5) and Ti(iv) complexes with the pinacol condensation product [^MeNacNacTi(OSiMe₃)(η²-pinacolate)] (3), and phosphanylphosphaalkenes Ph₂C[double bond, length as m-dash]P-PtBu₂ (2) and (fluorenyl)C[double bond, length as m-dash]P-PtBu₂ (6), respectively. The reaction with acetophenone leads to the titanium(iii) complex with the aldol condensation product as ligand [^MeNacNacTi(Cl){OC{Me(Ph)}CH₂(C[double bond, length as m-dash]O)Ph}] (8) and in parallel to phosphanylphosphaalkene (Ph)MeC[double bond, length as m-dash]P-PtBu₂ (9) and 5. The reactions of 1 with cyclic ketones (cyclopentanone and cyclohexanone) lead to Ti(iii) complexes [{(ArN[double bond, length as m-dash]C(Me)CHC(Me)[double bond, length as m-dash]NAr)((CH₂)₄CO)}Ti(Cl){PtBu₂-P(SiMe₃)((CH₂)₄CO)}] (10) and [{(ArN[double bond, length as m-dash]C(Me)CHC(Me)[double bond, length as m-dash]NAr)((CH₂)₅CO)}Ti(Cl){PtBu₂-P(SiMe₃)((CH₂)₅CO)}] (11), which are formed via the successive insertion of two molecules of ketone to one molecule of 1. The stability investigation of complexes 10 and 11 in a polar solvent (THF) revealed that under these conditions, the complexes decompose, resulting in titanium(iii) complexes with aldol condensation products and the expected phosphanylphosphaalkenes (CH₂)₄C[double bond, length as m-dash]P-PtBu₂ (10a) and (CH₂)₅C[double bond, length as m-dash]P-PtBu₂ (11a). In the reaction of 1 with cycloheptanone, only the Ti(iii) complex with the aldol condensation product [^MeNacNacTi(Cl){OC(CH₂)₆}CH(C[double bond, length as m-dash]O)(CH₂)₅] (12) was isolated. The structures 3, 5, 8, 10, 11, 11b and 12 were characterized by X-ray spectroscopy, while all the phosphanylphosphaalkenes were characterized by NMR spectroscopy.

Oligomerization of phosphaalkynes mediated by bulky N-heterocyclic carbenes: avenues to novel phosphorus frameworks

Reactions of RCP (R = tBu or Ad (admantyl)) with NHCs (SIMes, 1a; IMes, 1b and IDipp, 1d), leading to 1,2,3-triphosphetenes 2 and 3, a triphosphole 4, and a di-1,2-dihydro-1,2-diphosphete-substituted diphosphene 5, are reported.

Salen supported Al–O–CP and Ga–PCO complexes

The synthesis and reactivity of salen supported OCP adducts of aluminium and gallium is reported.

The Chemistry of the 2-Phosphaethynolate Anion

In all likelihood the first synthesis of the phosphaethynolate anion, PCO^- , was performed in 1894 when NaPH₂ was reacted with CO in an attempt to make Na(CP) accompanied by elimination of water. This reaction was repeated 117 years later when it was discovered that Na(OCP) and H₂ are the products of this remarkable transformation. Li(OCP) was synthesized and fully characterized in 1992 but this salt proved to be too unstable to allow for a detailed investigation of its chemistry. It was not until the heavier analogues of this lithium salt were isolated, Na(OCP) and K(OCP) (both of which are remarkably stable and can be even dissolved in water), that the chemistry of this new functional group could be explored. Here we review the chemistry of the 2-phosphaethynolate anion, a heavier phosphorus-containing analogue of the cyanate anion, and describe the wide breadth of chemical transformations for which it has been thus far employed. Its use as a ligand, in decarbonylative and deoxygenative processes, and as a building block for novel heterocycles is described. In the mere twenty-six years since Becker first reported the isolation of this remarkable anion, it has become a fascinating reagent for the synthesis of a vast library of, often unprecedented, molecules and compounds.

Limitations of Steric Bulk: Towards Phospha-germynes and Phospha-stannynes

The use of bulky aryl(silyl)amides (R) as substituents for the stabilisation of phospha-germynes and phospha-stannynes (R-Ge≡P and R-Sn≡P, respectively) is described. Such species can be transiently generated by photolysis of the phosphaketene precursors (RE(PCO); E=Ge, Sn). Utilisation of bulky amides R¹ and R² (R¹ =Ar**NSi(OtBu)₃ , where Ar**=2,6-bis[bis(4-tert-butylphenyl)methyl]-4-methylphenyl; R² =Ar***NSi(iPr)₃ , where Ar***=2,6-bis[bis(3,5-di-tert-butylphenyl)methyl]-4-methylphenyl) facilitates the formation of diphosphene-type dimers, [(RGe)P]₂ and [(RSn)P]₂ . In an effort to circumvent dimerisation, the bulkier R³ substituent (R³ =Ar***NSi(4-tert-butylphenyl)₃ ) was employed in an analogous series of experiments. This affords cyclic germylenes and stannylenes due to insertion of the terminal phosphide into Si-C bonds of the R³ substituent, which in case of the stannylene could act as a trap for another R³ -Sn≡P moiety. All attempts to isolate terminal phosphide species were unsuccessful due to the reactivity of such compounds towards the organic periphery of the bulky amides, highlighting the limitations of highly sterically demanding functionalities.

Simple Synthesis of Functionalized 2-Phosphanaphthalenes

A simple synthesis of sodium 2-phosphanaphthalene-3-olate (1) based on the extrusion of N₂ from phthalazine using Na[OCP] is reported. This heterocycle can be readily functionalized at the negatively charged oxygen center using a variety of electrophilic substrates. The coordination chemistry of both 1 and its neutral derivatives was explored, revealing their facile use as P-donor ligands for late-transition-metal complexes.

An isolable magnesium diphosphaethynolate complex

The reaction of magnesium chloride with two equivalents of sodium phosphaethynolate, Na[OCP]·(dioxane)_2.5 (1), yields a magnesium diphosphaethynolate complex, [(THF)₄Mg(OCP)₂] (3). The formation of compound 3 goes through a monosubstituted chloromagnesium phosphaethynolate Mg(OCP)Cl (2). The structure of 3 was determined via a single crystal X-ray diffraction study. For comparison, we also report the structure of a monomeric sodium phosphaethynolate complex, [Na(OCP)(dibenzo-18-crown-6)] (4).

Phosphirenium borate betaines from alkynylphosphanes and the halogeno-B(C6F5)2 reagents

A series of phosphanyl substituted alkynes R¹₂P–CC–R² [R¹₂P: Mes₂P or ^tBu₂P; R²: SiMe₃, Ph, ^tBu] reacts with the X–B(C₆F₅)₂ reagents [X: Cl, Br] to give thermally rather stable neutral zwitterionic phosphirenium borate products.

Borane-Stabilized Isomeric Dimers of the Phosphaethynolate Anion

The reactions of the phosphaethynolate anion ([PCO]^- ) with a range of boranes were explored. BPh₃ and [PCO]^- form a dimeric anion featuring P-B bonds and is prone to dissociation at room temperature. The more Lewis acidic borane B(C₆ F₅ )₃ yields a less symmetric dimer of [PCO]^- with P-B and P-O bonds. Less sterically demanding HB(C₆ F₅ )₂ and H₂ B(C₆ F₅ ) boranes form a third isomer with [PCO]^- featuring both boranes bound to the same phosphorus atom. Despite the unexpected thermodynamic preference for P-coordination, computational data illustrate that electronic and steric features impact the binding modes of the resulting dianionic dimers.

Synthesis of P2C2O2 and P2CO via NHC-mediated coupling of the phosphaethynolate anion

The reaction of the chloroimidazolium chloride salt, [NHC-Cl][Cl], NHC = C{N(2,6-ⁱPr₂C₆H₃)CH}₂ (1) with two equivalents of sodium phosphaethynolate, Na[OCP]·(dioxane)_2.5, results in the formation of NHC-{cyclo-(CO)-P₂-C(O)} (2) and NHC-P₂-C(O)-NHC (3).