Competitive Reactivity of Tautomers in the Degradation of Organophosphates by Imidazole Derivatives

The harmful impact caused by pesticides on human health and the environment necessitates the development of efficient degradation processes and control of prohibited stocks of such substances. Organophosphates (OPs) are among the most used agrochemicals in the world and their degradation can proceed through several possible pathways. Investigating the reactivity of OPs with nucleophilic species allows one to propose new and efficient catalyst scaffolds for use in detoxification. In light of the remarkable catalytic activity of imidazole (IMZ) at promoting dephosphorylation processes of OPs, the reactivity of 4(5)-hydroxymethylimidazole (HMZ) with diethyl-2,4-dinitrophenylphosphate (DEDNPP) and Paraoxon are evaluated by combining experimental and theoretical approaches. It is observed that HMZ is an efficient and regiospecific catalyst with reactivity modulated by competing tautomers. To propose an optimal IMZ-based catalyst, quantum chemical calculations were performed for monosubstituted 4(5)IMZ derivatives that might cleave DEDNPP. Both inductive effects and hydrogen bonding by the substituents are shown to influence barriers and mechanisms.     

Metathesis of P=C Bonds Catalyzed by N-Heterocyclic Carbenes

The catalytic metathesis of C=C bonds is a textbook reaction that has no parallel in the widely studied area of multiple bonds involving heavier p-block elements. A high-yielding P=C bond metathesis of phosphaalkenes (ArP=CPh₂, Ar=Mes, o-Tol, Ph) has been discovered that is catalyzed by N-heterocyclic carbenes (NHC=Me₂IMe, Me₂IⁱPr). The products are cyclic oligomers formally derived from ArP=PAr [i. e. cyclo-(ArP)_n; n=3, 4, 5, 6] and Ph₂C=CPh₂. Preliminary mechanistic studies of this remarkable transformation have established NHC=PAr (Ar=Mes, o-Tol, Ph) as key phosphinidene transfer agents. In addition, novel cyclic intermediates, such as, cyclo-(ArP)₂CPh₂ and cyclo-(ArP)₄CPh₂ have also been observed. This work represents a rare application of non-metal-based catalysts for transformations involving main-group elements.     

The coordination chemistry of selenophosphite ligands. Synthesis and characterization of heterometallic tetranuclear clusters [M{CpFe(CO)(2)P(Se)(OR)(2)}(3)](PF(6)) (M = Cu, Ag; R = (n)Pr, (i)Pr) and [Cu(mu-X) {CpFe(CO)(2)P(Se)(O(i)Pr)(2)}](2) (X = Cl, Br)

A neutral selenium donor ligand, [CpFe(CO)(2)P(Se)(OR)(2)] is used for the construction of Cu(I) and Ag(I) complexes with a well-defined coordination environment. Four clusters [M{CpFe(CO)(2)P(Se)(OR)(2)}(3)](PF(6)), (where M = Cu, R = (n)Pr, ; R = (i)Pr, and M = Ag, R = (n)Pr, ; R = (i)Pr, ) are isolated from the reaction of [M(CH(3)CN)(4)(PF(6))] (where M = Cu or Ag) and [CpFe(CO)(2)P(Se)(OR)(2)] in a molar ratio of 1 : 3 in acetonitrile at 0 degrees C. The reaction of [CpFe(CO)(2)P(Se)(O(i)Pr)(2)] with cuprous halides in acetone produce two mixed-metal, Cu(I)(2)Fe(II)(2) clusters, [Cu(mu-X) {CpFe(CO)(2)P(Se)(O(i)Pr)(2)}](2) (X = Cl, ; Br, ). All six clusters have been fully characterized spectroscopically ((1)H, (13)C, (31)P, and (77)Se NMR, IR), and by elemental analyses. X-Ray crystal structures of and consist of discrete cationic clusters in which three iron-selenophosphito fragments are linked to the central copper or silver atom via selenium atoms. Both clusters and crystallize in the noncentrosymmetric, hexagonal space group P6[combining macron]2c. The coordination geometry around the copper or silver atom is perfect trigonal-planar with Cu-Se and Ag-Se distances, 2.3505(7) and 2.5581(7) A, respectively. X-Ray crystallography also reveals that each copper center in neutral heterometallic clusters and is trigonally coordinated to two halide ions and a selenium atom from the selenophosphito-iron moiety. The structures can also be delineated as a dimeric unit which is generated by an inversion center and has a Cu(2)X(2) parallelogram core. The dihedral angle between the Cu(2)X(2) plane and the plane composed of Cp ring is found to be 24.62 and 84.58 degrees for compound and , respectively. Hence the faces of two opposite Cp rings are oriented almost perpendicular to the Cu(2)X(2) plane in , but are close to be parallel in . This is the first report of the coordination chemistry of the anionic selenophosphito moiety [(RO)(2)PSe](-), the conjugated base of a secondary phosphine selenide, which acts as a bridging ligand with P-coordination on iron and Se-coordination to copper or silver.     

Activating a Peroxo Ligand for C−O Bond Formation

Dioxygen activation for effective C?O bond formation in the coordination sphere of a metal is a long‐standing challenge in chemistry for which the design of catalysts for oxygenations is slowed down by the complicated, and sometimes poorly understood, mechanistic panorama. In this context, olefin–peroxide complexes could be valuable models for the study of such reactions. Herein, we showcase the isolation of rare “Ir(cod)(peroxide)” complexes (cod=1,5‐cyclooctadiene) from reactions with oxygen, and then the activation of the peroxide ligand for O?O bond cleavage and C?O bond formation by transfer of a hydrogen atom through proton transfer/electron transfer reactions to give 2‐iradaoxetane complexes and water. 2,4,6‐Trimethylphenol, 1,4‐hydroquinone, and 1,4‐cyclohexadiene were used as hydrogen atom donors. These reactions can be key steps in the oxy‐functionalization of olefins with oxygen, and they constitute a novel mechanistic pathway for iridium, whose full reaction profile is supported by DFT calculations.     

Redox reactions between phosphines (R3P; R = nBu, Ph) or carbene (iPr2IM) and chalcogen tetrahalides ChX4 (iPr2IM = 2,5-diisopropylimidazole-2-ylidene; Ch = Se, Te; X = Cl, Br)

The reactions between chalcogen tetrahalides (ChX(4); Ch = Se, Te; X = Cl, Br) and the neutral donors (n)Bu(3)P, Ph(3)P, or the N-heterocyclic carbene, 2,5-diisopropylimidazole-2-ylidene ((i)Pr(2)IM), have been investigated. In cases involving a phosphine, the chemistry can be understood in terms of a succession of two-electron redox reactions, resulting in reduction of the chalcogen center (e.g., Se(IV) --> Se(II)) and the oxidation of phosphorus to the [R(3)P-X] cation (P(III) --> P(V)). The stepwise reduction of Se(IV) --> Se(II) --> Se(0) --> Se(-II) occurs upon the successive addition of stoichiometric equivalents of Ph(3)P to SeCl(4), which can readily be monitored by 31P{(1)H} NMR spectroscopy. In the case of reacting SeX(4) with (i)Pr(2)IM, a similar two-electron reduction of the chalcogen is observed and there is the concomitant production of a haloimidazolium hexahaloselenate salt. The products have been comprehensively characterized, and the solid-state structures of [R(3)PX][SeX(3)] (9), [Ph(3)PCl](2)[TeCl(6)] (10), (i)Pr(2)IM-SeX(2) (11), and [(i)Pr(2)IM-Cl](2)[SeCl(6)] (12) have been determined by X-ray diffraction analysis. These data all support two electron redox reactions and can be considered in terms of the formal reductive elimination of X2, which is sequestered by the Lewis base.     

New Reactivity Patterns in 3H-Phosphaallene Chemistry [Aryl-P=C=C(H)-tBu]: Hydroboration of the C=C Bond,Deprotonation and Trimerisation

3H-Phosphaallenes, R−P=C=C(H)C−R’ ( 3 ), are accessible in a multigram scale on a new and facile route and show a fascinating chemical reactivity. BH₃(SMe₂) and 3 a (R=Mes*, R’=tBu) afforded by hydroboration of the C=C bonds of two phosphaallene molecules an unprecedented borane ( 7 ) with the B atom bound to two P=C double bonds. This compound represents a new FLP based on a B and two P atoms. The increased Lewis acidity of the B atom led to a different reaction course upon treatment of 3 a with H₂B-C₆F₅(SMe₂). Hydroboration of a C=C bond of a first phosphaallene is followed in a typical FLP reaction by the coordination of a second phosphaallene molecule via B−C and P−B bond formation to yield a BP₂C₂ heterocycle ( 8 ). Its B−P bond is short and the B-bound P atom has a planar surrounding. Treatment of 3 a with tBuLi resulted in deprotonation of the β-C atom of the phosphaallene ( 9 ). The Li atom is bound to the P atom as demonstrated by crystal structure determination, quantum chemical calculations and reactions with HCl, Cl-SiMe₃ or Cl-PtBu₂. The thermally unstable phosphaallene Ph−P=C=C(H)-tBu gave a unique trimeric secondary product by P−P, P−C and C−C bond formation. It contains a P₂C₄ heterocycle and was isolated as a W(CO)₄ complex with two P atoms coordinated to W ( 15 ).     

若干有机磷化合物中取代基对P=S振动频率的影响

本文研究了若干有机磷化合物的P=S振动频率ν~P=S与取代基的依赖关系。影响ν~P=S的主要因素有两个: 一是取代基的诱导效应, 另一个是取代基的振动与P=S振动所产生的耦合效应。     

The double H‐atom acceptability of the P=O group in new XP(O)(NHCH2C6H4‐2‐Cl)2 phosphoramidates [X = C6H5O– and CF3C(O)NH–]: a database analysis of compounds having a P(O)(NHR) group

In the hydrogen‐bond patterns of phenyl bis(2‐chlorobenzylamido)phosphinate, C₂₀H₁₉Cl₂N₂O₂P, (I), and N,N′‐bis(2‐chlorobenzyl)‐N′′‐(2,2,2‐trifluoroacetyl)phosphoric triamide, C₁₆H₁₅Cl₂F₃N₃O₂P, (II), the O atoms of the related phosphoryl groups act as double H‐atom acceptors, so that the P=O...(H—N)₂ hydrogen bond in (I) and the P=O...(H—N_amide)₂ and C=O...H—N_C(O)NHP(O) hydrogen bonds in (II) are responsible for the aggregation of the molecules in the crystal packing. The presence of a double H‐atom acceptor centre is a result of the involvement of a greater number of H‐atom donor sites with a smaller number of H‐atom acceptor sites in the hydrogen‐bonding interactions. This article also reviews structures having a P(O)NH group, with the aim of finding similar three‐centre hydrogen bonds in the packing of phosphoramidate compounds. This analysis shows that the factors affecting the preference of the above‐mentioned O atom to act as a double H‐atom acceptor are: (i) a higher number of H‐atom donor sites relative to H‐atom acceptor centres in molecules with P(=O)(NH)₃, (N)P(=O)(NH)₂, C(=O)NHP(=O)(NH)₂ and (NH)₂P(=O)OP(=O)(NH)₂ groups, and (ii) the remarkable H‐atom acceptability of this atom relative to the other acceptor centre(s) in molecules containing an OP(=O)(NH)₂ group, with the explanation that the N atom bound to the P atom in almost all of the structures found does not take part in hydrogen bonding as an acceptor. Moreover, the differences in the H‐atom acceptability of the phosphoryl O atom relative to the O atom of the alkoxy or phenoxy groups in amidophosphoric acid esters may be illustrated by considering the molecular packing of compounds having (O)₂P(=O)(NH) and (O)P(=O)(NH)(N)groups, in which the unique N—H unit in the above‐mentioned molecules almost always selects the phosphoryl O atom as a partner in forming hydrogen‐bond interactions. The P atoms in (I) and (II) are in tetrahedral coordination environments, and the phosphoryl and carbonyl groups in (II) are anti with respect to each other (the P and C groups are separated by one N atom). In the crystal structures of (I) and (II), adjacent molecules are linked via the above‐mentioned hydrogen bonds into a linear arrangement parallel to [100] in both cases, in (I) by forming R₂²(8) rings and in (II) through a combination of R₂²(10) and R₂¹(6) rings.     

Activation of P5R5 (R = Ph, Et) by a Rh-beta-diketiminate complex

(NacNac)Rh(C8H14))(N2) reacts with P5R5 to give complexes of formula (NacNac)Rh(P5R5) (R = Ph, Et); in the former species inversion of a P atom of P5Ph5 allows coordination to a Rh(I) centre, whereas in the later species a P-P bond undergoes oxidative addition to give a formally Rh(III) species.     

Reactions of trialkoxynitridomolybdenum with low-coordinate phosphorus compounds containing a P=N double bond

The reactions of N≡Mo(OR)(3) (R = (t)Bu, (i)Pr) with (Me(3)Si)(2)NPNSiMe(3) (1), (Me(3)Si)(2)NPN(t)Bu (2), (Me(3)Si)(2)NPS(N(t)Bu) (3) and (Me(3)Si)(2)NP(NSiMe(3))(2) (4) have been studied. Reported complexes were synthesized via 1,2-addition of an Mo-OR bond across the P=N bond, resulting in four-membered metallacycles of the corresponding σ(2)λ(3)-iminophosphine or σ(3)λ(5)-iminophosphorane with trialkoxynitridomolybdenum. The structure of all new compounds was elucidated by (1)H, (13)C and (31)P NMR spectroscopy. Compounds [(Me(3)Si)(2)N-P(NSiMe(3))(O-(t)Bu)]{((t)BuO)(2)Mo≡N} (5), [(Me(3)Si)(2)N-PS(N(t)Bu)(O-(t)Bu)]{((t)BuO)(2)Mo≡N} (7), [(Me(3)Si)(2)N-P(NSiMe(3))(2)(O-(t)Bu)]{((t)BuO)(2)Mo≡N} (8) and [(Me(3)Si)(2)N-P(NSiMe(3))(2)(O-(i)Pr)]{((i)PrO)(2)Mo≡N} (12) were also characterized by single X-ray analysis and shown to be metallacycles containing the Mo atom with an intact terminal nitrido ligand.     

Metabolism of Halogenated Alkanes by Cytochrome P450 enzymes. Aerobic Oxidation versus Anaerobic Reduction

The cytochromes P450 are a large class of heme‐containing enzymes that catalyze a broad range of chemical reactions in biosystems, mainly through oxygen‐atom transfer to substrates. A relatively unknown reaction catalyzed by the P450s, but very important for human health, is the activation of halogenated substrates, which may lead to toxicity problems. However, its catalytic mechanism is currently unknown and, therefore, we performed a detailed computational study. To gain insight into the metabolism of halogenated compounds by P450 enzymes, we have investigated the oxidative and reductive P450‐mediated activation of tetra‐ and trichloromethane as halogenated models with density functional theory (DFT) methods. We propose an oxidative halosylation mechanism for CCl₄ under aerobic conditions by Compound I of P450, which follows the typical Groves‐type rebound mechanism. By contrast, the metabolism of CHCl₃ occurs preferentially via an initial hydrogen‐atom abstraction rather than halosylation. Kinetic isotope effect studies should, therefore, be able to distinguish the mechanistic pathways of CCl₄ versus CHCl₃. We find a novel mechanism that is different from the well accepted P450 substrate activation mechanisms reported previously. Moreover, the studies highlight the substrate specific activation pathways by P450 enzymes leading to different products. These reactivity differences are rationalized using Marcus theory equations, which reproduce experimental product distributions.     

Collision-induced harpooning observed in the excimer formation in the oriented NF3 + oriented Kr*(3P2, MJ = 2) reaction

We have studied how the KrF* formation in the NF3 t Kr*(3P2) reaction depends on the mutual configuration between the orientation of the NF3 molecule and the alignment of the Kr*(3P2, M(J) = 2) atom in the collision frame. The molecular steric opacity function has been determined as a function of the atomic orbital alignment (M'(L)) in the collision frame. The molecular steric opacity function turns out to depend remarkably on M'(L) ; the |M'(L)| = 1 alignment is favorable at the molecular axis direction, whereas the M'(L) = 0 alignment is favorable at the sideways direction with a very poor reactivity at the molecular axis direction. The influence of deformation of the NF3 geometry on the electron affinity has been evaluated by ab initio calculation, and the M'(L) dependent intermolecular potential has been estimated from the interaction potential for the bromine-rare gas system. We propose the "collision-induced harpooning mechanism" as a novel process for the harpooning in which collisional deformation of the NF3 geometry with C(s) symmetry plays an important role as an initiating factor on electron transfer for the formation of NF3(-) due to increasing the electron affinity of NF3 and due to localizing the negative charge on the closest F-atom of NF3(-) anion. All experimental observations can support the collision-induced harpooning mechanism.     

The coordination chemistry of perfluorovinyl substituted phosphine ligands, a crystallographic and spectroscopic study. Co-crystallisation of both cis- and trans-isomers of [PtCl2{P(i)pr2(CF=CF2)}2] within the same unit cell

The coordination chemistry of the perfluorovinyl phosphines PEt2(CF=CF2), P(i)Pr2(CF=CF2), PCy,(CF=CF2) and PPh(CF=CF2)2 to rhodium(I), palladium(II), and platinum(II) centres has been investigated. The electronic properties of the ligands are estimated based on v(CO) and 1J(Rh-P) values. X-Ray diffraction data for the square-planar Pd(II) and Pt(II) perfluorovinyl-phosphine containing complexes allow estimates of the steric demand for the series of ligands PPh2(CF=CF2), PEt2(CF=CF2), P(i)Pr2(CF=CF2), PCy2(CF=CF2) and PPh(CF=CF2)2 to be determined. The (CF=CF2) fragment is found to be more electron withdrawing than (C6F5) yet sterically less demanding. These ligands therefore provide a range of electron-neutral to phosphite-like electronic properties combined with a range of steric demands. This study also reveals that short intramolecular interactions from the metal centre to the beta-fluorine atom cis to phosphorus of the CF=CF2 groups are observed in all-trans square planar complexes of the ligands. Unusually, the complex [PtCl2{P(i)Pr2(CF=CF2)}2] crystallises with both cis- and trans-isomers present in the unit cell. It appears that co-crystallisation of both isomers occurs in order to maximise fluorous regions in the crystal packing, and the extended structure displays short fluorine-fluorine contacts. The generation of mixed geometries seems to be a phenomenon of crystallisation, as solution phase NMR studies reveal the presence of only the trans-isomer.     

Dynamics of energy transfer in collisions of O(3P) atoms with a 1-decanethiol self-assembled monolayer surface

Chemical dynamics simulations are reported of energy transfer in collisions of O(3P) atoms with a 300 K 1-decanethiol self-assembled monolayer (H-SAM) surface. The simulations are performed with a nonreactive potential energy surface, developed from PMP2/aug-cc-pVTZ calculations of the O(3P) + H-SAM intermolecular potential, and the simulation results represent the energy transfer dynamics in the absence of O(3P) reaction. Collisions energies E(i) of 0.12, 2.30, 11.2, 75.0, and 120.5 kcal/mol and incident angles theta(i) of 15, 30, 45, 60, and 75 degrees were considered in the study (theta(i) = 0 degrees is the surface normal). The translational energy distribution of the scattered O(3P) atoms, P(E(f)), may be deconvoluted into Boltzmann and non-Boltzmann components, with the former fraction identified as f(B). The trajectories are also analyzed in terms of three types; that is, direct scattering from and physisorption on the top of the H-SAM and penetration of the H-SAM. There are three energy regimes in the scattering dynamics. For the low E(i) values of 0.12 and 2.30 kcal/mol, physisorption is important and both f(B) and the average final translational energy of the scattered O(3P) atom, E(f), are nearly independent of the incident angle. The dynamics is much different for hyperthermal energies of 75.0 and 120.5 kcal/mol, where penetration of the surface is important. For hyperthermal collisions, the penetration probability decreases as theta(i) is increased, with a significant transition between theta(i) of 60 and 75 degrees . Hyperthermal penetration occurs upon initial surface impact and is more probable if the impinging O(3P) atom may move down a channel between the chains. For E(i) = 120.5 kcal/mol, 90% of the trajectories penetrate at theta(i) = 15 degrees , while only 3% penetrate at theta(i) = 75 degrees. For the former theta(i), the energy transfer to the surface is efficient with E(f) = 4.04 kcal/mol, but for the latter theta(i), E(f) = 85.3 kcal/mol! Particularly interesting penetrating trajectories are those in which O(3P) is trapped in the H-SAM for times exceeding 60 ps, linger near the Au substrate, and strike the Au substrate and scatter directly. For E(i) = 11.2 kcal/mol, there is a transition between the scattering dynamics for the low and hyperthermal collision energies. Additional detail in the energy transfer dynamics is obtained from the final polar and azimuthal angles, the residence time on/in the H-SAM, the minimum height with respect to the Au substrate, and the number of inner turning points in the O-atom's velocity. Calculated values of E(f) vs the final polar angle, theta(f), are in qualitative agreement with experiment. The O(3P) + H-SAM nonreactive energy transfer dynamics, for E(i) of 11.2 kcal/mol and lower, are very similar to previously reported Ne + H-SAM simulations.     

Novel vanadium(V) compounds with a layer structure: synthesis,crystal structures,and solid state NMR spectroscopy of [(VO(2))(2)(4,4'-bpy)(0.5)(4,4'-Hbpy)(XO(4))] x H(2)O (X = P and As)

A novel vanadium(V) phosphate and the arsenate analogue, [(VO(2))(2)(4,4'-bpy)(0.5)(4,4'-Hbpy)(XO(4))].H(2)O (X = P, As; bpy = bipyridine), have been synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. They are the first structurally characterized compounds in the vanadium(V)/4,4'-bpy/phosphate (or arsenate) systems. The two compounds are isostructural and crystallize in the triclinic space group P macro (No. 2) with a = 7.9063(3) A, b = 10.2201(4) A, c = 12.1336(5) A, alpha = 113.4652(7) degrees, beta = 95.7231(7) degrees, gamma = 94.4447(7) degrees, and Z = 2 for the phosphate, and a = 7.8843(6) A, b = 10.3686(7) A, c = 12.2606(9) A, alpha = 113.464(1) degrees, beta = 95.560(1) degrees, gamma = 94.585(1) degrees, and Z = 2 for the arsenate. The structure consists of phosphate-bridged vanadium(V) double chains linked through 4,4'-bpy ligands to form a sheet with the monoprotonated 4,4'-Hbpy(+) ligand being coordinated to the metal atom as a pendent group. The (1)H MAS NMR spectrum exhibits four resonances at 14.2, 9.5, 7.2, and 3.7 ppm with an intensity ratio close to 1:6:6:2, corresponding to three different types of protons in 4,4'-bpy and 4,4'-Hbpy(+) and one type of protons in H(2)O. The peak at 14.2 ppm can be assigned to the proton bonded to the pyridine nitrogen atom, which confirms the presence of 4,4'-Hbpy(+).     

Parity alternation of ground-state P(n)(-) and P(n)(+) (n = 3-15) phosphorus clusters

The ground-state structures of neutral, cationic, and anionic phosphorus clusters P(n), P(n)(+), and P(n)(-) (n = 3-15) have been calculated using the B3LYP/6-311+G* density functional method. The P(n)(+) and P(n)(-) (n = 3-15) clusters with odd n were found to be more stable than those with even n, and we provide a satisfactory explanation for such trends based on concepts of energy difference, ionization potential, electron affinity, and incremental binding energy. The result of odd/even alternations is in good accord with the relative intensities of cationic and anionic phosphorus clusters observed in mass spectrometric studies.     

Crystal Structure of a Novel Complex Na_4[Y(PDC)_2(BTC)]·5H_2O with One-Dimensional Helical Network Structure (H2PDC = 2,6-Pyridinedicarboxylic acid)( H_3BTC = 1,3,5-Benzenetricarboxylic acid )

1 INTRODUCTION The assembly of coordination networks is a field of increasing interest[1~4]. Research along this line is induced by the idea that coordination networks have potential technological applications such as optoele- ctronic devices and microporous materials for shape and size separation and catalysis[5~7]. In this paper, there has been current interest in using polycarboxy- late as anion linking groups to support stable poly- meric coordination open frameworks with transition m…     

Building und Reaktionen des Phosphanyliden-Phosphorans (tBu)2P?P = PX(tBu)2 (X = Br,Cl)

Formation and Reaction of the Phosphanylidene-phosphorane (tBu)₂P? P = PX(tBu)₂ (X = Br, Cl) The formation of (tBu)₂P? P = P(Br)tBu₂ 1 from [(tBu)₂P]₂PLi and BrH₂C? CH₂Br begins with an exchange of Li against Br and is then determined by the migration of Br from the secondary P atom in [(tBu)₂P]₂PBr 6 to the primary P in 1 . Similarly, (tBu)₂P? P = PC1(tBu)₂ 2 is obtained starting from PCl₃ and LiP(tBu)₂. The formation of Phospanylidene—phosporane is not influenced by the choice o the halogene substituent, but the presence of the tBu groups is strongly required. (tBu)₂P? P(Li)? P(SiMe₃)₂ e. g., yields (tBu)₂P? P(br)? P(SiMe₃)₂ with BrH₂C? CH₂Br; however neither this nor (tBu)₂P? P(Cl)? P(SiMe₃)₂ do rearrange to a Phosphanylidene-phosphorane. The F₃C substituent could be neglected in this investigation as [(F₃C)₂P]₂P? SiMe₃ cannot be lithiated by means of BuLi. Compounds 1 and 2 display a charateristic temperature dependent behavior. While 1 at +20°C decomposes via the reactive intermediate (tBu)₂P? P to from the cyclophosphanes P₃[P(tBu)₂]₄, it gives crystals of [(tBu)₂P]₂P? p[P(tBu)₂]₂ at ?20°C (from a solution in toluene). Reacting 1 with tBuLi produces (tBu)₂P? P = P(H)tBu₂ 20 and (tBu)₂P? P(H)? P(tBu)₂ 14 . Initially, a transmetallation yield tBuBr and (tBu)₂ P? P=Pli(tBu)₂ 21 ,then LiBr and isobutene are eliminated and 20 is formed which can rearrange to produce 14 . Without the elimination of isobutene, 1 react with nBuLi to give 21 witch can be trapped with Me₃SiCl as (tBu)₂P? P(tBu)₂ 23 . The main product in in this reaction is however [(tBu)₂P]₂P? nBu 22 .