Pure hydrocarbon sorption properties of poly(1-trimethylsilyl-1-propyne) (PTMSP), poly(1-phenyl-1-propyne) (PPP), and PTMSP/PPP blends

Propane and n-butane sorption in blends of poly(1-trimethylsilyl-1-propyne) (PTMSP) and poly(1-phenyl-1-propyne) (PPP) have been determined. Solubilities of propane and n-butane increased as the PTMSP content in the blends increased. This result is consistent with the higher free volume of PTMSP-rich blends and the better thermodynamic compatibility between PTMSP and these hydrocarbons. Propane and n-butane sorption isotherms were well described by the dual-mode model for sorption in glassy polymers. PTMSP/PPP blends are strongly phase-separated, heterogeneous materials. A noninteracting domain model developed for sorption in phase-separated glassy polymer blends suggests that sorption in the Henry's law regions (i.e., the equilibrium, dense phase of the blends) is consistent with the model. However, Langmuir capacity parameters in the blends are lower than predicted from the domain model, suggesting that the amount of nonequilibrium excess free volume associated with the Langmuir sites depends on blend composition. © 1996 John Wiley & Sons, Inc.     

Hydrocarbon/hydrogen mixed gas permeation in poly(1-trimethylsilyl-1-propyne) (PTMSP), poly(1-phenyl-1-propyne) (PPP), and PTMSP/PPP blends

The gas permeation properties of poly(1-trimethylsilyl-1-propyne) (PTMSP), poly(1-phenyl-1-propyne) (PPP), and blends of PTMSP and PPP have been determined with hydrocarbon/hydrogen mixtures. For a glassy polymer, PTMSP has unusual gas permeation properties which result from its very high free volume. Transport in PPP is similar to that observed in conventional, low-free-volume glassy polymers. In experiments with n-butane/hydrogen gas mixtures, PTMSP and PTMSP/PPP blend membranes were more permeable to n-butane than to hydrogen. PPP, on the other hand, was more permeable to hydrogen than to n-butane. As the PTMSP composition in the blend increased from 0 to 100%, n-butane permeability increased by a factor of 2600, and n-butane/hydrogen selectivity increased from 0.4 to 24. Thus, both hydrocarbon permeability and hydrocarbon/hydrogen selectivity increase with the PTMSP content in the blend. The selectivities measured with gas mixtures were markedly higher than selectivities calculated from the corresponding ratio of pure gas permeabilities. The difference between mixed gas and pure gas selectivity becomes more pronounced as the PTMSP content in the blend increases. The mixed gas selectivities are higher than pure gas selectivities because the hydrogen permeability in the mixture is much lower than the pure hydrogen permeability. For example, the hydrogen permeability in PTMSP decreased by a factor of 20 as the relative propane pressure (p/p_sat) in propane/hydrogen mixtures increased from 0 to 0.8. This marked reduction in permanent gas permeability in the presence of a more condensable hydrocarbon component is reminiscent of blocking of permanent gas transport in microporous materials by preferential sorption of the condensable component in the pores. The permeability of PTMSP to a five-component hydrocarbon/hydrogen mixture, similar to that found in refinery waste gas, was determined and compared with published permeation results for a 6-Å microporous carbon membrane. PTMSP exhibited lower selectivities than those of the carbon membrane, but permeability coefficients in PTMSP were nearly three orders of magnitude higher. © 1996 John Wiley & Sons, Inc.     

Polymer characterization and gas permeability of poly(1-trimethylsilyl-1-propyne) [PTMSP], poly(1-phenyl-1-propyne) [PPP], and PTMSP/PPP blends

Pure gas and hydrocarbon vapor transport properties of blends of two glassy, polyacetylene-based polymers, poly(1-trimethylsilyl-1-propyne) [PTMSP] and poly(1-phenyl-1-propyne) [PPP], have been determined. Solid-state CP/MAS NMR proton rotating frame relaxation times were determined in the pure polymers and the blends. NMR studies show that PTMSP and PPP form strongly phase-separated blends. The permeabilities of the pure polymers and each blend were determined with hydrogen, nitrogen, oxygen, carbon dioxide, and n-butane. PTMSP exhibits unusual gas and vapor transport properties which result from its extremely high free volume. PTMSP is more permeable to large organic vapors, such as n-butane, than to small, permanent gases, such as hydrogen. PPP exhibits gas permeation characteristics of conventional low free volume glassy polymers; PPP is more permeable to hydrogen than to n-butane. In PTMSP/PPP blends, both n-butane permeability and n-butane/hydrogen selectivity increase as the PTMSP content of the blends increases. © 1996 John Wiley & Sons, Inc.     

Thermal oxidation of poly(1-trimethylsilylprop-1-yne) studied by IR spectroscopy

Thermal oxidation of poly(1-trimethylsilylprop-1-yne) was studied by IR spectroscopy in the 20—245 °C temperature interval. In the 20—160 °C temperature range, the reaction proceeds predominantly at the C—Me group as revealed by the decrease in the intensity of the bands of the methyl group bound to the C atom and the appearance of the bands of the hydroperoxide and methylene groups. The decomposition of hydroperoxides produces aldehydes and ethers. At 160—200 °C, oxidation occurs via two routes: at the C—Me and C=C groups, while the Me₃Si group remains unchanged. At 230—240 °C, the rate of the reaction occurring at the C=C bond is higher than the rates of the processes involving the MeC and Me₃Si groups. The relative content of the structural units was calculated for the samples oxidized at different temperatures. Plausible mechanisms of thermal oxidation of poly(1-trimethylsilylprop-1-yne) were considered on the basis of the data obtained.     

Long-term permeation properties of poly(1-trimethylsilyl-1-propyne) membranes in hydrocarbon—Vapor environment

Poly(1-trimethylsilyl-1-propyne) (PTMSP), a high free-volume glassy di-substituted polyacetylene, has the highest gas permeabilities of all known polymers. The high gas permeabilities in PTMSP result from its very high excess free volume and connectivity of free volume elements. Permeability coefficients of permanent gases in PTMSP decrease dramatically over time due to loss of excess free volume. The effects of aging on gas permeability and selectivity of PTMSP membranes continuously exposed to a 2 mol % n-butane/98 mol % hydrogen mixture over a period of 47 days are reported. The permeation properties of PTMSP membranes are quite stable when the polymer is continuously exposed to a gas mixture containing a highly sorbing organic vapor such af n-butane. The n-butane/hydrogen selectivity was essentially constant for the 47-day test period at a value of 29, or 88% of the initial value of the as-cast film of 33. Condensable gases such as n-butane may serve as a “filler” in the nonequilibrium free volume of the polymer, thereby preserving the high level of excess free volume. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1483–1490, 1997     

Alkynylhalocarbenes. 4. Generation of (alk-1-ynyl)halocarbenes from 3-substituted 1,1,1,3-tetrahalopropanes under the action of bases

When treated with KOH under phase-transfer catalysis or with Bu^tOK, 3-substituted (alkyl or phenyl) 1,1,3-tribromo-1-fluoropropanes 1a—c exclusively generate previously unknown (alk-1-ynyl)fluorocarbenes 5a—c, which react with olefins to give 1-(alk-1-ynyl)-1-fluorocyclopropanes 6a—h in 12—69% yields. Under analogous conditions, 3-alkyl- and 3-aryl-3-bromo-1,1,1-trichloropropanes 2a—c selectively afford (alk-1-ynyl)chlorocarbenes 7a—c, which are trapped by olefins to form the corresponding 1-(alk-1-ynyl)-1-chlorocyclopropanes 8a—k in 35—70% yields. (Phenylethynyl)chlorocarbene 7a is also selectively generated from 1,1,1,3-tetrachloro-3-phenylpropane (3a) upon its treatment with Bu^tOK. With an excess of 2,3-dimethylbut-2-ene or 2-methylpropene, carbene 7a yields 1-chloro-1-(phenylethynyl)cyclopropanes 8a or 8c, respectively. In contrast, 1,1,1,3-tetrachloroheptane 3b and 3-alkyl- and 3-phenyl-1,1,1,3-tetrabromopropanes 4a,c,f react with bases in the presence of olefins to give, along with the corresponding 1-(alk-1-ynyl)-1-halocyclopropanes 8a,c,d and 11a—f, vinylidenecyclopropanes 12a,c—g, which suggests the generation, under these conditions, both (alk-1-ynyl)halocarbenes 7b and 9a—c and vinylidenecarbenes 10 and 11a—c. The composition and structures of intermediate products in the reactions of tetrahalides 1b, 2a, 2b, 3a, and 3b with Bu^tOK were determined and the mechanisms for carbene generation in these reactions were proposed.     

Synthesis of 1-(2-polyfluoroacylaminophenyl)-3-polyfluoroalkylpropane-1,3-diones and 2-polyfluoroalkyl-4-quinolones

The condensation of 2-aminoacetophenone with R^FCO₂Et (R^F = CF₃, CF₂H, CF₂CF₂H) in the presence of LiH in THF or Bu^tOK in Bu^tOH affords either 2-polyfluoroalkyl-4-quinolones or 1-(2-polyfluoroacylaminophenyl)-3-polyfluoroalkylpropane-1,3-diones, depending on the ratio of the initial reactants. The latter are hydrolyzed in an acidic medium to produce 2-polyfluoroalkyl-4-quinolones. N-Methyl-2-trifluoromethyl-4-quinolone was synthesized from 2-aminoacetophenone, CF₃CO₂Et, and MeI in the presence of Bu^tOK.     

[Co4P2(PtBu2)2(CO)8] und [{Co(CO)3}2P4tBu4] aus Co2(CO)8 und tBu2P–P=P(Me)tBu2

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes. XIX. [Co₄P₂(P^tBu₂)₂(CO)₈] and [{Co(CO)₃}₂P₄^tBu₄] from Co₂(CO)₈ and ^tBu₂P–P=P(Me)^tBu₂ Co₂(CO)₈ reacts with ^tBu₂P–P=P(Me)^tBu₂ yielding the compounds [Co₄P₂(P^tBu₂)₂(CO)₈] ( 1 ) and [{η^2tBu₂P=P–P=P^tBu₂}{Co(CO)₃}₂] ( 2 a ) cis, ( 2 b ) trans. In 1 , four Co and two P atoms form a tetragonal bipyramid, in which two adjacent Co atoms are μ₂‐bridged by ^tBu₂P groups. Additionally, two CO groups are linked to each Co atom. In 2 a and 2 b , each of the Co(CO)₃ units is η²‐coordinated to the terminal P₂ units resulting in the cis‐ and trans‐configurations 2 a and 2 b . 1 crystallizes in the orthorhombic space group Pnnm (No. 58) with a = 879,41(5), b = 1199,11(8), c = 1773,65(11) pm. 2 a crystallizes in the monoclinic space group P2₁/n (No. 14) with a = 875,97(5), b = 1625,36(11), c = 2117,86(12) pm, β = 91,714(7)°. 2 b crystallizes in the triclinic space group P 1 (No. 2) with a = 812,00(10), b = 843,40(10), c = 1179,3(2) pm, α = 100,92(2)°, β = 102,31(2)°, γ = 102,25(2)°.     

Chemical modification of poly(substituted-acetylene). I. Synthesis and gas permeability of poly(1-trimethylsilyl-1-propyne)/poly (dimethylsiloxane) graft copolymer

In order to improve the selectivity and the stability and the stability for gas permeation of poly (1-trimethylsilyl-1-propyne) (PTMSP) membrane, it was chemically modified by grafting polydimethylsiloxane (PDMS) chains. The graft copolymers were synthesized by four different methods via metallation of PTMSP with n-butyllithium. PDMS content of the graft co-polymers was controlled in the range of 4–92 mol %. Very tough, thin membranes could be prepared from these graft copolymers using a solvent casting method. Thermal property and gas permeability of the copolymer membranes thus obtained were evaluated. These membranes were relatively thermally stable, and the softening points were over about 150°C. Oxygen permeability coefficients Po₂ and selectivity Po₂/PN₂ of PTMSP/PDMS graft copolymers depended on the PDMS content, the former was in the range of 1 X 10^?8 to 2 × 10^?7 cm³ (STP)· cm/(cm²· s · cm. Hg) and the latter was 2.0–3.1. Minimum values of PO₂ and PN₂ occured at PDMS content of about 55 mol %. The introduction of more than 60 mol % of PDMS resulted in oxygen permeability coefficient which was maintained for more than one moth (PO₂ = 2 ? 6 × 10 ^?8 cm ³ (STP)· cm/(cm²·s·cm Hg), PO₂/PN₂ = 2.3–2.7).     

Sorption,diffusion, and permeation of ethylbenzene in poly(1‐trimethylsilyl‐1‐propyne)

The solubility, diffusivity, and permeability of ethylbenzene in poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) at 35, 45 and 55 °C were determined using kinetic gravimetric sorption and pure gas permeation methods. Ethylbenzene solubility in PTMSP was well described by the generalized dual‐mode model with χ = 0.39 ± 0.02, b = 15 ± 1, and C^′_H = 45 ± 4 cm³ (STP)/cm³ PTMSP at 35 °C. Ethylbenzene solubility increased with decreasing temperature; the enthalpy of sorption at infinite dilution was −40 ± 7 kJ/mol and was essentially equal to the enthalpy change upon condensation of pure ethylbenzene. The diffusion coefficient of ethylbenzene in PTMSP decreased with increasing concentration and decreasing temperature. Activation energies of diffusion were very low at infinite dilution and increased with increasing concentration to a maximum value of 50 ± 10 kJ/mol at the highest concentration explored. PTMSP permeability to ethylbenzene decreased with increasing concentration. The permeability estimated from solubility and diffusivity data obtained by kinetic gravimetric sorption was in good agreement with permeability determined from direct permeation experiments. Permeability after exposure to a high ethylbenzene partial pressure was significantly higher than that observed before the sample was exposed to a higher partial pressure of ethylbenzene. Nitrogen permeability coefficients were also determined from pure gas experiments. Nitrogen and ethylbenzene permeability coefficients increased with decreasing temperature, and infinite dilution activation energies of permeation for N₂ and ethylbenzene were −5.5 ± 0.5 kJ/mol and −74 ± 11 kJ/mol, respectively. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1078–1089, 2000     

Synthesis and Chloride Affinity of Sterically Demanding Ditopic Lithium Bis(pyrazol‐1‐yl)borates

The synthesis and full characterization of the sterically demanding ditopic lithium bis(pyrazol‐1‐yl)borates Li₂[p‐C₆H₄(B(Ph)pz^R₂)₂] is reported (pz^R = 3‐phenylpyrazol‐1‐yl ( 3 ^Ph), 3‐t‐butylpyrazol‐1‐yl ( 3 ^tBu)). Compound 3 ^Ph crystallizes from THF as THF‐adduct 3 ^Ph(THF)₄ which features a straight conformation with a long Li···Li distance of 12.68(1) Å. Compound 3 ^tBu was found to function as efficient and selective scavenger of chloride ions. In the presence of LiCl it forms anionic complexes [ 3 ^tBuCl]⁻ with a central Li‐Cl‐Li core (Li···Li = 3.75(1) Å).     

Poly[1‐(trimethylgermyl)‐1‐propyne] and poly[1‐(trimethylsilyl)‐1‐propyne] with various geometries: Their synthesis and properties

The polymerization of 1,2‐disubstituted acetylenes [1‐(trimethylgermyl)‐1‐propyne and 1‐(trimethylsilyl)‐1‐propyne] initiated by Nb‐ and Ta‐based catalytic systems was studied within a wide temperature range (?10 to +80 °C) with solvents (cyclohexane, CCl₄, toluene, anisol, and n‐chlorobutane) with variable dielectric constants (2.023–7.390). Conditions ensuring the synthesis of poly[1‐(trimethylsilyl)‐1‐propyne] (PTMSP) containing 20–80% cis units and poly[1‐(trimethylgermyl)‐1‐propyne] (PTMGP) containing 3–65% cis units were determined. The PTMSP and PTMGP samples were amorphous, exhibited a two‐phase structure characterized by the presence of less ordered regions and regions with an enhanced level of ordering, and differed in solubility. A correlation was found between the cis/trans ratio and the morphology, the geometrical density of PTMSP and PTMGP films, and the gas permeability of the polymers. The gas permeability and solubility behavior of PTMSP and PTMGP were examined in terms of the molecular characteristics of the polymer samples (the thermodynamic Kuhn segment and the Kerr electrooptic effect). It was demonstrated that the gas permeability, as well as the solubility of the polymers, was defined by their supramolecular ordering, which depended on the lengths of continuous sequences composed of units of analogous microstructures and on the flexibility of macrochains. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2133–2155, 2003     

Phosphinophosphiniden-Phosphorane tBu2P?P = P(R)tBu2 aus Li(THF)2[η2-(tBu2P)2P] und Alkylhalogeniden

The Phosphinophosphinidene-phosphoranes ^tBu₂P? P = P(R)^tBu₂ from Li(THF)₂[η²-(^tBu₂P)₂P] and Alkyl Halides We report the formation of ^tBu₂P? P = P(R)^tBu₂ a and (^tBu₂)₂PR b (with R = Me, Et, ⁿPr, ⁱPr, ⁿBu, PhCH₂, H₂C = CH? CH₂ and CF₃) reactions of Li(THF)₂[η²-(^tBu₂P)₂P] 2 with MeCl, MeI, EtCl, EtBr, ⁿPrCl, ⁿPrBr, ⁱPrCl, ⁿBuBr, PhCH₂Cl, H₂C = CH? CH₂Cl or CF₃Br. In THF solutions the ylidic compounds a predominate, whereas in pentane the corresponding triphosphanes b are preferrably formed. With ClCH₂? CH = CH₂ only b is produced; CF₃Br however yields both ^tBu₂P? P = P(Br)^tBu₂ and ^tBu₂P? P = P(CF₃)^tBu₂, but no b . The ratio of a:b is influenced by the reaction temperature, too. The compounds ^tBu₂P? P = P(Et)^tBu₂ 4a and (^tBu₂P)₂PEt 4 b , e. g., are produced in a ratio of 4:3 at ?70°C in THF, and 1:1 at 20°C; whereas 1:1 is obtained at ?70°C in pentane, and 1:2 at 20°C. Neither ^tBuCl nor H₂C = CHCl react with 2 . The compounds a decompose thermally or under UV irradiation forming ^tBu₂PR and the cyclophosphanes (^tBu₂P)_nP_n.     

The Reactions of Carbon Monoxide with Silyl and Silenyl Lithium – Synthesis and Isolation of the First Stable Tetra‐Silyl Di‐Ketyl Biradical and 1‐Silaallenolate Lithium

Reactions of carbon monoxide (CO) with tBu₂MeSiLi and (E)‐(tBu₂MeSi)(tBuMe₂Si)C=Si(SiMetBu₂)Li?2 THF ( 4 ) were studied both experimentally and computationally. Reaction of tBu₂MeSiLi with CO in hexane yields the first stable tetra‐silyl di‐ketyl biradical [(tBu₂MeSi)₂COLi]^.₂ ( 3 ). Reaction of 4 with CO yields selectively and quantitatively the first reported 1‐silaallenolate, (tBu₂MeSi)(tBuMe₂Si)C=C=Si(SiMetBu₂)OLi?THF ( 5 ). Both 3 and 5 were characterized by X‐ray crystallography and biradical 3 also by EPR spectroscopy. Silaallenolate 5 reacts with Me₃SiCl to produce siloxy substituted 1‐silaallene (tBu₂MeSi)(tBuMe₂Si)C=C=Si(SiMetBu₂)OSiMe₃. The reaction of 4 with CO provides a new route to 1‐silaallenes. The mechanisms of the reactions of tBuMe₂SiLi and of 4 with CO were studied by DFT calculations.     

Reaktionen des tBu(Me3Si)P?P(Li)?P(tBu)2 mit CH3Cl und 1,2-Dibromethan

Reactions of tBu(Me₃Si)P? P(Li)? P(tBu)₂ with CH₃Cl and 1,2-Dibromoethane tBu(Me₃Si)P? P(Li)? P(tBu)₂ · 0.95 THF 1 with CH₃Cl (?70°C) yields tBu(Me₃Si)P? P = P(Me)(tBu)₂ 2 at ?70°C, with 1,2-Dibromoethane tBu(Me₃Si)P? PBr? P(tBu)₂ 3 (main product) and tBu(Me₃Si)P? P?P(Br)tBu₂ 4. 3 eliminates Me₃SiBr yielding the cyclotetraphosphane {tBuP? P[P(tBu)₂]}₂ 5 .     

Study of the transmetallation of silicon derivatives ofo-carboranes on treatment with BunLi

Silyl-substitutedo-carboranes 1-R-2-Me₃Si(CH₂) _n -1,2-C₂B₁₀H₁₀ (R=Me, Ph;n=0, 1) undergo transmetallation on treatment with BuⁿLi to form lithium derivatives ofo-carboranes, 1-R-2-Li(CH₂) _n -1,2-C₂B₁₀H₁₀, wheren=0, 1. A silicon derivative ofo-carborane, 1-Ph-2-(Me₃SiCHPh)-1,2-C₂B₁₀H₁₀, undergoes neither transmetallation nor metallation at the benzyl CH-group on treatment with BuⁿLi due to significant steric hindrance. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 492–494, March, 1998.     

Die Reaktionen von tBu2P–P=P(Me)tBu2 und (Me3Si)tBuP–P=P(Me)tBu2 mit PR3

The Reactions of ^tBu₂P–P=P(Me)^tBu₂ and (Me₃Si)^tBuP–P=P(Me)^tBu₂ with PR₃ ^tBu₂P–P=P(Me)^tBu₂ ( 1 ) reacts at 20 °C with PMe₃, PEt₃, P(c‐Hex)₃, P(p‐Tol)₃, PPh₂Me, PPh₂Et, PPhEt₂, PPh₂ⁱPr, PPh₃ and P(NEt₂)₃ yielding ^tBu₂P–P=PR₃ and ^tBu₂PMe; however, P^tBu₃, P^tBu₂(SiMe₃) and ^tBu₂PCl don't. ^tBu₂PH and 1 form ^tBu₂P–PH–P^tBu₂ which yields ^tBu₂P–P=PEt₃ when treated with PEt₃. Ph₂PH, ^tBuPH₂, PH₃, Ph₂PCl and EtOH don't substitute the ^tBu₂PMe group in 1 , instead, the molecule is decomposed. With PEt₃, (Me₃Si)^tBuP–P=P(Me)^tBu₂ forms (Me₃Si)^tBuP–P=PEt₃. The compounds ^tBu₂P–P=PR₃ decompose at 20 °C to different degrees giving P‐rich consecutive products of the phosphinophosphinidene.     

Reaktionen von (tBu)2P?PP(Br)tBu2 mit LiP(SiMe3)2, LiPMe2 und LiMe,LitBu, LinBu

Reactions of (tBu)₂P? P?P(Br)tBu₂ with LiP(SiMe₃)₂, LiPMe₂ and LiMe, LitBu and LinBu The reactions of (tBu)₂P? P?P(Br)tBu₂ 1 with LiP(SiMe₃)₂ 2 yield (Me₃Si)₂P? P(SiMe₃)₂ 4 and P[P(tBu)₂]₂P(SiMe₃)₂ 5 , whereas 1 with LiPMe₂ 2 yields P₂Me₄ 6 and P[(tBu)₂]₂PMe₂ 7 . 1 with LiMe yields the ylid tBu₂P? P?P(Me)tBu₂ (main product) and [tBu₂P]₂PMe 15 . In the reaction of 1 with tBuLi [tBu₂P]₂PH 11 is the main product and also tBuP? P?P(R)tBu₂ 21 is formed. The reaction of 1 with nBuLi leads to [tBu₂P]₂PnBu 17 (main product) and tBu₂P? P?P(nBu)tBu₂ 22 (secondary product).     

(Alk-1-ynyl)organylthiocarbenes: generation and reactions with olefins

1-Substituted 1-chloro-3-organylthiopropa-1,2-dienes 1a–f belonging to previously unknown type of allenic compounds were synthesized by chlorination of 1-organylthioalk-1-ynes 3a–f with N-chlorosuccinimide. The reactions of compounds 1a–f with Bu^tOK in hexane at –20 °C are accompanied by -elimination of HCl to give new alk-1-ynyl(organylthio)carbenes 2a–f, which add to olefins to form the corresponding 1-(alk-1-ynyl)-1-organylthiocyclopropanes 5 in yields of up to 60%. The electrophilic properties of carbenes 2 were confirmed experimentally.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2440–2447, November, 2004.     

Bildung und Struktur des iso-Tetraphosphans P(PtBu2)3: ein Molekül mit einem planaren,dreibindigen P-Atom

Formation and Structure of the iso -Tetraphosphane P(P^tBu₂)₃: a Molecule with a Planar Three-coordinated P Atom The iso-tetraphosphane P(P^tBu₂)₃ ( 1 ) was obtained by irradiating ^tBu₂P–P=P(Me)^tBu₂ ( 3 ). 1 forms hexagonal crystals (space group P6₃/m) with a = 1005,63(8), c = 1621,4(2) pm, Z = 2. The P(P^tBu₂)₃ molecules are arranged in a hexagonally close packed lattice. The four P atoms in each molecule are coplanar with P–P bond distances 219.08(4) pm and P–P–P angles 120°. The observed planar geometry is in accordance with ab initio calculations.