Lewis acid-catalyzed reactions of mono-aryl group substituted methylenecyclopropanes with diethyl ketomalonate

Mono-aryl group substituted methylenecyclopropanes (MCPs) 1 react with diethyl ketomalonate 2a, an activated ketone, to give the corresponding 7-hydroxy-5-oxa-spiro[2,4]heptan-6-one derivatives 6 with syn-configuration in moderate yields in the presence of water under the catalysis of Lewis acids such as Sc(OTf)₃, Yb(OTf)₃ or In(OTf)₃ at room temperature. The reaction mechanism has been discussed on the basis of an ¹⁸O-labeling experiment.     

Polymerization and copolymerization of functionalized 2‐alkoxy‐1‐methylenecyclopropanes to form new polymers having alkoxy substituents

The polymers with functionalized alkoxy groups and with narrow molecular weight distribution (M_w/M_n < 1.12) are obtained from the living polymerization of 2‐alkoxy‐1‐methylenecyclopropanes using π‐allylpalladium complex, [(PhC₃H₄)Pd(μ‐Cl)]₂, as the initiator. The polymers with oligoethylene glycol groups in the alkoxy substituent are soluble in water, and hydroboration of the C?C double bond and ensuing addition of the OH groups to C?N bond of alkyl isocyanate produce the polymers with urethane pendant groups. The reaction decreases solubility of the polymer in water significantly. Di‐ and triblock copolymers of the 2‐alkoxy‐1‐methylenecyclopropanes are prepared by consecutive addition of the two or three 2‐alkoxy‐1‐methylenecyclopropane monomers to the Pd initiator. The polymers which contain both hydrophobic butoxy or tert‐butoxy group and hydrophilic oligoethylene glycol group dissolve in water and/or organic solvents, depending on the substituents. The ¹H NMR spectrum of poly( 1a ‐b‐ 1h ) (? (CH₂C(?CH₂)CHOBu)_n? (CH₂C(?CH₂)CH(OCH₂CH₂)₃OMe)_m? ) in D₂O solution exhibits peaks because of the butoxy and ?CH₂ hydrogen in decreased intensity, indicating that the polymer forms micelle particles containing the hydrophilic segments in their external parts. Aqueous solution of the polymer with a small amount of DPH (DPH = 1,6‐diphenyl‐1,3,5‐hexatriene) shows the absorbance due to DPH at concentration of the polymer higher than 5.82 × 10^?5 g mL^?1. Other block copolymers such as poly( 1b ‐b‐ 1h ) and poly( 1a ‐b‐ 1g ) also form the micelles that contain DPH in their core. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 959–972, 2009     

Stereoselective fluorination of methylenecyclopropanes with N-F reagents: A modular entry to γ-fluorohomoallylic sulfonimides and γ-fluorohomoallylic amides

A convenient and efficient method for fluorination of methylenecyclopropanes is reported. This is exemplified in the stereoselective preparation of N-[(E)-3-fluorobut-3-en-1-yl]-benzenesulfonimides by the reaction of methylenecyclopropanes with N-fluorobenzenesulfonimide in good to excellent yields. Moreover, γ-fluorohomoallylic amides are synthesized using Selectfluor in R₃CN at 60 °C.     

Komplexchemie P-reicher Phosphane und Silylphosphane. XIV. Phosphinophosphiniden tBu2P?P als Ligand in den Pt-Komplexen [η2-{tBu2P?P}Pt(PPh3)2] und [η2-{tBu2P?P}Pt(PEtPh2)2]

Coordination Chemistry of P-rich Phosphanes and Silylphasphanes. XIV. The Phosphinophosphinidene ^tBu₂P? P as a Ligand in the Pt Complexes [η²-{^tBu₂P? P}Pt(PPh₃)₂] and [η²-{^tBu₂P? P}Pt(PEtPh₂)₂] [η²-{^tBu₂P? P}Pt(PPh₃)₂ 1 and [η²-{^tBu₂P? P}Pt(PEtPh₂)₂] 2 are the first complex compounds of ^tBu₂P? P 5 . They are formed in the reaction of ^tBu₂P? P ? P(Me)^tBu₂ 3 with [η²-{H₂C ? CH₂}Pt(PPh₃)₂] 6 or [η²-{H₂C ? CH₂}Pt(PEtPh₂)₂] 7 , respectively. Compound 1 is less stable than 2 and reacts on to [η²-{^tBu₂P? P} Pt(PPh₃)(P^tBu₂Me)] 10 with the coincidently formed ^tBu₂PMe. The molecular structures of 1 and 2 were derived from their ¹H and ³¹P-NMR spectra, 2 was additionally characterized by a X ray structure determination. 2 crystallizes in the monoclinic space group P2₁/n with a = 1222.36(7) pm, b = 1770.7(1) pm, c = 1729.7(1) pm, β = 108.653(6)°.     

The thermal rearrangements of 1,1,2,2,4,4-hexafluorospiropentane and perfluorospiropentane

The title compounds were synthesized $\text{via}$ CF₂: addition to the respective methylenecyclopropanes. The hexafluorospiropentane thermally rearranges to 2,2,4,4-tetrafluoro-1-(difluoromethylene)cyclobutane in competition with CF₂: extrusion, whereas perfluorospiropentane decomposes exclusively by CF₂: extrusion.     

Komplexchemie P-reicher Phosphane und Silylphosphane. XIII [1]. [η2-{tBu2P?PPtBu2} PtBr(PPh3)]

Coordination Chemistry of P-rich Phosphanes and Silylphosphanes. XIII [1]. [η²-{^tBu₂P? P?P^tBu²} PtBr(PPh₃)] [η²-{^tBu₂P? P?P^tBu₂} PtBr(PPh₃)] 1 is the first transition metal complex compound resulting from a phosphino-phosphinidene-phosphorane. The yellow crystals of 1 (fp. 201–203°C, decomp.) were obtained by reacting ^tBu₂P? P?P(Br)^tBu₂ with either (Ph₃P)₂Pt · C₂H₄, or with Pt(PPh₃)₄, resp. Compound 1 crystallizes triclinic in the space group P1 (no. 2) with a = 1076.80(8) pm, b = 1344.61(8) pm, c = 1381.16(9) pm, α = 81.773(6)°, β; = 85,110(8), γ = 88,776(7).     

Conversion of E4 (E4=P4, As4, AsP3) by Ni(0) and Ni(I) Synthons – A Comparative Study

The reactivity of white phosphorus and yellow arsenic towards two different nickel nacnac complexes is investigated. The nickel complexes [(L¹Ni)₂tol] ( 1 , L¹=[{N(C₆H₃ⁱPr₂-2,6)C(Me)}₂CH]⁻) and [K₂][(L¹Ni)₂(μ,η^{1 : 1}-N₂)] ( 6 ) were reacted with P₄, As₄ and the interpnictogen compound AsP₃, respectively, yielding the homobimetallic complexes [(L¹Ni)₂(μ-η²,κ¹:η²,κ¹-E₄)] (E=P ( 2 a ), As ( 2 b ), AsP₃ ( 2 c )), [(L¹Ni)₂(μ,η^{3 : 3}-E₃)] (E=P ( 3 a ), As ( 3 b )) and [K@18-c-6(thf)₂][L¹Ni(η^{1 : 1}-E₄)] (E=P ( 7 a ), As ( 7 b )), respectively. Heating of 2 a , 2 b or 2 c also leads to the formation of 3 a or 3 b . Furthermore, the reactivity of these compounds towards reduction agents was investigated, leading to [K₂][(L¹Ni)₂(μ,η^{2 : 2}-P₄)] ( 4 ) and [K@18-c-6(thf)₃][(L¹Ni)₂(μ,η^{3 : 3}-E₃)] (E=P ( 5 a ), As ( 5 b )), respectively. Compound 4 shows an unusual planarization of the initial Ni₂P₄-prism. All products were comprehensively characterized by crystallographic and spectroscopic methods.     

Unprecedented and Effective Synthesis of Thiazolines from Perfluoro-3-isothiocyanato-2-methyl-2-pentene and Certain P-Nucleofuges

The reactions of perfluoro-3-isothiocyanato-2-methyl-2-pentene with PPh₃ and P(NEt₂)₃ in the presence of NaBF₄, KI, and NaBPh4 form phosphonium salts with the heterocyclic substituent (4E)-5,5-bis(trifluoromethyl)-4-(tetrafluoroethylidene)-4,5-dihydro-1,3-thiazol-2-yl, instead of involving desulfurization and formation of P-F-containing products. The reaction with tris(pentafluorophenyl)phosphine fails. The reactions with P(OEt)₃ in the presence of ClSiMe₃ or (CH₃O)₂POSiMe₃ yield diethyl or dimethyl [(4E)-5,5-bis(trifluoromethyl)-4-(tetrafluoroethylidene)-4,5-dihydro-1,3-thiazol-2-yl]phosphonates and no intramolecular alkylation products. The ¹H, ¹³C, ¹⁹F, and ³¹P spectra are presented, and the reaction pathways are discussed. Potential mechanisms of the biological and catalytic activity of the reaction products are considered.     

The structure of trimethylenemethane-ML2 complexes and Their relationship to cycloaddition reactions

An electronic reason is offered why d¹⁰ and d⁸ trimethylenemethane-ML₂ complexes should be η³ rather than η⁴. This was checked by molecular orbital calculations of the extended Hückel type. Both sets of complexes can be regarded as zwitterionic with the uncomplexed methylene group for the d¹⁰ compounds anionic and cationic for the d⁸ analogs. In both cases, interconversion between the three equivalent η³ geometries does not proceed via an η⁴ structure. We find that η² geometries serve as way-points in this fluxional rearrangement. Implications are also drawn to the mode of cycloaddition of methylenecyclopropanes to electron deficient olefins by d¹⁰ ML_n catalysis and ring-opening of the methylenecyclopropanes.     

Metallkomplexe von Farbstoffen. VI. Phosphan-Nickel-, Palladium- und Platin-Komplexe sowie Pentamethyl-cyclopentadienyl-Rhodium- und Iridium-Komplexe von Bis(2-hydroxyaryl)azo-Farbstoffen

Metal Complexes of Dyes. Phosphine-Nickel, Palladium, Platinum Complexes and Pentamethylcyclopentadienyl Rhodium and Iridium Complexes of 2,2′-Dihydroxyazoarenes The terdentate dianions of 2,2′-dihydroxyazobenzene (L¹H), 1-(2-hydroxy-4-nitrophenylazo)-2-naphthol (L²H), 1-(2-hydroxy-5-nitrophenylazo)-2-naphthol (L³H) and 1-phenyl-3-methyl-4-(2-hydroxy-5-nitrophenylazo)-5-pyrazolone (L⁴H) form with chloro bridged complexes [(R₃P)MCl₂]₂ (M = Pd, Pt; R = Ph, nBu), [(n⁵-C₅Me₅)MCl₂]₂ (M = Rh, Ir) and with (nBu₃P)₂NiCl₂ the metal dye complexes (R₃P)ML (M = Ni, Pd, Pt) and (C₅Me₅)ML (M = Rh, Ir). The structures of (Ph₃P)PtL¹ and (nBu₃P)PdL³ have been determined by X-ray diffraction. For the complexes (n⁵-C₅Me₅)ML (M = Rh, Ir) with asymmetric metal centers two diastereoisomers are detected by nmr spectroscopy which points to the ?hydrazone”? form of the azo ligand with a pyramidalized N-atom.     

Ti-catalyzed ring-opening oxidative amination of methylenecyclopropanes with diazenes

The ring-opening oxidative amination of methylenecyclopropanes (MCPs) with diazenes catalyzed by py₃TiCl₂(NR) complexes is reported. This reaction selectively generates branched α-methylene imines as opposed to linear α,β-unsaturated imines, which are difficult to access via other methods. Products can be isolated as the imine or hydrolyzed to the corresponding ketone in good yields. Mechanistic investigation via density functional theory suggests that the regioselectivity of these products results from a Curtin–Hammett kinetic scenario, where reversible β-carbon elimination of a spirocyclic [2 + 2] azatitanacyclobutene intermediate is followed by selectivity-determining β-hydrogen elimination of the resulting metallacycle. Further functionalizations of these branched α-methylene imine products are explored, demonstrating their utility as building blocks.

The ring-opening oxidative amination of methylenecyclopropanes (MCPs) with diazenes catalyzed by py₃TiCl₂(NR) complexes is reported.     

Einfluß der Chelatbildner dppe und dppp auf die Bildung und die Eigenschaften der Pt-Komplexe des tBu2P–P

Coordination Chemistry of P-rich Phosphanes and Silylphosphanes. XV. Influence of the Chelate Compounds dppe and dppp on Formation and Properties of the Pt Complexes of ^tBu₂P–P The chelating ligands dppe and dppp replace the PPh₃ groups in [η²-{^tBu₂P–P}Pt(PPh₃)₂] 1 yielding [η²-{^tBu₂P–P}Pt(dppe)] 2 and [η²-{^tBu₂P–P}Pt(dppp)] 8 . However, they don't replace the phosphinophosphinidene ligand ^tBu₂P–P. dppm does not react at all with 1 . [η²-{H₂C=CH₂}Pt(dppe)] 3 yields in the presence of ^tBu₂P–P=P(Me)^tBu₂ 4 exclusively Pt(dppe)₂ 5 and elemental Pt; no 2 could be detected. Similarly, [η²-{H₂C=CH₂}Pt(dppp)] 7 reacts with 4 to give mainly Pt(dppp)₂ 9 and Pt; [η²-{tBu₂PP}Pt(PPh₃)₂] 8 is present only as a minor product. [η²-{^tBu₂P–P}Pt(dppe)] 2 crystallizes in the monoclinic space group P2₁/c (no. 14) with a = 1834.40(10) pm, b = 1679.70(10) pm, c = 1125.79(6) pm, β = 103.963(5)°.     

Mono-, di-, and tetra-aurated derivatives of barbituric acid,including a new type of polynuclear gold compound. Crystal structure of 1,3-bis(triphenylphosphinegold)-5,5-diethylbarbituric acid

Reaction of barbituric acid (2,4,6-pyrimidinetrione) or its derivatives with LAuCl (L = triphenylphosphine) gave 3-LAu-5,5-diethyl-, 1,3-(L'Au)₂-5,5-diethyl- (L′ = L or L′ = Cy₃P), 1,3-dimethyl-5,5-bis(LAu)-, or 1,3,5,5-tetrakis-(LAu)barbituric acid, which were characterized as N-, N,N′-, C,C′-, or N,N′,C,C-gold derivative,s respectively, by IR, ¹H, ¹³C and ³¹P NMR spectroscopy. In the case of 1,3-(LM)(L″M)-5,5-diethylbarbituric acid compounds with M = gold and L″ either Cy₃P, Ph₃As, or (4-tolyl)₃P, or ML = ML″ = HgMe were prepared. An X-ray diffraction study of 1,3-(LAu)₂-5,5-Et₂-pyrimidin-2,4,6-trione · 3C₆H₆ revealed that (a) the heterocyclic ring is planar, (b) there is no inter- or intra-molecular Au ⋯ Au interaction, and (c) the coordination around each gold atom is approximately linear (PAuN 178.3(4)°, with AuN 2.022(12) and AuP 2.233(5) Å. The molecular parameters are compared with those for barbituric acid and other barbiturates.     

Fluoridolyse von N-Phosphorylphosphazenen

Fluoridolysis of N-Phosphoryl Phosphazenes In the reaction of the N-phosphoryl phosphazenes X₃P?N? P(Y)X₂ (X = Cl, PhO, Et₂N, CF₃CH₂O, PrS, Ph; Y = O, S) ( 1 – 18 ) with Et₃N · nHF (n ≈? 3 or 0.6) fluoro derivatives of N-phosphoryl phosphazenes (see table 2) as well as N-phosphorylated imiddotetrafluorophosphates, [F₄P?N? P(Y)Cl₂]^? (Y = O, S), and imidopentafluorophosphates, [F₅P? N? P(Y)X₂]^2? or [F₅P? NH? P(O)X₂]^? (see table 3), are formed. t-BuNHPCl₂?N? POCl₂ reacts in acetonitrile with Et₃N or i-Pr₂EtN to form a product, representing probably the diazadiphosphetine ( 5 b ).     

Reaktionen des [η2-{P–PtBu2}Pt(PPh3)2] und [η2-{P–PtBu2}Pt(dppe)] mit Metallcarbonylen. Bildung von [η2-{(CO)5M · PPtBu2}Pt(PPh3)2] (M = Cr,W) und [η2-{(CO)5Cr · PPtBu2}Pt(dppe)]

Coordination Chemistry of P-rich Phosphanes and Silylphosphanes. XVI [1] Reactions of [g²-{P–P^tBu₂}Pt(PPh₃)₂] and [g²-{P–P^tBu₂}Pt(dppe)] with Metal Carbonyls. Formation of [g²-{(CO)₅M · PP^tBu₂}Pt(PPh₃)₂] (M = Cr, W) and [g²-{(CO)₅Cr · PP^tBu₂}Pt(dppe)] [η²-{P–P^tBu₂}Pt(PPh₃)₂] 4 reacts with M(CO)₅ · THF (M = Cr, W) by adding the M(CO)₅ group to the phosphinophosphinidene ligand yielding [η²-{(CO)₅Cr · PP^tBu₂}Pt(PPh₃)₂] 1 , or [η²-{(CO)₅W · PP^tBu₂}Pt(PPh₃)₂] 2 , respectively. Similarly, [η²-{P–P^tBu₂}Pt(dppe)] 5 yields [η²-{(CO)₅Cr · PP^tBu₂}Pt(dppe)] 3 . Compounds 1 , 2 and 3 are characterized by their ¹H- and ³¹P-NMR spectra, for 2 and 3 also crystal structure determinations were performed. 2 crystallizes in the monoclinic space group P2₁/n (no. 14) with a = 1422.7(1) pm, b = 1509.3(1) pm, c = 2262.4(2) pm, β = 103.669(9)°. 3 crystallizes in the triclinic space group P1 (no. 2) with a = 1064.55(9) pm, b = 1149.9(1) pm, c = 1693.2(1) pm, α = 88.020(8)°, β = 72.524(7)°, γ = 85.850(8)°.     

The Vinylidene/Acyl Coupling at Rhenium Centers

The reaction of [Re(CO₃)L₂Cl] (L = (MeI)₃P, 1a ; L = (i-PrO)₃P, 1b ; L = (PhO)₃P, 1c ; L = Me₃P, 1d ; L = Et₃P, 1e ) with t-BuLi and phenylacetylene in THF affords bis (phosphorus donor) (dicarbonyl) {η²(C,O)-[(E)-4,4-dimethyl-3-oxo-1-phenylpent-1-3n-2-yl]}rhenium (L = (MeO)₃P, 2b ; L = (PhO)₃P, 2c ; L = Me₃P, 2d ; L = Et₃P, 2c ). Compounds 2b and 2d were characterized by X-ray structure analysis.     

Komplexchemie P-reicher Phosphane und Silylphosphane. XI [1]. Bildung,Reaktionen und Strukturen von Chromcarbonylkomplexen aus Reaktionen von Li(THF)2[η2-(tBu2P)2P] mit Cr(CO)5 · THF und Cr(CO)4 · NBD

Transition Metal Complexes of P-rich Phosphanes and Silylphosphanes. XI. Formation, Reactions, and Structures of Chromium Carbonyl Complexes from Reactions of Li(THF)₂[η₂-(^tBu₂P)₂P] with Cr(CO)₅ · THF and Cr(CO)₄ · NBD Reactions of Li(THF)₂[η²-(^tBu₂P)₂P] 1 with Cr(CO)₅ · THF yield Li(THF)₂Et₂O[Cr(CO)₄{η²-(^tBu₂P)₂P}η¹-Cr(CO)₅] 2 and the compounds [Cr(CO)₄{η²-(^tBu₂P)₂PH}] 3 , [Cr(CO)₅{η¹-(^tBu₂P)₂PH}] 4 , (^tBu₂P)₂PH 5 and ^tBu₂PH · Cr(CO)₅ 6 . The formation of 3, 4, 5 and 6 is due to byproducts coming from the synthesis of 1. 2 reacts with CH₃COOH under formation of 3 . After addition of 12-crown-4 1 with NBD · Cr(CO)₄ in THF forms Li(12-crown-4)₂[Cr(CO)₄-{η²-(^tBu₂P)₂P}] 7 (yellow crystals). 7 reacts with CH₃COOH to 3 – which regenerates 7 with LiBu – with Cr(CO)₅THF to compound 2 , with NBD · Cr(CO)₄ in THF to 2 and 3 (ratio 1 : 1). With EtBr, 7 forms [Cr(CO)₄{η²-(^tBu₂P)₂PEt}] 8 , and [Cr(CO)₄{η²-(^tBu₂P)₂PBr}] 9 with BrCH₂? CH₂Br. The compounds were characterized by means of ¹H, ¹³C, ³¹P, ⁷Li NMR spectroscopy, IR spectroscopy, elementary analysis, mass spectra, and 2, 3 and 4 additionally by means of X-ray diffraction analysis. 2 crystallizes in the space group P1 with 2 formula units in the elementary cell; a = 10.137(9), b = 15.295(12), c = 15.897(14) Å; α = 101.82(7), β = 91.65(7), γ = 98.99(7)°; 3 crystallizes in the space group P2_t/n with 4 molecules in the elementary unit; a = 11.914(6), b = 15.217(10), c = 14.534(10) Å; α = 90, β = 103.56(5), γ = 90°. 4 : space group P1 with 2 molecules in the elementary unit; a = 8.844(4), b = 12.291(6), c = 14.411(7) Å, α = 66.55(2), β = 89.27(2), γ = 71.44(2)°.     

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.     

Synthese und Eigenschaften Pentamethylcyclopentadienyl-substituierter PPC- bzw. AsPC-Dreiring-Systeme

Synthesis and Properties of Pentamethylcyclopentadienylsubstituted PPC and AsPC three-membered Rings Via the reaction of bis-(pentamethylcyclopentadienyl)diphosphene [Cp*P?PCp*, 1 ] and 1-(pentamethylcyclopentadienyl)-2-(2,4,6-tri^tbutylphenyl)- diphosphene [Cp*P?PMes*, 2 ] with the diazomethanes N₂CHR [R = H, Si(CH₃)₃] the four new diphosphiranes Cp*PPCp*CHSi(CH₃)₃, 4a , Cp*PPMes*CHSi(CH₃)₃, 4b , Cp*PPCp*CH₂, 5a , Cp*PPMes*CH₂, 5b , are obtained. The formation of 4a results via a 2 + 3-cyclo-addition product, which could be proved by nmr spectroscopy. The reaction of As-(pentamenthylcyclopentadienyl)-P-(2,4,6-tri^tbutylphenyl) arsaphosphene [Cp*As?PMes*, 3 ] with diazomethane leads to 1-(pentamethylcyclopentadienyl)-2-(2,4,6-tri^tbutylphenyl)-1-arsa-2 -phosphacyclopropane [phospharsiran, Cp*AsPMes*CH₂, 6 ]. Analysis of the structures by nmr spectroscopy gives clear evidence for a trans-orientation of the substituents at the El? P bond (El = As, P) in all of the three membered ring systems. For the diphosphirane Cp*PPCp*CH₂ ( 5a ) a Cp*-phosphorus bond cleavage by thermolysis cannot be observed. From the reaction of compound 5a with Cr(CO)₅thf one obtains 1-(pentacarbonylchrom)-1,2-bis(pentamethylcyclopentadienyl)-1,2- diphosphacyclo-propane, 7 .     

Ruthenium carbonyl clusters derived from pyrazolyl substituted diphosphazanes: Crystal and molecular structure of a triruthenium cluster featuring a triply bridging μ3-η1:η1:η1 coordination mode of pyrazolate moiety

The radical initiated reactions of Ru₃(CO)₁₂ with pyrazolyl substituted diphosphazanes Ph₂PN(R)PPh(N₂C₃HMe₂-3,5) [R = (S)-*CHMePh (1) or CHMe₂ (2)] proceed via P–N(pyrazole) bond rupture resulting in the formation of phosphido clusters, [Ru₃(CO)₅(μ_sb-CO)₂(μ₃-N,N′-η¹:η¹:η¹-N₂C₃HMe₂-3,5){μ-P,P′-Ph₂PN(R)PPh}] [R = (S)-*CHMePh (3) or CHMe₂ (4)]. The pyrazolate moiety adopts an unusual triply bridging μ₃-η¹:η¹:η¹-mode of coordination in these clusters.