The Azo(Azoxy) Functionality as a π2 Component in Photo [2+2] cycloadditions ‘syn’- and ‘anti’-3,4-diazatricyclo[4.2.2.22,5]dodeca-3,7-diene,syntheses, photolyses,X-ray-structure analysis,and PE spectra

The propensity of the N?N bond to undergo photo [2 + 2] cycloadditions has been further explored. In the specifically designed 1,5-azo/enes 1–3 , no [2 + 2] cycloaddition has been observed upon either direct or sensitized excitation with light of various wave lengths at temperatures down to 77 K, in line with expectations based on X-ray ( 1 : d = 2.71 Å, ω = 129°) and PE measurements ( 1 : I₁ = 8.0₀, I₂ = 9.0₅ eV; 2 ; I₁ = 8.0₀, I₂ = 9.2₅eV). The steric/stereoelectronic demands for the participation of the N?N bond in pericyclic reactions are clearly more stringent than those for the C?C bond.     

New Heptalenes Substituted with Extended π-Systems

The synthesis of π-substituted heptalenecarboxylates or -dicarboxylates, starting with the easily available dimethyl 9-isopropyl-1, 6-dimethylheptalene-4, 5-dicarboxylate ( 2b ), are described. Treatment of 2b with t-BuOK and C₂Cl₆ at ?78° leads to the chemoselective introduction of a Cl substituent in Me-C(1) (see 5b in Scheme 1). Formation of the corresponding triphenylphosphonium salt 7b via the iodide 6b (Scheme 2) allowed a Wittig reaction with cinnamaldehyde in the two-phase system CH₂Cl₂/2N NaOH. Transformation of the 4, 5-dicar-boxylate of 2b into the corresponding pseudo-ester 10b allowed the selective reduction of the carbonyl function at C(4) with DIBAH to yield the corresponding 4-carbaldehyde 11b (Scheme 3). Wittig reaction of 11b with (benzyl) triphenylphosphonium bromide led to the introduction of the 4-phenylbuta-1, 3-dienyl substituent at C(4). The combination of both Wittig reactions led to the synthesis of the 1, 4-bis(4-phenylbuta-1, 3-dienyl)-substituted heptalene-5-carboxylate (all-E)- 17b (Scheme 5). In a similar manner, by applying a Horner-Wadsworth-Emmons reaction, followed by the Wittig reaction, the donor-acceptor substituted heptalene-5-carboxylate (E;E)- 22b was synthesized (Scheme7). Most of these new heptalenes are in solution, at room temperature, in thermal equilibrium with their double-bond shifted (DBS) isomers. In the case of (all-E)- 17b and (E;E)- 22b , irradiation of the thermal equilibrium mixture with light of λ -(439 ± 10) nm led to a strong preponderance ( > 90%) of the DBS isomers 17a and (E;E)- 22a , respectively (Schemes 6 and 7). Heating of the photo-mixtures at 40° re-established quickly the thermal equilibrium mixtures. Heptalenes-carboxylates (all-E)- 17a and (E;E)- 22a which represent the off-state of a 1,4-conjugative switch (CS) system show typical heptalene UV/VIS spectra with a bathochromically shifted heptalene band III and comparably weak heptalene bands II and I which appear only as shoulders (Figs. 4 and 5). In contrast, the DBS isomers (all-E)- 17b and (all-E)- 22b , equivalent to the on-state of a 1,4-CS system, exhibit extremely intense heptalene bands I and, possibly, II which appear as a broad absorption band at 440 and 445 nm, respectively, thus indicating that the CSs (all-E)- 17a ?(all-E)- 17b and (E;E)- 22a ?(E;E)- 22b are perfectly working.     

Intramolekularer Antiferromagnetismus in [Cr2(μ-NH2)3(NH3)6]I3

Intramolecular Antiferromagnetism in [Cr₂(μ-NH₂)₃(NH₃)₆]I₃ The magnetism of [Cr₂(μ-NH₂)₃(NH₃)₆]I₃ which consists of binuclear cations with NH₂^?-bridged face-sharing octahedral coordination polyhedra and a metal-metal separation of 264.9 pm can be explained by antiferromagnetically exchange-coupled Cr^III-3d³ pairs. The magnetochemical analysis in the temperature range 5 K – 295 K on the basis of the isotropic Heisenberg model (spin Hamiltonian ? = ?2 J?₁ · ?₂) leads to the parameter value J = ?98(3) cm^?1. Compared to the exchange coupling in corresponding binuclear chromium compounds with OH^? bridges and identical metal-metal separation the strength of the coupling is significantly enhanced (J_NH2/J_OH ≈? 1.6).     

Transition‐Metal π‐Ligation of a Tetrahalodiborane

The reaction of tetraiododiborane (B₂I₄) with trans‐[Pt(BI₂)I(PCy₃)₂] gives rise to the diplatinum(II) complex [{(Cy₃P)(I₂B)Pt}₂(μ₂:η³:η³‐B₂I₄)], which is supported by a bridging diboranyl dianion ligand [B₂I₄]^2?. This complex is the first transition‐metal complex of a diboranyl dianion, as well as the first example of intact coordination of a B₂X₄ (X=halide) unit of any type to a metal center.     

Pyrolysis of 2-phenylethylamines heats of formation of aminomethyl radicals R2NCH2 · (R = H,CH3)

A kinetic study of the very low-pressure pyrolysis of ethylbenzene (I), 2-phenylethylamine (II), and N,N-dimethyl 2-phenylethylamine (III) above 900 K yields the heats of formation of aminomethyl (A) and N,N-dimethylaminomethyl (B) radicals: ΔH_{?, 300 K}(A) = 30.3 and ΔH_{?, 300 K}(B) = 27.5 kcal/mol. The difference of stabilization energies E_s, (relative to methyl radicals): Δ = E_s(B) ? E_s(A) = (2 ± 1) kcal/mol, conforms to similar effects in methyl substituted alkyl and amino free radicals.     

π–π Dimerization of a mono(pyridyl–imine) platinum(II) chelate

The cation of the title complex salt, chlorido{2,2‐dimethyl‐N‐[(E)‐1‐(pyridin‐2‐yl)ethylidene]propane‐1,3‐diamine}platinum(II) tetrafluoridoborate, [PtCl(C₁₂H₁₉N₃)]BF₄, exhibits a nominally square‐planar Pt^II ion coordinated to a chloride ion [Pt—Cl = 2.3046 (9) Å] and three unique N‐atom types, viz. pyridine, imine and amine, of the tridentate Schiff base ligand formed by the 1:1 condensation of 1‐(pyridin‐2‐yl)ethanone and 2,2‐dimethylpropane‐1,3‐diamine. The cations are π‐stacked in inversion‐related pairs (dimers), with a mean plane separation of 3.426 Å, an intradimer Pt...Pt separation of 5.0785 (6) Å and a lateral shift of 3.676 Å. The centroid (Cg) of the pyridine ring is positioned approximately over the Pt^II ion of the neighbouring cation (Pt...Cg = 3.503 Å).     

NMR spectra of Δ3- and Δ4-pyrrolin-2-one

The spectra of Δ³- and Δ⁴-pyrrolin-2-one were analysed and the sign of all the coupling constants determined by tickling and triple resonance experiments. A positive allylic interaction (J_xz in 2 ) is reported and four-bond couplings are discussed in particular. Deuterium exchange affords evidence for the tautomeric equilibrium between 1 and 2 .     

1‐(β‐d‐Erythrofuranosyl)adenosine

The title compound, also known as β‐erythroadenosine, C₉H₁₁N₅O₃, (I), a derivative of β‐adenosine, (II), that lacks the C5′ exocyclic hydroxymethyl (–CH₂OH) substituent, crystallizes from hot ethanol with two independent molecules having different conformations, denoted (IA) and (IB). In (IA), the furanose conformation is ^OT₁–E₁ (C1′‐exo, east), with pseudorotational parameters P and τ_m of 114.4 and 42°, respectively. In contrast, the P and τ_m values are 170.1 and 46°, respectively, in (IB), consistent with a ²E–²T₃ (C2′‐endo, south) conformation. The N‐glycoside conformation is syn (+sc) in (IA) and anti (−ac) in (IB). The crystal structure, determined to a resolution of 2.0 Å, of a cocrystal of (I) bound to the enzyme 5′‐fluorodeoxyadenosine synthase from Streptomyces cattleya shows the furanose ring in a near‐ideal ^OE (east) conformation (P = 90° and τ_m = 42°) and the base in an anti (−ac) conformation.     

Kinetic studies of the reactions CH2I2 + HI⇄CH3I + I2 and 2 CH3I⇄CH4 + CH2I2 the heat of formation of the iodomethyl radical

The rate of the reaction CH₂I₂ + HI ? CH₃I + I₂ has been followed spectrophotometrically from 201.0 to 311.2°. The rate constant for the reaction fits the equation, log (k₁/M^?1 sec^?1) = 11.45 ± 0.18 - (15.11 ± 0.44)/θ. This value, combined with the assumption that E₂ = 0 ± 1 kcal/mole, leads to ΔH (CH₂I, g) = 55.0 ± 1.6 kcal/mole and DH (H? CH₂I) = 103.8 ± 1.6 kcal/mole. The kinetics of the disproportionation, 2 CH₃I ? CH₄ + CH₂I₂ were studied at 331° and are compatible with the above values.     

Synthesis and crystal structure of a copper(II) complex of the tridentate ligand di-(2-benzimidazolylmethyl)imine

A copper complex [Cu(IDB)Cl] · 0.5[CuCl₄]?·?H₂O (1) (IDB?=?di(2-benzimidazolylmethyl)imine) was synthesized and its structure was determined by X-ray single crystal diffraction. In this complex, the central copper(II) ion is four-coordinate, IDB serves as a neutral tridentate chelating ligand for the tetragonal copper ion. The cyclic voltammogram of complex 1 in CH₃CN gave two reversible redox waves (E _1/2,1?=??0.14?V and E _1/2,2?=?0.08?V versus SCE) which correspond to the Cu(II,?II)/Cu(I,?II) and Cu(II,?II)/Cu(II,?I) redox processes, respectively.     

Orientational Preference of Long,Multicenter Bonds in Radical Anion Dimers: A Case Study of π‐[TCNB]22− and π‐[TCNP]22−

The similar shape and electronic structure of the radical anions of 1,2,4,5‐tetracyanopyrazine (TCNP) and 1,2,4,5‐tetracyanobenzene (TCNB) suggest a similar relative orientation for their long, multicenter carbon?carbon bond in π‐[TCNP]₂^2? and in π‐[TCNB]₂^2?, in good accord with the Maximin Principle predictions. Instead, the two known structures of π‐[TCNP]₂^2? have a D_2h(θ=0°) and a C₂(θ=30°) orientation (θ being the dihedral angle that determines the rotation of one radical anion relative to the other along the axis that passes through center of the two six‐membered rings). The only known π‐[TCNB]₂^2? structure has a C₂(θ=60°) orientation. The origin of these preferences was investigated for both dimers by computing (at the RASPT2/RASSCF(30,28) level) the variation with θ of the interaction energy (E_int) and the variation of the E_int components. It was found that: 1) a long, multicenter bond exists for all orientations; 2) the E_int(θ) angular dependence is similar in both dimers; 3) for all orientations the electrostatic component dominates the value of E_int(θ), although the dispersion and bonding components also play a relevant role; and 4) the Maximin Principle curve reproduces well the shape of the E_int(θ) curve for isolated dimers, although none of them reproduce the experimental preferences. Only after the (radical anion)^.? ??? cation⁺ interactions are also included in the model aggregate are the experimental data reproduced computationally.     

Methyl 4‐O‐β‐D‐mannopyranosyl β‐D‐xylopyranoside

Methyl β‐D‐mannopyranosyl‐(1→4)‐β‐D‐xylopyranoside, C₁₂H₂₂O₁₀, (I), crystallizes as colorless needles from water, with two crystallographically independent molecules, (IA) and (IB), comprising the asymmetric unit. The internal glycosidic linkage conformation in molecule (IA) is characterized by a ϕ′ torsion angle (O5′_Man—C1′_Man—O1′_Man—C4_Xyl; Man is mannose and Xyl is xylose) of −88.38 (17)° and a ψ′ torsion angle (C1′_Man—O1′_Man—C4_Xyl—C5_Xyl) of −149.22 (15)°, whereas the corresponding torsion angles in molecule (IB) are −89.82 (17) and −159.98 (14)°, respectively. Ring atom numbering conforms to the convention in which C1 denotes the anomeric C atom, and C5 and C6 denote the hydroxymethyl (–CH₂OH) C atom in the β‐Xylp and β‐Manp residues, respectively. By comparison, the internal glycosidic linkage in the major disorder component of the structurally related disaccharide, methyl β‐D‐galactopyranosyl‐(1→4)‐β‐D‐xylopyranoside), (II) [Zhang, Oliver & Serriani (2012). Acta Cryst. C 68 , o7–o11], is characterized by ϕ′ = −85.7 (6)° and ψ′ = −141.6 (8)°. Inter‐residue hydrogen bonding is observed between atoms O3_Xyl and O5′_Man in both (IA) and (IB) [O3_Xyl...O5′_Man internuclear distances = 2.7268 (16) and 2.6920 (17) Å, respectively], analogous to the inter‐residue hydrogen bond detected between atoms O3_Xyl and O5′_Gal in (II). Exocyclic hydroxymethyl group conformation in the β‐Manp residue of (IA) is gauche–gauche, whereas that in the β‐Manp residue of (IB) is gauche–trans.     

Kinetics of the mercury(II)‐catalyzed substitution of coordinated cyanide ion in hexacyanoruthenate(II) by nitroso‐R‐salt

The kinetics and mechanism of Hg²⁺‐catalyzed substitution of cyanide ion in an octahedral hexacyanoruthenate(II) complex by nitroso‐R‐salt have been studied spectrophotometrically at 525 nm (λ_max of the purple‐red–colored complex). The reaction conditions were: temperature = 45.0 ± 0.1°C, pH = 7.00 ± 0.02, and ionic strength (I) = 0.1 M (KCl). The reaction exhibited a first‐order dependence on [nitroso‐R‐salt] and a variable order dependence on [Ru(CN)₆^4?]. The initial rates were obtained from slopes of absorbance versus time plots. The rate of reaction was found to initially increase linearly with [nitroso‐R‐salt], and finally decrease at [nitroso‐R‐salt] = 3.50 × 10^?4 M. The effects of variation of pH, ionic strength, concentration of catalyst, and temperature on the reaction rate were also studied and explained in detail. The values of k₂ and activation parameters for catalyzed reaction were found to be 7.68 × 10^?4 s^?1 and E_a = 49.56 ± 0.091 kJ mol^?1, ΔH^≠ = 46.91 ± 0.036 kJ mol^?1, ΔS^≠ = ?234.13 ± 1.12 J K^?1 mol^?1, respectively. These activation parameters along with other experimental observations supported the solvent assisted interchange dissociative (I_d) mechanism for the reaction. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 215–226, 2009     

Synthesis and Crystal Structure of meso-Δ,Λ-μ-Peroxo-μ-hydroxobis[bis(ethylenediamine)rhodium(III)]trifluoromethane Sulfonate

The reaction of the meso-diol, Δ,Λ-[(en)₂Rh(OH)₂Rh(en)₂]⁴⁺, with aqueous H₂O₂ and 1 equiv. of NaOH at 90° forms the μ-peroxo-μ-hydroxo-bridged species Δ,Λ-[(en)₂Rh(O₂,OH)Rh(en)₂]³⁺ in a yield of ca. 50%. The compound was crystallized as perchlorate and trifluoromethanesulfonate salts. The structure of the latter salt was determined by single-crystal X-ray diffraction. The crystals are triclinic with space group P1 and lattice constants a = 11.895(5), b = 12.491(4), c = 13.053(5) Å, α = 103.98(3), β = 92.59(3), γ = 119.52(6)°. The distances of the metal centres to the bridging peroxo ligand are 1.999(8) and 1.983(6) Å. The O? O distance in the peroxo group is 1.521(14) Å, and the dihedral angle of the Rh? O? O? Rh unit deviates 65° from planarity. The peroxo complex reacts reversibly with acid, and spectrophotometric studies suggest that the reaction involves protonation of the peroxo bridge, with pK_a = 2.70(2) at 25° in 1M NaClO₄.     

Cadmium(II) iodide and thiocyanate complexes adopted by polycyclic 1,4‐bis(pyridazin‐4‐yl)benzene: interplay of coordination and π–π stacking interactions

New complexes containing the 1,4‐bis(pyridazin‐4‐yl)benzene ligand, namely diaquatetrakis[1,4‐bis(pyridazin‐4‐yl)benzene‐κN²]cadmium(II) hexaiodidodicadmate(II), [Cd(C₁₄H₁₀N₄)₄(H₂O)₂][Cd₂I₆], (I), and poly[[μ‐1,4‐bis(pyridazin‐4‐yl)benzene‐κ²N²:N^2′]bis(μ‐thiocyanato‐κ²N:S)cadmium(II)], [Cd(NCS)₂(C₁₄H₁₀N₄)]_n, (II), demonstrate the adaptability of the coordination geometries towards the demands of slipped π–π stacking interactions between the extended organic ligands. In (I), the discrete cationic [Cd—N = 2.408 (3) and 2.413 (3) Å] and anionic [Cd—I = 2.709 (2)–3.1201 (14) Å] entities are situated across centres of inversion. The cations associate via complementary O—H...N^2′ hydrogen bonding [O...N = 2.748 (4) and 2.765 (4) Å] and extensive triple π–π stacking interactions between pairs of pyridazine and phenylene rings [centroid–centroid distances (CCD) = 3.782 (4)–4.286 (3) Å] to yield two‐dimensional square nets. The [Cd₂I₆]²⁻ anions reside in channels generated by packing of successive nets. In (II), the Cd^II cation lies on a centre of inversion and the ligand is situated across a centre of inversion. A two‐dimensional coordination array is formed by crosslinking of linear [Cd(μ‐NCS)₂]_n chains [Cd—N = 2.3004 (14) Å and Cd—S = 2.7804 (5) Å] with N²:N^2′‐bidentate organic bridges [Cd—N = 2.3893 (12) Å], which generate π–π stacks by double‐slipped interactions between phenylene and pyridazine rings [CCD = 3.721 (2) Å].     

Wolves in Sheep's Clothing: μ‐Oxo‐Diiron Corroles Revisited

For well over 20 years, μ‐oxo‐diiron corroles, first reported by Vogel and co‐workers in the form of μ‐oxo‐bis[(octaethylcorrolato)iron] (Mössbauer δ 0.02 mm s^?1, ΔE_Q 2.35 mm s^?1), have been thought of as comprising a pair antiferromagnetically coupled low‐spin Fe^IV centers. The remarkable stability of these complexes, which can be handled at room temperature and crystallographically analyzed, present a sharp contrast to the fleeting nature of enzymatic, iron(IV)‐oxo intermediates. An array of experimental and theoretical methods have now shown that the iron centers in these complexes are not Fe^IV but intermediate‐spin Fe^III coupled to a corrole^.2?. The intramolecular spin couplings in {Fe[TPC]}₂(μ‐O) were analyzed via DFT(B3LYP) calculations in terms of the Heisenberg–Dirac–van Vleck spin Hamiltonian H=J_Fe–corrole(S_Fe?S_corrole)+J_Fe–Fe′(S_Fe?S_Fe′)+J_{Fe′–corrole}(S_Fe′?S_corrole′), which yielded J_Fe–corrole=J_{Fe′–corrole′}=0.355 eV (2860 cm^?1) and J_Fe–Fe′=0.068 eV (548 cm^?1). The unexpected stability of μ‐oxo‐diiron corroles thus appears to be attributable to charge delocalization via ligand noninnocence.     

Theoretical Investigation into Electronic Structures and Charge Transfer Properties of π‐Conjugated System with Different Combinations of Thiophene and Vinyl/Butadiene

A series of combinations of thiophene and vinyl/butadiene were investigated by ab initio and DFT methods to explore their electronic structures and charge transfer properties. The results show that increasing thiophene ring and vinyl number is a rational strategy to raise the HOMO energy levels and lower the LUMO energy levels. Moving the vinyl from the periphery to the core has the slight effect on the HOMO and LUMO energy levels. Furthermore, replacing the middle vinyl and end‐capped vinyl of 3b (T5V4) with the butadiene can lower LUMO energy levels and then facilitate the electron injection. Above all, the close hole and electron reorganization energies (λ_h and λ_e) are observed from these compounds. However, the λ_es are smaller than their respective λ_hs in some compounds, which is relatively rare in organic materials. Especially, the promising ambipolar material 3c (T5B4) is recommended theoretically for possessing the equivalent minimum λ_h (0.24 eV) and λ_e (0.24 eV). The absorption wavelengths exhibit red shifts with the increasing of the thiophene ring and the vinyl number under the same configuration, which correspond to the reverse order of ΔE_H‐L and E_g. The linear relationships are found between experimental lowest singlet excited energies (E_exp) with theoretical values ΔE_H‐L and E_g.     

Structures and Dynamic Solution Behavior of Cationic,Two‐Coordinate Gold(I)–π‐Allene Complexes

A family of seven cationic gold complexes that contain both an alkyl substituted π‐allene ligand and an electron‐rich, sterically hindered supporting ligand was isolated in >90 % yield and characterized by spectroscopy and, in three cases, by X‐ray crystallography. Solution‐phase and solid‐state analysis of these complexes established preferential binding of gold to the less substituted C?C bond of the allene and to the allene π face trans to the substituent on the uncomplexed allenyl C?C bond. Kinetic analysis of intermolecular allene exchange established two‐term rate laws of the form rate=k₁[complex]+k₂[complex][allene] consistent with allene‐independent and allene‐dependent exchange pathways with energy barriers of ΔG^≠₁=17.4–18.8 and ΔG^≠₂=15.2–17.6 kcal mol^?1, respectively. Variable temperature (VT) NMR analysis revealed fluxional behavior consistent with facile (ΔG^≠=8.9–11.4 kcal mol^?1) intramolecular exchange of the allene π faces through η¹‐allene transition states and/or intermediates that retain a staggered arrangement of the allene substituents. VT NMR/spin saturation transfer analysis of [{P(tBu)₂o‐binaphthyl}Au(η²‐4,5‐nonadiene) ]⁺SbF₆^? ( 5 ), which contains elements of chirality in both the phosphine and allene ligands, revealed no epimerization of the allene ligand below the threshold for intermolecular allene exchange (ΔG^≠_298K=17.4 kcal mol^?1), which ruled out the participation of a η¹‐allylic cation species in the low‐energy π‐face exchange process for this complex.     

Two pentadehydropeptides with different configurations of the ΔPhe residues

Comparison of the crystal structures of two pentadehydropeptides containing ΔPhe residues, namely (Z,Z)‐N‐(tert‐butoxycarbonyl)glycyl‐α,β‐phenylalanylglycyl‐α,β‐phenylalanylglycine (or Boc⁰–Gly¹–Δ^ZPhe²–Gly³–Δ^ZPhe⁴–Gly⁵–OH) methanol solvate, C₂₉H₃₃N₅O₈·CH₄O, (I), and (E,E)‐N‐(tert‐butoxycarbonyl)glycyl‐α,β‐phenylalanylglycyl‐α,β‐phenylalanylglycine (or Boc⁰–Gly¹–Δ^EPhe²–Gly³–Δ^EPhe⁴–Gly⁵–OH), C₂₉H₃₃N₅O₈, (II), indicates that the Δ^ZPhe residue is a more effective inducer of folded structures than the Δ^EPhe residue. The values of the torsion angles ϕ and ψ show the presence of two type‐III′β‐turns at the Δ^ZPhe residues and one type‐II β‐turn at the Δ^EPhe residue. All amino acids are linked trans to each other in both peptides. β‐Turns present in the peptides are stabilized by intramolecular 4→1 hydrogen bonds. Molecules in both structures form two‐dimensional hydrogen‐bond networks parallel to the (100) plane.     

1, 3, 4, 4'‐Tetra(triphenylphosphanimin)‐2‐iodo‐2‐butenal‐4‐carboniumiodid, [O=C(NPPh3)C(I)=C(NPPh3)‐C(NPPh3)2]+I‐

Pale yellow single crystals of [O=C(NPPh₃)C(I)=C(NPPh₃)‐C(NPPh₃)₂]⁺I^‐·1.5 thf ( 1 ·1.5 thf) have been obtained by the reaction of INPPh₃ with thallium in thf suspension. They are characterized by IR spectroscopy and by a crystal structure determination. 1 ·1.5 thf crystallizes in the monoclinic space group P2₁/n, Z = 4, lattice dimensions at ‐83?C: a = 1101.7(1), b = 3449.0(2), c = 2000.4(1) pm, β = 104.88(1)?, R₁ = 0.0382. 1 can be understood as a cationic variation of (Z)‐2‐butenale in which all H atoms are substituted by triphenylphosphoraneimine residues and by a iodine atom, respectively.