Effect of finite extensibility on the viscoelastic properties of a styrene–butadiene rubber vulcanizate in simple tensile deformations up to rupture

Stress–strain and rupture data were determined on an unfilled styrene–butadiene vulcanizate at temperatures from ?45 to 35°C and at extension rates from 0.0096 to 9.6 min^?1. The data were represented by four functions: (1) the well-known temperature function (shift factor) a_T; (2) the constant strain rate modulus, F(t,T), reduced to temperature T₀ and time t/a_T, i.e., T₀F(t/a_T)/T; (3) the time-dependent maximum extensibility, λ_m(t/a_T); and (4) a function Ω(χ) where χ = (λ ? 1)λ_m⁰/λ_m, in which λ is the extension ratio and λ_m⁰ is the maximum extensibility under equilibrium conditions. The constant strain rate modulus characterizes the stress–time response to a constant extension rate at small strains, within the range of linear response; λ_m is a material parameter needed to represent the response at large λ; and Ω(χ) represents the stress–strain curve of the material in a reference state of unit modulus and λ_m = λ_m. The shift factor a_T was found to be sensibly independent of extension. At all values of t/a_T for which the maximum extensibility is time-independent, the relaxation rate was also found to be independent of λ. These observations indicate that the monomeric friction coefficient is strain-independent over the ranges of T and λ covered in the present study. It was found that λ_m⁰ = 8.6 and that the largest extension ratio at break, (λ_b)_max, is 7.3. Thus, rupture always occurs before the network is fully extended.     

Unusual Bonding and Properties in Main Group Element Chemistry: Rational Synthesis,Characterization, and Experimental Electron Density Determination of Mixed‐Valent Tetraphosphetes

Five dispirocyclic λ³,λ⁵‐tetraphosphetes [{R₂Si(NR¹)(NR²)P₂}₂] (R¹ = R² and R¹ ≠ R²) are easily prepared in almost quantitative yields via photolysis of the respective bis(trimethylsilyl)phosphanyldiazaphosphasiletidines with intense visible light. These deep‐yellow low‐coordinate phosphorus compounds can be considered as the first higher congeners of the well‐known cyclodiphosphazenes. The tetraphosphetes are remarkably stable in air and show unexpected molecular properties related to the unique bonding situation of the central four‐π‐electron four‐membered phosphorus ring. The extent of rhombic distortion of the central P₄ ring is remarkable due to an unusually acute angle at the σ²‐phosphorus atoms. All of the P?P bonds are approximately equal in length. The distances are in the middle of the range given by phosphorus single and double bonds. The anisotropic absorption of visible light that can easily be observed in the case of the yellow/colorless dichroic crystals of [{Me₂Si(NtBu)(NtBu)P₂}₂] and the exceptional ³¹P NMR chemical shift of the σ²‐phosphorus atoms are the most remarkable features of the λ³,λ⁵‐tetraphosphetes. In the case of [{Me₂Si(NtBu)(NtBu)P₂}₂], the Hansen–Coppens multipole model is applied to extract the electron density from high‐resolution X‐ray diffraction data obtained at 100 K. Static deformation density and topological analysis reveal a unique bonding situation in the central unsaturated P₄ fragment characterized by polar σ‐bonding, pronounced out‐of‐ring non‐bonding lone pair density on the σ²‐phosphorus atoms, and an additional non‐classical three‐center back‐bonding contribution.     

Ultimate tensile properties of elastomers. VII. Effect of crosslink density on time–temperature dependence

Data on tensile strength and elongation at break for a series of Viton A-HV vulcanizates are discussed. The data were obtained at various extension rates at temperatures from ?5 to 230°C (25 ? T — T_g ? 260°C) on seven vulcanizates having crosslink densities v_e (estimated from C₁ in the Mooney-Rivlin equation) from 0.46 × 10^?5 to 24.4 × 10^?5 mole/cm³. At an extension rate of 1 min^?1, an increase in v_e affects the tensile strength σ_b (based on the undeformed cross-sectional area) and the true tensile strength σ_bσ_b (based on the cross-sectional area of a deformed specimen) as follows: σ_b is essentially constant at a low temperature; it passes through a decided maximum at intermediate temperatures; and it increases to a plateau at elevated temperatures. In contrast, λ_bσ_b decreases markedly at all temperatures, an exception being the most lightly crosslinked vulcanizate(s). Application of time—temperature superposition to the ultimate-property data gave log a_T; its temperature dependence is that typical of nonpolar rubbery polymers. Data on the vulcanizates were compared in corresponding temperature states by plotting log 273σ_b/T, log 273λ_bσ_b/T, and (λ_b — 1)/(λ_b — 1)_max against logt_b/(t_b)_max, where t_b is the temperature-reduced time to break and (t_b)_max is the value at which the ultimate extension ratio λ_b attains its maximum, (λ_b)_max. Except for the most lightly crosslink vulcanizate, the comparison shows that 273λ_bσ_b/T and (λ_b — 1)/(λ_b — 1)_max are substantially independent of (or only weakly dependent on) crosslink density, that 273λ_b/T increases with v_e, and that 273λ_b/T ∝? v_e^0.6 and λ_b ∝? v_e^?0.4 at a large value of t_b/(t_b)_max.     

Atomic level picture of stress relaxation in polymer melts

We have been developing a physical picture on the atomic level of stress relaxation in polymer melts by means of computer simulation of the process in model systems. In this article we treat a melt of freely jointed chains, each with N = 200 bonds and with excluded-volume interactions between all nonbonded atoms, that has been subjected to an initial constant-volume uniaxial extension. We consider both the stress relaxation history σ(t) based on atomic interactions, and the stress history σ_e(t; N_R) based on subdividing the chain into segments with N_R bonds each, with each segment regarded as an entropic spring. It is found that at early times σ(t) > σ_e(t; N_R) for all N_R, and that, for the remainder of the simulation, there is no value of N_R for which σ(t) = σ_e(t; N_R) for an extended period; by the end of the simulation σ(t) has fallen just below the value σ_e(t; 50). The decay of segment orientation, 〈P₂(t; N_R)〉, and of bond orientation 〈P₂(t; 1)〉, is computed during the simulation. It is found that the decay of the atom-based stress σ(t) is closely related to that of 〈P₂(t; 1)〉. This result may be understood through the concept of steric shielding. The change in local structure of the polymer melt during relaxation is also studied. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 143–154, 1998     

Phosphorus Centers of Different Hybridization in Phosphaalkene‐Substituted Phospholes

Phosphole‐substituted phosphaalkenes (PPAs) of the general formula Mes*P?C(CH₃)?(C₄H₂P(Ph))?R 5 a – c (Mes*=2,4,6‐tBu₃Ph; R=2‐pyridyl ( a ), 2‐thienyl ( b ), phenyl ( c )) have been prepared from octa‐1,7‐diyne‐substituted phosphaalkenes by utilizing the Fagan–Nugent route. The presence of two differently hybridized phosphorus centers (σ²,λ³ and σ³,λ³) in 5 offers the possibility to selectively tune the HOMO–LUMO gap of the compounds by utilizing the different reactivity of the two phosphorus heteroatoms. Oxidation of 5 a – c by sulfur proceeds exclusively at the σ³,λ³‐phosphorus atom, thus giving rise to the corresponding thioxophospholes 6 a – c . Similarly, 5 a is selectively coordinated by AuCl at the σ³,λ³‐phosphorus atom. Subsequent second AuCl coordination at the σ²,λ³‐phosphorus heteroatom results in a dimetallic species that is characterized by a gold–gold interaction that provokes a change in π conjugation. Spectroscopic, electrochemical, and theoretical investigations show that the phosphaalkene and the phosphole both have a sizable impact on the electronic properties of the compounds. The presence of the phosphaalkene unit induces a decrease of the HOMO–LUMO gap relative to reference phosphole‐containing π systems that lack a P?C substituent.     

Growth of carbonyl index in the degradation of polypropylene by UV irradiation

The growth of the carbonyl index in the degradation of polypropylene by UV irradiation, with and without UV stabilizer, has been measured and interpreted. From the kinetics of the degradation process the mathematical expression of the growth of the carbonyl index was derived using the steady-state treatment for short-lived intermediates, except for the alkyl radical P. For polypropylene without UV stabilizer and for polypropylene with UV absorber or excited-state quencher, the growth of the carbonyl index was related to UV irradiation time by X = Ae^λ1t + Be^λ2t. While in the presence of an antioxidant or radical scavenger, the general form was X = Ae^λ1t + Be^λ2t + C. The values of A, B, λ₁, λ₂, and C were obtained by fitting the experimental data into the equation. It was found that the error was about 15%.     

Application of a new structural theory to polymers. I. Uniaxial stress in crosslinked rubbers

A continuum rheological theory, endowed with generalized structural significance, has recently been developed. Based on nonequilibrium thermodynamics, it relates stress σ, strain rate \documentclass{article}\pagestyle{empty}\begin{document}$\dot \varepsilon$\end{document} and temperature in terms of material evolution through a series of structural states. The theory has previously had success in dealing with crystalline metals and surface physics, and here it is applied to crosslinked rubbery polymers in the nominally amorphous condition. Structure is believed to be related to interchain associations, chain entanglements, chain ends, and other defects in the hypothetical ideal network which by itself would lead to neo-Hookean predictions in uniaxial deformation, σ^nH ∝ λ² — λ^?1, where λ is the stretch ratio. Predictions are made for σ(λ) in both tension and compression and shown to be more compatible with data than either σ^nH(λ) or the Mooney—Rivlin expression σ^MR(λ). Only two parameters are required, moduli G_o (reflecting initial structure) and G_s (the steady-state condition), and rate effects are incorporated through G_o(\documentclass{article}\pagestyle{empty}\begin{document}$\dot \varepsilon$\end{document}) and G_s(\documentclass{article}\pagestyle{empty}\begin{document}$\dot \varepsilon$\end{document}). The phenomena of yielding and stress softening in cyclic tensile loading are also predicted, suggesting advantages to this approach relative to conventional viscoelastic continuum models.     

A new spectral memory of filled rubbers

We recently discovered that shearing particle‐reinforced rubbers in oscillation at a frequency f_a at a small strain γ_a (e.g., ～1% strain) for time t_a can often produce a spectrum hole or drop in the strain‐dependent dissipation spectra of the materials. The location of the hole (or localized perturbation in the loss modulus or loss tangent) depends on the aging strain amplitude γ_a. The depth of this hole is influenced by both the oscillatory aging frequency f_a and the aging duration t_a, and follows a simple power relationship of the product of f_a and t_a. The exponent for the power relationship is a function of filler concentration. These attributes of the spectral hole in filled rubbers are not sensitive to the frequency used to postanalyze the hole. This new memory effect occurs at very small strains and involves material stiffening during the strain aging, and both of those features are quite different from the Mullins effect in filled elastomers. We interpret this newly discovered memory character of filled rubbers from a much broader concept of structure pinning in a condensed frustrated system and consider that the agglomeration of filler particles in rubber matrix shares common physics with granular materials and glass‐forming materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 859–869, 2010     

Aluminium Diphosphamethanides: Hidden Frustrated Lewis Pairs

The synthesis and characterisation of two aluminium diphosphamethanide complexes, [Al(tBu)₂{κ²P,P′‐Mes*PCHPMes*}] ( 3 ) and [Al(C₆F₅)₂{κ²P,P′‐Mes*PCHPMes*}] ( 4 ), and the silylated analogue, Mes*PCHP(SiMe₃)Mes* ( 5 ), are reported. The aluminium complexes feature four‐membered PCPAl core structures consisting of diphosphaallyl ligands. The silylated phosphine 5 was found to be a valuable precursor for the synthesis of 4 as it cleanly reacts with the diaryl aluminium chloride [(C₆F₅)₂AlCl]₂. The aluminium complex 3 reacts with molecular dihydrogen at room temperature under formation of the acyclic σ²λ³,σ³λ³‐diphosphine Mes*PCHP(H)Mes* and the corresponding dialkyl aluminium hydride [tBu₂AlH]₃. Thus, 3 belongs to the family of so‐called hidden frustrated Lewis pairs.     

Molecular mobility of ultrasonically devulcanized silica‐filled poly(dimethyl siloxane)

We used NMR relaxation and pulsed‐gradient diffusion measurements at 70 °C in precipitated silica‐filled poly(dimethylsiloxane) (PDMS; silicone rubber) after crosslinking, after subsequent devulcanization by intense ultrasound, and after subsequent revulcanization. As in unfilled PDMS, transverse relaxation displays three distinct rate components attributed to an entangled and crosslinked network (similar in T₂), light sol plus dangling network fragments, and unreactive trace oligomers. Ultrasound produces copious amounts of extractable sol. The T₂ relaxation times decreased modestly with increasing filler content, but they and the components' proportions correlated mainly with the sol fraction, that is, the network degradation. In rupturing the network, devulcanization produces large diffusing fragments and dangling ends; revulcanization largely reverses these effects. The rates and amplitudes of the bimodal diffusivity distribution confirmed this conclusion. The weakness of the effects of filler suggests that ultrasound devulcanization is easily adaptable to the recycling of the preponderantly particulate‐filled industrial rubbers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 454–465, 2003     

A sulfur(II) complex of a dithioimidodiphosphinate

The structure of bis[P,P‐di‐tert‐butyl‐N‐(di‐tert‐butylphosphorothioyl)phosphinimidothioato‐κS]sulfur(II) toluene solvate (systematic name: 5,13‐dibutyl‐7,7,11,11‐tetramethyl‐8,9,10‐trithia‐6,12‐diaza‐5λ⁵,7λ⁵,11λ⁵,13λ⁵‐tetraphosphaheptadeca‐6,11‐diene‐5,13‐dithione toluene solvate), C₃₂H₇₂N₂P₄S₅·C₇H₈, at 173 K has monoclinic (C2/c) symmetry. The S^II centre of (SP^tBu₂NP^tBu₂PS–)₂S is coordinated in an S‐monodentate fashion to two [(SP^tBu₂)₂N]⁻ monoanions. The molecule resides on a twofold axis which bisects the central S atom. The internal P—S distance is ca 0.19 Å longer than the terminal P=S bond and there is a compensating alternation in P—N bond distances. The central S—S—S angle is 106.79 (8)°. The toluene solvent molecule is disordered about a twofold axis.     

The superposition of small deformations on large deformations: Measurements of the incremental relaxation modulus for a polyisobutylene solution

The incremental relaxation modulus ΔG(t) for a concentrated solution of polyisobutylene has been determined from step-shear experiments in which a small deformation Δγ was superimposed on a large deformation γ₁; ΔG(t) was found to decrease with increasing γ₁ and to increase with the time t_e after the imposition of the large deformation. It was also observed that the “apparent relaxation specturm” associated with δG(t) narrows and shifts to shorter times when compared to the spectrum associated with the linear viscoelastic relaxation modulus G(t). The results are well described by the nonlinear constitutive equation of the BKZ elastic fluid theory.     

Evaluation of the relaxation modules from the response to a constant rate of strain followed by a constant strain

The stress response σ(t) to a constant rate of strain $ \dot \varepsilon $ ε during the period 0 < t ≤ t^* and to the constant strain ε^* $ ( = \dot \varepsilon t*) $ thereafter is considered in terms of the Boltzmann superposition principle. When t ≤ t^*, the data directly give the constant-rate modulus F (t) ≡ σ(t)/ε(t), which can be converted straightforwardly into the relaxation modulus E(t). Results from illustrative calculations show that a reduction in the relaxation rate effects a decrease in [σ(t^*)/ε^*]/E(t^*) and also in the time at which [σ(t)/ε^*]/E(t) becomes essentially unity. To evaluate E(t) at t > t^*, F(t) is first obtained from σ(t) and F(t ? t^*) by using a derived equation similar to that presented by Meissner. Thereafter, F(t) is transformed into E(t). For illustration, E(t) for a rubbery solid is evaluated over some 2.5 decades of time from its response to a strain rate of 0.25 min^?1 for 0.40 min and thereafter to the attained strain of 0.10 for 5.4 min.     

Synthesis and Reactions of the Novel Diphosphine,iPrN = C[CH2P(NiPr2)2]2

Abstract

The aldimine nBuN=CHiPr and phosphorus trichloride react to give phosphorus(III) amides in a 1:1 and 2:1 molar ratio. An imine-enamine tautomerism is proposed. In a [4+1] cycloaddition reaction diacetyl-(N-n-butyl)diimine and λ³σ³P-species, RPCl₂ or EtOPCl₂, form 1,2,3λ⁵σ⁴ -diazaphospholenes¹. The same diimine and (Et₂N)₂ PCl is furnishing annellated azaphospholenes¹. A 1,3,4λ⁵ σ⁴ -diazaphospholanium is formed from a λ³σ³ -phosphenium and iPrN=CMe₂ ². Phosphorus(III) amides P(NR₂)₃ (R= Me, Et) and O-trimethylsilylated diacetyldioxime give rise to yield the first monocyclic pentaazaphosphoranes.     

Tayloring standard TDDFT approaches for computing UV/Vis transitions in thiocarbonyl chromophores

We report the development of an accurate computational procedure for the calculation of the n → π* (λ_max?1) and π → π* (λ_max?2) transitions of a set of thiocarbonyl derivatives. To ensure converged results, all calculations are carried out using the 6‐311+G(2df,p) basis set for time‐dependent calculations, and the 6‐311G(2df,p) for the ground‐state geometrical optimization. Starting with two hybrids, PBE0 and B3LYP, the Hartree–Fock exchange percentage (α) used is optimized in order to reach excitation energies that fit experimental data. It turns out that BLYP(α) is the more adequate functional for calibration. For the n → π* excitation, the optimal α value lies in the 0.10–0.20 interval, whereas for the π → π* process setting α equal to 0.10 provides the most accurate results. The corresponding mean absolute errors (MAE) are limited to 17 nm for λ_max?1, and to 10 nm for λ_max?2, allowing a consistent and accurate prediction of both transitions. We also assess the merits of the ZINDO//AM1 scheme and it turns out that the semi‐empirical method only provides a poor prediction of the λ_max of thiocarbonyl derivatives, especially for the n → π* transition. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Entanglement networks of 1,2-polybutadiene crosslinked in states of strain. VII. Stress-birefringence relations

Crosslinks are introduced by γ irradiation into 1,2-polybutadiene while strained in uniaxial extension near T_g with stretch ratio λ₀, thereby trapping a proportion of the entanglements originally present. The stress at any subsequent strain λ is accurately given by the sum σ_N + σ_x, where σ_N is the stress contributed by a trapped entanglement network with λ = 1 as reference and a Mooney–Rivlin stress-strain relation, and σ_x is that contributed by a crosslink network with λ = λ₀ as reference and neo-Hookean stress-strain relation. The birefringence is accurately given as δn = ?_Nσ_N + ?_xσ_x, where the ?'s are the respective stress-optical coefficients. From measurements at λ = λ₀ where σ_x = 0, ?_N can be determined separately. For polymer with 88% 1,2 microstructure, ?_N and ?_x are nearly equal and independent of irradiation dose, though strongly dependent on temperature. For polymer with (95–96)% 1,2, ?_N and ?_x are different (even opposite in sign) and dependent on dose. This behavior is associated with a side reaction of cyclization by the γ irradiation, which is inhibited by the 1,4 moiety in the polymer with lesser 1,2 content. It is responsible for residual birefringence in the state of ease (λ = λ_s) where σ_N = –σ_x and the stress is zero.     

Über die Oxo‐cyclotetraphosphane (PBut)4O1–4

Contributions to the Chemistry of Phosphorus. 243 On the Oxocyclotetraphosphanes (PBu^t)₄O_1–4 Under suitable conditions, the reaction of tetra‐tert‐butylcyclotetraphosphane, (PBu^t)₄, with dry atmospheric oxygen gives rise to the corresponding monoxide (PBu^t)₄O ( 1 ) which has been isolated by column chromatography. The reaction with hydrogen peroxide furnishes a mixture of oxocyclotetraphosphanes (PBu^t)₄O_1–4 consisting of two constitutionally isomeric dioxides (PBu^t)₄O₂ ( 2 a , 2 b ), the trioxide (PBu^t)₄O₃ ( 3 ), and the tetraoxide (PBu^t)₄O₄ ( 4 ), in addition to 1 . According to the ³¹P NMR parameters the oxygen atoms are exclusively exocyclically bonded to the phosphorus four‐membered ring. Which of the P atoms are present as λ⁵‐phosphorus follows from the different low‐field shifts of the individual P nuclei compared with the starting compound. Accordingly, 1 is 1,2,3,4‐Tetra‐tert‐butyl‐1‐oxocyclotetraphosphane, 2 a and 2 b are 1,2,3,4‐Tetra‐tert‐butyl‐1,2‐dioxo‐ and ‐1,3‐dioxocyclotetraphosphane, respectively, 3 is 1,2,3,4‐Tetra‐tert‐butyl‐1,2,3‐trioxocyclotetraphosphane, and 4 is 1,2,3,4‐Tetra‐tert‐butyl‐1,2,3,4‐tetraoxocyclotetraphosphane. When the oxidation reaction proceeds a fission of the P₄ ring takes place.     

Viscoelasticity of textile fibers at finite strains

Experimental data obtained from stress–strain curves of five different textile fibers, at a series of different, constant strain rates covering a range of 6^1/2 decades have been used to study two methods of nonlinear viscoelastic analysis proposed elsewhere. According to the first of these, time and strain effects are factorizable so that stress σ, strain ε and time t are related by the equation σf₁(ε)/ε = f(t),. This is shown to be unsatisfactory with the present materials, but an empirical modification to σf₁(ε)/ε = f₂(ε) + f(t) is satisfactory. According to the second, general nonlinear viscoelastic behavior can be described by an equation which reduces to the form σ/ε = F₁(t) + εF₂(t) + ε²F₃(t) + when applied to extension at a constant strain rate. This series is shown to be strongly divergent except at fairly small stains. In fact, if it is truncated after about three terms, which are as many as can be estimated with any significance in the present experiments, it is applicable only to strains of about 3–4% and less. Numerical techniques which enable standard statistical procedures to be used have been devised to perform the above analyses and are described in detail.     

Mechanical properties of natural rubber vulcanizates in finite deformation

Mechanical properties of four kinds of natural rubber vulcanizates differing in vulcanization conditions, and consequently in degree of crosslinking (having values of the Mooney-Rivlin constant C₁ ranging from 0.68 to 1.98) were observed under orthogonal biaxial stretching in a range of strain invariants I_i from 3.4 to 9.0 (extension ratios λ_i from 0.7 to 3.0). The results obtained were analyzed by two methods. One method employed the Valanis-Landel postulate that the strain-energy function W(λ₁, λ₂, λ₃) is a separable symmetric function of the principal extension ratios, i.e., W(λ₁,λ₂,λ₃) = w(λ₁) + w(λ₂) + w(λ₃); the other utilized the contour plots of ?W(I₁, I₂)/?I₁ and ?W(I₁, I₂)/?I₂ surface within the (I₁, I₂) domain. The postulate for W was examined in detail with good agreement with experimental results. The dependences of ?W(I₁, I₂)/?I₁ and ?W(I₁, I₂)/?I₂ surfaces on the degree of crosslinking and temperature were further investigated, with the following conclusions. The surfaces have fairly steep slopes for the region of relatively small deformation (i.e., I₁ < 5) and become flat with increasing I_i for all the test specimens. The slope becomes less steep with decreasing degree of crosslinking. The values of ?W/?I₁ increase linearly and the ?W(I₁,I₂)/?I₂ surface becomes flat, both with increasing temperature: i.e., the temperature dependence of ?W/?I₁ further depends on I_i. The ?W(I₁,I₂)/?I₂ surface has a maximum near 40°C.     

Palladium(II)‐Komplexe des 1,1,3,3,5,5‐Hexakis(dimethylamino)‐λ5‐[1,3,5]triphosphinins

Palladium(II) Complexes of 1,1,3,3,5,5‐Hexakis(dimethylamino)‐λ⁵‐[1,3,5]triphosphinine 1,1,3,3,5,5‐Hexakis(dimethylamino)‐1λ⁵‐3λ⁵‐5λ⁵‐[1,3,5]triphosphinine ( 5 ) reacts with (benzonitrile)₂PdCl₂ to give the chelate complex dichloro(dodeca‐N‐methyl‐1λ⁵,3λ⁵,5λ⁵‐1,3,5‐triphosphinine‐1,1,3,3,5,5‐hexaamin‐C²,C⁴)palladium ( 6 ). In a pyridine‐d₅ solution of 6 the complex dichloro(dodeca‐N‐methyl‐1λ⁵,3λ⁵,5λ⁵‐1,3,5‐triphosphinine‐1,1,3,3,5,5‐hexaamin‐C²)((²H₅)pyridine‐N)palladium ( 7 ) is formed. The solute 7 could not be isolated as a solid, because elimination of the solvent regenerates 6 quantitatively. Properties, nmr and ir spectra of 6 and 7 are reported. 6 is characterized by the results of an X‐ray structural analysis.