Conductometric titration study of the reactions of some trialkylphosphines with bromine,iodine and iodine bromide

The reactions of tributyl-, trioctyl-, and tricyclohexyl-phosphine with bromine, iodine and iodine bromide have been studied by conductometric titration in acetonitrile. In general, evidence was obtained for the formation, in solution, of highly conducting 0.5 : 1, 1 : 1, and 2 : 1 adducts. The 1 : 1 and 2 : 1 adducts (R₃PX₂ and R₃PX₄) were isolated and the electrolytic conductivity of their acetonitrile solutions measured. Values of molar conductivity are reported; these point to strong electrolyte behaviour, hence the 1 : 1 and 2 : 1 adducts must be formulated as the phosphonium salts, R₃PX⁺X^? and R₃PX⁺X₃^? respectively.     

The identification of some new mixed‐valence phosphorus thiohalides in solution

The reaction of a phosphorus trihalide PX₃ (X = Cl, Br, or I) with a thiophosphorus halide P(S)Y₃ (Y = Cl or Br) in the presence of zinc powder as a halogen acceptor has led to the formation of several new mixed‐valence phosphorus species in solution. These include examples with two or three phosphorus atoms present, such as Y₂P(S)PX₂ and Y₂P(S)P(X)P(S)Y₂, or halogen exchange derivatives thereof. Structural assignments for these species have been made on the basis of ³¹P NMR shift, multiplicity, intensity, and coupling constant data. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:156–160, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20590     

Theoretical studies of the oxidative addition of PhBr to Pd(PX3)2 and Pd(X2PCH2CH2PX2) (X = Me, H, Cl)

The density functional theory calculations were used to study the influence of the substituent at P on the oxidative addition of PhBr to Pd(PX₃)₂ and Pd(X₂PCH₂CH₂PX₂) where X = Me, H, Cl. It was shown that the C_ipso-Br activation energy by Pd(PX₃)₂ correlates well with the rigidity of the X₃P-Pd-PX₃ angle and increases via the trend X = Cl < H < Me. The more rigid the X₃P-Pd-PX₃ angle is, the higher the oxidative addition barrier is. The exothermicity of this reaction also increases via the same sequence X = Cl < H < Me. The trend in the exothermicity is a result of the Pd(II)-PX₃ bond strength increasing faster than the Pd(0)-PX₃ bond strength upon going from X = Cl to Me. Contrary to the trend in the barrier to the oxidative addition of PhBr to Pd(PX₃)₂, the C_ipso-Br activation energy by Pd(X₂PCH₂CH₂PX₂) decreases in the following order X = Cl > H > Me. This trend correlates well with the filled d_π orbital energy of the metal center. For a given X, the oxidative addition reaction energy was found to be more exothermic for the case of X₂PCH₂CH₂PX₂ than for the case of PX₃. This effect is especially more important for the strong electron donating phosphine ligands (X = Me) than for the weak electron donating phosphine ligands (X = Cl).     

Novel Properties of Iodophosphonium Ions: Kinetically Labile Behaviour and Secondary Bonding

Abstract

Neutral species R₃PX₂ in equilibria with halogenophosphonium halides R₃PX⁺X^? do not always contain hypervalent phosphorus (10-P-5)! Iodophosphonium ions R₃PI⁺ show R₃P-I… X interaction in many cases, leading to hypervalent iodine (10-I-2). Evidence for secondary IX bonds is provided by n.m.r. spectra and X-ray crystal structure determinations.     

Quantum-chemical study of donor-acceptor interactions in rhodium(I) carbonyl carboxylate complexes with phosphine ligands

The DFT B3LYP method was used to optimize the geometries, calculate the IR spectra, and analyze the electronic structures of carbonyl(carboxylato)(phosphine)rhodium(I) complexes, namely, trans-[Rh(Cl)(CO)(PPh₃)₂], trans-[Rh(OCOR)(CO)(PPh₃)₂] (R = H, CH₃, and CF₃), and trans-[Rh(OCOH)(CO)(PX₃)₂], and free PX₃ molecules (X = H, F, CH₃, i-Pr, Cy, and Ph). A linear correlation between v(CO) in the IR spectra of trans-[Rh(OCOH)(CO)(PX₃)₂] and the HOMO energy of the free PX₃ molecule was found for phosphines with nonaromatic substituents X. It was concluded that the electronic state of the CO group is mainly determined by the σ-donor properties of phosphines. The distinctive features of the electronic structure of triphenylphosphine are discussed.     

Backbone modified small bite-angle diphosphines: Synthesis and molecular structures of [M(CO)4{X2PC(RR)PX2}] (M = Mo, W; X = Ph, Cy; R = H, Me, Et, Pr, allyl, R = Me, allyl)

A range of new small bite-angle diphosphine complexes, [M(CO)₄{X₂PC(R¹R²)PX₂}] (M = Mo, W; X = Ph, Cy; R¹ = H, Me, Et, Pr, allyl, R² = Me, allyl), have been prepared via elaboration of the methylene backbones in [M(CO)₄(X₂PCH₂PX₂)] as a result of successive deprotonation and alkyl halide addition. When X = Ph it proved possible to replace both methylene protons but for X = Cy only one substitution proved possible. This is likely due to the electron-releasing nature of the cyclohexyl groups but may also be due to steric constraints. Attempts to prepare the bis(allyl) substituted complex [Mo(CO)₄{Ph₂PC(allyl)₂PPh₂}] were only moderately successful. The crystal structures of nine of these complexes are presented.     

Intramolecular Interactions of Phosphor-Containing Groups with an Aromatic Fragment in Different Conformations

Abstract

Geometrical and electronic structure of conformers was studied by optical spectroscopy and quantum chemistry methods. The interaction mechanism of phosphor-containing groups with an aromatic fragment in YC₆H₄PX₂ (Y = H, Cl, Me, OMe, NMe₂, C(O)OR; × = Alk, OAlk, NAlk₂, Cl) and YC₆H₄P(Z)X₂ (Y = H, C1, Me, OMe, NMe₂; × = Alk, OAlk, NAlk₂, F, C1; Z = O, S) compounds is discussed. In case of bisector conformation (A), where the benzene ring plane coincides with a XPX-angle bisectrix, ll-acceptor action of phosphorus-containing groups increases with X varying in a series: Alk <NAlk₂ ≈ OAlk ≤ F4 << C1. These properties are displayed in ground and excited states of molecules, and are determined by interaction of PX₂ and P(Z)X₂ vacant group orbitals antisymmetric with respect to bisector plane with aromatic fragment π-orbitals. For phosphorchloride groups [sgrave]-π-conjugation dominates and the d-π-conjugation contribution is small. π-acceptor effect for P(0)X₂is weaker than for PX₂ and P(S)X₂ groups (especially in excited states) which is due to competitive transfer of electron density from oxygen to PX₂ fragment. In case of the gonal conformation (B) where benzene ring and bisector plane of PX₂ fragment are perpendicular, π-donor effect of PAlk₂ group is found to be 2–4 times weaker than for NAlk₂. According to quantum-chemical calculations with the MNDO method ArPX₂ the stabilization of conformer B for ArPX₂ increases in a series X: C1 <C=N <F <H <CH₃; and for ArP(0)X₂ the main conformation is (A).     

Endo- and Exocyclic Substitutions in α-P4S3I2

Two isomers each of α-P₄S₂SeX₂ and α-P₄SSe₂X₂ (X=Cl, Br) have been identified by ³¹P-NMR spectroscopy in mixtures obtained from thermal reaction of PX₃ and P₄S_1.4Se_1.6. Systematic changes in chemical shifts and coupling constants with electronegativity of the ligand by exocyclic substitution and with alteration of the molecular geometry by the replacement of sulfur by selenium are reported.     

A theoretical study of the elimination process of methane from a platinum complex

A theoretical analysis of the dissociative reaction cis-PtH(CH₃)(PX₃)₂ → Pt(PX₃)₂ + CH₄ is presented. Several aspects of the effect on the mechanism of this reductive elimination when the substituent X is changed (X₃  (CH₃)₃, case I and X₃  CH₂Cl(CH₃)₂, case II), are considered and compared with the corresponding experimental facts. This indicates the following: the kinetic barrier for case I is small and even if a concerted mechanism is implied, an almost spontaneous process is strongly indicated. The activation energy is lowered in case II, where the presence of an electronegative substituent makes even easier the performance of a spontaneous process. The study of the reaction pathway was carried out through an Extended Hückel calculation.     

Effective charges on atoms in some phosphorus-containing compounds from XPS data

We have calculated the charges on the atoms in 19 phosphorus compounds of the type PX₃, PX₃P, YPX₃, PX₅ by solution of the system of equations connecting the chemical shifts E_b of the inner electronic levels of the atoms with charges qA on the atoms. We have shown that for their compounds, we cannot choose a universal constant of proportionality between E_b(P) and qp. The technique used in this work, taking into account the molecular potential, allows us to describe well the effect of substitutents on the charge of the phosphorus atom. We observe a correlation between the charges qp obtained within the given approach and the MNDO method.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 4, pp. 485–490, July–August, 1990.     

Untersuchung der Iouenassoziation im System Natriummetavanadat-Natriumchlorid-Wasser mit der Ultrazentrifuge

Zusammenfassung Am Beispiel des Systems Na₄(VO₃)₄-NaCl-H₂O wird untersucht, in welcher Weise Ultrazentrifugenmessungen im Sedimentationsgleichgewicht durchgeführt werden müssen, um die molare Masse und die Ladungszahl von Polymerelektrolyten in ternären Systemen unter der Bedingung von nicht vernachlässigbaren Wechselwirkungen zwischen Polymerund Fremdelektrolyt zu bestimmen. Es erweist sich, daß die experimentellen scheinbaren molaren Massen nicht nur auf die Polymerkonzentration Null extrapoliert werden müssen, sondern auch auf die Fremdelektrolytkonzentration Null. Es gelingt, die Ableitung (alnyPX_z/amBx)mPX_z an der StellemPX_z = 0 mol kg_-1 mit einer scheinbaren mittleren Ladungszahlz _app des Polymeranions zu korrelieren. Zwischen dieser und der stöchiometrischen Ladungszahlz des Polymeranions besteht die Beziehungz _app = Z =az, so daß die Dissoziationskonstante des Polymerelektrolyten für die summarische Dissoziation berechnet werden kann. Die aus dieser Korrelation folgenden Abhängigkeiten der scheinbaren mittleren Ladungszahlen und der Ableitung (alnypx _z /amBX)Mpx _z = 0 von der Konzentration des Fremdelektrolyten werden experimentell bestätigt.

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Summary The system Na₄(VO₃)₄-NaCl-H₂0 is taken as an example for ultracentrifugal measurements at sedimentation equilibrium to determine the molar mass and the valency of a polymer electrolyte in a ternary system when interactions exist between the polymer and the supporting electrolyte. The experimental apparent molar mass is obtained by extrapolation to zero value of concentration of both the polymeric and supporting electrolyte. It is possible to correlate the quantity (alnyPX _z /amBX)^mPX_z at the point ^m PX _z = 0 mole kg^-1 with the apparent valency _zapp of the polymeric anion.z _app is related to the stoichiometric valency by the equationz _app = _z =a.Z. Thus the dissociation constant can be calculated for complete dissociation of the polymer electrolyte. The dependence of _zapp and (aln _y PX _z /a ^m _BX ) ^m PX _z = 0 on concentration of the supporting electrolyte called for in the correlation is verified experimentally.

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Mit 4 Abbildungen und 4 Tabellen     

The effects of isotopomers in the state-selected photofragmentation of BCl3+, PCl3+ and PBr3+

Analysis of the shapes of time-of-flight (TOF) peaks of singly-charged polyatomic cations produced in photoelectron–photoion coincidence spectra allows a determination of the total mean kinetic energy released into translational motion of the fragment species, 〈KE〉_t. In turn, this value can indicate the mechanism of unimolecular photofragmentation. We show that in cases where the daughter ion has more than one isotopomer, allowance must be made for them in analysing the TOF distributions. Otherwise, values for 〈KE〉_t are obtained which are too large. Examples are given from recent work by us on state-selected (BCl₃⁺)¹→BCl₂⁺+Cl and (PX₃⁺)¹→PX₂⁺+X (X=Cl,Br).     

Über die kristallstrukturen von Me3SnO2PCl2 und Me3SnO2PMe2 und das schwingungsspektrum von Me3SnO2PMe2

Me₃SnO₂PMe₂ is prepared by treatment of Me₃SnNEt₂ with Me₂PO₂H in methylene chloride. The vibrational spectrum is discussed. Crystal structure determinations from X-ray diffraction data have been carried out with single crystals of Me₃SnO₂PMe₂ (R 0.076, 819 observe independent reflexions), and Me₃SnO₂PCl₂ (R 0.051, 1127 observed independent reflexions), showing polymer chains of SnMe₃ groups and O₂PX₂ (X = Cl, Me) units in both cases. The phosphinate chains form vast helices whereas the dichlorophosphate forms almost planar chains.     

Substituent effects in second row molecules: Molecular orbital studies of phosphorus(III) compounds

Substituent effects in directly bonded P(III) compounds are investigated by ab initio MO calculations of relative energies and the results compared with those for the corresponding nitrogen species. The investigation covers substitution by X = BH₂, CH₃, NH₂, OH, F in PHX^-, PH₂X, and PH₃X⁺ series molecules with some attention also to PX₃ and PX₃H⁺ species. Except for compounds containing the π-acceptor substituent BH₂, σ-interactions dominate substitution behaviour but the second row species tolerate electron withdrawal better than their first row analogues, the severe destabilization of NH₂X and NH₃X⁺ by σ-electron withdrawal being absent from PH₂X and PH₃X⁺. In contrast to the σ-withdrawing NH₂ group, the PH₂ group is characterized as a mild σ-donor. PH^- is a σ-donor and PH⁺₃ a σ-acceptor. π-Bonding to the second row atom is an important means of maintaining electroneutrality in the PH₃X⁺ series, where dπ functions have a bigger role than pπ functions.     

Transition Metal Chemistry of Diphosphazanes and Diphosphazane Monosulfides

Abstract

The reactions of chiral diphosphazanes. Ph₂PN((S)-*CHMePh)PPhY (Y =Ph, N₂C₃HMe₂-3,5) with [CpRu (PPh₃)₂Cl] and those of the monosulfides, Ph₂PN(R)P(S)Ph₂ (R = (S)-*CHMePh or CHMe₂) with Ru₃(CO)₁₂. [RhCl(cod)]₂ and [RhCI(CO)₂]₂ have been investigated. Molybdenum-palladium heterometallic complexes of the diphosphazanes, MeN(P(OR)₂)₂ (R = CH₂CF₃ or Ph) have been synthesised. Some unusual complexes have been obtained by the reductive carbonylation of cobalt and ruthenium halides in the presence of diphosphazanes, RN(PX₂)₂ (R = Me, X = OCH₂CS or OPh; R = CHMe₂, X = Ph). The structures of the products have been elucidated by NMR spectoscopy and in some cases confirmed by X-ray crystallography (e.g., 1–4).     

Bestimmung der molaren Masse und der Ladungszahl von Polymerelektrolyten mit der Ultrazentrifuge

Zusammenfassung In der vorliegenden Arbeit wird das Sedimentationsgleichgewicht der Systeme Na₆[H₂W₁₂O₄₀]—NaCI—H₂O und Na₆[H₂W₁₂O₄₀]—NaClO₄— H2O untersucht. Die scheinbare molare Masse Mapp des Natriummetawolframats wird in beiden Systemen als Funktion der Natriummetawolfrarnat-Anfangspartialdichte ₀ ^PX _z gemessen. Durch lineare Extrapolation der Funktion Mapp = Mapp (PP,, ) auf die Polymerelektrolyt-Anfangspartialdichte Null können die Grenzwerte der scheinbaren molaren Masse (Mapp)o ermittelt werden. Aus den (Mapp)o-Werten wird die Abhängigkeit der Größe (ln _PXz /m _BX ) _mPXz von der NaCI- bzw. NaClO₄-Molalität berechnet.Die Bestimmung der molaren Masse und der (stöchiometrischen) Ladungszahl eines Polymerelektrolyten aus den experimentell ermittelten (Mapp)o-Werten unter Anwendung der Lamm-Williams-Gleichung wird diskutiert. Zur Ermittlung der beiden Größen müssen mehrere Versuchsreihen mit zwei verschiedenen Fremdelektrolyten durchgeführt werden. Externe Messungen sind nicht erforderlich.Man erhält auf diese Weise verläßliche Werte so-wohl der molaren Masse als auch der (stächiometrischen) Ladungszahl.

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Summary The sedimentation equilibria of the systems sodium metatungstate-sodium chloride-water and sodium metatungstate-sodium perchlorate-water are investiated. In both systems the apparent molecular mass Mapp of sodium metatungstate (PX _z) is measured in dependence on partial density ₀ ^PX _z before centrifugation. By linear extrapolation of the function Mapp = Mapp ( ₀ ^PX _z the limiting value (Mapp)o for ₀ ^PX _z = 0 is obtained. The variation with sodium chloride and sodium perchlorate molality of the quantity (ln _{PX z} ^m _BX )mPX_z is calculated from (Mapp)o data.The determination of the molecular mass and the algebraic valency of a polymeric ion by means of the (Mapp)o values calculated by Lamm-Williams equation is discussed. In order to obtain these two quantities at least two series of experiments are required, each of which using a different supporting electrolyte. External measurements are not necessary. In this way reliable values for the molecular mass as well as for the stoichiometric valency are obtained.

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Mit 5 Abbildungen und 3 Tabellen     

Pentafluorphenyl-substituierte Phosphorane [1]

Pentafluorophenyl Substituted Phosphoranes Synthesis and reactions of penthafluorphenyl substituted phosphoranes, (C₆F₅)_n?PX_5?n, (X = F, Cl), are reported. The stereochemistry of these compounds is discussed.     

Influence d'un ou de plusieurs groupements tertiobutyle sur le comportement magnétooptique du doublet libre d'un atome de phosphore tricoordonné

A magnetooptical study of some halogenotertiobutylphosphines is performed in order to improve the so-called regular relationship which seemed to exist between the magnetic rotation, ?dP, of the lone pair and the bond angles in PX₃ compounds. It is clearly shown that, in any case, ?dP is largely lower than the extreme value which was observed in PX₃ molecules for which XPX=100°. Thus, the existence of the previously invoked relationship vanishes and the question remains as to why there exists a maximum of ?dP for XPX of 100°.     

Synthetic,spectral, thermal and antimicrobial studies of bis(N,N‐dialkyldithiocarbamato)arsenic(III) and antimony(III) complexes with diphenyldithiophos‐phate and diphenyldithiophosphinate

Bis(N,N‐dialkyldithiocarbamato)arsenic(III)/antimony(III) diphenyldithiophosphate/diphenyldi‐thiophosphinate complexes of the type [R₂NCS₂]₂MS(S)PX₂ [where M = As and Sb; NR₂ = N(CH₃)₂, N(C₂H₅)₂ and N(CH₂)₄; X = OC₆H₅ and C₆H₅] have been synthesized and characterized by physico‐chemical, spectral [UV, IR and NMR (¹H, ¹³C and ³¹P)] and thermal (TG, DTA and DSC) analysis. The TG analysis shows single‐step decomposition of the complex to Sb₂S₃. These complexes have been screened for antibacterial and antifungal activity using the disc diffusion method. All the complexes have shown good activity as antibacterial and antifungal agents, which increased on increasing the concentration. Chloroamphenicol and terbinafin were used as standards for the comparison. Copyright © 2006 John Wiley & Sons, Ltd.     

Analyse conformationnelle theorique (methode CNDO/2) de quelques composes ditertiobutyles du phosphore (III) P(t-Bu)2X (X = H,F)

Optimized geometries and conformational analysis of P(t-Bu)₂F and P(t-Bu)₂H molecules are investigated within the framework of the CNDO/2 approximation. The CPC angles are found to be equal to 114° in agreement with the 113°8 value provided by X-ray study of the trans-NiBr₂ [P(t-Bu)₂F]₂ square planar complex. Therefore, it seems that the highest XPX value in the PX₃ series is observed for di-tert-butyl derivatives and not for the tri-tert-butylphosphine.