New conformational flexible phosphane and phosphane oxide macrobicycles

The synthesis of two large diastereomeric phosphane oxide macrobicycles 3 and 4 succeeded in comparatively good yield by a tripod-coupling strategy using the tripodal components 1 and 2 as building blocks. ¹H, ¹³C and ³¹P NMR spectra of the two cage compounds are in accordance with a time-averaged D_3h symmetry each, which in the case of 3 can be attributed to a fast interconversion of two degenerate in,out-structures. Kinetic measurements of the reduction of both diastereomeric macrobicycles, and the results of an inversion experiment also support the assumption that the phosphane and phosphane oxide cage molecules described herein are conformational flexible and undergo fast homeomorphic isomerisation. The bisiminophosphorane derivative 8 was prepared and assigned as an out,out-isomer. An alternative tripod-capping reaction between bisphenol 10 and capping reagent 2 did not result in the formation of macrobicyclic products. Instead, three complex structures 11, 12 and 13 with macrocyclic sub-units could be isolated.     

Palladium(II) complexes of phosphane ligands with ammonium-functionalized carbosilane substituents

The synthesis of diphenylarylphosphane and 1,2-bis(diarylphosphanyl)ethane ligands, where the aryl group is -C₆H₄CH₂CH₂SiMe₂CH₂OC₆H₄-3-NMe₂, their palladium(II) complexes, and their corresponding ammonium-quaternized derivatives is described. These new phosphanes were devised as models of potentially water-soluble dendritic carbosilane ligands, although the solubility brought about by the quaternized N-trimethylanilinium groups is scarce. The palladium(II) complexes have been fully characterized by ¹H, ¹³C, and ³¹P NMR spectroscopy and mass spectrometry, and have been tested in the Hiyama cross-coupling reaction between tri(methoxy)phenylsilane and 3-bromopyridine in aqueous sodium hydroxide solution.     

Synthesis, characterization, and coordination chemistry of several novel electroneutral phosphane ligands

The reaction of fluorocarbon (R_f) reagents C₂F₅Li or C₂F₃Li with diaminochlorophosphanes (R₂N)₂PCl produced four new phosphane ligands of the type (R₂N)₂P(R_f). Addition of (Et₂N)₂PCl to ethereal solutions of C₂F₅Li or C₂F₃Li produced (Et₂N)₂PC₂F₅1 and (Et₂N)₂PC₂F₃2; treatment of (C₄H₄N)₂PCl and (C₄H₈N)₂PCl with C₂F₅Li afforded (C₄H₄N)₂PC₂F₅3 and (C₄H₈N)₂PC₂F₅4. All ligands were isolated as colorless, high-boiling liquids. Substitution reactions of 1-4 with Mo(CO)₆ in a refluxing alkane solvent yielded complexes of the type (L)Mo(CO)₅ (L = (Et₂N)₂PC₂F₅, 5; (Et₂N)₂PC₂F₃6; (C₄H₄N)₂PC₂F₅7 and (C₄H₈N)₂PC₂F₅8) as colorless solids in low to moderate (25-62%) yields. Complexes 5, 7 and 8 were structurally characterized by single crystal X-ray diffraction. A comparison of IR stretching frequencies and X-ray bond length data suggests these ligands approximate the electronic influence of phosphites.     

Strategies for the synthesis of chiral, bidentate bis(perfluoroorganyl)phosphane ligands

Chiral, bidentate phosphane ligands, so-called PP ligands, are most frequently synthesized by reacting chiral ditosylates with diarylphosphanide ions.To use the P(CF₃)₂⁻ ion in nucleophilic substitution reactions, it is necessary to reduce the negative hyperconjugation, which is associated with a C-F activation. For this reason we synthesized different bis(trifluoromethyl)phosphanido complexes of mercury, silver and tungsten and investigated their use in nucleophilic substitution reactions. The most reactive compound, resulting from this study so far, is the pentacarbonylbis(trifluoromethyl)phosphanidotungstenate, [W{P(CF₃)₂}(CO)₅]⁻, which exhibits nearly the same bonding situation for the P(CF₃)₂ unit as in the free P(CF₃)₂⁻ ion. For use in synthesis of bis(trifluoromethyl)phosphane derivatives, Lewis acids are desirable, which stabilize the P(CF₃)₂⁻ ion by an intermediary formation of a donor acceptor adduct and can be split off after the synthesis of bis(trifluoromethyl)phosphane derivatives, as could be achieved using the extremely weak Lewis acids, CS₂ and acetone. These results could be established in the synthesis of the first example of an chiral, bidentate bis(trifluoromethyl)phosphane derivative.To synthesize a chiral, bidentate bis(pentafluorophenyl)phosphane derivative, a different synthetic strategy is necessary that does not involve the P(C₆F₅)₂⁻ ion, which decomposes even at low temperature. The implementation of functional P(CN)₂⁻ ions leads to the synthesis of functional, chiral bidentate dicyanophosphane derivatives which finally can be transformed into the corresponding bis(pentafluorophenyl)phosphane derivatives.     

Advances in Organophosphorus Chemistry Based on Dichloro(methyl)phosphane

Besides phosphorus trichloride and phosphane, dichloro(methyl)phosphane is gaining importance as a starting material for the synthesis of organophosphorus compounds. It provides ready access to phosphonic, phosphinic and phosphonous acid derivatives, as well as their secondary products. The synthetic and application potential of organophosphorus compounds—based on industrially produced dichloro(methyl)phosphane—is illustrated by means of numerous examples.     

Pseudoheptacoordination and pseudohexacoordination in tris(2-N,N-dimethylbenzylamino)phosphane

The phosphane (C(6)H(4)-2-CH(2)NMe(2))(3)P (1) upon recrystallization from various solvents yielded the structurally different forms 1A, 1C, 1B(1), and 1B(2). Phosphane oxide (C(6)H(4)-2-CH(2)NOMe(2))(3)PO (2) was obtained from 1 by oxidation with hydrogen peroxide. X-ray analysis provided molecular structures for 1A, 1B(1), 1B(2), and 2. Phosphanes 1A and 1B(1) have pseudohexacoordinate frameworks as a result of the formation of two P-N donor interactions, 1B(2) has a pseudoheptacoordinate geometry due to the presence of three P-N interactions, and 2 resides in a tetrahedral geometry. The presence of the flexible dimethylaminobenzyl group in 1A, 1C, 1B(1), and 1B(2) is reasoned to be responsible for this variation in coordination geometry. Phosphane oxide 2 has very strong donor oxygen atoms from N-oxide groups but they are involved in competition with the presence of hydrogen bonding, which results in the lack of donor coordination. High-resolution (1)H, (13)C, and (31)P NMR measurements are also reported. The results provide evidence for the low-energy threshold required to allow hypercoordinated phosphorus to alter coordination geometry.     

Dimerization of methyl acrylate by homogeneous transition metal catalysis. Part II. Activation of dihydridoruthenium(II) phosphane complexes by CF3 3H

The tail-to-tail dimerization of methyl acrylate (MA) in the presence of H₂Ru(PPh₃)₄ (1) or H₂(CO)Ru(PPh₃) ₃ (2) and CF₃SO₃H to give a mixture of linear dimers is described. In neat methyl acrylate at 85°C the reaction shows turnover numbers of 300 in 20 h and 640 in 7 d. Mechanistic studies show that the initial step of the reaction is the reduction of H₂Ru(PPh₃)₄ (1) by MA to form Ru(MA)₂ (PPh₃)₂ (5). After activation with CF₃SO₃H the catalytically active species contains only one phosphane ligand. The basic mechanistic features of the dimerization reaction have been revealed by ²H NMR spectroscopy involving the use of CF₃SO₃D. The deuterium-labelling studies indicate the intermediate formation of a ruthenium(II) hydride complex. Subsequent olefin insertions in this complex, followed by β-hydride elimination,lead to the linear dimeric products.     

Synthesis and structures of (3-methyl-2-pyridyl)diphenylphosphane derivatives of metal clusters

An unsymmetric bidentate ligand (3-methyl-2-pyridyl)diphenylphosphane (P(Mepy)Ph₂) is able to react with various tetranuclear transition metal clusters such as HRuCo₃(CO)₁₂, HRuRh₃(CO)₁₂ and Rh₄(CO)₁₂. The synthesis and crystal structures of HRuCo₃(CO)₁₀(P(Mepy)Ph₂) (1), HRuRh₃(CO)₁₀(P(Mepy)Ph₂) (2), RuRh₂(CO)₉(P(Mepy)Ph) (3) and Rh₆(CO)₁₄(P(Mepy)Ph₂) (4) are described. In 1, 2 and 4 the phosphane ligand replaces the carbonyls and acts as a bridging bidentate P-N group. The formation of 3 includes degradation of both the metal cluster core and the ligand itself. One of the P-C bonds in the ligand is cleaved and the ligand caps a metal triangle with a bridging phosphido group together with the nitrogen donor. The reaction between dinuclear Rh₂(CO)₄Cl₂ and P(Mepy)Ph₂ gives a binuclear Rh₂(μ-CO)Cl₂(P(Mepy)Ph₂)₂ (5) with bridging ligands in a head-to-tail arrangement. The crystal structure is also given.     

The Molecular Structure of the 1:1 Adduct of Silver Cyanide with Tri(1‐cyclohepta‐2,4,6‐trienyl)phosphane,Ag(CN)[P(C7H7)3]

The complex Ag(CN)[P(C₇H₇)₃] is the first (and so far only) mononuclear 1:1 derivative of AgCN with a tertiary phosphane ligand.     

A Cu(I) cluster bearing a bridging phosphane ligand

The solid state structure of a Cu(I) cluster bearing bridging phosphane ligands is described. This Cu₄ cluster results from a formal Cl-abstraction of the CH₂Cl₂ solvent. This derivative is the first example of a multinuclear Cu(I) complex bearing bridging phosphane ligands in which the Cu(I) centers have different coordination geometries. The four Cu(I) ions participate in metallophilic interactions within this cluster. Interestingly, despite the gross molecular structure being highly dissymmetrical, the μ-P atoms bridge symmetrically the metal centers.     

Synthese monomerer Silber(I)‐Halogenid‐Komplexe mit T‐förmigem Bau – Kristallstrukturanalyse von [P(C6H4CH2NMe2‐2)3]AgBr

Synthesis of Monomeric T‐Shaped Silver(I) Halide Complexes – Crystal Structure Analysis of [P(C₆H₄CH₂NMe₂‐2)₃]AgBr Treatment of the tetrapodal phosphane P(C₆H₄CH₂NMe₂‐2)₃ ( 1 ) with equimolar amounts of the silver(I) halides AgX ( 2 a : X = Cl, 2 b : X = Br) produces in tetrahydrofuran at 25 °C the monomeric silver(I) complexes [P(C₆H₄CH₂NMe₂‐2)₃]AgX with planar coordination at the Ag atoms ( 3 a : X = Cl, 3 b : X = Br) in excellent yields. From complex 3 b a single X‐ray crystal structure analysis was carried out. Mononuclear 3 b crystallizes in the monoclinic space group P2₁/c with the cell parameters a = 14.504(6), b = 11.034(3), c = 17.604(5) Å, β = 102.86(4)°; V = 2746.6(16) ų; Z = 4; 2953 observed unique reflections, R₁ = 0.0805. Complex 3 b consists of monomeric sub‐units with a planar T‐shaped arrangement formed by the atoms Ag1, N1, P1 as well as Br1, whereby the P1–Ag1–Br1 array is almost linear orientated.     

Enantioselective Phosphine‐Catalyzed Formal [4+4] Annulation of α,β‐Unsaturated Imines and Allene Ketones: Construction of Eight‐Membered Rings

The first highly enantioselective phosphine‐catalyzed formal [4+4] annulation has been developed. In the presence of amino‐acid‐derived phosphines, the unprecedented [4+4] annulations between benzofuran/indole‐derived α,β‐unsaturated imines and allene ketones proceeded smoothly, thus affording azocines, bearing either a benzofuran or an indole moiety, in excellent yields and with nearly perfect enantioselectivities (≥98 % ee in most cases). This work marks the first efficient asymmetric construction of optically enriched eight‐membered rings by phosphine catalysis.     

Silicon containing ferrocenyl phosphane ligands

New ferrocenyl phosphane ligands incorporating Si-P linkages, [(η-C₅H₄SiMe₂PR₂)₂Fe], where R=Ph and Me, and the corresponding metal complexes [Mo(CO)₄(L)] have been prepared and characterised. The molecular structures of [(η-C₅H₄SiMe₂PR₂)₂Fe], where R=Ph and Me have been determined by single crystal X-ray diffraction.     

Complexes of germanium(IV) fluoride with phosphane ligands: structural and spectroscopic authentication of germanium(IV) phosphane complexes

The first phosphane complexes of germanium(iv) fluoride, trans-[GeF(4)(PR(3))(2)] (R = Me or Ph) and cis-[GeF(4)(diphosphane)] (diphosphane = R(2)P(CH(2))(2)PR(2), R = Me, Et, Ph or Cy; o-C(6)H(4)(PR(2))(2), R = Me or Ph) have been prepared from [GeF(4)(MeCN)(2)] and the ligands in dry CH(2)Cl(2) and characterised by microanalysis, IR, Raman, (1)H, (19)F{(1)H} and (31)P{(1)H} NMR spectroscopy. The crystal structures of [GeF(4)(diphosphane)] (diphosphane = Ph(2)P(CH(2))(2)PPh(2) and o-C(6)H(4)(PMe(2))(2)) have been determined and show the expected cis octahedral geometries. In anhydrous CH(2)Cl(2) solution the complexes are slowly converted into the corresponding phosphane oxide adducts by dry O(2). The apparently contradictory literature on the reaction of GeCl(4) with phosphanes is clarified. The complexes trans-[GeCl(4)(AsR(3))(2)] (R = Me or Et) are obtained from GeCl(4) and AsR(3) either without solvent or in CH(2)Cl(2), and the structures of trans-[GeCl(4)(AsEt(3))(2)] and Et(3)AsCl(2) determined. Unexpectedly, the complexes of GeF(4) with arsane ligands are very unstable and have not been isolated in a pure state. The behaviour of the germanium(iv) halides towards phosphane and arsane ligands are compared with the corresponding silicon(iv) and tin(iv) systems.     

Tris(benzophenoneimino)phosphane and Related Compounds

A new group of bases with benzophenoneiminyl (bpi) moiety has been synthesized and characterized in this work. The title compound tris(benzophenoneimino)phosphane (P(bpi)₃) 1 was prepared with a convenient one-pot approach: benzophenone imine was deprotonated using MeMgCl and reacted with PBr₃ in diglyme. The method could be considered as a method of choice for preparing other (amino)phosphanes in case lithio-intermediates and/or protonated phosphane is out of consideration. Phosphane 1 is further used to prepare a range of related phosphonium cations and phosphazenes. Phosphonium cations were deprotonated to assess the stability of the resulting phosphonium ylides. In some cases, the bulky substances were capable of forming P−N heterocycles. Experimental (MeCN) and computational (MeCN, THF, gas-phase) basicities of benzophenone imine, phosphane 1 , phosphonium ylides, and phosphazenes, as well as some representative XRD structures, are presented and discussed.     

Gas-phase reactions of chromium and chromium fluoride cations CrFn+ (n = 0-4) with phosphane

The reactions of chromium and chromium fluoride monocations CrFn+ (n = 0-4) with phosphane are investigated by Fourier-transform ion cyclotron resonance mass spectrometry. Besides condensing slowly with phosphane, Cr+ is unreactive. The ionic products of the chromium fluoride cations are as follows: (i) CrF+ yields CrPH2+ and subsequently CrPH3+; (ii) from CrF2+, the ions PH3+, Cr+, and CrF2H+ are generated; and (iii) both CrF3+ and CrF4+ yield PH3+. The structure and formation of [Cr,P,H3]+ are investigated by collision-induced dissociation and isotopic labeling experiments. For the neutral species [P,H3,F2] formed by reaction of CrF2+ with phosphane, the structures are interrogated by quantum-mechanical calculations at the MP2/6-31++G** level of theory.     

Chemical bonding in phosphane and amine complexes of main group elements and transition metals

The geometries and bond dissociation energies of the main group complexes X3B-NX3, X3B-PX3, X3Al-NX3, and X3Al-PX3 (X = H, Me, Cl) and the transition metal complexes (CO)5M-NX3 and (CO)5M-PX3 (M = Cr, Mo, W) have been calculated using gradient-corrected density functional theory at the BP86/TZ2P level. The nature of the donor-acceptor bonds was investigated with an energy decomposition analysis. It is found that the bond dissociation energy is not a good measure for the intrinsic strength of Lewis acidity and basicity because the preparation energies of the fragments may significantly change the trend of the bond strength. The interaction energies between the frozen fragments of the borane complexes are in most cases larger than the interaction energies of the alane complexes. The bond dissociation energy of the alane complexes is sometimes higher than that of the borane analogues because the energy for distorting the planar equilibrium geometry of BX3 to the pyramidal from in the complexes is higher than for AlX3. Inspection of the three energy terms, DeltaE(Pauli), DeltaE(orb), and DeltaE(elstat), shows that all three of them must be considered to understand the trends of the Lewis acid and base strength. The orbital term of the donor-acceptor bonds with the Lewis bases NCl3 and PCl3 have a higher pi character than the bonds of EH3 and EMe3, but NCl3 and PCl3 are weaker Lewis bases because the lone-pair orbital at the donor atoms N and P has a high percent s character. The calculated DeltaE(int) values suggest that the trends of the intrinsic Lewis bases' strengths in the main-group complexes with BX3 and AlX3 are NMe3 > NH3 > NCl3 and PMe3 > PH3 > PCl3. The transition metal complexes exhibit a somewhat different order with NH3 > NMe3 > NCl3 and PMe3 > PH3 > PCl3. The slightly weaker bonding of NMe3 than that of NH3 comes from stronger Pauli repulsion. The bond length does not always correlate with the bond dissociation energy, nor does it always correlate with the intrinsic interaction energy.     

Structural, MALDI-TOF-MS, magnetic and spectroscopic studies of new dinuclear copper(II), cobalt(II) and zinc(II) complexes containing a biomimicking μ-OH bridge

The Py(2)N(4)S(2) octadentate coordinating ligand afforded dinuclear cobalt, copper and zinc complexes and the corresponding mixed metal compounds. The overall geometry and bonding modes have been deduced on the basis of elemental analysis data, MALDI-TOF-MS, IR, UV-vis and EPR spectroscopies, single-crystal X-Ray diffraction, conductivity and magnetic susceptibility measurements. In the copper and zinc complexes, a μ-hydroxo bridge links the two metal ions. In both cases, the coordination geometry is distorted octahedral. Magnetic and EPR data reveal weakly antiferromagnetic high spin Co(II) ions, compatible with a dinuclear structure. The magnetic characterization of the dinuclear Cu(II) compound indicates a ferromagnetically coupled dimer with weak antiferromagnetic intermolecular interactions. The intra-dimer ferromagnetic behaviour was unexpected for a Cu(II) dimer with such μ-hydroxo bridging topology. We discuss the influence on the magnetic properties of non-covalent interactions between the bridging moiety and the lattice free water molecules.     

Lanthanide diruthenium(II,III) compounds showing layered and PtS-type open framework structures

Two types of lanthanide diruthenium phosphonate compounds, based on the mixed-valent metal-metal bonded paddlewheel core of Ru(2)(hedp)(2)(3-) [hedp = 1-hydroxyethylidenediphosphonate, CH(3)C(OH)(PO(3))(2)], have been prepared with the formulas Ln(H(2)O)4[Ru(2)(hedp)(2)(H(2)O)2].5.5H(2)O (1.Ln, Ln = La, Ce) and Ln(H(2)O)4[Ru(2)(hedp)(2)(H(2)O)(2)].8H(2)O (2.Ln, Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er). In both types, each Ru(2)(hedp)2(H2O)23- unit is linked by four Ln(3+)ions through four phosphonate oxygen (OP) atoms and vice versa. The geometries of the {LnO(P4)} group, however, are different in the two cases. In 1.Ln, the geometry of {LnO(P4)} is closer to a distorted plane, and thus a square-grid layer structure is found. In 2.Ln, the geometry of {LnO(P4)} is better described as a distorted tetrahedron; hence, a unique PtS-type open-framework structure is observed. The channels generated in structures 2.Ln are filled with water aggregates with extensive hydrogen-bond interactions. The magnetic and electrochemical properties are also investigated.     

The influence of phosphane coligands on the nuclearity of rhodium(I) 4-thiolatobenzoic acid complexes

[RhCl(PR3)3] (R = Ph, Et) reacts with the potassium salt of 4-mercaptobenzoic acid to give a mixture of the monomeric and dimeric complexes, [Rh(SC6H4COOH)(PR3)3] and [{Rh(-SC6H4COOH)(PR3)2}2], respectively. With the labile PPh3 coligand, the dimer is the major product, while for the electron-richer coligand PEt3, the equilibrium is easily shifted to the monomer by the addition of excess PEt3. Phosphane dissociation and dimerization could be prevented by using the chelating coligand PPh(C2H4PPh2)2. [{Rh(-SC6H4COOH)(PPh3)2}2] (2b), [Rh(SC6H4COOH)(PEt3)3] (3a), and [Rh(SC6H4COOH){PPh(C2H4PPh2)2}] (4) were fully characterized by nuclear magnetic resonance and infrared spectroscopy, mass spectrometry, and elemental analysis. The molecular structures of 2b and 4 were determined by X-ray structure analysis. In solution, the lability of the phosphane ligands leads to the decomposition of 2b. One of the decomposition products, namely, the mixed-valent complex [{RhIRhIII(-SC6H4COO)(-SC6H4COOH)(SC6H4COOH)(PPh3)3}2] (5), was characterized by X-ray structural analysis. The dinuclear rhodium(III) complex [{Rh(-SC6H4COO)(SC6H4COOH)(PEt3)2}2] (6) was shown to be a byproduct in the synthesis of 3a, and this demonstrates the reactivity of the rhodium(I) complexes toward oxidative addition. The structurally characterized complexes 2b, 4, 5, and 6 show hydrogen bonding of the free carboxyl groups.