3676-91-3Relevant academic research and scientific papers
Cross-linked normal hexagonal and bicontinuous cubic assemblies via polymerizable gemini amphiphiles
Pindzola, Brad A.,Jin, Jizhu,Gin, Douglas L.
, p. 2940 - 2949 (2003)
The synthesis and lyotropic liquid-crystalline (LLC) phase behavior of a homologous series of intrinsically cross-linkable gemini surfactants are described. These novel bis(alkyl-1,3-diene)-based phosphonium gemini amphiphiles exhibit "normal" hexagonal (HI), Type I bicontinuous cubic (QI), and lamellar (Lα) phases in water, and can be photocross-linked with retention of phase architecture in each case. On the basis of their locations on the phase diagram, their powder X-ray diffraction profiles, and the physical properties of the cross-linked materials, the QI phases formed by these gemini monomers are consistent with four possible bicontinuous cubic architectures with P or I space group symmetry that have been identified previously for small molecule amphiphiles. The extent of polymerization (i.e., the degree of diene conversion) achieved in the LLC phases was determined to be in the 23% to 71% range using UV-vis spectrometry, which is more than sufficient to extensively stabilize the systems. The resulting cross-linked HI, Lα, and QI phases are stable up to 300 °C in air. To our knowledge, these reactive amphiphiles constitute the first example of a polymerizable gemini surfactant, and the first example of a cross-linkable amphiphile system that can be polymerized in both the HI and a QI mesophase with retention of phase microstructure.
Proton transfer: Vs. oligophosphine formation by P-C/P-H σ-bond metathesis: Decoding the competing Br?nsted and Lewis type reactivities of imidazolio-phosphines
Cica?-Hudi, Mario,Feil, Christoph M.,Birchall, Nicholas,Nieger, Martin,Gudat, Dietrich
supporting information, p. 17401 - 17413 (2020/12/28)
Studies of the protonation and alkylation of imidazolio-phosphides and deprotonation of imidazolio-phosphines reveal a complex behaviour that can be traced back to an interplay of Br?nsted-type proton transfers and Lewis-type P-P bond formation reactions. As a consequence, the expected (de)protonation and (de)alkylation processes compete with reactions producing cyclic or linear oligophosphines. A careful adjustment of the conditions allows us to selectively address each reaction channel and devise specific synthesis methods for primary, secondary and tertiary imidazolio-phosphines, imidazolio-alkylphosphides, and cyclic oligophosphines, respectively. Mechanistic studies reveal that oligophosphines assemble in sequential P-P bond formation steps involving the condensation of cationic imidazolio-phosphines via σ-bond metathesis and concomitant elimination of an imidazolium ion. Imidazolio-phosphides catalyse these transformations. Computational model studies suggest that the metathesis proceeds in two stages via an initial nucleophilic substitution under expulsion of a carbene, and a subsequent proton transfer step that generates an imidazolium cation and provides the driving force for the whole transformation. As energy barriers are predicted to be low or even absent, different elementary steps are presumed to form a network of mutually coupled equilibrium processes. Cyclic oligophosphines or their dismutation products are identified as the thermodynamically favoured final products in the reaction network.
Process for preparing (metal) alkylphosphonites I
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Page column 3-4, (2008/06/13)
The invention relates to a process for the preparation of (metal) salts of alkylphosphonous acids, which comprises reacting elemental yellow phosphorus with halogen-free alkylating agents in the presence of at least one base. The invention also relates to the use of the (metal) salts of alkylphosphonous acids prepared by this process.
Reactions of difluorosilylene with amines, phosphines and halomethanes the first evidence of the insertion of difluorosilylene into tetrafluorosilane
Chang, Chih-Wei,Liu, Chao-Shiuan,Lee, Chi-Young
, p. 445 - 452 (2007/10/03)
The reactions of SiF2/SiF4 with amines, phosphines and various halomethanes were studied. The results show that in the presence of strong Lewis base (Et3N, HNEt2, PR3, PR2Cl), SiF2 inserts initially into SiF4 to form Si2F6, which was followed by subsequent reactions leading to products containing SiF3 groups. This is the first report of the insertion of SiF2 into SiF4. When the reactants were a weaker base (such as RPCl2, CX3Br, X=F, Cl), insertion of SiF2 into P-Cl and C-Br bonds became predominant.
Lewis acidic titanium species: the synthesis, structure, bonding and molecular modelling considerations of the complexes Ti(NR2)3Cl (R = Me, Et)
Dick, David G.,Rousseau, Roger,Stephan, Douglas W.
, p. 357 - 362 (2007/10/02)
Reaction of simple amides with TiCl4 affords mixed amido-chloride species Ti(NR2)4-nCln.The trisamide-chloride species Ti(NR2)3Cl can be prepared directly employing three equivalents of amide or by reaction Ti(NR2)4 with TiCl4.The compound Ti(NMe2)3Cl, 1, crystallizes in the trigonal space group , with a = 11.525(5), c = 14.939(3) Angstroem, Z = 6, and V = 1718(1) Angstroem3.The compound Ti(NEt2)3Cl, 2, crystallizes in the monoclinic space group P21/c, with a = 8.385(2) Angstroem, b = 15.958(2) Angstroem, c = 14.230(4) Angstroem, β = 107.79(1) deg, Z = 4, and V = 1813(1) Angstroem3.The geometry of the Ti coordination sphere in these complexes is best described as pseudo-tetrahedral.The structural data are consistent with Ti-N multiple bonding.Preliminary results of EHMO calculations are consistent with d?-p? Ti-N bonding.Attempts to replace the halides with phosphides (LiPR2, R = Me, Et, Ph) led not to the Ti(IV) phosphido species, but rather to redox chemistry yielding Ti(III) amides and P2R4.The barrier to rotation about the Ti-N bonds has been considered.Variable temperature 1H NMR studies reveal that the barrier is small.Extended Hueckel total energy minimization calculations have been performed.In addition, MMX calculations of the barrier Ti-N rotation are reported.The results of these calculations imply that the rotational barrier is dominated by steric effects. Key words: titanium amides, structures, Ti-N bonding.
PRINCIPLES OF PHOSPHORUS CHEMISTRY
Bock, Hans
, p. 3 - 53 (2007/10/02)
An up-to-date concept of bonding in phosphorus compounds has to be based on the reality of molecular states.Molecules, which change their structure with energy, at present are best rationalized in terms of topology and symmetry, effective nuclear potentials and charge distribution.To reduce the complexity of the resulting manifold, comparison of equivalent states of chemical calculations, is strongly recommended.Adding the time-scale, molecular dynamics within the numerous degrees of freedom become important, also as a basis to gain some understanding og the rather complex microscopic reaction pathways of medium-sized molecules.Examples are presented to illustrate the use of spectroscopic "fingerprints" for the analysis and optimization of gasphase reactions as well as the benefit of inherent information on molecular states for the preparative phosphorus chemist.The catalytic dehydrochlorination of alkyldichlorophosphanes RH2C-PCl2 -> RHC=PCl -> R-CP and their dechlorination on magnesium metal surface are discussed in some detail as well as the generation of other unsaturated phosphorus molecules like Cl-P=O, Cl-P=S, ClP(=O)2, Cl-P(=S)2 or H3C-P=CH2.Approximate energy hypersurface calculations for the gasphase equilibrium P4 = 2P2 or for the unexpected dehydration (H3C)2HP=O -> H2O + H3C-P=CH2, which includes chemical activation, provide some insight into microscopic reaction pathways of phosphorus compounds.
OBERFLAECHEN-REAKTIONEN 15 Heterogene Dechlorierungen von Phosphorchloriden (X)PCl3 und R-PCl2 an , , x/TiO2> und sowie spektroskopische Evidenz fuer das Entstehen von Diphospha-dicyan PC-CP aus Cl2P-CC-PCl2
Bock, H.,Bankmann, M.
, p. 167 - 191 (2007/10/02)
Stimulated by the successful generation of unsaturated molecules with low-coordinated phosphorus centers by heterogeneous surface dechlorination, Cl2P-CC-PCl2 is synthesized and characterized by PE and mass spectra.In addition, curls, wool and catalysts x/TiO2> or are tested as potential dechlorinating agents for phosphorus halides like OPCl3, SPCl3, H3C-PCl2, H5C2-PCl2, (H3C)3C-PCl2 or H5C6-PCl2 in a gasflow reactor under reduced pressure and yield, inter alia, the following representative results: due to the thermodynamically favored formation of , or at the Mg surface, P4 is the only gaseous product identified from reactions of OPCl3 and SPCl3 with metal at higher temperatures.On the contrary, passing H3C-PCl2 at 600K over yields a reaction mixture containing P(CH3)3, (H3C)2P-P(CH3)2 (H3C-P)5 and CH4, which suggests an intermediate formation of surface phosphinidenes Mg>.Analogously, the pentamer (H3C-H2C-P)5 can be isolated from ethyldichlorophosphane.Reaction of the evaporated diphospha-cyanogen precursor Cl2P-C-PCl2 with the catalyst produces predominantly PCl3, and P4, but PE and mass spectra provide evidence that also minor amounts of the hitherto unknown molecule PC-CP are formed.
Evidence for Surface Phosphinidene Intermediates Mg> in the Heterogeneous Dechlorination of Alkyldichlorophosphanes RPCl2 by Mg Metal
Bock, Hans,Bankmann, Martin
, p. 1130 - 1132 (2007/10/02)
The heterogeneous dechlorination of alkyldichlorophosphanes by Mg metal at 600 K yields chemisorbed products which include penta-alkylcyclopentaphosphanes (RP)5, in addition to RnPH(3-n), R2P-PR2, P4, RH, and R-R, and thus provides evidence for surface phosphinidene intermediates Mg>.
Electron-transfer chemistry of (Me5C5)2Yb: Cleavage of diorganoperoxide and related chalcogenides to give (Me5C5)2Yb(ER)(L) (E = O, S, Se, or Te; L = a Lewis base). Crystal structure of (Me5C5)2Yb(TePh)(NH3)
Berg, David J.,Andersen, Richard A.,Zalkin, Allan
, p. 1858 - 1863 (2008/10/08)
The divalent metallocenes of ytterbium (Me5C5)2Yb(OEt2) or (Me5C5)2Yb(NH3)2 react with molecules of the type REER to give the trivalent ytterbium complexes (Me5C5)2Yb(ER)(L), where L is OEt2 or NH3, E is S, Se, or Te, and R is a phenyl or substituted phenyl group. The ammonia complexes are easier to characterize than the diethyl ether complexes since the latter complexes lose ether in the solid state and give unsatisfactory microanalytical data whereas the ammonia complexes give satisfactory elemental analyses. In addition, the line width of the Me5C5 protons in the 1H NMR spectra of the diethyl ether complexes is ca. 500 Hz whereas the line width at half-height is ca. 50 Hz for the ammonia complexes, consistent with the notion that the barrier to chemical exchange is higher for the ammonia complexes. The peroxides ROOR, where R is Me3C or Me3Si, give the alkoxides (Me5C5)2Yb(OR)(NH3), and Et2NC(S)SS(S)CNEt2 gives the known (Me5C5)2Yb(S2CNEt2). In contrast, dialkyl dithiophosphinates give (Me5C5)2Yb(S2PR2) and R2PPR2, where R is Me or Et. The synthetic routes developed in this work are the best methods currently available for synthesis of these trivalent species. The crystal structure of (Me5C5)2Yb(TePh)(NH3) has been done. The crystals are orthorhombic, P212121, with a = 11.823 (3) ?, b = 25.917 (6) ?, c = 8.539 (2) ?, and V = 2616.5 ?3. For Z = 4, the calculated density is 1.69 g cm-3. The structure was refined by full-matrix least squares to a conventional R factor of 0.046 [4991 data, F2 > σ(F2)]. The Yb-Te distance is 3.039 (1) ?, and the Yb-Te-C(Ph) angle is 113.0 (3)°.
