Reactions of the cyclic diphosphadiazanes (XPNR)(2) (X = Cl, Br; R = 2,6-dimethylphenyl = Dmp, 2,6-diisopropylphenyl = Dipp) with GaX(3) followed by 4-(dimethylamino)pyridine (DMAP) give the corresponding trimers (XPNR)(3). An unusual cyclophosphazanium tetrachlorogallate salt [(DippN)(3)P(3)Cl(2)][GaCl(4)] has been isolated from the reaction of (ClPNDipp)(2) with GaCl(3) and represents an intermediate in the disproportionation process. Dissociation of the gallate ion on reaction of [(DippN)(3)P(3)Cl(2)][GaCl(4)] with DMAP releases a halide ion, which associates with the dicoordinate phosphenium center to give (ClPNDipp)(3). The observations indicate that the presence of medium-sized substituents at nitrogen (R) thermodynamically destabilize the dimer with respect to the trimer, without offering sufficient stabilization of the monomer, as observed for MesNPX (Mes* = 2,4,6-tri-tert-butylphenyl) (Mes* > Dipp > Dmp). Nevertheless, lability of the N-P bond in these derivatives of (XPNR)(2) allows for transformations between dimer and trimer that may include transient existence of the corresponding monomer. Manipulation of substituent steric strain to modify the relative stability of phosphazane oligomers provides a new methodology for diversification of phosphazane chemistry. 相似文献
The development of batteries and fuel cells has brought to light a need for carbon anode materials doped homogeneously with electrocatalytic metals. In particular, combinations of electrocatalysts in carbon have shown promising activity. A method to derive functional carbon materials is the pyrolysis of metallopolymers. This work describes the synthesis of a bifunctional phosphonium-based system derived from a phosphane-ene network. The olefin functionality can be leveraged in a hydrogermylation reaction to functionalize the material with Ge. Unaffected by this radical addition, the bromide counterion of the phosphonium cation can be used to subsequently incorporate a second metal in an ion-complexation reaction with CuBr2. The characterization of the polymers and the derived ceramics are discussed. 相似文献
Reactivity of primary phosphines with two stoichiometric equivalents of imine results in the formation of bis-α-aminophosphines ( 2 a – e ), which can be subsequently oxidized in the presence of S8 or H2O2 to generate air stable bis-α-aminophosphine sulfides ( 2 b – m(S/O) ). To elucidate the mechanism of this three-component reaction, Hammett analysis, kinetic isotope effect (KIE), and trapping experiments were performed. Ultimately a P(V)–P(III) tautomerization is invoked, followed by nucleophilic attack by the P(III) species to generate the desired products. 相似文献
DABling with sulfur : Sulfur(II) dications can be prepared using α‐diimines to stabilize the positive charge (see scheme; DAB=diazabutadiene, Dipp=2,6‐diisopropylphenyl, OTf=CF3SO3). The bonding is best described as that of a N,N‐chelated sulfur(II) dication; these species represent the first sulfur‐based structural mimics of N‐heterocyclic silylene compounds and phosphenium cations.
Highly reactive electrophilic compounds centered around multicationic main‐group elements are notoriously difficult to isolate. In the Communication on page 2210 ff., P. J. Ragogna and co‐workers describe the synthesis and characterization of salts of sulfur(II) dications stabilized by two chelating nitrogen atoms. These species are the first sulfur‐based analogues of N‐heterocyclic silylene compounds and are the most recent addition to the family of compounds featuring divalent p‐block elements. Mitch Zimmer is acknowledged for the cover design.
The room-temperature reaction between the Dipp2DAB ligand, SnCl2, and SeCl4 results in the quantitative formation of a dicationic N-heterocyclic "carbenoid". This represents the first example of a chalcogenium dication that mimics the ubiquitous Arduengo-type carbenes; however, the electronic structure is significantly different. 相似文献
We investigate nonlinear oscillations in a fourth-order partialdifferential equation which models a suspension bridge. Previouswork establishes multiple periodic solutions when a parameterexceeds a certain eigenvalue. In this paper, we use Leray-Schauderdegree theory to prove that if the parameter is increased further,beyond a second eigenvalue, then additional solutions are created. 相似文献
A new 14pi-electron tricyclic organoarsenium cation (5-hydrophenarsazinium, AN, C12H9AsN+) has been prepared in situ and used as a Lewis acceptor with trimethylphosphine, triphenylphosphine, bis(diphenylphosphino)methane (dppm), bis(dimethylphosphino)methane (dmpm), and 1,4-bis(diphenylphosphino)benzene (dppb) ligands. Solid-state structures and spectroscopic characterization data are reported for complexes of the general formula [AN-PMe3]+, [AN-PPh3]+, [AN-dppm]+, [AN-dppm-AN]2+, [AN-dmpm-AN]2+, and [AN-dppb-AN]2+ as tetrachlorogallate salts. Depending on reaction stoichiometry, dppm forms adducts at one or both of the donor sites. Structural comparisons with analogous complexes of phosphenium cations provide interesting similarities and differences. 相似文献