Quantum Chemical Calculations of the Structure,Property and Stability of Penta-coordinated Carbonium Ions Derived from Normal Butane

The structure and energy of the carbonium ions formed upon protonation of butane were studied by the DFT methods. Four stable structures are identified for the protonated form of n-butane, the energy increases in the following order： C2HC3〈C1HC2〈C2HH〈C1HH, and the stability decreases in the following order C2HC3〉C1HC2〉C2HH〉C1HH. The stability of the penta-coordinated carbonium ions may be explained by the electron distribution in the three-center-two-electron bonds. The delocalization of the penta-coordinated carbonium ion CHC with three-center-two-electron bonds on positive charges was stronger than that of the penta-coordinated earbonium ion CHH with three-center-two-electron bonds and its stability was higher than that of the penta-coordinated carbonium ion CHH with three-center-two-electron bonds.

Cooperative catalytic effects between the penta-coordinated Al and Al_(2)O_(3)in Al_(2)O_(3)-AlPO_(4)for aldol condensation of methyl acetate with formaldehyde to methyl acrylate

The bare amorphous Al_(2)O_(3)-AlPO_(4)and Cs/Al_(2)O_(3)-AlPO_(4)catalysts were developed for the aldol condensation of methyl acetate with formaldehyde to methyl acrylate.The structure and property of catalyst were characterized by XRD,XPS,BET,Pyridine-IR,FT-IR,^(27)Al-MASNMR,NH_(3)-/CO_(2)-TPD and SEM.The correlation between structural features and acid-base properties was established,and the loading effect of the cesium species was investigated.Due to cooperative catalytic effects between the penta-coordinated Al and Al_(2)O_(3),the weak-Ⅱacid and medium acid site densities and the product selectivity were improved.While the basic site densities of these catalysts were almost in proportion to the conversion of methyl acetate.The loaded Cs could form new basic sites and change the distribution of acid sites which further enhance the catalytic performance.As a result,the 10Cs/8AlP was proved to be an optimal catalyst with the yield and selectivity of 21.2%and 85%for methyl acrylate respectively.During the reaction,a deactivation behavior was observed on 10Cs/8AlP catalyst due to the carbon deposition,however,it could be regenerated by thermal treatment in the air atmosphere at 400℃.

Synthesis and Crystal Structure of a New Penta-coordinated Cu(Ⅱ) Complex:Cu(C_(17)H_(13)F_3O_3)_2·C_5H_5N

A new copper（II） complex 3, Cu（C17H13F3O3）2·C5H5N, has been synthesized and characterized by single-crystal X-ray diffraction. It crystallizes in monoclinic, space group C2/c with a = 17.8511（7）, b = 17.4136（7）, c = 13.9425（7） A, β = 124.4830（10）°, V = 3572.5（3） A^3, Z = 4, C39H29CuF6NO6, Mr = 785.17,/7（000） = 1604, T = 292（2） K, Dc = 1.460 g/cm^3 and p = 0.691 mm^-1. The structure was refined to R = 0.0477 and wR = 0.1110 for 2935 observed reflections with I 〉 2σ（I）. For the title compound, X-ray analysis reveals that the copper（II） is penta-coordinated by four oxygen atoms from the corresponding 1-（4-（benzyloxy）phenyl）-4,4,4-trifluorobutane-1,3-dione ligands and one nitrogen atom of pyridine, forming a distorted square pyramidal geometry. It is found that the trifluoromethyl group, F（1）/F（1＇）, F（2）/F（2＇） and F（3）/F（3＇））, is disordered over two orientations in an approximate 3：1 ratio.

(31)~P NMR and ESI-MS Studies on Some Intermediates of the Peptide Coupling Reagents Triphenyl-chlorophosphoranes

The intermediates of the Appel coupling reagents were studied in acetonitrile, dimethoxyethane and dioxane by P NMR, C NMR spectrum and ESI-MS. In dioxane a new high 31 13 coordinated phosphorous compound with P NMR shift at -39 ppm was observed. The ESI-MS 31 showed that it could be a penta-coordinated phosphorous compound containing dioxane. The carboxyl activated intermediates were also studied in three solvents.

Intermolecular Phosphoryl Transfer Between Serine and Histidine Residues

A novel intermolecular phosphoryl transfer from O-trimethylsilyl-N-(O, O-diisopropyl) phosphoryl serine trimethylsilyl ester to N, Nbis(trimethylsilyl) histidine trimethylsilyl ester was studied through electrospray ionization mass spectrometry (ESI-MS). It was proposed that the transfer reaction went through penta-coordinated phosphorus intermediate.

Penta-coordinated phosphorus structure analysis on kinases

In this paper, based on the known crystal structures of Square Pyramid (SP) and Trigonal Bipyramid (TBP) penta-coordinated phosphorus compounds containing amino acid side chains, such as amino, carboxyl, hydroxyl or thiol, a software designed to survey the P(5)-Structure of phosphorylated proteins. By this software, it was found that 382 of 398 phos- phorus-related kinases (96%) from current PDB could go through the penta-coordinated phos- phorus transition state or intermediate. For example, in protein 1HE8, amino group in Lysine16 was within 3.58 ?from the phosphorus atom, and a potential TBP structure consisting GNP2 and NZ could be overlapped with an authentic TBP with an RMSD value of 0.71 ?.

Penta-coordinate phosphorous compounds and biochemistry

The relationship between penta-coordinate phosphorus compounds and biochemistry is briefly reviewed. Some interesting phenomena such as peptide formation, ester formation, ester exchange on phosphorus and N to O migration occur at room temperature when the amino group of amino acid is associated with phosphoryl group. Serine or threonine in conjugate of nucleo-side-amino acid could recognize different nucleobases. N-phosphoryl Histine and Ser-His dipep-tide could cleavage nucleic acid, protein and ester in neutral medium. It is found that the above phenomena all undergo penta-coordinate intermediate of phosphorus atom, which is proposed as the key factor to determine their activities.

Ligand Exchange Between Penta-Coordinated Phosphoryl Serine and Histidine Compounds

With the assistance of HPLC-ESI-MS/MS,the self-assembly products of serine and histidine penta-coordinated phosphorus compound were separated and identified. The expectative product was seryl-histidine dipeptide,but it was found that there was almost equimolar amount of histidyl-histidine dipeptide as well as seryl-histidine dipeptide. The mechanism was speculated that there was ligand exchange between penta-coordinated phosphoryl serine and histidine in the reaction process. As a result,two types of dipeptide were produced.

Penta-Coordinate Phosphorus Intermediates Analysis on Phospho-related Proteins

In this paper, based on known crystal structures of square pyramid （SP） and trigonal bipyramid （TBP） penta coordinated phosphorus compounds containing amino acid side chains, such as amino, carboxyl, hydroxyl or thiol, a software for survey the P（5）-structure of phosphorylated proteins was derived. By this software, it was found that 382 of 398 phosphorus related kinases （96%） from current PDB could go through the penta-coordinated phosphorus transition state or intermediate.

Phosphorus-doped iron-nitrogen-carbon catalyst with pentacoordinated single atom sites for efficient oxygen reduction

Single-atomic Fe-N4 is the well-acknowledged active site in iron-nitrogen-carbon(Fe-N-C)material for oxygen reduction reaction(ORR).The adjusting of the electronic distribution of Fe-N4 is promising for further enhancing the performance of the Fe-N-C catalyst.Herein,a phosphorus(P)-doped Fe-N-C catalyst with penta-coordinated single atom sites(FeNPC)is reported for efficient oxygen reduction.Fe K-edge X-ray absorption spectroscopy(XAS)verifies the coordination environment of single Fe atom,while density functional theory(DFT)calculations reveal that the penta-coordination and neighboring doped P atoms can simultaneously change the electronic distribution of Fe-N_(4)and its adsorption strength of key intermediates,reducing the reactionfree energy of the potential-limiting step.Electrochemical tests validate the remarkable intrinsic ORR activity of FeNPC in alkaline media(a half-wave potential(E_(1/2))of 0.904 V vs.reversible hydrogen electrode(RHE)and limited current density(JL)of 6.23 mA·cm^(−2))and an enhanced ORR performance in neutral(E_(1/2)=0.751 V,J_(L)=5.27 mA·cm^(−2))and acidic media(E_(1/2)=0.735 V,JL=5.82 mA·cm^(−2))with excellent stability,highlighting the benefits of optimizing the local environment of singleatomic Fe-N4.