PubMed Health⌕ Search

Biomedical subjects

Pingrong Wei

Publications and source records attributed to Pingrong Wei.

8 recordsLinked to original sources
PubMed2006

Pseudotetrahedral polyhalocubanes: synthesis, structures, and parity violating energy differences.

All possible pseudotetrahedral, stable polyhalocubanes were prepared, and their structures were proven by NMR spectroscopy and X-ray crystallography. Parity violating energy differences (DeltaEpv) and vibrational frequency shifts were computed. The DeltaEpv values are predicted to be one to two orders of magnitude smaller than those for the corresponding polyhalomethanes. However, the DeltaEpv energy ordering is the same as that for the methane analogues. For both substance classes, the (S) isomers are, with the exception of the bromochlorofluoroiodo derivatives, more stable than the (R) forms.

Journal Article↗
PubMed2005

P-H and P-P bond activation by Ni(I) and Fe(I) beta-diketiminato-complexes.

Reactions of ((NacNac)Ni)2(mu-eta3-eta3-C6H5Me) (NacNac = HC(CMeNC6H3(i-Pr)2)2) with PH2Ph or PHPh2 proceeds in a facile manner to afford the Ni(I)-phosphine adducts (NacNac)Ni(PH2Ph) and (NacNac)Ni(PHPh2) , respectively. The related reactions of the Fe(I) complex (NacNac)Fe(eta2-CH2CPh2) with PH2Ph resulted in the formation of [(NacNac)Fe(mu2-PPh)]2. Alternatively was also obtained from the reaction of [(NacNac)Fe(mu-Cl)]2 with PHPh2 and Na/K. The Ni(II) di-phosphosphine bridged compound [((NacNac)Ni)2(mu4-(PPh)2)] was prepared via reaction of ((NacNac)Ni)2(mu-eta3-eta3-C6H5Me) with P5Ph5. Crystallographic data are reported for compounds .

Journal Article↗
PubMed2005

On the chemistry of Zn-Zn bonds, RZn-ZnR (R = [{(2,6-Pri2C6H3)N(Me)C}2CH]): synthesis, structure, and computations.

Potassium reduction of RZn(mu-I)2Li(OEt2)2 (R = [{(2,6-Pri2C6H3)N(Me)C}2CH]) affords the second compound with a Zn-Zn bond, RZn-ZnR. The air- and moisture-sensitive title compound was characterized by 1H NMR, elemental analyses, and single-crystal X-ray diffraction. The Zn-Zn bond was determined to be 2.3586(7) A; this value is only about 0.05 A longer than the Zn-Zn bond reported for Cp*Zn-ZnCp* (Cp* = C5Me5), the first reported compound with a Zn-Zn bond. In addition, density functional theory (DFT) computations on related model RZn-ZnR compounds provide insight into the intriguing Zn-Zn bond.

Journal Article↗
PubMed2005

Steric effects in metathesis and reduction reactions of phosphinimines with catechol- and pinacolboranes.

A series of catecholboryl-phosphinimide complexes with the general formula (mu-(R(3)PN)Bcat)(x)() (cat = O(2)C(6)H(4)) have been synthesized via associative metathetical reactions. For R = Et, n-Bu, Ph, and i-Pr and R(3) = n-Bu t-Bu(2) X-ray crystallography as well as solution NMR spectroscopy and reactivity studies reveal that these species are dimeric. In the case of R = t-Bu, the steric congestion results in the monomeric species, t-Bu(3)PNBcat. Similarly, reactions of R(t-Bu)(2)PNH (R = n-Bu, t-Bu) and i-Pr(3)PNH with pinacolborane (HBO(2)C(2)Me(4) = HBpin) led to the formation of n-Bu(t-Bu(2))PNBpin, t-Bu(3)PNBpin, and i-Pr(3)PNBpin. Analogous reactions of smaller phosphinimines R(3)PNH (R = Et or n-Bu) with pinacolborane (HBpin) generated free phosphine and the boron-containing product HN(Bpin)(2). In the related reactions of R(3)PNPh or R(3)PNAd (R = Et and n-Bu) and HBpin, the white crystalline solids PhHN(Bpin) or AdHN(Bpin) were isolated. HN(Bpin)(2) was also derived from the reaction of Et(3)PNSiMe(3) and HBpin. Kinetic studies showed this reaction is first order in both reagents with a rate constant of 1.3(7) x 10(-4) s(-1). A mechanism involving a 1:1 donor-acceptor interaction of the phosphinimine and borane affording reduction of the phosphinimine to phosphine with concurrent formation of borylamine is proposed. Computational studies were performed to probe the steric effects on these reactions of phosphinimine and borane. Model reactions involving t-Bu(3)PNH showed a lower activation barrier for protonolysis in comparison to phosphinimine reduction. In contrast, for the smaller phosphinimine H(3)PNH, the activation barriers for phosphinimine reduction are lower. The causes of these steric effects are considered.

Journal Article↗
PubMed2005

A metallocene-complexed dibismuthene: Cp2Zr(BiR)2 (Cp = C5H5; R = C6H3-2,6-Mes2).

The zirconocene-complexed dibismuthene, Cp2Zr(BiR)2 (Cp = C5H5; R = C6H3-2,6-Mes2), was prepared by the reaction of sodium metal with Cp2ZrCl2 and RBiCl2. The air- and moisture-sensitive dark reddish/brown compound is the first organometallic compound containing Bi-Zr bonds and the only example of a ZrBi2 ring. Moreover, our computations on associated model systems offer insight into the nature of the interaction of the heaviest dipnictene with a metallocene center.

Journal Article↗
PubMed1998

Chelated Borates: Synthesis, Reactivity, and Cation Formation.

The ligands N-salicylidene-o-aminophenol (LH(2)), N-(5-chlorosalicylidene)-o-aminophenol (L(Cl)H(2)), and N-(5-bromosalicylidene)-o-aminophenol (L(Br)H(2)) were used to prepare a series of borates having the formulas LBOR (R = Me (1), Et (2), (n)Pr (3), (n)Bu (4)), L(Cl)BOR (R = Me (5), Et (6), (n)Pr (7), (n)Bu (8)), and L(Br)BOR (R = Me (9), Et (10), (n)Pr (11), (n)Bu (12)). Either 1-4 or 9-12 could be combined with HOSiPh(3), to form unique compounds possessing a single B-O-Si linkage, LBOSiPh(3) (13) and L(Br)BOSiPh(3) (14), respectively. The charged species, [LB(thf)](+)OTf(-) (15) forms when 1 is combined with HOTf. It can be used as a catalyst for the oligomerization of propylene oxide. By comparison, [(n)Bu(2)B](+)OTf(-) effects the oligomerization to the same extent as 15, but the neutral species, 1-4, 13, and 14 do not, even under forcing conditions. All of the compounds were characterized by melting point, (1)H NMR, IR, elemental analyses, and, in the case of 13, by X-ray crystallography.

Journal Article↗