The Low Basicity of Phosphabenzenes: First Examples of Protonation, Alkylation, and Silylation Reactions

Zhang, Yun; Tham, Fook S.; Nixon, John F.; Taylor, C. Peter; Green, Jennifer C.; Reed, Christopher A.

doi:10.1002/ange.200800878

Cited by 11 publications

(7 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thermal pyrolysis in the presence of both C 2 H 2 and PH 3 yields various gaseous species that are essential for the SANG growth: aromatic hydrocarbon molecules, P 4 , phosphorine (C 5 H 5 P), and phosphinoline (C 9 H 7 P) (Figure S2) . In particular, phosphorine, a predominant derivative in this work, is known as a noncollagen macromolecule with high calcium-binding capacity and strong phosphate-solubilizing fertility. − The reaction of phosphorine on the surface of calcium-rich glass fibers may result in a phosphorine–Ca 2+ complex, producing a molecular species that favorably bound to the phosphate generated through reaction of the derived P 4 . , These phosphate-binding molecular species may promote formation of amorphous calcium phosphate compounds that are eventually transformed into the apatite crystal. ,, Growth over the initial 30 s showed the formation of both amorphous and crystalline calcium phosphate nanoparticles (Figures a and S3a). After 120 s, most nanoparticles changed into crystals and some slowly started to elongate (Figures b and S3b).…”

Section: Resultsmentioning

confidence: 89%

Single-Crystal Apatite Nanowires Sheathed in Graphitic Shells: Synthesis, Characterization, and Application

Jeong

Cha²,

Park

et al. 2013

ACS Nano

View full text Add to dashboard Cite

Vertically aligned one-dimensional hybrid structures, which are composed of apatite and graphitic structures, can be beneficial for orthopedic applications. However, they are difficult to generate using the current method. Here, we report the first synthesis of a single-crystal apatite nanowire encapsulated in graphitic shells by a one-step chemical vapor deposition. Incipient nucleation of apatite and its subsequent transformation to an oriented crystal are directed by derived gaseous phosphorine. Longitudinal growth of the oriented apatite crystal is achieved by a vapor-solid growth mechanism, whereas lateral growth is suppressed by the graphitic layers formed through arrangement of the derived aromatic hydrocarbon molecules. We show that this unusual combination of the apatite crystal and the graphitic shells can lead to an excellent osteogenic differentiation and bony fusion through a programmed smart behavior. For instance, the graphitic shells are degraded after the initial cell growth promoted by the graphitic nanostructures, and the cells continue proliferation on the bare apatite nanowires. Furthermore, a bending experiment indicates that such core-shell nanowires exhibited a superior bending stiffness compared to single-crystal apatite nanowires without graphitic shells. The results suggest a new strategy and direction for bone grafting materials with a highly controllable morphology and material conditions that can best stimulate bone cell differentiation and growth.

show abstract

Section: Resultsmentioning

confidence: 89%

Single-Crystal Apatite Nanowires Sheathed in Graphitic Shells: Synthesis, Characterization, and Application

Jeong

Cha²,

Park

et al. 2013

ACS Nano

View full text Add to dashboard Cite

show abstract

“…A more recent example is the protonation of the weakly basic P atom in a phosphabenzene to give an isolable salt (Figure ) . Although triflic acid is strong enough to protonate phosphabenzenes, the triflate anion reacts with the protonated product causing a rearrangement reaction, with the driving force presumably being that of strong P−O bond formation.…”

Section: Protonationmentioning

confidence: 99%

“…22 A more recent example is the protonation of the weakly basic P atom in a phosphabenzene to give an isolable salt (Figure 5). 23 Although triflic acid is strong enough to protonate phosphabenzenes, the triflate anion reacts with the protonated product causing a rearrangement reaction, with the driving force presumably being that of strong P-O bond formation. The carborane anion is a poorer nucleophile; therefore, the reaction is arrested at the protonation stage.…”

Section: Protonationmentioning

confidence: 99%

H⁺, CH₃⁺, and R₃Si⁺ Carborane Reagents: When Triflates Fail

2009

View full text Add to dashboard Cite

For decades, triflic acid, methyl triflate, and trialkylsilyl triflate reagents have served synthetic chemistry well as clean, strong electrophilic sources of H + , CH 3 + , and R 3 Si + , respectively. However, a number of weakly basic substrates are unreactive toward these reagents. In addition, triflate anion can express undesired nucleophilicity toward electrophilically activated substrates.In this Account, we describe methods that replace triflatebased electrophilic reagents with carborane reagents. Using carborane anions of type CHB 11 R 5 X 6 -(R ) H, Me, X; X ) Br, Cl), members of a class of notably inert, weakly nucleophilic anions, significantly increases the electrophilicity of these reagents and shuts down subsequent nucleophilic chemistry of the anion. Thus, H(carborane) acids cleanly protonate benzene, phosphabenzene, C 60 , etc., while triflic acid does not. Similarly, CH 3 (carborane) reagents can methylate substrates that are inert to boiling neat methyl triflate, including benzene, phosphabenzenes, phosphazenes, and the pentamethylhydrazinium ion, which forms the dipositive ethane analogue, Me 6 N 2 2+. Methyl carboranes are also surprisingly effective in abstracting hydride from simple alkanes to give isolable carbocation salts, e.g., t-butyl cation.Trialkylsilyl carborane reagents, R 3 Si(carborane), abstract halides from substrates to produce cations of unprecedented reactivity. For example, fluoride is extracted from freons to form carbocations; chloride is extracted from IrCl(CO)(PPh 3 ) 2 to form a coordinatively unsaturated iridium cation that undergoes oxidative addition with chlorobenzene at room temperature; and silylation of cyclo-N 3 P 3 Cl 6 produces a catalyst for the polymerization of phosphazenes that functions at room temperature. Although currently too expensive for widespread use, carborane reagents are nevertheless of considerable interest as specialty reagents for making reactive cations and catalysts.

show abstract

“…The investigation of the interactions with highly reactive cations is still a highly active area of current research. 9,19,29,38- 40 Far less studied are reactions resulting in the functionalization of the carbon cluster atom that, in principle, can be achieved by two different strategies: either after or in advance of the halogenation of the eleven boron vertices. The incorporation of a functional group to the cluster carbon atom results in [1-Rcloso-1-CB 11 Hal 11 ]anions (R = functional group; Hal = F, Cl, Br, I) with a weakly coordinating periphery that are attractive building blocks for many applications, for example as ligands in coordination chemistry.…”

Section: Introductionmentioning

confidence: 99%

Salts of the 1-cyanocarba-closo-dodecaborate anions [1-NC-closo-1-CB11X11]− (X = H, F, Cl, Br, I)

2010

View full text Add to dashboard Cite

The caesium and tetraethylammonium salts of the 1-cyanocarba-closo-dodecaborate anions [1-NC-closo-1-CB(11)X(11)](-) (X = H, F, Cl, Br, I) were synthesized from CsLi[closo-1-CB(11)X(11)] and phenylcyanate. All anions are stable against aqueous acids and bases, except for the fluorinated anion [1-NC-closo-1-CB(11)F(11)](-) that immediately reacts with water. The Cs(+) and [Et(4)N](+) salts of the anions were characterized by IR, Raman and multinuclear NMR spectroscopy as well as by MALDI and ESI mass spectrometry. The thermal properties of the Cs[1-NC-closo-1-CB(11)X(11)] (X = H, Cl, Br, I) and of some of their tetraethylammonium salts were studied by differential scanning calorimetry. The crystal structures of [Et(4)N][1-NC-closo-1-CB(11)H(11)] and Cs[1-NC-closo-1-CB(11)Cl(11)] were determined and the discussion of the structural and spectroscopic properties is supported by density functional and (RI)-MP2 calculations. A first insight into the hydrolysis of the [1-NC-closo-1-CB(11)F(11)](-) anion is presented and its reactions with water are compared to those of other undecafluorinated carba-closo-dodecaborate anions. The reduced hydrolytic stability of the [1-NC-closo-1-CB(11)F(11)](-) anion in comparison to its homologues is related to differences in the carbon-boron and boron-boron bond lengths of the {closo-1-CB(11)} cage and to different partial charges of the cluster atoms.

show abstract

The Low Basicity of Phosphabenzenes: First Examples of Protonation, Alkylation, and Silylation Reactions

Cited by 11 publications

References 25 publications

Single-Crystal Apatite Nanowires Sheathed in Graphitic Shells: Synthesis, Characterization, and Application

Single-Crystal Apatite Nanowires Sheathed in Graphitic Shells: Synthesis, Characterization, and Application

H⁺, CH₃⁺, and R₃Si⁺ Carborane Reagents: When Triflates Fail

Salts of the 1-cyanocarba-closo-dodecaborate anions [1-NC-closo-1-CB11X11]− (X = H, F, Cl, Br, I)

Contact Info

Product

Resources

About

The Low Basicity of Phosphabenzenes: First Examples of Protonation, Alkylation, and Silylation Reactions

Cited by 11 publications

References 25 publications

Single-Crystal Apatite Nanowires Sheathed in Graphitic Shells: Synthesis, Characterization, and Application

Single-Crystal Apatite Nanowires Sheathed in Graphitic Shells: Synthesis, Characterization, and Application

H+, CH3+, and R3Si+ Carborane Reagents: When Triflates Fail

Salts of the 1-cyanocarba-closo-dodecaborate anions [1-NC-closo-1-CB11X11]− (X = H, F, Cl, Br, I)

Contact Info

Product

Resources

About

H⁺, CH₃⁺, and R₃Si⁺ Carborane Reagents: When Triflates Fail