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The phosphorus–oxygen bond formation reactions often observed for the sterically crowded triarylphosphines and their radical cations were studied by DFT calculation. The oxidations of the trimethyl-, triphenyl-, and trimesityl-phosphines to the corresponding phosphine oxides with peroxides are shown to proceed through the SN2 like transition states and the overall influence of the steric hindrance on the activation energy is limited. The reaction of the radical cation of tris(2,4,6-triisopropylphenyl)phosphine with oxygen to give the heterocyclic phosphonium cation is modeled by employing (2,6-diisopropylphenyl)diphenylphosphine and the comparison of the intermediates suggests highly exergonic nature of the reaction. [ABSTRACT FROM AUTHOR]

The sterically crowded triarylphosphine bearing two phenothiazine moieties as redox sites was synthesized. The cyclic voltammogram of the phosphine exhibits three-step reversible oxidation, and the comparison with that of the triarylphosphine bearing one phenothiazine moiety suggests delocalization of positive charges during redox process. [ABSTRACT FROM AUTHOR]

A sterically crowded triarylphosphine bearing an ester group, (4-ethoxycarbonyl-2,6-diisopropylphenyl)bis(2,4,6-triisopropylphenyl)phosphine, was synthesized by the lithiation of the corresponding (bromoaryl)phosphine followed by the reaction with excess diethyl carbonate. The ester was obtained as lemon yellow crystals and exhibits the blueshifted UV-Vis absorption and fluorescence as compared with the orange-colored corresponding aldehyde and ketone. The effect of the substitution of an ester group on the photophysical and redox properties of the sterically crowded triarylphosphine is discussed, and the properties of the sterically crowded triarylphosphines bearing an aldehyde, a ketone, and an ester groups are briefly reviewed. [ABSTRACT FROM AUTHOR]

A novel sterically crowded triarylphosphine, [4-methyl-2,6-bis(2-methylphenyl)phenyl]bis(2,4,6-triisopropylphenyl)phosphine (1), was synthesized by the reaction of 4-methyl-2,6-bis(2-methylphenyl)phenylcopper(I) with chlorobis(2,4,6-triisopropylphenyl)phosphine. Triarylphosphine1exhibits a low inversion barrier, a reversible oxidation at low potential, and a UV absorption in long wavelength typical of sterically crowded triarylphosphines. The mCPBA oxidation of1gave the corresponding phosphine oxide of more crowded and rigid structure. [ABSTRACT FROM PUBLISHER]

A novel sterically crowded triarylphosphine bearing a 2,6-diaryl-4-bromophenyl group, [4-bromo-2,6-bis(4-tert-butylphenyl)phenyl]bis(2,4,6-triisopropylphenyl)phosphine (1), was synthesized. The X-ray crystallography revealed that the bond angles and lengths around the phosphorus atom (110.9°, 1.846 Å) are comparable to those of tris(2,4,6-triisopropylphenyl)phosphine and its derivatives. Triarylphosphine1is reversibly oxidized to the radical cation at the potential close to that of the typical sterically crowded (bromoaryl)phosphine, (4-bromo-2,6-diisopropylphenyl)bis(2,4,6-triisopropylphenyl)phosphine, and exhibits the UV absorption at long wavelength (λmax332 nm) characteristic of the sterically crowded triarylphosphines. Thus, triarylphosphine1can be regarded to be a promising candidate for the key synthetic intermediate or building block to the functional molecules bearing sterically crowded triarylphosphine moieties. [ABSTRACT FROM PUBLISHER]

Synthesis, redox properties, and electronic spectra of the sterically crowded triarylphosphines conjugated with π-electron systems, especially electron acceptors such as carbonyl group, are briefly reviewed. The sterically crowded triarylphosphines conjugated with various π-electron systems were synthesized from the common synthetic intermediate, (bromoaryl)phosphine, by conventional manner. The sterically crowded triarylphosphines conjugated with the electron acceptors exhibit visible absorption and fluorescence with large Stokes shift. Large solvent effect, redshift in polar solvent, and good correlation with the difference of the oxidation potential of the phosphine moiety and the reduction potential of the acceptor moiety suggest polar excited state resulting from HOMO-LUMO transition. [ABSTRACT FROM PUBLISHER]

Tris(2,6-diisopropyl-4-methoxyphenyl)phosphine (1) was synthesized to investigate substituent effect of methoxy groups on the properties of crowded triarylphosphines. Methoxy groups slightly lower the first oxidation potential of 1 and contribute blue-shift of UV-Vis absorption as compared with the corresponding 2,4,6-triisopropylphenyl derivative. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented on the relapse of several types of T cell lymphoma.

Extremely crowded triarylphosphines were synthesized by the reaction of arylcopper(I) reagents with chlorophosphines, and the relationship between molecular structure and redox properties was studied by X-ray crystallography and cyclic voltammetry. As the substituent on phosphorus became bulkier, bond lengths and angles around phosphorus atom became longer and larger, and oxidation potential was significantly lowered. Especially, tris(2,4,6-triisopropylphenyl)phosphine had an extremely crowded structure and was oxidized to a stable radical cation at an extraordinarily low oxidation potential. Novel redox systems possessing the crowded triarylphosphine structure as one of the redox sites were designed and synthesized. [ABSTRACT FROM AUTHOR]

Reaction of tris(2,4,6-triisopropylphenyl)phosphine with iodine in air afforded a phosphonium triiodide resulting from the oxidation to the radical cation followed by the reaction with a molecular oxygen and the cyclization with the ortho-isopropyl group. [ABSTRACT FROM PUBLISHER]

Explains the construction of multistep redox system composed of phosphorus functional groups using triarylphosphines and sterically protected diphosphenes as redox centers. Characteristics of tetraaryldiphosphanes; Structure of the multistep redox systems possessing phosphorus and ferrocene redox centers.

Dihydrotetraphosphorylthiophene 2 was syntheiszed by the addition of sodium hydrosulfide to 2 equivalents of diphosphorylacetylene 1 followed by cyclization. Oxidation of 2 with mCPBA afforded tetraphosphorylthiophene 3. The corresponding selenium compounds 4 and 5 were analogously synthesized. [ABSTRACT FROM AUTHOR]

Presents a study that investigated synthesis, structure and redox properties of the sterically protected phosphaquinone 1, phosphaquinomethane 2, phosophathienoquinomethanes 3, diphosphaquinone 4 and diphosphathienoquinones. Methods used to synthesize the phosphaquinoid skeletons; Application of cyclic voltammetry in the study.

Investigates the synthesis of phosphoryl substituted acetylenes and their reaction with transition metal complexes. Characteristics of various phosphoryl- and bis(phosphoryl)acetylenes.