Systematic Studies on Homo- and Heteronuclear Doubly Bonded Compounds of Heavier Group 15 Elements

The first stable phosphabismuthene (R 1 --P=Bi--R 2 ) and stibabismuthene (R 1 --Sb=Bi--R 2 ) were successfully synthesized by taking advantage of efficient steric protection groups, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt), 2,6-bis[bis(trimethylsilyl)-methyl]-4-[tris(trimethylsilyl)methyl]phenyl (Bbt), and 2,4,6-tri- t -butylphenyl (Mes*). Their spectroscopic properties and structural parameters were systematically compared with those of previously reported stable, homonuclear, doubly bonded systems, such as diphosphene, diarsene, distibene, and dibismuthene.     

Facile [3+2] dimerization and formal dehydrogenative coupling mode of a cyanophenylphosphaallene

Due to a facile head-to-tail [3+2] dimerization, even a sterically demanding group such as the Mes^∗ (2,4,6-tri-tert-butylphenyl) group around the PCC moiety did not allow us to isolate 3-(4-cyanophenyl)-1-(2,4,6-tri-tert-butylphenyl)-1-phosphaallene from the elimination reaction of 2-bromo-3-(4-cyanophenyl)-1-(2,4,6-tri-tert-butylphenyl)-1-phosphaprop-1-ene with DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), and the corresponding 1,4-diphosphafulvene containing cyano groups was obtained and characterized. Theoretical studies on the [3+2] dimerization of phosphaallene characterize possible intermediates affording 1,4-diphosphafulvenes and also suggest the cyano group effect to facilitate the saturation of the PC double bonds. On the other hand, 1,2-bis(4-cyanophenyl)-3,4-bis[(2,4,6-tri-tert-butylphenyl)phosphinidene]cyclobutene was obtained from 2-bromo-3-(4-cyanophenyl)-3-trimethylsiloxy-1-(2,4,6-tri-tert-butylphenyl)-1-phosphaprop-1-ene together with the 3-(4-cyanophenyl)-1-phosphaallene.     

2,4,6-三萘基-1,3,5-三嗪的合成与光谱行为

本文通过Suzuki偶联反应高效合成了两种三萘基三嗪化合物,即2,4,6-三(1-萘基)-1,3,5-三嗪(T1NT)和2,4,6-三(2-萘基)-1,3,5-三嗪(T2NT). 考察了介质的极性、温度以及THF-H₂O二元溶剂体系中的溶解性等因素对它们吸收和发射光谱行为的影响.研究发现, 由于T1NT比T2NT具有更好的分子平面性,其激发态下分子内电荷转移的程度较大,导致其在溶液中吸收光谱、发射光谱比T2NT呈现显著红移.冻结态下,分子平面性较差的T2NT显示出较短波长的发光.     

The Reaction of Methyl 2,4,6-Tri-0-benzoyl-3-0-benzyl-β-D-galactopyranoside with 1,1-Dichloromethyl Methyl Ether

When methyl 2,4,6-tri-0-benzoyl-3-0-benzyl-β-D-galacto-pyranoside (JO is treated in purified chloroform at 55-60′ with excess of dichloromethyl methyl ether in the presence of a catalytic amount of freshly fused zinc chloride for 1 h the corresponding α-glycosyl chloride 2 can be isolated by column chromatography in 75-80% yield. Compound 2 is an important intermediate in the synthesis of oligosaccharides containing a glycosyl-3-0-galactosyl sequence. Under the described reaction conditions the conversion 1 - 2 is accompanied by a slow anomerisation of 1 to give methyl 2,4,6-tri-0-benzoyl-3-0-benzyl-α-D-galactopyranoside. Prolonged treatment of 2 with the used excess of the reagent results in complete debenzylation of the substrate and the conversion of the putative 2,4,6-tri-O-benzoyl-α-D-galactopyranosyl chloride into the corresponding 3-0-formyl and 3-0-dichloromethyl derivatives.     

An effective synthesis of α-glycosides of -acetylneuraminic acid derivatives by use of 2-deoxy-2β-halo-3β-hydroxy-4,7,8,9-tetra- -acetyl- -acetylneuraminic acid methyl ester

Condensation of a new glycosyl donor, methyl 5-acetamido-4, 7,8,9-tetra- -acetyl-2,3-dibromo-2,3,5-trideoxy-β- -2-nonulopyranosonate with various acceptors such as methyl 2,3,4-tri- -benzyl-α- -glucopyranoside, cholesterol, methyl 2,4,6-tri- -bonzyl-α- -galactopyranoside, and nethyl 5-acetamido-4,7,9-tri- -acetyl-2,6-anhydro-3,5-dideoxy- -non-2-enopyranosonate gave only the corresponding β-glycosides. The 3α-bromo group of the glycoaides obtained above was reduced with tributylstannane to the corresponding glycosids, which were deprotected to give the free glycoaides in high yields.     

Preparations and properties of polymers containing 3,4-bis[(2,4,6-tri-t-butylphenyl)phosphinidene]-1,2-di(2-thienyl)cyclobutene moieties

Reaction of 1,8-bis[5-{(2,4,6-tri-t-butylphenyl)phosphinoethynyl}-2-thienyl]octane with butyllithium followed by treatment with 1,2-dibromoethane afforded a new polymer containing 3,4-bis[(2,4,6-tri-t-butylphenyl)phosphinidene]-1,2-di(2-thienyl)cyclobutene units. The polymer was allowed to react with bis(benzonitrile)dichloropalladium to give the polymer complex. A Sonogashira coupling reaction between ethynyltrimethylsilane and 4-bromonitrobenzene proceeded in DMF at 100 °C to give 4-nitro(trimethylsilylethynyl)benzene in the presence of the polymer complex, CuI, and triethylamine.     

Preparation, properties, and catalytic activity of transition-metal complexes containing a ligated 2-methyl-3,3-diphenyl-1,3-diphosphapropene skeleton

2-Methyl-3,3-diphenyl-1-(2,4,6-tri-t-butylphenyl)-1,3-diphosphapropene behaved as an unsymmetrical chelating ligand for transition metal complexes and the 1,3-diphosphapropene moiety was hydrolyzed to afford the 1,3-diphosphapropan-1-ol derivative upon coordination. The palladium complex showed catalytic activity for the Sonogashira coupling reaction.     

Unusual face-to-face pi-pi stacking interactions within an indigo-pillared M3(tpt)-based triangular metalloprism

A triangular metalloprism, [((CO)3Re(mu-2)Re(CO)3)3(mu3-1)2], self-assembled from Re2(CO)10, 2,4,6-tri-4-pyridyl-1,3,5-triazine (tpt, 1), and indigo (H2(2)), represents a fairly novel example of strong face-to-face pi-pi interactions between the central triazine rings of the tpt ligands that bow significantly inward distorting the prismatic structure.     

Ligand effect of bulky 2,2-dialkyl-1-phosphaethenes on Au-catalyzed cycloisomerization of 1,6-enynes and lactonization of pent-4-ynoic acids

2,2-Dimethyl- and 2-benzyl-2-methyl-1-(2,4,6-tri-tert-butylphenyl)-1-phosphaethenes were employed as ligand of mononuclear chlorogold(I) complexes, which catalyzed cycloisomerization of 1,6-enyne affording vinylcyclopentene exclusively in the absence of silver co-catalyst. The reaction mechanisms are discussed based on DFT calculations. In addition to the cycloisomerization, the phosphaalkene-chlorogold(I) complexes catalyzed cyclization of pent-4-ynoic acids providing γ-methylene-γ-lactones under basic conditions.     

Dicarboxylate-bridged ruthenium complexes as building blocks for molecular nanostructures

Ruthenium complexes with bridging dicarboxylate ligands were combined with 1,2-di-4-pyridylethylene (dpe), 2,4,6-tri-4-pyridyltriazine (4-tpt), or 2,4,6-tri-3-pyridyltriazine (3-tpt) to give a tetranuclear rectangle or hexanuclear coordination cages. The cages display a trigonal-prismatic geometry, as evidenced by single-crystal X-ray crystallography. The 4-tpt-based cages are able to encapsulate polyaromatic molecules such as pyrene, triphenylene, or coronene, whereas the 3-tpt-based cages were found to be incompetent hosts for these guests.     

Reactions of 1,2-di(2-thienyl)-3,4-bis[(2,4,6-tri-t-butylphenyl)phosphinidene]cyclobutene

Reactions of a sterically protected 1,2-di(2-thienyl)-3,4-bis[(2,4,6-tri-t-butylphenyl)phosphinidene]cyclobutene were investigated. The diphosphinidenecyclobutene reacted with elemental sulfur or transition metal reagents to form a thiaphosphirane derivative or the corresponding transition metal complexes, respectively. Reactions of the di(2-thienyl)diphosphinidenecyclobutene with butyllithium followed by treatment with electrophiles afforded functionalized di(2-thienyl)diphosphinidenecyclobutene derivatives.     

Synthesis and properties of air-stable 1,3-diphosphacyclobutane-2,4-diyls and the related compounds

A kinetically stabilized phosphaalkyne bearing a bulky Mes^∗ (2,4,6-tri-t-butylphenyl) group is useful compound to prepare an enormous number of highly stable 1,3-diphosphacyclobutane-2,4-diyls through reactions with a lithium reagent and an electrophile. By utilizing this synthetic protocol, we prepared several non-symmetrical 1,3-diphosphacyclobutane-2,4-diyls in which the substituents on the phosphorus are different. Furthermore, we succeeded in preparation and characterization of novel air-tolerant symmetrical 2,4-bis(2,4,6-tri-t-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyls bearing the identical alkyl substituents on the phosphorus atoms. Structures and properties of the 1,3-diphosphacyclobutane-2,4-diyls indicate characters as singlet ground-state carbon centered biradicals. In addition to those biradicals, we succeeded in preparation and isolation of a novel P-heterocyclic air-stable neutral radical as well as a P-heterocyclic cation radical.     

Theoretical study of Ln(III) complexes with polyaza-aromatic ligands: geometries of [LnL(H2O)n]3+ complexes and successes and failures of TD-DFT

The accuracy and the usefulness of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations for the theoretical study of Ln (La, Eu, Lu) complexes have been investigated. The geometries calculated at the DFT level for [Ln(H2O)nL]3+ complexes have been successfully compared with crystallographic data. TD-DFT is able to offer valuable insights into VUV spectra of lanthanide complexes. However, the results obtained on the largest ligand (i.e., 2,4,6-tri-(pyridin-2-yl)-1,3,5-triazine (Tptz)) have to be considered as a failure of TD-DFT.     

Built to order: molecular tinkertoys from the [Re(6)(mu(3)-Se)(8)](2+) clusters

Ligand substitution of [Re(6)(mu(3)-Se)(8)(PEt(3))(5)(CH(3)CN)](SbF(6))(2) (1) with pyridyl-based ligands, 2,4,6-tri-4-pyridyl-1,3,5-triazine (L1) and 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (L2), produced respectively the star-shaped tricluster (T1) and tetracluster (T2) arrays, wherein three (T1) and four (T2) units of the [Re(6)(mu(3)-Se)(8)](2+) core-containing clusters are interconnected by the corresponding bridging ligands. These novel supramolecular assemblies were characterized by a combination of NMR ((1)H and (31)P) spectroscopy, ESI-MS, and microanalysis. The molecular and solid-state structures of T1 have also been established by single-crystal X-ray diffraction.     

Verbindungen des Germaniums und Zinns. 3. Sterisch überladene Alkylarylstannane durch Übertragung und Isomerisierung von 2,4,6-Tri-tert-butylphenylgruppen

Compounds of Germanium and Tin. 3. Sterically Congested Alkylarylstannanes by Transfer and Isomerization of 2,4,6-Tri-tert-butylphenyl Groups Reaction of SnBr₄ and SnI₄ with 2,4,6-tri-tert-butylphenyllithium (ArLi) by rearrangement of two Ar-groups gives the stannanes ArR₂SnBr ( 3 ) and ArR₂SnI ( 4 ), R = 2-methyl-2(3,5-di-tert-butylphenyl)propyl, which by a further transalkylation reaction with methyl lithium yield ArR₂SnCH₃ ( 5 ). However, treatment of 3 and 4 with tert-butyl lithium exclusively leads to ArR₂SnH ( 6 ) which surprisingly is also obtained by reaction of ArRSnCl₂ with tert-butyl lithium, presumably by an intermolecular R-group transfer. The structures of 5 and 6 were confirmed by X-ray crystallography.     

Membrane for in situ optical detection of organic nitro compounds based on fluorescence quenching

Fluorescent membrane formulations for detecting organic nitro compounds by fluorescence quenching were evaluated. The most sensitive membrane is prepared by solvent casting from cyclohexanone to incorporate pyrenebutyric acid into cellulose triacetate plasticized with isodecyl diphenylphosphate. The response follows the Stern-Volmer law for 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT). The membrane also responds to hexahydro-1,3,5-tri- nitro-1,3,5-triazine (RDX). For a given set of conditions, the primary factor determining sensitivity is the extent to which each nitro compound partitions into the membrane. Detection limits are ca. 2 mg l^?1 for DNT and TNT and 10 mg l^?1 for RDX. Nitrogen purging prior to the measurement enhances the sensitivity and eliminates interference from oxygen. The membrane is designed to be used for remote optical in situ screening of groundwater for contamination by explosives.     

Charge gating and electronic delocalization over a denderimeric assembly of trinuclear ruthenium clusters

A zeroth-order dendrimer was formed using a tridentate bridging ligand, 2,4,6-tri-4-pyridyl-S-triazine, and the redox-active trinuclear ruthenium cluster Ru3O(OAc)6(CO)(py)(H2O). The electronic properties of this dendrimer were probed using cyclic voltammetry. IR spectroelectrochemistry was performed at both low (-30 degrees C) and room temperature. The IR spectroelectrochemical response at -30 degrees C was straightforward, but at room temperature, the dendrimer exhibits an unusual and complex series of electronic behaviors, including intramolecular cluster-to-bridging-ligand charge transfer, gated electron transfer, and dynamic exchange on the IR time scale.     

新型树形化合物1,3,5-三-[7-(7-甲基-2,2-二-(2,2-二羟甲基-3-羟基丙氧基羰基)-6,8-二氧杂螺[3.5]-壬基)]苯的合成

以丙酮和甲酸乙酯为原料, 在醇钠的作用下合成了1,3,5-三乙酰基苯(1). 1与二溴新戊二醇在酸的作用下发生缩酮化反应, 制成1,3,5-三-(1-甲基-2,6-二氧杂-4,4-二溴甲基环己基)苯(2). 2与5,5-二甲基-4,6-二氧杂-1,3-环己二酮在乙醇钠的作用下合成了1,3,5-三-[7-(7-甲基-2,2-二-乙氧羰基-6,8-二氧杂螺[3.5]-壬基)]苯(3). 将3在氯仿中与季戊四醇进行酯交换反应得到产物1,3,5-三-[7-(7-甲基-2,2-二-(2,2-二羟甲基-3-羟基丙氧基羰基)-6,8-二氧杂螺[3.5]-壬基)]苯(4). 收率为47.7%. 标题化合物及中间产物使用IR, ¹H NMR和MS或元素分析进行了表征.     

Reaction of a diphosphene with various halogens

Bis(2,4,6-tri-$\text{tert}$-butylphenyl) diphosphene reacts with various halogens to give the corresponding phosphoric dihalides, haloarene, and arene depending upon the halogen and solvent used.     

Stability and equilibria of free radicals—III Preparation of stable, sterically shielded, diarylnitrogen radicals with donor and acceptor aryl groups in the same molecule

Diarrylamines ArNHAr′ (Ar = 2,4,6-tri-, 2,6-di- or 2,4-dinitrophenyl, and Ar′ = phenyl or a phenyl with electron-donating substituents) were prepared; their IR and UV spectra, electrooxidation and electroreduction potentials were studied. Oxidation of picryl- and 2,6-dinitrophenyl-substituted compounds with Ag₂O affords paramagnetic solution giving ESR signals with Ar′ has MeO or NR₂ substituents. Radicals IVi and Vi are stable even in crystalline state.