3-(Dimethylboryl)pyridine: synthesis, structure, and remarkable steric effects in scrambling reactions

A facile method for the synthesis of 3-(dimethylboryl)pyridine (1a) is described. Compound 1a assembles into a rigid cyclic tetramer stabilized via intermolecular boron-nitrogen coordination bonds both in the crystalline state and in solution. The outstanding structural feature of 1a, as compared with previously reported 3-(diethylboryl)pyridine (2a) (which adopts a cone conformation), is that the tetramer of 1a adopts a 1,2-alternate conformation. To investigate the effect of substituents at the boron atom on the stabilities of the oligomers, scrambling experiments of the component molecules using 1, 2, and 3-(di-n-butylboryl)pyridines 3 were carried out. Although heating at 80-90 degrees C for 20 h was required to attain the equilibrium of the scrambling reactions when the component molecules of the tetramers were 2 or 3, the scrambling in 1 proceeded under relatively mild conditions (60 degrees C, 3 h). This difference in reaction conditions required for 1, as compared to conditions required for 2 or 3, could not be explained solely by the stabilities based on bond lengths or THC. It appears that whereas only an S(N)1-type pathway may be involved in the scrambling of 2 or 3, both S(N)1- and S(N)2-type mechanisms operate simultaneously during scrambling reactions of 1 or an intermediate mechanism between S(N)1 and S(N)2 operates, which was supported by kinetic studies and calculations using model compounds.     

Synthesis and Crystal Structure of 2 Benzoyl Pyridine Thiosemicarbazato Palladium(II) Chloride

1　ＩＮＴＲＯＤＵＣＴＩＯＮＲｅｃｅｎｔｌｙ,ｔｈｉｏｓｅｍｉｃａｒｂａｚｏｎｅｓｈａｖｅａｔｔｒａｃｔｅｄｍｕｃｈａｔｔｅｎｔｉｏｎｗｉｔｈｉｎｂｉｏｌｏｇｉｃａｌｓｙｓｔｅｍａｎｄｃｏｏｒｄｉｎａｔｉｏｎｃｈｅｍｉｓｔｒｙ.[1-3]ＩｔｈａｓｂｅｅｎｐｏｓｔｕｌａｔｅｄｔｈａｔｍａｎｙＮｈｅｔｅｒｏｃｙｃｌｉｃｃａｒｂａｌｄｅｈｙｄｅｔｈｉｏｓｅｍｉｃａｒｂａｚｏｎｅｓａｃｔａｓｔｒｉｄｅｎｔａｔｅＮ2Ｓｌｉｇａｎｄｓｗｈｉｃｈｂｏｎｄｔｏｉｒｏｎｏｒｃｏｐｐｅｒｉｎｔｈｅｓｙｎｔｈｅｓｉｓｏｆｐ…     

Nido-6-metalladecaborane chemistry: Molecular structure and fluxionality of [6,6,6,6-(CO)2(PPh3)2-nido-6-WB9H13]

The molecular and crystal structure of the nido-6-tungstadecaborane [6,6,6,6-(CO)₂(PPh₃)₂-nido-6-WB₉H₁₃] (1) has been determined showing that the tungsten atom is incorporated into the 6-position of a nido 10-vertex (WB₉) cage. The tungsten atom has a seven-coordinate capped trigonal prismatic environment and is bonded to two hydrogen and three boron atoms of the {B₉H₁₃} cage, in addition to two CO groups and two PPh₃ ligands. Variable-temperature (−90°C to +50°C) ³¹P{¹H} NMR spectroscopy of 1 reveals that the exo-polyhedral ligands about the tungsten atom are fluxional with respect to PPh₃ site exchange with an activation energy (ΔG‡), at the coalescence temperature (−73°C), of <38 kJ mol⁻¹.     

Facile hydrometalation of alkynes by nido-1,2-(CpRuH)(2)B(3)H(7) yielding novel Ru-B edge-bridging alkylidenes. Stepwise conversion of HCtbd1;CC(O)OMe into nido-1,2-(CpRuH)(2)-3-HOB-4-MeC-5-MeOC-BH(3), Cp = eta(5)-C(5)Me(5)

The reaction of the alkyne HCCC(O)OMe with 7 sep 1,2-(Cp*RuH)2B3H7 leads to hydroboration plus hydroruthenation to produce nido-1,3-mu-Me{C(O)OMe}C-1,2-(Cp*Ru)2B3H7, a compound with an exocluster ruthenium-boron mu-alkylidene that exists in two isomeric forms. Both isomers undergo rearrangement with intramolecular chelation of the carbonyl oxygen at a boron site, thereby opening the cluster and generating arachno-2,3,-mu(C)-5-eta1(O)-Me{C(O)OMe}C-1,2-(Cp*Ru)2B3H7. Further heating leads to deoxygenation of the carbonyl fragment by a boron center concurrent with insertion of the carbon atom into the metallaborane cage to give nido-1,2-(Cp*RuH)2-3-HOB-4-MeC-5-MeOC-BH3.     

Synthesis and Crystal Structure of Ni(Ⅱ) Complex with N-Salicylaldehyde-N''-phenoxyacetylhydrazine Ligand

The title complex NiL(py)3, where H2L = N-salicylaldehyde-N'-phenoxyacetyl hydrazine, was prepared and characterized by X-ray diffraction. The single crystal of the title compound, Ni(C15H12N2O3)(C5H5N)3, is of monoclinic, space group P21/c with a = 11.900(1), b = 9.6855(7), c = 23.658(2)A,β = 92.357(2)°, V = 2724.5(4) A3, Z = 4, F(000) = 1176, Dc = 1.376 g/cm3, μ = 0.753 mm-1, R = 0.0332 and Wr = 0.0820. The coordination polyhedron around the nickel atom is an elongated octahedron. The basal plane consists of one phenol oxygen, one amine carbonyl oxygen and one hydrazine nitrogen atoms from the ligand L2- and one nitrogen atom from one coordinated pyridine ligand, while the axial sites are occupied by two nitrogen atoms of two coordinated pyridine ligands.     

A New Carborane Cage: Hexacarba-arachno-dodecaborane(12)

A drum-shaped cage built up from six carbon and six boron atoms is proposed for the structure of 2 based on the comparison of experimental and calculated NMR chemical shifts. The novel arachno carborane 2 was obtained upon treatment of bis(diethylboryl)ethyne ( 1 ) with an excess of tetraethyldiborane(6) [Eq. (a)].     

异双核化合物PdMo(μ-Ph~2Ppy)~2(μ-CO)(CO)~2I~2.0.5CH~2Cl~2的合成和晶体结构

本文合成了新的异双核化合物PdMo(μ-Ph~2Ppy)~2(μ-CO)(CO)~2I~2.0.5CH~2Cl~2, 对它进行了表征, 并测定其晶体和分子结构。该化合物属PI空间群, a=0.9500(2), b=1.1302(2), c=1.993(1)nm, α=102.82(3),β=101.21(3), γ=94.57(2)°, D~x=1.82g/cm^3, Z=2, R=0.064。晶体结构测定表明, 该化合物具有Pd-Mo键, 键长为0.28596(9)nm。如将Pd-Mo键考虑在内, Pd原子为d^9五配位构型, Mo原子为d^5七配位构型。两者的形式氧化态均为+1。     

A new mode of reactivity for pyridine N-oxide: C-H activation with uranium(IV) and thorium(IV) bis(alkyl) complexes

Uranium(IV) and thorium(IV) bis(alkyl) complexes of the type (C5Me5)2AnR2 (An = U, Th; R = CH3, CH2Ph) activate the sp2 and sp3 hybridized C-H bonds in pyridine N-oxide and lutidine N-oxide to produce the corresponding cyclometalated complexes, (C5Me5)2An(R)[eta2-(O,C)-ONC5H4] and (C5Me5)2An(R)[eta2-(O,C)-ON-2-CH2-5-CH3-C5H3]. These provide rare examples of C-H activation chemistry mediated by actinide metal centers. This chemistry is in contrast to the known oxygen atom transfer reactivity patterns of pyridine N-oxides with oxophilic metal complexes and constitutes a new mode of reactivity for pyridine N-oxides.     

一维链状配位聚合物[Cu(CH3COO)(C5H5N)2]n的合成与晶体结构

The coordination polymer [Cu(CH3COO)(C5H5N)2]n was synthesized and its crystal structure has been determined by X-ray diffraction technique.The crystal belongs to monoclinic,space group C2/c with a=1.183 2(1) nm,b=1.512 1(2) nm,c=1.3911(1) nm,β=97.137(3)°,V=2.469 6(4) nm3,C12H13CuN2O2,Mr=280.78,Z=8,Dc=1.510 g·cm-3,μ=1.759 mm-1,F(000)=1 152,R1=0.048 2 and wR2=0.122 5 for 1 515 observed reflections [1>2σ(Ⅰ)].In the crystal the copper(Ⅲ) atom is tetra-coordinated primarily by two oxygen atoms of two symmetry-related carbexyl groups of acetate anions and two nitrogen atoms of two pyridine ligands in a parallelogram fashion.All of the pyridine rings linked to Cu(1) and Cu(2) are arranged centrosymmetrically on Cu(1).The neighboring copper complex molecules are linked together by the carboxylate oxygen atom of acetate anions to form an infinite one-dimensional linear chain structure.Moreover,π-π stacking interactions between intrachain pyridine molecules play the crucial role in constructing of the supramolecular structure.CCDC:709977.     

Syntheses of the first amine-dicarboxyboranes and their bis(methylester) and bis(N-ethylamide) derivatives

Amine-bis(N-ethylcarbamoyl)boranes [A.BH(CONHEt)(2), 3; A = trimethylamine (Me(3)N, a), quinuclidine (Q, b), pyridine (py, f), 4-picoline (pic, g)] have been prepared after deprotonation of [amine-bis(C-hydroxy-N-ethylimidate)hydroboron(2+)] cations (2), which were formed by the hydrolysis of [amine-bis(ethylnitrilium)hydroboron(2+)]tetrafluoroborates (1). Numerous representatives of 3 [A = diethylamine (Et(2)NH, c), piperidine (pip, d), pyrrolidine (pyrr, e), 4-aminopyridine (4-NH(2)-py, h), 4-(dimethylamino)pyridine (DMAP, i), imidazole (Him, j), 1-methylimidazole (Mim, k)] have been prepared by base exchange reactions from 3a. 3a-e are extremely stable in aqueous media, either acidic or alkaline, probably because of the considerable steric hindrance of possible reaction centers. However, they were transformed into amine-dicarboxyboranes [A.BH(COOH)(2), 4a-e] in acidic medium under vigorous conditions (100-130 degrees C). This transformation was accompanied by significant decomposition, probably owing to the protonation on the N atom, resulting in the rupture of the B-N bond. As an exception, 4b, where N atom in a rigid bicycle is not prone to attacks, could be isolated in very good yield. On the other hand, amine-bis(N-ethylcarbamoyl)boranes containing amines with sp(2)-hybridized N atoms (3f-k) undergo complete decomposition under similar conditions probably because of the increased hydridic character of the hydrogen adjacent to boron. Base exchange reactions starting from 4b resulted in the ammonium salts of 4c-e, h, i of composition [A.BH(COOH)(COO(-))][AH(+)], which in turn could be transformed into the diacids 4, except 4h, by protonation. As salt formation indicates, the 4 compounds are stronger acids as univalent acids than the corresponding A.BH(2)(COOH) complexes. 4a-e, i were readily esterified into amine-bis(methoxycarbonyl)boranes (5a-e, i) in methanol, employing a catalytic amount of HBr. 5a-e, i are stable in alkaline medium but are readily hydrolyzed in acidic medium. Hydrolysis of [amine-bis(C-methoxy-N-ethylimidate)hydroboron(2+)] cations did not give the corresponding bisesters 5 in alkaline, neutral, or acidic medium.     

A new type of hexaosmium boride cluster, H3Os6(CO)16B, that does not conform to electron counting rules

A new type of hexaosmium boride cluster, H3Os6(CO)16B, was produced in the thermolysis of H3Os3(CO)9(BCO). This complex is an 86 valence electron cluster, but the Os6 framework does not possess one of the geometries previously observed for Os6 clusters that have 86 valence electrons. [HOs6(CO)18]- and [Os6(CO)18]2- have octahedral frameworks while that of H2Os6(CO)18 is a face-capped square pyramid. The Os6 framework of H3Os6(CO)16B can be viewed as being derived from a pentagonal bipyramid that is missing one equatorial vertex. It contains an interior boron atom. Alternatively, it can be viewed like the 84 valence cluster Os6(CO)18 as either a bicapped tetrahedron, with a boron atom residing on the edge of the tetrahedron that is common to the capped faces, or a face-capped trigonal bipyramid, with the boron atom on an equatorial edge of the bipyramid that is also an edge of the capped face. H3Os6(CO)16B was characterized by 1H, and 11B, 13C NMR, IR, and mass spectroscopies and single-crystal X-ray diffraction analysis. The molecular structure was determined from two separate crystals. The analysis of each crystal yielded virtually identical structures, but their volumes differed by 36 A3 due to differences in packing in the unit cell. Data for crystal I of H3Os6(CO)16B: monoclinic P2(1/n), a = 9.954(2) A, b = 15.780(4) A, c = 16.448(3) A, beta = 91.07(1) degrees, Z = 4. Data for crystal II of H3Os6(CO)16B: monoclinic P2(1/n), a = 9.927(2) A, beta = 16.623(2) A, b = 16.0233(10) A, beta = 97.78(1) degrees, Z = 4.     

Synthesis of boron chelates from N-(pyrid-2-YL)- and (N-4-methylpyrid-2-YL) cyanoacetamides and their tautomeric transformations

Chelate complexes in which the boron atom is bound to the pyridine N atom and the O atom of the deprotonated ligand were synthesized by reaction of N-(pyrid-2-yl)- and N-(4-methylpyrid-2-yl) cyanoacetamides. A new type of intrachelate tautomeric transformation was discovered: the complexes obtained can exist in solutions in the form of two tautomers, which are derivatives of acetimidic acid or the corresponding ketene N,O-acetals.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 164–168, January, 1991.     

Synthesis and Crystal Structure of Rctt-1-(2-benzoxazolyl)-2-(4-chlorophenyl)-4-phenyl-3-(4-pyridinyl)cyclobutane

1INTRODUCTIONThephotodimerizationof1,2-bisarylethenederivativesisaconvenientwayforsynthesizingtetraarylsubstitutedcyclobutane.Forthisreason,thephotochemistryofstilbeneandstyrylpyridinederivativeshasbeenextensivelystudied[1,2].UpontheirradiationwithUVlight(?=300～400nm),thesemonomersareconvertedtohead-to-tailphotodimersinpolarsolventwithperfectyields.Inrecentyears,ourgrouphasbeenstudyingthephotodimerizationreactionsofheteroarylethenescontainingbenzoxazolyl[3]andphenyloxazolyl[4]groups.Itw…     

High-frequency and field EPR investigation of (8,12-diethyl-2,3,7,13,17,18-hexamethylcorrolato)manganese(III)

High-field and frequency electron paramagnetic resonance (HFEPR) of solid (8,12-diethyl-2,3,7,13,17,18-hexamethylcorrolato)manganese(III), 1, shows that in the solid state it is well described as an S = 2 (high-spin) Mn(III) complex of a trianionic ligand, [Mn(III)C(3)(-)], just as Mn(III) porphyrins are described as [Mn(III)P(2)(-)](+). Comparison among the structural data and spin Hamiltonian parameters reported for 1, Mn(III) porphyrins, and a different Mn(III) corrole, [(tpfc)Mn(OPPh(3))], previously studied by HFEPR (Bendix, J.; Gray, H. B.; Golubkov, G.; Gross, Z. J. Chem. Soc., Chem. Commun. 2000, 1957-1958), shows that despite the molecular asymmetry of the corrole macrocycle, the electronic structure of the Mn(III) ion is roughly axial. However, in corroles, the S = 1 (intermediate-spin) state is much lower in energy than in porphyrins, regardless of axial ligand. HFEPR of 1 measured at 4.2 K in pyridine solution shows that the S = 2 [Mn(III)C(3)(-)] system is maintained, with slight changes in electronic parameters that are likely the consequence of axial pyridine ligand coordination. The present result is the first example of the detection by HFEPR of a Mn(III) complex in solution. Over a period of hours in pyridine solution at ambient temperature, however, the S = 2 Mn(III) spectrum gradually disappears leaving a signal with g = 2 and (55)Mn hyperfine splitting. Analysis of this signal, also observable by conventional EPR, leads to its assignment to a manganese species that could arise from decomposition of the original complex. The low-temperature S = 2 [Mn(III)C(3)(-)] state is in contrast to that at room temperature, which is described as a S = 1 system deriving from antiferromagnetic coupling between an S = (3/2) Mn(II) ion and a corrole-centered radical cation: [Mn(II)C(*)(2-)] (Licoccia, S.; Morgante, E.; Paolesse, R.; Polizio, F.; Senge, M. O.; Tondello, E.; Boschi, T. Inorg. Chem. 1997, 36, 1564-1570). This temperature-dependent valence state isomerization has been observed for other metallotetrapyrroles.     

On the directed gas phase synthesis of the imidoborane molecule (HNBH)--an isoelectronic molecule of acetylene (HCCH)

The elementary reaction of ground state boron atoms, (B((2)P(j))), with ammonia (NH(3)(X(1)A(1))) was conducted under single collision conditions at a collision energy of 20.5 ± 0.4 kJ mol(-1) in a crossed molecular beams machine. Combined with electronic structure calculations, our experimental results suggested that the reaction was initiated by a barrier-less addition of the boron atom to the nonbonding electron pair of the nitrogen atom forming a weakly bound BNH(3) collision complex. This intermediate underwent a hydrogen shift to a doublet HBNH(2) radical that decomposed via atomic hydrogen loss to at least the imidoborane (HBNH(X(1)Σ(+)) molecule, an isoelectronic species of acetylene (HCCH(X(1)Σ(g)(+))). Our studies are also discussed in light of the isoelectronic C(2)H(3) potential energy surface accessed via the isoelectronic carbon-methyl system.     

Synthesis and Structure of a Novel Compound [Cu_2(EDTA)(Py)_2(H_2O)_2]·2H_2O

1 INTRODUCTION Multinuclear coordination compounds have attrac-ted much attention due to their distinctive optical, elec-tric and magnetic properties as well as enzyme ana-logue[1～4]. It is important for carboxylic acid to de-sign this compound[5～8]. EDTA is a useful titrant formetal determination because EDTA molecule is easyto coordinate with a metal atom (1:1). Other types ofEDTA-M compounds are seldom to know except Ln2-M3(EDTA)3(H2O)11?12H2O[5] and (UO2 )2EDTA[9]. …     

Reversible intramolecular C-C bond formation/breaking and color switching mediated by a N,C-chelate in (2-ph-py)BMes2 and (5-BMes2-2-ph-py)BMes2

A diboron compound with both 3-coordinate boron and 4-coordinate boron centers, (5-BMes2-2-ph-py)BMes2 (1) and its monoboron analogue, (2-ph-py)BMes2 (2) have been synthesized. Both compounds are luminescent but have a high sensitivity toward light. UV and ambient light cause both compounds to isomerize to 1a and 2a, respectively, via the formation of a C-C bond between a mesityl and the phenyl group, accompanied by a drastic color change from yellow or colorless to dark olive green or dark blue. The structures of 1a and 2a were established by 2D NMR experiments and geometry optimization by DFT calculations. Both 1a and 2a can thermally reverse back to 1 and 2 via the breaking of a C-C bond, with the activation barrier being 107 and 110 kJ/mol, respectively. The N,C-chelate ligands in 1 and 2 were found to play a key role in promoting this unusual and reversible photo-thermal isomerization process on a tetrahedral boron center. Reactions with oxygen molecules convert 1a and 2a to 5-BMes2-2-[(2-Mes)-ph]-pyridine (1b) and 2-(2-Mes)-ph-pyridine (2b), respectively.     

含水杨醛缩对硝基苯甲酰腙的钒酰配合物和钴配合物的合成和晶体结构

本文合成了含水杨醛缩对硝基苯甲酰腙(简写为H2L)的钒酰配合物VOL(CH3OH)(CH3O)(1,C16H16N3O7V,Mr=413.26)和钴配合物[CoL(C5H5N)3]NO3C5H5N(2,C34H29N8O7Co,Mr=720.58)。配合物1属单斜晶系,空间群为P21/c,a=7.3253(3),b=18.8237(9),c=12.9014(5)?b=91.672(1),V=1778.2(1)3,Z=4,F(000)=848,m(MoKa)=0.603mm1,R=0.0470,wR=0.1312。配合物2属单斜晶系,空间群为P21/c,a=11.4196(8),b=17.157(1),c=17.081(1)?b=96.8233(9),V=3323.0(4)3,Z=4,F(000)=1488,m(MoKa)=0.578mm1,R=0.0455,wR=0.1311。在配合物1中,钒(V)原子由周围的酰氧基原子、配体L2的3个配位原子,去质子化甲醇的甲氧基原子和配位甲醇的氧原子配位,形成畸变的VO(ONO)(O)(O)八面体配位构型。晶体内每2个分子间通过氢键作用缔合成中心对称的分子对,OH…N氢键键长为2.861(4)?键角163.20。晶体中存在着弱p-p共轭作用。在配合物2中,钴(Ⅲ)原子由1个L2的3个配位原子和3个配位吡啶分子的3个氮原子配位,呈N4O2八面体配位构型。     

Synthesis and Structural Characterization of Pd[CH3O（O）C6H3CHNNC（S）NH2]（C5H5N）

1 INTRODUCTION Palladium (Ⅱ) coordination and organometallic compounds usually show square planar environments at the metal center[1], and have experienced an im- portant development in the past years due to their acting as intermediates in different types of catalytic reactions and numerous applications in organic synthesis[2]. Although palladium plays an increase- ingly recognized role as a biometal[3], little is known about the structure and function of palladium compounds in living …