Ring-borylated 15-electron and 17-electron ansa-chromocene complexes, their physical properties and molecular structures

A detailed study of the thermal decomposition of the zwitterionic, ring-borylated ansa-chromocene hydrido carbonyl complex [Cr(CO)H{Me(4)C(2)(C(5)H(4))[C(5)H(3)B(C(6)F(5))(3)]}] (2) is described. This complex is formed in the reaction between [Cr(CO){Me(4)C(2)(C(5)H(4))(2)}] (1) and B(C(6)F(5))(3) in toluene at -78 degrees C. Above -25 degrees C, 2 decomposes to a 50:50 mixture of the low-spin, 17e Cr(III) complexes [Cr(CO){Me(4)C(2)(C(5)H(4))[C(5)H(3)B(C(6)F(5))(3)]}] (3b) and [Cr(CO){Me(4)C(2)(C(5)H(4))(2)}][HB(C(6)F(5))(3)] (4). Carbon monoxide elimination from 3 b generates high-spin, 15 e [Cr{Me(4)C(2)(C(5)H(4))[C(5)H(3)B(C(6)F(5))(3)]}] (3a), which coordinates two other electron-donating ligands, such as xylyl isocyanide, PMe3, and PPh(2)Me to form the low-spin, 17 e electron complexes 3c, 3d, and 3e, respectively. High-spin, 15 e [Cr{Me(4)C(2)(C(5)H(4))(2)}][HB(C(6)F(5))(3)] (5) is generated by heating 3 b in toluene at 100 degrees C and periodically removing the evolved CO. Efforts to isolate more than a few X-ray quality crystals of 5 were thwarted by its tendency to form an insoluble precipitate (6) with the same molecular formula. Heating the solution of 5 at 120 degrees C results in its partial conversion (ca. 28 %) to 3a, thereby allowing the formation of 3a in yields as high as 74 % from the reaction between 1 and B(C(6)F(5))(3). The X-ray crystal structures of 3 b-e and 5 are described. Cyclic voltammetry measurements on 3 a-e reveal a dramatic reduction in the redox potentials of the complexes relative to their non-borylated analogues. DFT calculations show that this is due primarily to electrostatic stabilization of the oxidized species by the negatively charged borylate group. EPR and 19F NMR spectroscopy allow 3a to be distinguished from its Lewis base adducts 3 b-e and reveal the relative affinities of different Lewis bases for the chromium.     

Reactivity of 17- and 19-electron organometallic complexes. Formation of bent sandwich 19-electron radical cation complexes of ruthenium and osmium

The redox behavior of sandwich indenyl complexes of the general formula (⁵-C₉H₇)ML (M=Ru and L=⁵-C₉H₇ (1), ⁵-C₅H₅ (2), ⁵-C₅Me₅ (3); M=Os, L=⁵-C₉H₇ (4)) has been studied in THF, MeCN, and CH₂Cl₂ by cyclic voltammetry and controlled potential electrolysis on a Pt electrode in the –85 to +20 °C temperature range. The title complexes have been found to undergo reversible one-electron oxidation to the corresponding radical cations, whose stabilities and reactivities depend on the nature of both the metal and °-ligands and of the nucleophilic properties of the solvent. The fast interaction of the electrogenerated 17-electron radical cations with nucleophiles yields bent sandwich 19-electron radical cations, [(⁵-C₉H₇)M(L)(Nu)]⁺ (Nu = Cl^–, MeCN, or THF), the latter undergoing one-electron oxidation to the corresponding [(⁵-C₉H₇)M(L)(Nu)]²⁺ dications. In the case of Nu=THF, the reaction of the electrogenerated 17-electron radical cations with nucleophiles appears to be reversible. Radical cations [(⁵-C₉H₇)₂M]^+· (M=Ru, Os) have been characterized by ESR spectra.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2394–2399, December, 1995.     

Controlled synthesis of poly(methyl methacrylate) catalyzed by 17-electron closo-ruthenacarboranes and aliphatic amines

The radical polymerization of methyl methacrylate catalyzed by systems based on paramagnetic closo-ruthenacarboranes with diphosphine ligands is studied. Effects of the structure of metallocomplex catalysts on the rate of polymerization and the molecular-mass characteristics of the polymers are investigated. It is shown that the addition of amines to the reaction solution makes it possible to reduce the concentration of metallacarborane catalysts to hundredths of a percent, while control over the polymerization process remains at a high level.     

A novel synthesis of carbene complexes of manganese and molybdenum containing the trichlorogermyl group

A number of carbene complexes of formulas Cl₃GeMn(CO)₄C(OR′)R and C₅H₅Mo(CO)₂(GeCl₃)C(OR′)CH₃ (R = CH₃, C₆H₅; R′ = CH₃, C₂H₅) have been prepared by the reaction of [N(C₂H₅)₄]GeCl₃ with CH₃Mn(CO)₅, C₆H₅Mn(CO)₅, or C₅H₅Mo(CO)₃CH₃ followed by alkylation of the resulting trichlorogermylacylcarbonylmetallate ion. The compound C₅H₅Mo(CO)₂(GeCl₃)$\text{COCH}{}_2\text{CH}{}_2\text{C}$H₂ has been prepared directly by the reaction of [N(C₂H₅)₄]GeCl₃ with C₅H₅Mo(CO)₃(CH₂)₃Br.     

Charge-transfer complexes of phenothiazine derivatives with π-electron acceptors

Charge-transfer complexes (CTC) of some phenothiazine derivatives with -electron acceptors were obtained. They were used to determine the ionization potentials of the investigated donor compounds. The complexing constants of phenothiazine and some of its N-substituted derivatives were found. The experimental data obtained make it possible to draw conclusions relative to their configurations.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 497–501, April, 1973.     

Bis-aryldiazo complexes of manganese

The first bis-aryldiazo complexes containing manganese of the type MnX(N₂Ph)₂(PPh₃)₂ and Mn(CO)(N₂Ph)₂(PPh₃)₂⁺PF₆^? have been prepared from Mn(CO)₂(N₂Ph)(PPh₃)₂ (X  Cl, Br, NCO). In addition, the mixed aryldiazonitrosyl analogues and the dinitrosyl analogues have been prepared in order to compare their spectroscopic properties with the bis-aryldiazo complexes. The preparation of the rhenium complex Re(CO)₂(N₂Ph)(PPh₃)₂ is also reported.     

拓扑结构高分子的高效“点击”合成

树枝状、梳形、超枝化、星形、及H形等支链结构和环形、多环形等结构的拓扑高分子具有不同于直链结构高分子的独特性能,是一类在材料改性、纳米科技和生物医药等领域有着重要应用前景的新型功能性聚合物材料,日益受到人们的重视,但其复杂的结构导致它们的合成非常繁琐并因此束缚其实际应用.具有定量、快速、高效和高选择性、反应条件温和、产物单一、易于分离等特点的点击反应(click reaction)的应用极大地推动了拓扑结构高分子合成方法的发展.本文就炔/叠氮1,3-偶极环加成反应(CuAAC)、硫醇-烯/炔、胺-丙烯酸酯、Diels-Alder环加成等点击反应应用于树枝状、超枝化、环形、星型等拓扑结构高分子的合成做一简要介绍,并提出了进一步的研究方向.     

Hyperbranched macromolecules bridged salicylaldimine cobalt complexes: synthesis,characterization and ethylene oligomerization studies

A series of novel 1.0 generation (1.0G) hyperbranched macromolecules bridged salicylaldimine cobalt complexes were synthesized in high yields. The compounds were characterized by fourier transform infrared (FT-IR) spectroscopy, ultraviolet (UV) visible spectroscopy, electrospray ionization mass spectrometry (ESI–MS), elemental analysis and thermal gravimetric analysis (TGA), as well as were investigated as precatalysts for the oligomerization of ethylene. Upon activation with methylaluminoxane (MAO) and diethylaluminumchloride (DEAC), the cobalt precatalysts showed moderate catalytic activities in the range of 10⁵ g/(mol Co h) in ethylene reactivity with the high selectivity for the butenes and high carbon number olefins products. The correlation between cobalt complexes and their catalytic activities and product distribution were investigated in detail under various reaction parameters. The research results showed that the catalytic activities of precatalysts increased with the increase of ethylene pressure and Al/Co molar ratio; however, the catalytic activities firstly increased and then decreased with the increase of reaction temperature. The highest activity of 2.54 × 10⁵ g/(mol Co h) and 50.18% selectivity of high number carbon olefins was obtained under the reaction temperature of 25 °C, ethylene pressure of 0.5 MPa, and Al/Co molar ratio of 1500. In addition, the nature of solvent and co-catalyst, as well as the structure of precatalysts, significantly affected both the activity and the product distribution of the resultant catalysts.     

Positive cooperativity in the template-directed synthesis of monodisperse macromolecules

Two series of oligorotaxanes R and R' that contain -CH(2)NH(2)(+)CH(2)- recognition sites in their dumbbell components have been synthesized employing template-directed protocols. [24]Crown-8 rings self-assemble by a clipping strategy around each and every recognition site using equimolar amounts of 2,6-pyridinedicarboxaldehyde and tetraethyleneglycol bis(2-aminophenyl) ether to efficiently provide up to a [20]rotaxane. In the R series, the -NH(2)(+)- recognition sites are separated by trismethylene bridges, whereas in the R' series the spacers are p-phenylene linkers. The underpinning idea here is that in the former series, the recognition sites are strategically positioned 3.5 ? apart from one another so as to facilitate efficient [π···π] stacking between the aromatic residues in contiguous rings in the rotaxanes and consequently, a discrete rigid and rod-like conformation is realized; these noncovalent interactions are absent in the latter series rendering them conformationally flexible/nondiscrete. Although in the R' series, the [3]-, [4]-, [8]-, and [12]rotaxanes were isolated after reaction times of <5-30 min in yields of 72-85%, in the R series, the [3]-, [4]-, [5]-, [8]-, [12]-, [16]-, and [20]rotaxanes were isolated in <5 min to 14 h in 88-98% yields. It follows that while in the R' series the higher order oligorotaxanes are formed in lower yields more rapidly, in the R series, the higher order oligorotaxanes are formed in higher yields more slowly. In the R series, the high percentage yields are sustained throughout, despite the fact that up to 39 components are participating in the template-directed self-assembly process. Simple arithmetic reveals that the conversion efficiency for each imine bond formation peaks at 99.9% in the R series and 99.3% in the R' series. This maintenance of reaction efficiency in the R series can be ascribed to positive cooperativity, that is, when one ring is formed it aids and abets the formation of subsequent rings presumably because of stabilizing extended [π···π] stacking interactions between the arene units. Experiments have been performed wherein the dumbbell is starved of the macrocyclic components, and up to five times more of the fully saturated rotaxane is formed than is predicted based on a purely statistical outcome, providing a clear indication that positive cooperativity is operative. Moreover, it would appear that as the R series is traversed from the [3]- to the [4]- to the [5]rotaxane, the cooperativity becomes increasingly positive. This kind of cooperative behavior is not observed for the analogous oligorotaxanes in the R' series. The conventional bevy of analytical techniques (e.g., HR-MS (ESI) and both (1)H and (13)C NMR spectroscopy) help establish the fact that all the oligorotaxanes are pure and monodisperse. Evidence of efficient [π···π] stacking between contiguous arene units in the rings in the R series is revealed by (1)H NMR spectroscopy. Ion-mobility mass spectrometry performed on the R and R' series yielded the collisional cross sections (CCSs), confirming the rigidity of the R oligorotaxanes and the flexibility of the R' ones. The extended [π···π] stacking interactions are found to be present in the solid-state structures of the [3]- and [4]rotaxanes in the R series and also on the basis of molecular mechanics calculations performed on the entire series of oligomers. The collective data presented herein supports our original design in that the extended [π···π] stacking between contiguous arene units in the rings of the R series of oligorotaxanes facilitate an essentially rigid rod-like conformation with evidence that positive cooperativity improves the efficiency of their formation. This situation stands in sharp contrast to the conformationally flexible R' series where the oligorotaxanes form with no cooperativity.     

Protonation of manganese phosphonioallenyl complexes

The addition of phosphines to the manganese allenylidene complexes Cp(CO)₂MnCCC(Ph)R (R = H, Ph) proceeds selectively at the C_α atom to result in the α-phosphonioallenyl complexes Cp(CO)₂Mn⁻-C(⁺PR₃¹)CC(Ph)R. The protonation of the latter affords the η²-(1,2)-phosphonioallenes Cp(CO)₂Mn{η²-(1,2)-HC(⁺PR₃¹)CC(Ph)R}, rather than the phosphoniovinylcarbenes Cp(CO)₂MnC(⁺PR₃¹)-HCC(Ph)R. All complexes obtained are stereochemically rigid and do not isomerize into the η²-(2,3)-phosphonioallene isomers.     

Stable shell structures in hydrogen-bonded complexes

Neutral clusters (NH₃) _n ((CH₃)₃N) _m and (H₂O) _n ((CH₃)₃N) _m , prepared in a pulsed nozzle supersonic expansion, are ionized by multiphoton ionization and investigated with a reflectron time-of-flight mass spectrometry technique. The observed mixed cluster ions display a maximum intensity atm=2(n+1) whenn ≦ 5 for (NH₃) _n ·((CH₃)₃N) _m H⁺ andm=n+2 whenn ≦ 4 for (H₂O) _n ((CH₃)₃N) _m H⁺ indicating that the cluster ions with these combinations have a stable closed shell structure. However, the pattern begins to break down whenn>5 for ammonia system andn>4 for water system. Thereupon, the most intense peaks are reached with one molecule less than the pattern required, i.e.m=2(n+1)?1 whenn=6 for (NH₃) _n ((CH₃)₃N) _m H⁺ andm=(n+2)?1 whenn=5 for (H₂O) _n ((CH₃)₃N) _m H⁺. These findings strongly suggest the onset of hydrogen-bonded ring structures from chain-like ones at critical cluster sizes. This is also supported by the studies of the metastable decomposition.     

An interdependent site exchange process of some 16-electron bis-acetylene-molybdenum complexes

The propeller-like rotations of each of the coordinated acetylenes in the 16-electron complex (η⁵-C₅H₅)Mo(PhCCMe)₂Cl are not independent and the barrier to rotation of one of the acetylenes is influenced by the orientation of the other. The barrier for the propeller-like rotation of the coordinated acetylenes in the similar cationic bis-acetylene complex, [(η⁵-C₅H₅)Mo(HOH₂CCCCH₂OH)₂CO]Cl is >5 kcal/mol higher than in the neutral bis-acetylene (η₅-C₅H₅)Mo(PhCCCH₃)₂Cl.