Syntheses, structures, and dynamic properties of M(CO)2(η-C3H5)(en)(X) (M = Mo, W; X = Br, N3, CN) and [(en)(η-C3H5)(CO)2M(μ-CN)M(CO)2(η-C3H5)(en)]Br (M = Mo, W)

Mononuclear compounds M(CO)₂(η³-C₃H₅)(en)(X) (X = Br, M = Mo(1), W(2); X = N₃, M = Mo(3), W(4); X = CN, M = Mo(5), W(6)) and cyanide-bridged bimetallic compounds [(en)(η³-C₃H₅)(CO)₂M(μ-CN)M(CO)₂(η³-C₃H₅)(en)]Br (M = Mo (7), W(8)) were prepared and characterized. These compounds are fluxional and display broad unresolved proton NMR signals at room temperature. Compounds 1-6 were characterized by NMR spectroscopy at −60 °C, which revealed isomers in solution. The major isomers of 1-4 adopt an asymmetric endo-conformation, while those of 5 and 6 were both found to possess a symmetric endo-conformation. The single crystal X-ray structures of 1-6 are consistent with the structures of the major isomer in solution at low temperature. In contrast to mononuclear terminal cyanide compounds 5 and 6, cyanide-bridged compounds 7 and 8 were found to adopt the asymmetric endo-conformation in the solid state.     

Synthesis and fluxional behaviour of new “heavy fluorous” cyclopentadienes

The new “heavy fluorous” cyclopentadienes C₅H_6−n[M(C₂H₄C₆F₁₃)₃]_n (M = Si, n = 1 (3); n = 2 (4) and M = Sn, n = 1 (10)) were synthesized by reaction of cyclopentadienyl lithium with BrSi(C₂H₄C₆F₁₃)₃ (2) or commercial BrSn(C₂H₄C₆F₁₃)₃. Fluorous cyclopentadienes prepared in this manner contain three or six C₆F₁₃ groups, which significantly increase their solubility in perfluorinated solvents. They also provide intermediates for titanium complexes suitable for fluorous biphase catalysis. All three isomers of silylcyclopentadienes 3 and 4 were identified and fully characterized by two dimensional NMR spectroscopy, which was performed at low temperature. The allylic isomers 3a and 4a undergo degenerate metallotropic rearrangement. This fluxional behaviour was compared with the behaviour of previously prepared cyclopentadienes 6 and 7 (C₅H_6−n[SiMe₂(C₂H₄C₈F₁₇)]_n where n = 1, 2, respectively). The presence of allylic isomers 6a and 7a was further confirmed by Diels-Alder cycloaddition of the strong dienophile tetracyanoethylene (TCNE), providing compounds 8 and 9.     

A structural investigation of the carbocation complex [{Cp(CO)2Fe}2{μ-(C3H5)}]PF6

The reaction of the propanediyl complex [{Cp^∗(CO)₂Fe}₂{μ-(C₃H₆)}] (Cp^∗ = η⁵-C₅(CH₃)₅) with the hydride abstractor Ph₃CPF₆ in dry CH₂Cl₂ resulted in the formation of the carbocation complex [{Cp^∗(CO)₂Fe}₂{μ-(C₃H₅)}]PF₆. The complex formed triclinic crystals in the space group with Z = 1. In the structure one metal is bonded in the η²-fashion, forming a chiral metallacyclopropane structure with the carbocation, while the other is σ-bonded to the same carbocation ligand. However, NMR evidence indicates that the structure observed in the solid state is not preserved in solution because the metallacyclopropane ring opens up, giving a structure in which more positive charge is localized on the β-CH carbon and which could be fluxional.     

Synthesis and characterization of a planar chiral and chiral-at-metal ruthenium N-heterocyclic carbene complex

This report describes the conversion of the neutral planar chiral arene-tethered complex [Ru(η⁶:η¹-Me₂NC₆H₄C₆H₄PCy₂)Cl₂ (1), into [Ru(η⁶: η¹-Me₂NC₆H₄C₆H₄PCy₂)(1,3-dibutylimidazol-2-ylidene)Cl]BF₄ (2) via silver transmetallation. The cationic title complex is also chiral-at-metal, and forms stereoselectively as a result of the directing effect of the arene-tethered ligand. The structure in solution and in the solid state was examined; a puckered distortion of the η⁶-arene was noted in the crystal structure, along with a hindered rotation of the NHC in solution. As a comparison to the previously reported phosphine analogues, the dication derived from 2 was used to catalyze the asymmetric Diels-Alder reaction of methacrolein and cyclopentadiene.     

The rotational spectrum of the cyclopentadienylallylnickel complex

The rotational spectrum of cyclopentadienylallylnickel, C₃H₅NiC₅H₅, has been studied using a pulsed molecular beam Fourier transform microwave spectrometer. Twelve a-type transitions were analyzed to obtain rotational and centrifugal distortion constants for the parent C₃H₅⁵⁸NiC₅H₅ complex. The measured rotational constant A = 3107.603(93) MHz is about 160.0 MHz larger than the predicted DFT value, providing evidence for possible fluxional motion in the complex. The large distortion constants, on the order of 100 kHz, provide further evidence for fluxional motion. The experimental constants B = 1302.38(22) and C = 1276.40(15) MHz are in good agreement with the DFT calculated values and confirm the η³-bonding of the allyl ligand to the Ni–C₅H₅ moiety. DFT calculations provide a V₅ barrier for internal rotation about the Ni–C₅H₅ axis of 53 cm⁻¹, with the lowest energy conformation having the central allyl c-atom eclipsed with respect to two C₅H₅ carbon atoms. Several additional rotational lines, possibly those of an exited torsional state, were observed but not assigned.     

Fluxional behavior of methyl-substituted tricarbonyl(tropone)iron complexes and their different reactivity

The compositions of regioisomeric mixtures of tricarbonyliron complexes of 2-methyltropone (1a,b), 3-methyltropone (2a,b) and 2,6-dimethyltropone (3a,b) are studied and compared with the results of ab initio computations. The structures, frontier orbitals, and population analysis are evaluated by means of density functional theory. The thermodynamic and kinetic parameters of regioisomerizations are determined using dynamic ¹H NMR technique. The influence of methyl-substituent(s) on the equilibrium ratio of regioisomers resulting from the haptotropic rearrangement is discussed. Significant differences in the reactivity of C-protonized methyl- and dimethyl-substituted tricarbonyl(tropone)iron complexes 4–6 in nucleophilic additions and corresponding O-trimethylsilylated complexes 7–9 in [3+2] cycloadditions are explained in terms of electronic and steric effects of the methyl group(s). Various hydroazulenone cycloadducts of tricarbonyl(η⁴-2,6-dimethyltropone)iron 3a,b have been prepared by stereoselective [3+2] cycloaddition with Fp-reagents 12–14 and characterized. Formerly proposed mechanism of [3+2] cycloaddition was approved.     

二苯基膦基锂与富烯的反应—取代茂铁衍生物的合成与表征

二苯膦基锂与６，６－二甲基富烯发生环外双键的加成反应，生成含膦取代环戊二烯基负离子（Ⅰ），它与ＦｅＣｌ２络合，生成１，１＇，二（１－二苯膦基－异丙基）茂铁（Ⅱ）。（Ⅱ）与ＰｄＣｌ２（ＰｈＣＮ）２反应，生成杂双核络合物（Ⅲ）。茂铁（Ⅱ）为单斜晶系，空间群Ｐ２１／ｃ，晶胞参数ａ＝１．３３８２（５）ｎｂ，ｂ＝０．８５５０（１）ｎｍ，ｃ＝１．７３０９（４）ｎｍ，β＝１０９．１６（２）°，Ｖ＝１．８７０８２     

Synthesis,Characterization and Reactivity of the Tricarbonyl(formylcycloheptatrienyl)iron‐Anion [(η3‐C7H6CHO)Fe(CO)3]−

Deprotonation of the readily available organometallic aldehyde derivative [(η⁴‐C₇H₇CHO)Fe(CO)₃] ( 2 ) with NaN(SiMe₃)₂ in benzene solution at ambient temperature afforded the anionic formylcycloheptatrienyl complex Na[(η³‐C₇H₆CHO)Fe(CO)₃] ( 3 ). The anion is fluxional in solution and displays a unique ambident reactivity towards electrophiles (MeI, Me₃SiCl). New substituted [(η⁴‐RC₇H₆CHO)Fe(CO)₃] and [(η⁴‐heptafulvene)Fe(CO)₃] complexes have been identified as the products. Treatment of 3 with 0.5 equivalents of dimeric [(COD)RhCl]₂ (COD = 1,5‐cyclooctadiene) afforded the functionalized Fe‐Rh cycloheptatrienyl complex [(μ‐C₇H₆CHO)(CO)₃FeRh(COD)] ( 7 ) in up to 86 % yield. Carbonylation of 7 under an atmosphere of CO led to facile conversion to the heterobimetallic pentacarbonyl derivative [(μ‐C₇H₆CHO)(CO)₃FeRh(CO)₂] ( 8 ), which is also accessible in lower yield from the direct reaction of 3 with [Rh(CO)₂Cl]₂.     

Stochastic Bullvalene Architecture Modulates Structural Rigidity in π-Rich Macromolecules

The synthesis and processing of π-rich polymers found in novel electronics and textiles is difficult because chain stiffness leads to low solubility and high thermal transitions. The incorporation of “shape-shifting” molecular cages into π-rich backbone provides an ensemble of structural kinks to modulate chain architecture via a self-contained library of valence isomers. In this work, we report the synthesis and characterization of (bullvalene-co-phenylene)s that feature smaller persistence lengths than a prototypical rigid rod polymer, poly(p-phenylene). By varying the amount of bullvalene incorporation within a poly(p-phenylene) chain (0–50 %), we can tune thermal properties and solution-state conformation. These features are caused by stochastic bullvalene isomers within the polymer backbone that result in kinked architectures. Synthetically, bullvalene incorporation offers a facile method to decrease structural rigidity within π-rich materials without concomitant crystallization. VT NMR experiments confirm that these materials remain dynamic in solution, offering the opportunity for future stimuli-responsive applications.     

钌多氢化合物的低温FTIR光谱研究

在氢气氛下合成了新化合物Ｒｕ２Ｈ４（ＣＯ）２（ＰＰｈ３）４，建立了可至液氮温度的原位红外测试装置，在室温至液氮温度下进行了外多氢化合物的结构研究。发现ＲｕＴ４（ＣＯ）ＰＰｈ３）３在室温下会发生分子氢与原子氢的结构流变，Ｒｕ２Ｈ４（ＣＯ）（ＰＰｈ３）４则随温度变化而出现桥氢与端氢的结构转化现象。