Stable Lewis Base Adducts of Tetrahalodiboranes: Synthetic Methods and Structural Diversity

A series of 22 new bis(phosphine), bis(carbene), and bis(isonitrile) tetrahalodiborane adducts has been synthesized, either by direct adduct formation with highly sensitive B₂X₄ precursors (X=Cl, Br, I) or by ligand exchange at stable B₂X₄(SMe₂)₂ precursors (X=Cl, Br) with labile dimethylsulfide ligands. The isolated compounds have been fully characterized using NMR spectroscopy, elemental analysis, and, for 20 of these compounds, single-crystal X-ray diffraction, revealing an unexpected variation in the bonding motifs. In addition to the classical B₂X₄L₂ diborane(4) bis-adducts, certain more sterically demanding carbene ligands induce a halide displacement which led to the first halide-bridged monocationic diboron species, [B₂X₃L₂]A (A=BCl₄, Br, I). Furthermore, low-temperature 1:1 reactions of B₂Cl₄ with sterically demanding N-heterocyclic carbenes led to the formation of kinetically unstable mono-adducts, one of which was structurally characterized. A comparison of the NMR spectra and structural data of new and literature-known bis-adducts shows several trends pertaining to the nature of the halides and the stereoelectronic properties of the Lewis bases employed.     

Ketiminate supported aluminum(III) complexes: Synthesis, characterization and reactivity

The reaction of LLi, (L = [RNC(Me)CHC(Me) = O] (R = C₂H₄NEt₂)), with AlCl₃ at −78 °C forms the mono-ketiminate product, LAlCl₂, 1, while the same reaction at 0 °C affords the bis-ketiminate complex, [{(LH)₂AlCl}(Cl₂)], 2, Reduction of 1 with Li^o, K^o or Mg^o yielded an unusual dimeric aluminum(III) species, [L′AlCl]₂, 3, where C-C coupling of the ligand backbone is observed.     

Bifunctional Gyroidal MOFs: Highly Efficient Lewis Base and Lewis Acid Catalysts

A family of gyroidal metal–organic frameworks (STUs) composited with transition metal ions and bi‐imidazolate ligands (BIm) were prepared and applied as both Lewis base and acid catalysts. Benefiting from the intrinsic basicity of the ligands and the Lewis acidic sites of the open metal centres, the STUs materials show excellent catalytic activities as Lewis base for the Knoevenagel condensation reaction between various aldehydes and malononitrile, and as Lewis acid for cyanosilylation reactions. Among these STUs, STU‐4 (Ni(BIm)) shows the best catalytic efficiency (conversions >99 %) in both Knoevenagel condensation and cyanosilylation reactions under mild conditions, providing thus an advanced material for both Lewis base and Lewis acid catalysis.     

Synthesis and Characterization of Polynuclear Metal Complexes with Bridging Ketoiminato and Thioiminato Schiff Base Ligands

Bimetallic and trimetallic complexes of stoichiometry [M(acacen)M′Y₂], [M(sacacen)M′Y₂], and {[M(acacen)]₂M′Y₂} have been prepared by reaction of the appropriate square-planar Schiff base metal complex with various secondary metal salts in toluene and/or absolute ethanol. Systems which are reported here include those where M = Cu(II); M′ = Cu(II), Ni(II), Co(II), Mn(lI) and Zn(II); Y^? = Cl^?, Br^?, and NO₃ ^?. Trinuclear complexes have been isolated only for {[Cu(acacen)]₂M′(NO₃)₂} where M′ = Cu(lI) or Mn(II); binuclear complexes result from all other combinations. The geometry of the chelated Cu(II) ion is square-planar in the bimetallic complexes and possibly square-pyramidal in the trimetallic compounds, while that of the secondary metal ion depends on the coordination preference of M′, the nature of Y^? and whether the bridging donor atoms are oxygen or sulfur. Probable structures of the new polynuclear complexes have been deduced from spectral, conductivity and magnetic measurements.     

Synthesis and Structural Characterization of Some New Magnesium Formamidinates

[Mg(Form)₂(THF)] [Form = bis(2,6‐dimethylphenyl)formamidinate (XylForm) ( 1 ), bis(2,6‐diethylphenyl)formamidinate, (EtForm) ( 2 ), bis(2,6‐diisopropylphenyl)formamidinate (DippForm) ( 3 )] are conveniently synthesized by treating bis(2,6‐dimethylphenyl)formamidine, bis(2,6‐diethylphenyl)formamidine, or bis(2,6‐diisopropylphenyl)formamidine, respectively, with half an equivalent of dibutylmagnesium in THF. Compounds 1 – 3 are mononuclear species in the solid state with five coordinate central metal atoms. The ¹H NMR chemical shift of the formamidinate formyl proton exhibits a correlation with ligand sterics wherein increasing bulk leads to a shift to higher field.     

Schiff碱双核Mn配合物的合成、结构和性能研究

Five manganese complexes of Schiff base were synthesized： [Mn^Ⅳ，Ⅳ(μ-O)(Salen)]₂·DMF·H₂O (1)， [Mn^Ⅳ，Ⅳ(μ-O)(5-BrSalen)]₂·DMF·0.5H₂O (2)， {Mn^Ⅳ，Ⅳ(μ-O)[Sal(1，2-pn)]}₂·H₂O (3)， {Mn^Ⅳ，Ⅳ(μ-O)[5-Br-Sal(1，2-pn)]}₂·H₂O (4)， {Mn^Ⅳ，Ⅳ(μ-O)[5-CH₃-Sal(1，2-pn)]}₂·2H₂O (5)， and were characterized by element analysis， IR and UV-Vis spectra. The results of cyclic voltammogram show that Schiff base ligands can drop the potential of manganese and steady high oxide state of manganese. The magnetic properties of 1 and 3 have also been studied. The results show that there is a weak ferromagnetically coupling of Mn^Ⅳ₂ pair at room and low temperature， and the interactions of complex 3 are weaker than complex 1.     

A Soft Grip: Magnesium Complexes with a Phosphine‐Modified Phosphonium Diylidic Lewis Base

Simple strategies to obtain magnesium complexes with the soft chelating diylidic ligand [Ph₂PCHPPh₂(fluorenylidene)]^? (dppmflu^?) were developed to evaluate the influence of the hard acid (cation) and soft base (anion) mismatch on the stability and reactivity of the formed derivatives. Deprotonation of the precursor Ph₂PCH₂PPh₂(flu) (dppmfluH) by an alkylmagnesium derivative or magnesium amide provided access to [{Mg(dppmflu)(μ‐nBu)}₂], [Mg(dppmflu){N(SiMe₃)₂}], and [{Mg(dppmflu)(μ‐Me)}₂], which were used as starting materials for further investigations. The reaction of [{Mg(dppmflu)(μ‐nBu)}₂] with PhSiH₃ in the presence of THF allowed isolation of the magnesium hydride complex [{Mg(dppmflu)(μ‐H)(thf)}₂] without a stabilizing nitrogen donor ligand. Prolonged heating enforced ligand redistribution and [{Mg(dppmflu)(μ‐H)(thf)}₂] was converted to [Mg(dppmflu)₂] and MgH₂. The homoleptic derivative [Mg(dppmflu)₂], in which the magnesium center is in a very soft ligand environment, can open a THF molecule by frustrated Lewis pair reactivity to give [{Mg(dppmflu)(μ‐OC₄H₈dppmflu)}₂].     

Structural,Mechanistic, Spectroscopic,and Preparative Studies on the Lewis Base Catalyzed,Enantioselective Sulfenofunctionalization of Alkenes

The full details of mechanistic investigation on enantioselective sulfenofunctionalization of alkenes under Lewis base catalysis are described. Solution spectroscopic identification of the catalytically active sulfenylating agent has been accomplished along with the spectroscopic identification of putative thiiranium ion intermediates generated in the enantiodetermining step. The structural insights gleaned from these studies informed the design of new catalyst architectures to improve enantioselectivity. In addition, structural modification of the sulfenylating agents had a significant and salutary effect on the enantioselectivity of sulfenofunctionalization which was demonstrated to be general for trans disubstituted alkenes. Whereas electronic modulation had little effect on the rate and selectivity, steric bulk on arylsulfenylphthalimides was very beneficial.     

Electrochemical Synthesis and Characterization of Tin(IV) Complexes of Dianionic Terdentate Schiff Base Ligands

Tin(IV) complexes of the series of dianionic terdentate Schiff bases N‐[(2‐pyrroyl)methylidene]‐N′‐tosylbenzene‐1,2‐diamine, (H₂L¹), N‐[(2‐hydroxyphenyl)methylidene]‐N′‐tosylbenzene‐1,2‐diamine (H₂L²) and some R substituted 2‐{[(2‐hydroxyphenyl)imino]methyl}phenols [R = H (H₂L³), 4,6‐(OCH₃)₂ (H₂L⁴), 3‐(OC₂H₅) (H₂L⁵) and 3,5‐Br₂ (H₂L⁶)] have been synthesized. The compounds were obtained by the electrochemical oxidation of a tin anode in a cell containing an acetonitrile solution of the corresponding ligand. The complex [SnL¹₂] was also obtained by reaction of SnCl₂·2H₂O and H₂L¹ in methanol in the presence of triethylamine. The crystal structure of the ligand [H₂L⁶] and the complexes [SnL¹₂] (1) , [SnL²₂] (2) , [SnL³₂] (3) and [SnL⁶₂] (6) were determined by X‐ray diffraction. In the complexes, the tin atom is in an octahedral environment coordinated by two dianionic terdentate ligands. Spectroscopic data for the complexes (IR, ¹H and ¹¹⁹Sn NMR and mass spectra) are discussed and related to structural information.     

大环Schiff碱化合物的合成、表征及其荧光活性研究

含乙酰丙酮类大环Schiff碱化合物一般都具有良好的荧光活性．采用模板合成法,用对苯二胺与乙酰丙酮反应合成得到的Schiff碱配体（H2L）与烷基二胺（即1,2-乙二胺,1,3-丙二胺,1,4-丁二胺）反应合成了3种新型大环Schiff碱化合物,通过元素分析,^1H NMR,IR,MS,UV,摩尔电导等手段对合成得到的化合物进行了组成和结构表征,同时在DMF溶液中对大环Schiff碱锌（Ⅱ）配合物的荧光活性进行了初步研究．     

Synthesis,Reactivity, and Structural Characterization of Dioxovanadium(V) Complexes with Tridentate Schiff Base Ligand: Vanadium Complexes in Supramolecular Networks

The synthesis, characterization and crystal structure analysis of the ammonium salt of the dioxovanadium(V) complex NH₄[VO₂(salhyph)] with the tridentate Schiff base ligand derived from salicylaldehyde and benzoic acid hydrazide (H₂salhyph) is reported. NH₄[VO₂(salhyph)] crystallizes in the monoclinic space group Pn with a = 708.8(2), b = 1444.3(3), c = 717.1(2) pm and β = 101.09(2)°. The vanadium atom of the dioxovanadium(V) moiety has a distorted square‐pyramidal coordination geometry. Extensive hydrogen bonding is observed between the ammonium cation and the oxygen atoms coordinated to the vanadium atom yielding to a two‐dimensional network, where the complex anions are arranged in a bilayer. Additional crystal packing within the bilayer appears to be controlled mostly by π stacking between the aromatic rings of the ligand. The reactions of NH₄[VO₂(salhyph)] with several proton acidic compounds including water, methanol, and proton acids lead to neutral monooxovanadium(V) and dioxovanadium(V) complexes ([VO₂(Hsalhyph)], [V₂O₃(salhyph)₂] and [VO(OMe)(salhyph)(HOMe)]).     

Asymmetric Hydrogenation of Ketones and Enones with Chiral Lewis Base Derived Frustrated Lewis Pairs

The concept of frustrated Lewis pairs (FLPs) has been widely applied in various research areas, and metal‐free hydrogenation undoubtedly belongs to the most significant and successful ones. In the past decade, great efforts have been devoted to the synthesis of chiral boron Lewis acids. In a sharp contrast, chiral Lewis base derived FLPs have rarely been disclosed for the asymmetric hydrogenation. In this work, a novel type of chiral FLP was developed by simple combination of chiral oxazoline Lewis bases with achiral boron Lewis acids, thus providing a promising new direction for the development of chiral FLPs in the future. These chiral FLPs proved to be highly effective for the asymmetric hydrogenation of ketones, enones, and chromones, giving the corresponding products in high yields with up to 95 % ee. Mechanistic studies suggest that the hydrogen transfer to simple ketones likely proceeds in a concerted manner.     

呋喃甲酰基吡唑啉酮双席夫碱配合物的合成及其生物活性

呋喃甲酰基吡唑啉酮双席夫碱配合物的合成及其生物活性李锦州＊于文锦杜晓燕（哈尔滨师范大学化学系哈尔滨１５００８０）（哈尔滨医科大学公共卫生学院哈尔滨）关键词酰基吡唑啉酮，双席夫碱，配合物，合成，生物活性１９９７－０６－１６收稿，１９９７－０９－０９修回...     

One-Electron Bonds in Frustrated Lewis Pair TPB Ligands: Boron Behaving as a Lewis Base

Owing to its versatility in synthetic chemistry, TPB (tris[2-diisopropylphospino)phenyl]borane) is a very important frustrated Lewis Pair. The unusual stability of the neutral radical (TPB)Cu has been related to the presence of a one-electron B−Cu bond. Herein we show, through the use of different computational chemistry methods, that the existence and nature of this kind of A⋅⋅⋅M bond (A=donor atom, M=transition metal) depends on the surrounding chemical structure, and can be genuine one-electron sigma bonds only if appropriate metal ligands (Y), able to trap the charge in the desired region, are chosen. This ability is modulated by the subtle balance between the electronegativity of the different atoms along the A⋅⋅⋅M⋅⋅⋅Y bond paths. Most importantly, contrary to many TPB complexes in which boron acts as a Lewis acid, in one-electron-bond-containing structures boron behaves as a Lewis base.     

非天然氨基酸水杨醛席夫碱铜配合物的合成与表征

合成了N-亚水杨基β-丙氨酸铜(1)和N-亚水杨基牛磺酸铜(2)两种新配合物,用元素分析、摩尔电导、红外光谱、热重差分析、X-射线粉末衍射对所合成的配合物进行了表征,并对X-射线粉末衍射数据进行了指标化.两种配合物的组成分别为Cu(sal-β-ala)*H2O(1),Cu(sal-tau)*2H2O(2),X-射线粉末衍射数据指标化结果表明,两种配合物均属于正交晶系,晶胞参数分别是1a=1.4981nm,b=1.8246nm,c=2.1985nm;2a=0.9454,b=1.7092nm,c=2.2254.     

Synthesis,Structure, and Reactivity of Lewis Base Stabilized Plumbacyclopentadienylidenes

Plumbacyclopentadienylidenes, in which the lead atoms have divalent states and are coordinated by THF, pyridine and N‐heterocyclic carbene, were synthesized and characterized. The THF‐ and pyridine‐stabilized compounds can be regarded as rare examples of hypervalent 10‐X‐4 species. The equilibrium between the THF adduct and the free plumbacyclopentadienylidene was evidenced by spectroscopic analysis and theoretical calculations. The THF adduct in benzene converted into a plumbylene dimer, where one of the lead centers is coordinated by THF and the other lead atom is coordinated by a divalent lead atom, the dimer gradually decomposing into spiroplumbole. The THF adduct unexpectedly reacted with trifluoroborane and trichlorogallane to afford fluoroborole and chlorogallole, which are the first examples of non‐annulated fluoroborole and gallole, respectively.     

Four- and five-coordinate magnesium compounds containing ketiminate ligands. Synthesis and characterization of L2Mg, L2Mg(LH), and L2Mg(Py), where L = MeC(O)CHC(NAr)Me

Magnesium complexes containing ketiminate ligands were synthesized and characterized. MgBu₂ reacted readily in toluene with two equiv. of [MeC(O)CHC(NHAr)Me], where Ar = 2,6-diisopropylphenyl, to generate [MeC(O)CHC(NAr)Me]₂Mg (1) in 43% yield. The four-coordinate magnesium compound 1 is very moisture sensitive and acts as a Lewis acid, accepting one equiv. of Lewis base to form five-coordinate magnesium compounds. Compound [MeC(O)CHC(NAr)Me]₂Mg[MeC(O)CHC(NHAr)Me] (2) was obtained in 57% yield from the reaction in toluene of MgBu₂ with three equiv. of [MeC(O)CHC(NHAr)Me]. Treatment of 1 with one equiv. of free ketimine ligands [MeC(O)CHC(NHAr)Me] also led to the formation of 2. The bulky η¹-ketimine of 2 can be replaced with a less bulky Lewis base such as pyridine. Treatment of 1 with excess pyridine in toluene at ambient temperature led to the formation of compound [MeC(O)CHC(NAr)Me]₂Mg[NC₅H₅] (3) as colorless crystalline solids in 51% yield. Compounds 1, 2, and 3 were characterized by NMR and X-ray crystallography. Compounds 2 and 3 showed no activity toward the polymerization of ε-caprolactone at 25 °C after 3 h. However, when the temperature was increased to 70 °C, compounds 2 and 3 efficiently catalyzed polymerization of ε-caprolactone to generate high molecular weight poly-ε-caprolactones. The polydispersity index (PDI) of these poly-ε-caprolactones is in the range 1.57-3.18.     

异烟酰肼缩水杨醛Schiff碱配合物的合成与表征

采用直接合成法用异烟酰肼、水杨醛合成了异烟酰肼缩水杨醛Schiff碱,并以此为配体合成了Zn（Ⅱ）、Co（Ⅲ）、Ni（Ⅱ）的配合物．对配合物进行了元素分析,红外光谱,紫外光谱,差热-热重分析及摩尔电导的测试等表征,推测配合物的组成分别为[Zn（H2O）L],[Co（H2O）2（HL）2]NO3-H2O,[Ni（H2O）2HL]NO3,其中L=C13 H9O2N3．     

杂环苄基锡氨基硫脲席夫碱配合物的合成与表征

二苄基二氯化锡和三苄基氯化锡分别与水杨醛缩氨基硫脲,含羟基芳香醛(酮)缩氨基硫脲的席夫碱钠盐反应,合成了10种新的有机锡配合物,其结构经1H NMR,119Sn NMR,IR和元素分析表征。结果表明,中心锡原子均为五配位杂单环结构。