Why are SiX5(-) and GeX5(-) (X = F, Cl) stable but not CF5(-) and CCl5(-)?

The possible existence of the CF(5)(-), CCl(5)(-), SiF(5)(-), SiCl(5)(-), GeF(5)(-), and GeCl(5)(-) anions has been investigated using ab initio methods. The species containing Si and Ge as central atoms were found to adopt the D(3h)-symmetry trigonal bipyramidal equilibrium structures whose thermodynamic stabilities were confirmed by examining the most probable fragmentation channels. The ab initio re-examination of the electronic stabilities of the SiF(5)(-), SiCl(5)(-), GeF(5)(-), and GeCl(5)(-) anions [using the OVGF(full) method with the 6-311+G(3df) basis set] led to the very large vertical electron detachment (VDE) energies of 9.316 eV (SiF(5)(-)) and 9.742 eV (GeF(5)(-)), whereas smaller VDEs of 6.196 and 6.452 eV were predicted for the SiCl(5)(-) and GeCl(5)(-) species, respectively. By contrast, the high-symmetry and structurally compact anionic CF(5)(-) and CCl(5)(-) systems cannot exist due to the strongly repulsive potential predicted for the X(-) (F(-) or Cl(-)) approaching the CX(4) (CF(4) or CCl(4)). The formation of weakly bound CX(4)···X(-) (CF(4)···F(-) and CCl(4)···Cl(-)) anionic complexes (consisting of pseudotetrahedral neutral CX(4) with the weakly tethered X(-)) might be expected at low temperatures (approaching 0 K), whereas neither CX(5)(-) (CF(5)(-), CCl(5)(-)) systems nor CX(4)···X(-) (CF(4)···F(-) and CCl(4)···Cl(-)) complexes can exist in the elevated temperatures (above 0K) due to their susceptibility to the fragmentation (leading to the X(-) loss).     

Zinc(II) 5-(2′-hydroxyphenyl)-3-(4-X-phenyl)pyrazolinates and their adducts with N and P donor ligands: synthesis,spectral, biological,and anti-inflammatory investigations

Synthesis, spectral, biological, and anti-inflammatory investigations of a series of complexes of zinc(II) with 5-(2′-hydroxyphenyl)-3-(4-X-phenyl)pyrazolines of the type (C₁₅H₁₂N₂OX)₂Zn (where X =–H,–Cl,–CH₃,–OCH₃) are presented. The complexes were synthesized by reaction of anhydrous zinc(II) chloride with sodium salts of pyrazoline in 1 : 2 molar ratio. Adducts with N and P donor ligands (2,2′-bipyridine, 1,10-phenanthroline and triphenylphosphine) were prepared in 1 : 1 molar ratio. The complexes were characterized by elemental analyses, molecular weight, conductivity, IR, electronic, ¹H, ¹³C, ³¹P NMR, and FAB mass spectral studies. All complexes are amorphous. Tetrahedral geometry around zinc confirms the presence of two bidentate pyrazoline ligands in zinc(II) 5-(2′-hydroxyphenyl)-3-(4-X-phenyl)pyrazolinates. In adducts pyrazoline is monodentate. Bidentate and monodentate pyrazoline were confirmed by IR, ¹H, ¹³C, and ³¹P NMR spectral data. All metal complexes were tested for their antibacterial and antifungal activities. Anti-inflammatory activity was also carried out by the carrageenan-induced rat paw edema test. Brine shrimp bioassay was also carried out to study in-vitro cytotoxic properties.     

Synthesis and Characterization of Nickel(Ⅱ) and Copper(Ⅱ) Complexes with Schiff Base (1R,2R)-(-)-Diaminocyclohexane-N,N'-bis(3-tert-butyl-5-(4'-benzoic acid)-salicylidene)

Two homochiral metallosalen complexes,Ni(salen) (salen=(1R,2R)-(-)-diaminocyclohexane-N,N'-bis(3-tert-butyl-5-(4'-benzoic acid)-salicylidene) 1 and Cu(salen) 2,have been synthesized and characterized by IR,microanalysis,TGA,powder and single-crystal X-ray crystallography. Both 1 and 2 crystallize in orthorhombic space group P2_12_12 with Z=4. For 1,α= 12.082(2),b = 15.447(3),c = 18.784(4)(A),V= 3505.7(12) (A)~3,M_r = 731.50,D_c = 1.386 g/cm~3,μ= 0.606 mm~(-1),F(000)=1544,the final GOOF=1.043,R=0.0496 and wR=0.1248 for 4791 observed reflections with Ⅰ> 2σ(Ⅰ). For 2,α=12.181(2),b=15.501(3),c=18.877(4)(A),V= 3564.3(12)(A)~3,M_r=736.33,Dc = 1.372 g/cm~3,μ=0.665 mm~(-1),F(000)=1548,the final GOOF= 1.062,R=0.0575 and wR=0.1508 for 4562 observed reflections with Ⅰ> 20(Ⅰ). The crystal structures of 1 and 2 are isostructural with very similar supramolecular structures. An infinite two-dimensional network is generated by hydrogen bonding interactions and intermolecular π…π interactions.     

Syntheses,characterizations, crystal structures,and in vitro antitumor activities of chiral triorganotin(IV) complexes containing (S)-(+)-2-(4-isobutyl-phenyl)propionic and (R)-(+)-2-(4-hydroxyphenoxy)propionic acid ligands

Four new chiral triorganotin(IV) carboxylates, [(R₃Sn)(O₂C₁₃H₁₇)] _n (R?=?Me 1, Ph 2), [(R₃Sn)(O₂C₁₃H₁₇)] (R?=?n-Bu 3), and [(R₃Sn)(O₄C₉H₉)] _n (R?=?Me 4), have been synthesized by reaction of (S)-(+)-2-(4-isobutyl-phenyl)propionic acid and (R)-(+)-2-(4hydroxyphenoxy)propionic acid with triorganotin(IV) chloride in the presence of sodium ethoxide. The complexes have been characterized by elemental analyses, FT-IR, NMR (¹H, ¹³C, and ¹¹⁹Sn) spectra, and X-ray crystallography diffraction analyses. Structural analyses show that 1 has a 1-D infinite chiral zigzag chain structure. Complexes 2 and 4 have a 1-D spring-like chiral helical chain with a channel, while 3 is a monomer. Antitumor activities of 1–4 have been studied.     

Spectroscopy and stereochemistry of the optically active copper(II), cobalt(II) and nickel(II) complexes with Schiff bases N,N′-(1R,2R)-(−)-1,2-cyclohexylenebis(3-methylbenzylideneiminato) and N,N′-(1R,2R)-(−)-1,2-cyclohexylenebis(5-methylbenzylideneiminato)

Schiff bases obtained from N,N′-(1R,2R)-1,2-cyclohexanediamine and 2-hydroxy-3-methylbenzaldehyde, 2-hydroxy-5-methylbenzaldehyde, have been used as ligands for copper(II), cobalt(II) and nickel(II). The complexes were characterized with UV–Vis, circular dichroism (CD), infrared, diamagnetic and paramagnetic ¹H NMR spectroscopy. CD spectra revealed exciton coupled π→π* transitions. Assignments of LMCT and d–d transitions in CD spectra of Ni(II), Co(II) and Cu(II) complexes is proposed. CD data are characteristic for central ion tetrahedral distortion from the planarity and λ conformation of the cyclohexane ring. ¹H NMR of Ni(II) complexes exhibited significant coordination shifts of CHN and ring protons which are in the closest proximity to Ni(II). The ¹H NMR paramagnetic spectra of Co(II) complexes revealed the most upfield shifted resonance at −60 ppm assigned to CHN and −28 ppm to hydrogen atom at C(5′) of the phenyl ring. Results of spectral analyses suggest central ions in a distorted square-planar geometry with N₂O₂ chromofore group.     

Hydrocarbon (π- and σ-) complexes of nickel,palladium and platinum: Synthesis,reactivity and applications

With the exception of metallocenes, transition metal complexes with hydrocarbon ligands only are rare. However, complexes of this type containing Group 10 metals are known and have been shown to be quite stable. These complexes are versatile precursors for many organometallic compounds. In addition, such compounds can play an important role in many reactions including C–H or C–C activation reactions and have useful applications in the thermal and photochemical production of metal films by chemical vapour deposition (CVD). The present review summarizes the synthesis, properties and chemistry of hydrocarbon complexes of Group 10 metals of the type L_nM or L_nMR₁R₂ (where L_n = σ- or π-hydrocarbon ligands; M = Ni, Pd and Pt; R₁, R₂ = σ-hydrocarbon ligands) without the involvement of any hetero donor ligands such as N, P, O and S in the metal coordination spheres.     

Synthesis of (4R,5S)-(−)- and (4S,5S)-(+)-L-Factors and Muricatacin from D-Glucose

Abstract

In connection with our projects on the synthesis of biologically active 5-hydroxyalkan-4-olides which have a chiral 2.3-diol unit,¹ we have carried out the synthesis of (4R,5S)-(?)- and (4R,5S)-(+)-L-factors (1).² the proposed autoregulators from Streptomyees griseus, and muricatacin (2),³ a biologically active constituent from the seeds of Annona muricata L. via 2.3-dihydroxy aldehydes derived from D-glucose. Hex-3-enofuranose4 was prepared by the elimination of thetriflate derived from D-glucose.     

Synthesis,mesomorphic and dielectric properties of 4-(cyanomethoxy)phenyl 4-alkoxybenzoates, 4-(cyanomethoxy)-4′-alkoxyazo- and -azoxybenzenes

Preparation methods were developed for homologs of 4-(cyanomethoxy)phenyl 4-alkoxybenzoates (C₇, C₈, C₉), 4-(cyanomethoxy)-4′-alkoxyazo (C₂, C₃, C₆), -azoxybenzenes (C₃, C₆) whose composition and structure were proved by elemental analysis and ¹H NMR spectra. 4-(Cyanomethoxy) group destabilizes the mesophase, consequently, only four among the compounds obtained exhibit the thermotropic nematic mesomorphism.     

Syntheses,spectroscopy, and catalysis of (η 4-cod)Rh(I)-complexes with (R or S)-2-(salicylaldimine)-2-phenylethanol or (rac)-2-(salicylaldimine)-1-phenylethanol

Condensation of salicyldehyde with (R or S)-2-amino-2-phenylethanol or rac-2-amino-1-phenylethanol gives enantiopure (R or S)-2-(salicylaldimine)-2-phenylethanol (R- or S-H₂L1) or (rac)-2-(salicylaldimine)-1-phenylethanol (rac-H₂L2). The Schiff bases coordinate to [Rh(η ⁴-cod)(μ-O₂CCH₃)]₂ to afford mononuclear [Rh(η ⁴-cod){(R or S)-2-(salicylaldiminato)-2-phenylethanol-κ ² N,O}], [Rh(η ⁴-cod)(R- or S-HL1)] (1 or 2), or [Rh(η ⁴-cod){(rac)-2-(salicylaldiminato)-1-phenylethanol-κ ² N,O}], [Rh(η ⁴-cod)(rac-HL2)] (3). The Schiff base and complexes are characterized by IR-, UV/Vis-, ¹H/¹³C-NMR-, mass-spectroscopy, circular dichroism (CD), and polarimetry. The synthetic and spectroscopic results suggest that deprotonated Schiff base coordinates to [Rh(η ⁴-cod)] as a six-membered N,O-chelate with distorted square planar geometry at rhodium. CD and polarimetry measurements show the enantiopurity of the Schiff bases as well as the complexes in solution. The in situ system composed of [Rh(η ⁴-cod)Cl]₂ and S-H₂L1 has been used as a catalyst for the reduction of acetophenone into rac-1-phenylethanol with 85% conversion in diphenylsilane at 0–5°C.     

Syntheses,Structures,and Luminescent Properties of Zinc(Ⅱ) and Silver(Ⅰ) Complexes Based on 1-(4?-Carboxylatobenzyl)-3-(pyrazin-2-yl)pyrazole

Two novel coordination compounds, [Zn(CBPP)2(H2O)2]·3H2O(1) and[Ag(CBPP)·2H2O](2)(HCBPP = 1-(4?-carboxylatobenzyl)-3-(pyrazin-2-yl)pyrazole), were hydrothermally synthesized and characterized. Compound 1 crystallizes in monoclinic, space group C2 with a = 26.221(4), b = 8.4211(7), c = 14.295(3) ?, β = 114.561(8)o, V = 2705.9(2) ?3, Dc = 1.587 g/cm3, C28H28Cl2N8O9 Zn, Mr = 685.97 F(000) = 1416, μ(Mo Kα) = 0.926 mm-1, Z = 4, R = 0.0287, w R = 0.1076 for 2818 observed reflections(I 2σ(I)), and R = 0.0300, w R = 0.1110 for all data. In 1, each deprotonated CBPP-ligand with a bidentate coordination mode connects two Zn(II) atoms to generate a 1D helical chain along the b axis. The adjacent chains intersect with each other through hinged Zn(II) ions to build up an interesting two-dimensional network. Compound 2 crystallizes in monoclinic, space group P21/n with a = 6.3544(1), b = 11.7195(3), c = 19.3188(4) ?, β = 94.297(2)o, V = 1434.64(5) ?3, Dc = 1.894 g/cm3, C14H13 Ag N4O4, Mr = 409.15 F(000) = 816, μ(Mo Kα) = 11.536 mm-1, Z = 4, R = 0.0456 and w R = 0.1184 for 2402 observed reflections(I 2σ(I)), and R = 0.0517, w R = 0.1275 for all data. In 2, each ligand binds two Ag(I) atoms in a tridentate coordination mode to form an infinite zigzag chain. Their thermal and photoluminescent properties were also investigated.     

Synthesis of 2-(hydroxyphenylamino)- and 2-(aminophenylamino)-4-methylquinolines and N,N′-bis(4-methylquinolin-2-yl)benzenediamines

2-(Hydroxyphenylamino)- and 2-(aminophenylamino)-4-methylquinolines and N,N′-bis(4-methylquinolin-2-yl)benzenediamines were synthesized by reactions of 2-chloro-4-methylquinolines with o-, m-, and p-aminophenols and o-, m-, and p-phenylenediamines.     

Trichloro- and triisopropoxy-niobium(V) and tantalum(V) bis -( O,O ′-alkylene dithiophosphates): synthesis and characterization

Trichloro- and triisopropoxy-niobium(V) and tantalum(V) alkylene dithiophosphates, (M = Nb(V) or Ta(V); G =–CHMeCHMe–,–CMe₂CMe₂–,–CH₂CMe₂CH₂–,–CH₂CEt₂CH₂–or–CMe₂CH₂CHMe–and X = Cl or OPrⁱ) have been synthesized by reaction of metal(V) chloride, MCl₅, or triisopropoxymetal(V) dichloride, (PrⁱO)₃MCl₂, with the sodium salts of O,O′-alkylene dithiophosphoric acids, in 1 : 2 molar ratio in THF under anhydrous conditions. These pink-purple or light-yellow compounds are viscous, semi-solid or solid, hydrolyzable and soluble in common organic solvents. These compounds have been characterized by elemental analyses, molecular weight determinations and spectral studies like IR and heteronuclear NMR (¹H, ¹³C and ³¹P), which indicated a bidentate mode of chelation of dithio ligands, leading to a pentagonal bipyramidal geometry around the niobium(V) or tantalum(V) centers.     

Ruthenium(II) nitro-nitroso-bis-{1-(alkyl)-2-(β-napthylazo)imidazole}: Synthesis,spectroscopy, electrochemistry and reactivity

Aquation of blue cis-trans-cis-[RuCl₂(β-NaiR)₂] (1) leads to the synthesis of solvento species, blue-violet cis-trans-cis-[Ru(OH₂)₂(β-NaiR)₂](ClO₄)₂ (2), [β-NaiR = C₁₀H₇-N=N-C₃H₂-NN, abbreviated as N,N′-chelator, R = Me] that have been reacted with NaNO₂ in warm EtOH resulting in violet dinitro complexes of the type, [Ru(NO₂)₂(β-NaiR)₂] (3). The nitrite complexes are useful synthons of electrophilic nitrosyls, and on triturating the dinitro compounds with cone. HClO₄ nitro-nitrosyl derivatives, [Ru(NO₂)(NO)(β-NaiR)₂]²⁺ (4) are isolated. The chemical oxidation of aqua complex (2) by excess aqueous eerie solution in 1 (N) H₂SO₄ leads to the spontaneous formation of a yellow colored species. The electrophilic behaviour of metal bound nitrosyl has been proved by reacting with a bicyclic ketone, camphor, containing an active methylene group and an arylhydrazone with an active methine group. The diazotization of the primary aromatic amines with a strongly electrophilic mononitrosyl complex in acetonotrile and dichloromethane solution was thoroughly studied. Electrocatalytic oxidation of benzyl alcohol was examined.     

Synthesis and Structural Determination of (2R,4S,SS)-( )-Threo-5-(2,2-dichloroacetamido)-4-(4-nitrophenyl)-2-aryl-1,3-dioxanes

Acetalscanbesynthesizedinanumberofways.Themainproblemintheacetalformationinacidicmediumistoshifttheequilibriumtotherightbyremovalofthewaterformedduringthereactionl.Wesynthesized(2R,4S,SS)-( )-threo-5-(2,2-dich(4-nitrophenyl)-2-aryl-1,3-dioxanesbyacet...     

Synthesis and Crystal Structure of Bis(nitrate)- bis(N,N''''-dimethyl-N,N''''-dibenzenyl-urea)uranyl(Ⅱ)

1 INTRODUCTION Tri-butyl phosphate (TBP) has been widely used as the extraction reagent in U-Th fuel to separate uranium from thorium. But di-butyl phos- phate (DBP) and butyl phosphate (MBP), the radio- lytic products of TBP, exhibit some coordinated ability to the fission elements, such as Zr and Nb. The substitutes for TBP have being studied for several decades[1～4]. The physical and chemical properties of amides are similar to those of TBP and they selectively extract U(Ⅵ…     

(S)-(-)-norlaudanosine和(S)-(-)-O,O-dimethylcoclaurine的合成

以高藜芦胺为起始原料,经N-磺酰化反应制得高藜芦磺酰胺(2);2分别与芳乙烯甲醚经对甲苯磺酸催化的Pictet-Spengler反应后用金属钠脱除Ts基团合成了(±)-norlaudanosine(5a)和(±)-O,O-dimethylcoclaurine(5b);使用半量拆分法,以N-乙酰-L-苯丙氨酸为拆分剂,制得(S)-(-)-5a和(S)-(-)-5b,其结构经1H NMR,13C NMR,IR,MS和HR-ESI-MS确证。     

Infrared and Raman spectra of 2-(α-hydroxybenzyl)thiamine, 2-(α-hydroxycyclohexylmethyl)thiamine,their protonated forms and their complexes with zinc(II), cadmium(II) and mercury(II)

The infrared and Raman spectra of the ligands; 2-(α-hydroxybenzyl)thiaminium chloride (HBT), 2-(α-hydroxycyclohexylmethyl)thiaminium chloride (HCMT), and their protonated forms HBT·HCl and HCMT·HCl, as well as of their zwitterionic type complexes Zn(HBT)Cl₃, Cd(HBT)Cl₃, Hg(HBT)Cl₃ and Zn(HCMT)Cl₃, Cd(HCMT)Cl₃, Hg(HCMT)Cl₃, have been recorded in the region 4000-50 cm⁻. Several characteristic bands have been identified or tentatively assigned and are discussed in relation to the structures of the complexes. It is concluded from the spectra that the complexes are isostructural and that the bonding site of the ligands is the N(1′) atom of the pyrimidine moiety.     

Enantioselective synthesis of (S)- and (R)-α-methylserines: application to the synthesis of (S)- and (R)-N-Boc-N,O-isopropylidene-α-methylserinals

This report describes the synthesis of enantiomerically pure (S)- and (R)-α-methylserines on a multigram scale, starting from the Weinreb amide of 2-methyl-2-propenoic acid and using a stereodivergent synthetic route that involves a Sharpless asymmetric dihydroxylation reaction. As a synthetic application of these quaternary α-amino acids, they were used as starting materials in the synthesis of the well-known valuable homochiral (S)- and (R)-N-Boc-N,O-isopropylidene-α-methylserinal building blocks.     

Crystal and molecular structure of (μ-η2,η3-propargyl)- bis(cyclopentadienyl)tetracarbonyldimolybdenum tetrafluoroborate and (μ-η2,η3-1,1-dimethylpropargyl)- bis(cyclopentadienyl)tetracarbonyldimolybdenum tetrafluoroborate

An X-ray study of [(μ-η²,η³-HCCCH₂)Cp₂Mo₂(CO)₄]⁺(BF₄⁻) (1) and [(μ-η²,η³-HCCCMe₂)Cp₂Mo₂(CO)₄]⁺(BF₄⁻) (2) reveals their structures to be similar to the structure of neutral compounds of the series (μ-η²,η²-RCCR)Cp₂Mo₂(CO)₄, the difference between 1 and 2 being mainly due to the markedly different MoC⁺ bond lengths, which accounts for different stability and fluxional behavior of these compounds in solution.