Static and dynamic properties of anionic intermolecular aggregates: the I−–benzene–Ar n case

Molecular dynamics simulations on the I^?–benzene–Ar _n clusters have been carried out using an atom(ion)-bond model to describe the nonelectrostatic contribution to the total interaction. Results for I^?–benzene–Ar and I^?–benzene–Ar _n (n = 3, 18 and 25) are presented and some predicted properties are compared with those of the alkali cation–benzene clusters solvated by Ar atoms.     

13C n.m.r. spectra of 2-substituted pyrimidines

¹³C n.m.r. chemical shifts and carbon-proton coupling constants of 2-substituted pyrimidines are reported. The carbon chemical shifts are correlated with π-electron densities. Substituents which cause deshielding at the directly bound carbon (e.g. NH₂, OCH₃ and F) exert a more powerful effect in the benzene series than in the pyridine or pyrimidine series. The carbon-proton coupling constants do not correlate with the electronegativity of the substituents. Carbon-proton coupling constants and proton-proton coupling constants over the same number of bonds do not obey the Karabatsos relationship. The changes in the carbon-proton coupling constants in 2(1H)-pyrimidinone and 2(1H)-pyrimidinethione which accompany anion and cation formation are reported.     

Molybdenum-95 nuclear magnetic resonance of a series of phosphine and phosphite substituted molybdenum carbonyls Mo(CO)6−n (L) n (n=1, 2, 3, 4, 5)

Molybdenum-95 NMR spectra of a series of phosphine and phosphite substituted molybdenum carbonyls Mo(CO)_6-n L _n [L=P(OCH₃)₃ n=1, 2, 3, 4, 5,L=P(OC₂H₅)₃ n=1, 2, 3,L=P(C₆H₅)₃ n=1] including isomers (cis,trans,fac,mer) are reported, A large range of chemical shifts is found for the title compounds. The coupling constants¹ J(⁹⁵Mo-³¹P) are derived either from⁹⁵Mo-NMR spectra or³¹P-NMR spectra. Syntheses of the measured compounds were performed by thermal or photochemical ligand substitution.

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Molybdän-95 NMR einer Reihe von Phosphin- und Phosphit-substituierten Molybdäncarbonylen Mo(CO)_6–n(L) _n (n=1, 2, 3, 4, 5)

Zusammenfassung Es werden die⁹⁵Mo-NMR-Spektren der im Titel genannten Verbindungen mitL=P(OCH₃)₃ n=1–5,L=P(OC₂H₅)₃ n=1–3 undL=P(C₆H₅)₃ n=1, einschließlich von Isomeren (cis, trans, fac, mer) angegeben. Für die chemischen Verschiebungen wurde ein sehr weiter Bereich beobachtet. Die Kopplungskonstanten¹ J(⁹⁵Mo-³¹P) wurden entweder von den⁹⁵Mo- oder³¹P-NMR-Spektren ermittelt. Die Synthese der Verbindungen erfolgte mittels thermischem oder photochemischem Ligandenaustausch.

     

π-Allymetal chemistry 8. Uncatalyzed cis-trans isomerization of n3-allyl (pentachloropehnyl) palladium (II) complex

Two geometrical isomers of an n³-crotyhlpalladium(II) complex, Pd(n³-crotyl)(C₆Cl₅)(PPh₃) have been found to undergo uncatalyzed mutual interconversion in benzene above room temperature. The rate constants of the isomerization have been determined by the ¹H NMR method at 45–67°C, and thermodynamic data calculated. The large decrease of the rate on adding free tripheylphosphine ligand is attributed to occurrence of a dissciative isomerization path involving a 3-coordinate intermediate. Reductive elimination of the complex takes place at much slower rates than the isomerization to afford MeCHCHCH₂C₆Cl₅ selectively.     

A Theoretical Study of LiHe+ n , NaHe+ n , and MgHe+ n Complexes, with n=1, 2, 3, 4

The LiHe⁺ _n , the NaHe⁺ _n , and the MgHe⁺ _n complexes with n=1, 2, 3, 4 were studied using ab initio calculations with the MP2/6-311+G(3df, 3pd) method. The complexes are found to be stable. For the n=1 complexes, previous results were available and the calculations performed are in good agreement with those results. This lends credibility to the results obtained for the complexes with higher n.     

Metal Ion‐tuned Complexes based on Benzene‐1, 2, 4, 5‐tetracarboxylic Acid and the Semirigid Ligand 1, 4‐Bis(2‐methylbenzimidazol‐1‐ylmethyl) Benzene

Abstract. Two metal‐organic coordination polymers [Co(bmb)(btc)_0.5]_n( 1 ) and {[Zn(bmb)_0.5(btc)_0.5(H₂O)] · 0.5bmb · H₂O}_n ( 2 ) [H₄btc = benzene‐1, 2, 4, 5‐tetracarboxylic acid, bmb = 1, 4‐bis(2‐methylbenzimidazol‐1‐ylmethyl) benzene] were prepared under hydrothermal conditions. Single‐crystal X‐ray diffraction indicates that both complexes have a 2D framework structure with (4 · 6²) (4² · 6² · 8²) topology. Interestingly, the hydrogen bonds in 2 form a fascinating meso‐helix. The catalytic activity of 1 for oxidative coupling of 2, 6‐dimethylphenol (DMP) and the photoluminescence properties of 2 were investigated. Furthermore, the complexes were investigated by IR spectroscopy and thermogravimetric analysis.     

Syntheses,crystal structures and luminescent properties of two new Zn(II) coordination polymers based on a dicarboxylate and different imidazole-containing ligands

To investigate the effect of different imidazole-containing ligands on the structure of coordination polymers, two new Zn(II) coordination polymers based on 1,4-cyclohexanedicarboxylic acid (H₂cda) and two different imidazole-containing ligands, [Zn(cda)(bib)_0.5]_n (1) and [Zn(cda)(bmib)_0.5]_n (2) (bib = 1,4-bis(imidazol-1-yl)benzene and bmib = 1,4-bis(2-methylimidazol-3-ium-yl)benzene), have been synthesized and characterized by single-crystal X-ray diffraction. Complex 1 shows a 3-D structure with point symbol (4.8².10³).(4.8²). Complex 2 displays a 2-D layer structure with an –AB– stacking sequence.     

Syntheses,Structures, and Properties of Two Dicyanamide‐Bridged Polymers with a Schiff‐base Ligand

The dicyanamide‐bridged polymers with Schiff‐base ligand, [CoNaL(dca)]_n ( 1 ) and [Mn₂L(dca)₂]_n ( 2 ) [H₂L = bis(3‐methoxysalicylidene)benzene‐1,2‐diamine, dca = dicyanamide] were synthesized and characterized by elemental analyses, IR spectrroscopy and single‐crystal X‐ray diffraction. The solid‐state structures reveal that polymer 1 has double dca bridged loop‐like 1D chains, in which the heterodinuclear Co²⁺‐Na⁺ units (LCoNa) are bridged by dca with coordination mode μ_1,3,5. In polymer 2 , homodinuclear Mn²⁺‐Mn²⁺(LMnMn) units are linked by dca in μ_1,5‐bridging mode to form 2D planes. Magnetic susceptibility studies on 2 reveals antiferromagnetic coupling interactions between the adjacent Mn²⁺ ions in the LMnMn unit.     

Alternativ-Liganden. XXXII [1]. Neue Tetraphosphan-Nickelkomplexe mit Tripod-Liganden des Typs XM′ (OCH2PMe2)n(CH2CH2PR2)3 – n (M′ = Si,Ge; n = 0 – 3)

Alternative Ligands. XXXII [1]. Novel Tetraphosphane Nickel Complexes with Tripod-Ligands of the Type XM′(OCH₂PMe₂)_n(CH₂CH₂PR₂)_{3 – n} (M′ = Si, Ge; n = 0 – 3) Tripod Ligands of the type XM′(OCH₂PMe₂)_n(CH₂CH₂PMe_{23 – n} (M′ = Si, Ge; n = 0 – 3) ( 1 – 6 , Table 1) have been used together with PPh₃ or PMe₃ for the preparation of novel tetraphosphane complexes of Nickel. The representatives LNiPPh₃ ( 7 – 12 ) are obtained by reaction of Ni(COD)₂ (COD = 1,5-cyclooctadiene) with the corresponding ligands and PPh₃ in toluene in moderate yields. The synthesis of the derivatives LNiPMe₃ ( 13 – 18 ) is partly ( 16 – 18 ) accomplished in analogy to the Ph₃P-complexes; compounds 13 – 16 are obtained in higher yields by reaction of Ni(PMe₃)₄ with the respective ligand. As a rule, 13 – 18 cannot be separated from by-products. The trinuclear complex FSi(CH₂CH₂PMe₂)₃[Ni(PMe₂CH₂CH₂)₃SiF]₃ ( 19 ) is formed together with 18 in the reaction of Ni(COD)₂ with 6 and PMe₃. The new compounds have been characterized (if possible) by analytical (C, H), but in general by spectroscopic investigations (IR; ¹H-, ¹³C-, ¹⁹F-, ³¹P-NMR; MS). A weak, but significant Ni → Si interaction through the cage is indicated by the following results: (i) Large low-field shifts δδ_F of 35.2 ppm ( 12 ), 38.3 ppm ( 18 ) and 37.7 ppm ( 19 ); (ii) ⁶J(PF) coupling constants [or ³J(PNiSiF) through the cage] of 6.0 Hz ( 12 ) and 7.6 Hz ( 18 ) together with a low-field shift δδ_Si of 12.8 ppm ( 12 ); (iii) NiSi distances of 3.95 Å in 7 and 3.92 Å in 12 , accompanied by a compression of the cage along the Ni ··· Si axis. An additional release from the high charge density on Ni results from π-backbonding to the phosphane ligands.     

Ab-initio study of Na n F n and Na n F n−1 clusters: atypical structures

Alkali halide clusters Na _n F _n have most frequently cuboid structures and Na _n F _n?1 clusters are derived from Na _n F _n by removing a F^? centre. An excess electron localises on the site of the removed F^? ion. In this paper, other kind of clusters are studied at the SCF level: i) The non-cubic structures. ii) The cubic Na _n F _n?1 for which the excess electron has no defined site. Due to very large size of these species (at least 27 atoms!) some equivalent fictive linear and planar geometries are studied.     

Pseudochalkogen-Verbindungen. XVI. IR-spektroskopische Untersuchungen an Cyanamidomonophosphaten, [PO4−n (NCN)n]3−

Pseudochalkogen Compounds. XVI. Infrared-spectroscopic Investigations of Cyanamidomonophosphates, [PO_4?n(NCN)_n]^3? Infrared spectroscopic investigations of trisodium cyanamidomonophosphates of the general type Na₃[PO_4?n(NCN)_n] · aq (n: 1, 2, 3) are reported. The vibrational spectra of the compounds are confirming very clearly the special position of cyanamidophosphates within the group of substituted phosphates: Cyanamidophosphates are characterized by a full participation of pseudochalkogen groups representing NCN substituents into the mesomeric system of the anions and an only slight shortening of the P? O distances in comparision to [PO₄]^3?. Characteristic frequencies between 970 and 1150 cm^?1 are attributed to v(PO_4?nN_n)-stretching frequencies. A partial ¹⁵N labelling of the monocyanamidophosphate anion, [PO₃NCN]^3? leads to some splitting or shifting of frequencies being connected with vibrations of the NCN group; isolated v(P? N) stretching frequencies cannot be found.     

Effect of addition of trifluoroacetic acid on the photophysical properties and photoreactions of aromatic imides

The UV and IR spectra of N-methyl-1,8-naphthalimide in benzene showed a two-step consecutive complexation (hydrogen bond formation) with trifluoroacetic acid (TFA). The equilibrium constant K₁ for the first complexation in benzene was determined from the UV spectrum to be 48 M⁻¹. The fluorescence intensities of the imide in benzene were found to be remarkably enhanced by the addition of TFA. Furthermore, photochemical cyclobutane formation of the imide with styrene in benzene was enhanced by the addition of TFA. Enhancement of the fluorescence intensity and the photoreaction of the imide by complexation with TFA was explained by a decrease of the efficiency of the intersystem crossing from ¹(ππ^∗) to ³(nπ^∗), that results from an increase in the energy of the ³(nπ^∗) level due to the complexation.     

NMR study (1H, 13C, 29Si, 31P and 199Sn) of the (C2H5)3-n P{EIVB(CH3)3}n compounds (EIVB = C,Si; Sn; n = 0, 1, 2,3)

¹H, ¹³C, ²⁹Si, ³¹P and ¹¹⁹Sn high-resolution NMR spectra of the series (C₂H₅)₃-_n P{E^IVB(CH₃)₃}_n (E^IVB = C, Si Sn; n = 0, 1, 2, 3) have been studied at 90 and 300 Mc. The observed trend of chemical shifts and coupling constants are discussed in terms of inductive effects, through-space interactions and rehybridization of the phosphorus atom. Conclusive arguments in favor of d-orbital participation in the P-E^IVB bonds were not found.     

Synthesis and Crystal Structures of Two Complexes [Mn2(L)2(H2bta)2(H2O)]n and[Cu2(L)(H2bta)0.5(H2O)]n

Two new complexes, [Mn₂(L)₂(H₂bta)₂(H₂O)]_n ( 1 ) and [Cu₂(L)(H₂bta)_0.5(H₂O)]_n ( 2 ) (H₄bta=1,2,4,5‐benzene‐tetracarboxylic acid, L=imidazo[4,5‐f][1,10]phenathroline) were prepared under hydrothermal conditions and their structures determined by single‐crystal X‐ray diffration. The X‐ray diffraction reveals that complex 1 , consisting of two crystallographically independent fragments A1 and A2, displays an interesting 3D supramolecular network constructed with ABAB sequence through hydrogen bonding interactions. In complex 2 , the copper atoms connected by the H₂bta^2? ligands, the chains also are assembled into a 3D honeycomb configuration network formed by moleculars and aromatic π‐π stacking interactions.     

Synthesis and some properties of furylacrylates of aluminium(III) and titanium(IV)

Summary Compounds of the type [M(OPrⁱ)_m–n(FA)_n] (where m = 3 and n = 1 to 3 when M = Al; and m = 4 and n = 1 to 4 when M = Ti) have been synthesised by the reactions of aluminium and titanium isopropoxides with furylacrylic acid (HFA) in benzene. The corresponding tertiary butoxide derivatives, [M(OBu^t)_m–n(FA)_n], were also obtained by the alcohol-interchange technique. These compounds have been characterised by elemental analysis, and i.r. and p.m.r. spectra.     

NMR study (1H, 13C, 31P) of the (C2H5)3-n. PXn compounds (X = Cl,Br, I; n = 0, 1, 2, 3)

The ¹H, ¹³C and ³¹P NMR data are reported for the (C₂H₅)_3-nPX_n compounds (X = Cl, Br, I; n = 0, 1, 2, 3). The chemical shifts are interpreted in terms of inductive and through-space effects of the X substituents together with a rehybridization of the phosphorous atom. The results of the coupling constants are in good agreement with the chemical shifts.     

Rapid Interception of CnF2n+1(O)SO. Radical with Copper-Based Carbene: A Novel Access to Perfluoroalkanesulfinate Ester

In this communication, an unprecedented interception of C_nF_2n+1(O)SO^. radical with a copper-based carbene has been established. Distinguished by wide substrate scopes and mild reaction conditions, this novel radical–carbene coupling reaction (RCC reaction) provides a fundamentally different and mechanistically interesting strategy for the synthesis of perfluoroalkanesulfinate esters.     

Perhalogenmethylmercapto-heterocyclen, (VII) [1] konkurrenzreaktionen elektronenarmer,substituierter aromaten um die halogenmethylmercapto- BZW. Chlorgruppe von Cl3-nFnCSCl in starken saeuren

Electron-deficient aromatics, such as 2,5-bis(trifluoromethylmercapto)thiophene ($\text{1a}$) or (trifluoromethylmercapto)benzene ($\text{8a}$), react with F₃CSCl in the presence of F₃CSO₃ as a catalyst to give mainly 3-chloro-2,5-bis(trifluoromethylmercapto)thiophen ($\text{3a}$) and 1-chloro-4- or 2-(trifluoromethylmercapto)benzene ($\text{10}$, respectively. This reaction competes with the one expected to result in 2,3,5-tris(trifluoromethylmercapto)thiophene ($\text{2a}$) and 1,4- and 1,2-bis(trifluoromethylmercapto)benzene ($\text{9}$,$\text{9′}$), respectively. Further reactions of deactivated aromatics with Cl_3-nF_nCSCl show that the chlorine substitution is in general catalysed by strong acids. Reaction mechanisms are proposed for both Substitutions. The Cl_3-nF_nCS group in aromatics exerts a -M-effect in the case of an attack of a positive ion, e.g. H^⊕, the well-known +M-effect in the case of reactions with positively polarized molecules, e.g. CF₃S^β+Cl^β-.     

Synthesis and X-Ray Crystal Structures of Fe2Ru(CO)12−n (CNBu t ) n and FeRu2(CO)12−n (CNBu t ) n (n=1, 2)

The clusters Fe₂Ru(CO)_12–n (CNBu ^t ) _n (3, n=1; 4, n=2), FeRu₂(CO)_12–n (CNBu ^t ) _n (5, n=1, 6, n=2) and FeRu₂(CO)₁₁(CNCy) (5a) have been prepared by direct substitution from the parent carbonyl precursors Fe₂Ru(CO)₁₂ (1) and FeRu₂(CO)₁₂ (2). All compounds have been characterized spectroscopically and clusters 3, 4, 5, and 6 by single crystal X-ray determinations. In all cases, the isonitrile ligands adopt axial or pseudo-axial positions on a ruthenium atom. The structures of 3–5 are very similar to their parent clusters, but the extent of metal framework disorder is significantly less. Cluster 6 adopts the same C _2v Fe₃(CO)₁₂ type structure as 4, and thus differs markedly from the parent compound 2, which has a D ₃ structure .     

Synthese und Kernresonanzspektren von Methylphenyl-substituierten Trisilylphosphanen PSi3 Me n Ph 9−n

Trisilylphosphanes of the type PSi₃ Me _x Ph _9–x are formed when sodium/potassiumphosphide reacts with methylphenylchlorosilanesMe _n Ph _3–n SiCl or with mixtures of methylphenylchlorosilanes. The phosphanes (SiMe ₃) _n P (SiMe _m Ph _3–m )_3–n (n, m=0, 1, 2, 3) were separated and purified by destillation or crystallization and their²⁹Si as well as³¹P-NMR-spectra were recorded.