Bridged bimetallic complexes of molybdenum tris(dimethylpyrazolyl)borates

Summary The syntheses of [MoL^*(NO)(OR)NHC₆H₄NH₂)], [MoL^*(NO)I(NHC₆H₄NHMoL^*(NO)(OR)] (L^*=tris(3,5-dimethylpyrazolyl)borate; R=Me, Et,n-Pr,i-Pr,n-Bu and C₅H₁₁), and [{MoL^*(NO)(OR)}₂NHC₆H₄NH] (R=Me, Et andn-Pr) are described, the compounds being characterised by elemental analyses, i.r. and¹H n.m.r. spectroscopy.     

Preparation of complexes formed in the reaction between diironnanocarbonyl and tetraalkyl(phenyl)diphosphine disulfides,R2P(S)P(S)R2 (R=Et,n -Pr,n -Bu,Ph)

Fe₂(CO)₉ and R₂P(S)P(S)R₂ (R = Et, n-Pr, n-Bu, Ph) react to form two types of cluster complexes Fe₃(CO)₉(μ₃-S)₂ (1), Fe₂(CO)₆(μ-SPR₂)₂ (2A)–(2D), [2A, R = Et; 2B, R = n-Pr; 2C, R = n-Bu; 2D, R = Ph]. The complexes result from phosphorus–phosphorus bond scission; in the former sulfur abstraction has also occurred. The complexes have been characterized by elemental analyses, FT-IR and ³¹P-[¹H]-NMR spectroscopy and mass spectrometry.     

Limiting Partial Molar Volumes of Electrolytes in 2-Methyl-2-Butanol <Emphasis Type="Bold">+</Emphasis> Water Mixtures at 298.15 K

Partial molar volumes at infinite dilution, V⁰₂, of alkali–metal halides (LiCl, NaCl KCl RbCl CsCl, NaBr, KBr, KI), tetra-n-alkylammonium bromides, R₄NBr (R=Me, Et, n-Pr, n-Bu, n-Pen), NaBPh₄, and Ph₄PCl have been determined in binary solvent mixtures of water with 2-methyl-2-butanol covering the water-rich region and the alcohol-rich region at 298.15 K. V⁰₂ for alkali–metal halides show relatively little dependence on the solvent composition. However, in the case of hydrophobic electrolytes the observed effects are more pronounced. A good linear dependence between V⁰₂(R₄NBr) and the molecular weight of the tetra-n-alkylammonium cation is found. Limiting single-ion volumes have been obtained using the assumption that V⁰(Ph₄P⁺)–V⁰(BPh^–₄)=2.0 cm³-mol^–1. The trends in the single-ion volumes are discussed in both solvent regions.     

Catalytic synthesis and transformations of magnesacycloalkanes

Catalytic cyclometallation of bicyclo[2.2.1]hept-2-ene, spirocyclo[2.2.1]hept-2-ene-7.1'-cyclopropane andendo-tricyclo[5.2.1.0^2,6]deca-3,8-diene (dicyclopentadiene) with R₂Mg (R =n-Pr,n-Bu) leading to the formation of polycyclic magnesacyclopentanes (MC) has been studied. The yield of MC and the selectivity of the reaction have been shown to depend on the ratio of starting reagents, the solvent, and temperature. The most probable scheme of the transformation studied is proposed.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 165–169, January, 1993.     

Electron impact and chemical ionization mass spectra of alkyldiphenylphosphine oxides

In the 70 e V electron impact mass spectra of a series of alkyldiphenylphosphine oxides (R?₂PO, R = Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, t-Bu, neopentyl, n-decyl), molecular ions of low abundance are observed and [M + H]⁺ ions are formed to a small extent at high sample pressures. The major ions include [?₂PO]⁺, [?₂POH]⁺; [?₂CH₂PO]⁺ and [?₂CH₂POH]⁺ which are formed by rearrangement and cleavage processes. The chemical ionization mass spectra obtained with methane and isobutane reagents consist of [M + H]⁺ ions. The proton affinity of R?₂PO was found to be 219 ± 2.5 kcal mol^?1.     

The thiolate anion as a nucleophile Part XI. Effect of the size of the nucleophile

The nucleophilic substitution reactions of some simple fluorobenzenes, C₆H_6?xF_x with sodium methanethiolates Na⁺SR^?(R=Et, $\text{i}$-Pr, $\text{t}$-Bu) have been studied. Some fully substituted products, C₆H_6?x(SR)_x, could be obtained in DMF as solvent with R = Et and $\text{i}$-Pr, but not when R = $\text{t}$-Bu. All the new products isolated have been characterized by elemental analysis, and NMR (H-1 and F-19), infrared and mass spectroscopy.     

Lignin-type, α,β-unsaturated aldehydes of lignin-type in organic solvents

A 1:1 reaction of [HO(CH₂)₃]₃P with 4-hydroxy-3-methoxy-cinnamaldehyde (coniferaldehyde) or 3,5-dimethoxy-4-hydroxycinnamaldehyde (sinapaldehyde) in acetone at room temperature affords phosphonium zwitterions of the type R₃P⁺CH(4-O^?-Ar)CH₂CHO; other phosphines [R = Et, n-Bu, (CH₂)₂CN, and p-Tol] do not react under the same conditions. In alcohols R??OH(D) [R?? = CD₃, Et, (CD₃)₂CD, s-Bu, HOCH₂CH₂], the above phosphines (except the cyano-derivative) and those where R = i-Pr, Cy, Me₂Ph, MePh₂ do react within an equilibrium established between the reactants and the zwitterion-hemiacetal products R₃P⁺CH(4-O^?-Ar)CH₂CH(OH)(OR??) that are formed as a mixture of two diastereomers. The nature of the phosphine and the alcohol affects the equilibrium and the diastereomeric ratio.     

Nitrile Cluster Compounds [(M6X12)X2(RCN)4] (M=Nb, Ta; X=Cl, Br; R=Et, n-Pr, n-Bu)

Three new series of mixed-ligand clusters of the [(M₆X₁₂)X₂(RCN)₄] (M=Nb, Ta; X=Cl, Br; R=Et, n-Pr, n-Bu) composition have been prepared. It is supposed that four nitrile molecules and two halogen atoms are coordinated to the terminal octahedral coordination sites of the [M₆X₁₂]²⁺ unit.     

Base hydrolysis of mono-alkylsubstituted chloropentaamminecobalt(III) complexes

Summary The preparation of the series ofcis- andtrans-[Co(NH₃)₄(RNH₂)Cl]²⁺ complexes (withcis, R = Me orn-Pr andtrans, R = Me, Et,n-Pr,n-Bu ori-Bu) is described. The u.v-visible spectra indicate a decrease of the ligand field on increasing chain length. Infrared spectra show an enhanced Co-Cl bond strength compared to the pentaammine. Partial molar volumes of the complex cations do not reveal steric compression. From proton exchange studies in D₂O it follows that [Co(NH₃)₅Cl]²⁺ and thecis- andtrans-[Co(NH₃)₄-(CH₃NH₂)C1]²⁺ complexes exchange the amine protons on the grouptrans to the chloro faster than those on thecis. A coordinated methylamine group exchanges its amine protons slower than a corresponding NH₃ group in the parent pentaammine, but the methyl introduction accelerates the exchange of the other NH₃ groups. The aquation of thetrans-alkylamine complexes (studied at 52° C) is acceleratedca. 10 times compared to the parent pentaammine, irrespective of the nature of the alkyl group. Thecis complexes do not show this acceleration of aquation. In base hydrolysis (studied at 25° C) thecis complexes are the most reactive (a factor 20 over the parent ion). Thecis/trans product ratio in base hydrolysis and the competition ratio in the presence of azide ions were calculated from the 500 MHz¹H n.m.r. spectra, which display distinctly different alkyl resonances for each individual complex. Thecis ions react under stereochemical retention of configuration; thetrans compounds give 10±1%trans tocis rearrangement. The ionic strength (4 mol dm^–3) and the pH do not affect this result. The same product ratio is obtained in methanol-water and DMSO-water mixtures. Ammoniation in liquid ammonia gives the same ratios as in base hydrolysis, base-catalyzed solvolysis in neat methylamine gives stereochemical retention for both thecis- andtrans-methylamine ion. The product competition ratio (Co-N₃)/(Co-OH₂) for thecis compounds and the bulkier amines (R =n- andi-Bu), 15–25% at 1 mol dm^–3N ₃ ^– , isca. twice that of thetrans compounds and the pentaammine. The results are interpreted in the classical conjugate base mechanism, and discussed in the context of current ideas about stereochemistry of base hydrolysis.Prof. C. R. Píriz Mac-Coll from Uruguay is a guest at the Free University of Amsterdam.     

Synthesis and spectroscopic characterization of bis(N-alkyldithiocarbamato)nickel(II) complexes: crystal structures of [Ni(S2CNH(n-Pr))2] and [Ni(S2CNH(i-Pr))2]

Bis(N-alkyldithiocarbamato)nickel(II) complexes (1–5) [Ni(S₂CNHR)₂] (where R?=?Me, Et, n-Pr, i-Pr, n-Bu) were synthesized by the reaction of NiCl₂?·?6H₂O and the corresponding sodium salt of N-alkyldithiocarbamate in 1?:?2 molar ratio in aqueous medium. These bis(N-alkyldithiocarbamato)nickel(II) complexes (1–5) were characterized by elemental analysis, UV-Visible, IR, and ¹H/¹³C-NMR spectroscopy. The crystallographic investigation of [Ni(S₂CNH(n-Pr))₂] (3) and [Ni(S₂CNH(i-Pr))₂] (4) revealed distorted square-planar geometry around nickel(II). The dithiocarbamates have anisobidentate coordination with nickel and the dithiocarbamates are trans.     

Mass spectra of new heterocycles: X. Fragmentation of the molecular ions of 1-alkyl(cycloalkyl,aryl)-3-alkoxy(aryl)-2-methylsulfanyl-1<Emphasis Type="Italic">H</Emphasis>-pyrroles

The mass spectra of previously unknown 1-alkyl(cycloalkyl, aryl)-3-alkoxy(aryl)-2-methylsulfanyl-1H-pyrroles were studied. Fragmentation of all 3-alkoxy-substituted pyrroles under electron impact (70 eV) follow both ether and sulfide decomposition paths; In particular, 1-R-substituted 3-methoxy-2-methylsulfanyl-1H-pyrroles (R = Me, Et, i-Pr, s-Bu, cyclo-C₅H₉, cyclo-C₆H₁₁, Ph) lose methyl radical group from both methoxy and methylsulfanyl groups. The mass spectra of 1-sec-butyl- and 1-cycloalkylpyrroles also contained a strong peak (10–49%) from odd-electron [M — C _n H_2n ]^+· ion formed via cleavage of the N-R bond with synchronous hydrogen transfer. Cleavage of the O-Alk bond in the fragmentation of 3-alkoxy-1-isopropyl-2-methylsulfanyl-1H-pyrroles (Alk = Et, i-Pr, t-Bu) was accompanied by rearrangement process leading to the corresponding alkene and odd-electron 1-isopropyl-2-methylsulfanyl-1H-pyrrol-3-ol ion. The main fragmentation path of 1-alkyl-2-methylsulfanyl-3-phenyl-1H-pyrroles (Alk = Me, i-Pr) under electron impact involves dissociation of the S-Me bond with formation of rearrangement 1H-[1]benzothieno[2,3-b]pyrrol-8-ium ion.     

The effect of alkyl substituents in nickelocenes on the catalytic dimerization of ethylene

(C₅H₄ i-Pr)₂Ni exhibits the highest catalytic activity in the dimerization of ethylene among the nickelocenes, (C₅H₄R)₂Ni (R = H, Et,n-Pr,i-Pr, ori-Bu) and their analogs (C₅H₄R)Ni(C₃H₅) (R = H,i-Pr). The higher activity is accompanied by lower selectivity with respect to 1-butene and with higher yields of 1-hexene. It is suggested that the introduction of an alkyl substituent in the cyclopentadienyl ring of nickelocene favors the generation of hydride sites involving the nickel atom. These sites participate in the process of ethylene dimerization.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 970–972, May, 1993.     

Tautomeric and Conformational Isomerism of Mercaptoacetylhydrazones of Methyl Alkyl Ketones

Mercaptoacetylhydrazones of methyl alkyl ketones (Alk = Me, Et, Pr, i-Pr, i-Bu, s-Bu, t-Bu) exist in solutions as a tautomeric mixture of linear and cyclic 1,3,4-thiadiazine forms.The linear hydrazone form exists as a set of conformers caused by restricted rotation of the amide group relative to the C–N bond. It is shown that tautomeric equilibrium constants correlate with the steric constants of the alkyl substituents, E_S.     

Kinetic study on the ligand exchange reactions between bis(alkylxanthato)palladium(II)and bis(N,N-dialkyldithiocarbamato)palladium(II)by high-performance liquid chromatography

The rate constants and equilibrium constants of ligand exchange reactions between his(alkylxanthato)palladium(Ⅱ),Pd(S_2COR)_2(R=Am,n-Hex,Bz),and bis(N,N-dialkyldithiocarbamato)palladium(Ⅱ),Pd(S_2CNR_2)_2(K=Et,n-Pr,n-Bu),in chloroform solution have been determined ina temperature range of 20—50°C by means of high-performance liquid chromatography.It was foundthat both the forward and reverse reactions are of second order.All of the equilibrium constants Kdetermined are 10.3±1.0,much greater than the value(K=4)calculated statistically which indicatesthat the ternary complexes are more stable than the binary complexes.The experimental resultsrevealed that the reaction rate decreases with the increase in the size of R and R~1 groups and the latterare more remarkable,consistent with the deduction of steric effect.The activation parameters ofthe reactions have been calculated.In reaction series(11)and(12)(in the text)the isokinetic tempera-tures B=390±8K and β=346±15 K have been observed respectively.A plausiblemechanism in-volving an eight-membered ring intermediate has been proposed on the basis of experimental results.     

Photochemical reactions of chromium hexacarbonyl with tetraalkyldiphosphine disulfides

New complexes [Cr(CO)₄(R₂P(S)P(S)R₂)] and [Cr₂(CO)₁₀(-R₂P(S)P(S)R₂)] (R = Me, Et, Pr ⁿ , Bu ⁿ ), (1a)–(1d) and (2a)–(2d) [(1a), R = Me; (1b), R = Et; (1c), R = Pr ⁿ ; (1d), R = Bu ⁿ ; (2a), R = Me; (2b), R = Et; (2c), R = Pr ⁿ ; (2d), R = Bu ⁿ ] have been prepared by the photochemical reaction of Cr(CO)₆ with R₂P(S)P(S)R₂ (R = Me, Et, Pr ⁿ and Bu ⁿ ) and characterized by elemental analyses, FT-i.r., ³¹P-[¹H]-n.m.r. spectroscopy and FAB-mass spectrometry. The spectroscopic data suggest cis-chelate bidentate coordination of the ligand in [Cr(CO)₄(R₂P(S)P(S)R₂)] and cis-bridging bidentate coordination of the ligand between two metals in [Cr₂(CO)₁₀(-R₂P(S)P(S)R₂)] (R = Me, Et, Pr ⁿ and Bu ⁿ ).     

Regioselectivity in the amination of azines: Reaction of pyrazine derivatives with <Emphasis Type="Italic">O</Emphasis>-mesitylenesulfonylhydroxylamine

Treatment of 2-X-substituted pyrazines [X = H, Me, Et, Pr, i-Pr, t-Bu, MeCH(OH), H₂N, AcNH] with O-mesitylenesulfonylhydroxylamine gave the corresponding 2-X- and 3-X-(1-amino)pyrazin-1-ium mesitylenesulfonates. 2-Alkylpyrazines (X = Me, Et, Pr, i-Pr) displayed a correlation between the logarithms of the concentration ratio of 2- and 3-substituted cations and substituent steric constants. Wider series of substituted pyrazines [X = H, Me, Et, Pr, i-Pr, MeCH(OH), H₂N, AcNH] conformed to a multiparameter correlation between the logarithms of the concentration ratio of 2- and 3-substituted cations, on the one hand, and substituent constants σ_I, σ_R^o, and E _s^o, on the other. The obtained data on the regioselectivity of amination of pyrazines were interpreted in terms of DFT/PBE/3Z quantum-chemical calculations.     

Synthesis,characterization, biological activities,crystal structure and DNA binding of organotin(IV) 5-chlorosalicylates

New organotin(IV) carboxylates, R₂SnL₂ (R=n-Bu: 1), R₂Sn(Cl)L (R=n-Bu: 2), and R₃SnL (R=Me: 3; n-Bu: 4; Ph: 5) have been synthesized by stirring 5-chloro-2-hydroxybenzoic acid HL with KOH and R₂SnCl₂ (R=n-Bu)/R₃SnCl (R=Me, n-Bu, Ph) in methanol at room temperature. The complexes along with ligand have been characterized by FTIR, (¹H, ¹³C) NMR, EI-MS, and single-crystal XRD crystallography. FTIR data indicated bidentate coordination of carboxylate. NMR data suggested six- or five-coordinate geometry of organotin(IV) carboxylates. Single-crystal XRD of 1 demonstrated skew-trapezoidal geometry around the tin center, with the basal plane occupied by four oxygens and the two butyl groups lying in distorted axial position. Complexes 1, 2, and 5 exhibited interaction with SS-DNA (salmon sperm) and suggests intercalating mode of binding. The complexes displayed significant antimicrobial activities against bacterial and fungal strains as compared to free ligand. The hemolytic activity of the complexes was lower compared to Triton-X 100 (positive control, 100% lysis) and higher than phosphate-buffered saline (negative control, 0% lysis). Complex 4 was the most potent inhibitor of bacterial/fungal growth.     

Synthesis of Boron–Nitrogen–Phosphorus Compounds from N-Silylphosphoranimines

Two modes of reactivity of N-silylphosphoranimines have been utilized to prepare the title compounds containing either B–N=P or Si–N=P–N–B linkages. First, silicon-nitrogen bond cleavage reactions of the N-silylphosphoranimines, Me₃SiN=PMe(R)OCH₂CF₃ (1: R=Me, 2: R=Ph), with various chloroboranes gave the new N-borylphosphoranimines, Ph(Me₂N)B–N=PMe₂OCH₂CF₃ (2) and [(Me₃Si)₂N](Cl)B–N=PMe₂OCH₂CF₃ (10). In other cases, however, the expected B–N=P products were unstable and cyclic phosphazenes [Me(R)P=N]_3,4 were obtained. Second, deprotonation-substitution reactions of the aminophosphoranimines, Me₃SiN=P(R)Me–N(R)H, were used to prepare a series of novel (borylamino)-phosphoranimines, Me₃SiN=P(R)(Me)–N(R)–B(NMe₂)₂ (18: R=Me, R=t-Bu; 19: R=R=Me; 20: R=Ph, R=t-Bu; 21: R=Ph, R=Me) and Me₃SiN=PMe₂–N(t-Bu)–B(Ph)X (22: X=NMe₂, 23: X=OCH₂CF₃). All of the new boron–nitrogen–phosphorus products were fully characterized by multinuclear NMR (¹H, ¹³C, and ³¹P) spectroscopy and elemental analysis.     

Etudes sur les composés organométalliques V [1]. Action de la pyridine sur les organomagnésiens

By the action of pyridine on various Grignard reagents at room temperature, new diorganomagnesium complexes R₂Mg · 2pyridine (R=Ph, n-Bu, t-Bu and Et) were prepared and analyzed. Anomalous results were obtained with methyl- or benzylmagnesium reagents.     

Effect of substituents,solute–solute–non-polar solvent interactions and temperature on the spectral properties of bis(dithiophosphato)copper(II) complexes

Extended studies by e.p.r. and electronic spectroscopy on the effect of different non-polar solvents, temperature and disulfide concentration on the spectral properties of bis(dithiophosphato)copper(II), Cu[(RO)₂PS₂]₂, complexes [R = Me, Et and i-Pr] are reported. The molar absorptivity and e.p.r. intensity are very sensitive to the shape and size of the remote ligand substituents and increase in the order: Me < Et < i-Pr. The nature of the solvent and time after dissolution are also important regarding the magnitude of the e.p.r. intensity and molar absorptivity which, 1 h after dissolution, do not follow Beer's law. The molar absorptivities obtained at a given Cu^II(R₂–dtp)₂ concentration increase in the solvent order: n-hexane < n-heptane < CCl₄ < PhMe < PhH < CHCl₃. Twenty-four hours after dissolution the same samples exhibit: (i) linearity between absorbance and concentration of Cu^II(R₂–dtp)₂; (ii) a significant increase in molar absorptivity which is not equal for all the complexes studied and follows the same substituent and solvent orders. Beer's law is satisfied above 5 × 10^–4 M for [(RO)₂PS₂]₂Cu (R = Et, i-Pr) and above 3 × 10^–3 M for [(MeO)₂PS₂]Cu. A significant additional increase, ca. 30–40%, of molar absorptivity, is obtained by increasing the solution temperature from 20 to 50 °C. The molar absorbtivity remains unchanged during 2–3 days after reducing the temperature. Further increase of molecular absorbtivity appears after addition of the corresponding disulfide of dithiophosphate [(RO₂)PS₂–S₂P(RO)₂] to Cu^II[(RO)₂PS₂]₂. The molar absorptivity of Cu[(i-PrO)₂PS₂]₂ increases from 4.8 × 10³ cm^–1 M^–1, 1 h after dissolving the complex up to 2 × 10⁴ cm^–1 M^–1 after addition of the corresponding disulfide. The observed effects are explained on the basis of a self-redox reaction taking place in this type of sulfur containing copper(II) complexes.