Heteroorganic betaines

The structures of 6,6-dimethyl-6-silafulvene C₅H₄SiMe₂ (3), its donor-acceptor complex with ammonia. C₅H₄SiMe₂·NH₃, dimethylfulvene, a number of cyclopentadienylides, methylenetrimethylphosphorane (6), and silicon-containing organophosphorus betaine⁻C₅H₄SiMe₂CH₂PMe₃ ⁺ (13), the product of nucleophilic addition of6 to3, were calculated using the density functional approach. For compound13, the potential energy minimum corresponds to the conformation withgauche-arrangement of the cyclopentadienyl anionie and trimethylphosphonium cationic centers and a C−Si−C−P dihedral angle of 30.5°, which is due to the Coulomb attraction between these centers. According to calculations, betaine13 is rather stable toward decomposition into3 and6 (ΔH ^o=42 kcal mol⁻¹, ΔG ^Δ=30 kcal mol⁻¹). The main channel of thermal decomposition of compound13 involves an intramolecular nucleophilic substitution, which proceeds with elimination of trimethylphosphine and results in 1,1-dimethyl-1-silaspiro[2,4]hepta-4,6-diene, which then undergoes a ready and irreversible isomerization into 6,6-dimethyl-6-silabicyclo[3.2.0]hepta-1,3-diene owing to the [1.5]-sigmatropic shift of the C−Si bond. For Part 4, see Ref. 1. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1850–1857, November, 2000.     

Formation of borosilicate glasses from silicon alkoxides and metaborate esters in dry non-aqueous solvents

The reaction of metaborate esters (RO)₃B₃O₃ [R = Me, Et, ClCH₂CH₂–, Cl₃CCH₂–, ClCH₂CH₂CH₂–, (ClCH₂)₂CH–] with Si(OR)₄ (R = Me, Et), either neat or in dry propan-2-one or dry THF at room temperature, led to gels which when dried and heated in air for 20 mins at 600°C afforded borosilicate glasses in high ceramic yields. The dried gels and glasses were characterized by elemental analysis, TGA, IR, and powder XRD, and solid-state MAS ²⁹Si and ¹¹B NMR. The gelling reaction was investigated by solution ¹¹B and ²⁹Si NMR. These NMR studies indicated B–O–Si reaction intermediates and a mechanism involving alkoxy exchange and various condensation/elimination reactions of the borosilicate esters have been proposed.     

Reactions of 1,1,3,3-tetramethyldisilazane with dicobalt octacarbonyl and iron pentacarbonyl. Thermal decomposition of the cobalt and iron carbonyl silazane complexes

The reaction of (HMe₂Si)₂NH with Co₂(CO)₈ gives the complex [Co₂(CO)₇(SiMe₂)₂NH₂]⁺[Co(CO)₄]⁻. Its thermal decomposition starts with dissociation into the “acid” HCo(CO)₄ and the “base” Co₂(CO)₇(SiMe₂)₂NH. After that, the base and the initial complex decompose further under the action of HCo(CO)₄. The final products of this reaction are CO, NH₃, Co, volatile dimethylcyclosilazane, and a solid residue consisting of cobalt particles encapsulated into a polymethylsiloxane matrix and possessing properties of mixed para- and ferromagnetics with an ultimate specific magnetization of 64–74 G g⁻¹. Tetramethyldisilazane reacts with iron pentacarbonyl under UV irradiation to give relatively stable 1,3-bis(tetracarbonylthydrideiron)-1,1,3,3-tetramethyldisilazane. This product contains Fe−H…N hydrogen bonds, which stabilize it against dehydrogenation and cyclization to diironcyclodisilazane. Thermal decomposition of this product was investigated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2537–2544, December, 1998.     

Synthesis of α,ω-dihalopermethyloligosilanes and silane-siloxane copolymers

α,ω-Dibromopermethyloligosilanes, Br(SiMe₂) _n Br (n=2–4, 6), were prepared by the reaction of dodecamethylcyclohexasilane with bromine. The reaction of (Me₂Si)₆ with MCl₄ (M=Sn, Ti) proceeds with the cleavage of Si−Si- and Si−C-bonds with the formation of α,ω-dichloropermethyloligosilanes, Cl(SiMe₂) _n Cl (n=2–4, 6), and chloro derivatives of cyclohexasilane, Cl _m Si₆Me_12−m (m=1, 2). Silane-siloxane copolymers of regular structure were obtained by heterofunctional copolycondensation of α,ω-dihalopermethyloligosilanes with 1,5-dihydroxyhexamethyltrisiloxane. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1513–1517, August, 1997.     

Effects of substituents and n-donors on the energies of Si←N,Si←O,and Si=C bonds in hypervalent silenes

The effect of the nature of substituents at sp²-hybridized silicon atom in the R₂Si=CH₂ (R = SiH₃, H, Me, OH, Cl, F) molecules on the structure and energy characteristics of complexes of these molecules with ammonia, trimethylamine, and tetrahydrofuran was studied by the ab initio (MP4/6-311G(d)//MP2/6-31G(d)+ZPE) method. As the electronegativity, χ, of the substituent R increases, the coordination bond energies, D(Si← N(O)), increase from 4.7 to 25.9 kcal mol⁻¹ for the complexes of R₂Si=CH₂ with NH₃, from 10.6 to 37.1 kcal mol⁻¹ for the complexes with Me₃N, and from 5.0 to 22.2 kcal mol⁻¹ for the complexes with THF. The n-donor ability changes as follows: THF ≤ NH₃ < Me₃N. The calculated barrier to hindered internal rotation about the silicon—carbon double bond was used as a measure of the Si=C π-bond energy. As χ increases, the rotational barriers decrease from 18.9 to 5.2 kcal mol⁻¹ for the complexes with NH₃ and from 16.9 to 5.7 kcal mol⁻¹ for the complexes with Me₃N. The lowering of rotational barriers occurs in parallel to the decrease in D _π(Si=C) we have established earlier for free silenes. On the average, the D _π(Si=C) energy decreases by ∼25 kcal mol⁻¹ for NH₃· R₂Si=CH₂ and Me₃N·R₂Si=CH₂. The D(Si←N) values for the R₂Si=CH₂· 2Me₃N complexes are 11.4 (R = H) and 24.3 kcal mol⁻¹ (R = F). sp²-Hybridized silicon atom can form transannular coordination bonds in 1,1-bis[N-(dimethylamino)acetimidato]silene (6). The open form (I) of molecule 6 is 35.1 and 43.5 kcal mol⁻¹ less stable than the cyclic (II, one transannular Si←N bond) and bicyclic (III, two transannular Si←N bonds) forms of this molecule, respectively. The D(Si←N) energy for structure III was estimated at 21.8 kcal mol⁻¹. Dedicated to Academician N. S. Zefirov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1952–1961, September, 2005.     

Heteroorganic betaines

The [Ph₃P⁺−CMe₂−SiMe₂−SEt]Br⁻ salt was prepared by the reaction of betaine Ph₃P⁺−CMe₂SiMeR−S⁻ (1a: R=Me) with EtBr. Acetylation of betaine1a or Et₃P⁺−CHMeSiMe₂−S⁻ (2a) afforded 2,2,6-trimethyl-1,3-dioxa-2-silacyclohex-5-ene-4-thione      

Fluxional rearrangement in congested ruthenium(II) complexes containing pyrimidine- and/or pyridine-based dithioether ligands

The solvento species obtained by the treatment of cis-RuCl₂(N,N-L)₂ [L = di-2-pyridyl sulfide (dps), di-2-pyrimidyl sulfide (dprs)] with AgPF₆, reacted with dithioethers L′ [L′ = 2,6-bis(2-pyridylthiomethyl)pyridine (pytmp), 2,6-bis(2-pyrimidylthiomethyl)pyridine (prtmp) and 2,6-bis{2-(4-methyl)pyrimidylthiomethyl} pyridine (mprtmp)] to afford the compounds [Ru(N,N-L)₂(N,S-L′)][PF₆]₂. The ¹H NMR spectra indicate that L′ is chelated through S and N atoms with the formation of a four-membered ring. As a consequence, the ruthenium and sulfur atoms are stereogenic centers with ∆ and Λ and (R) and (S) configurations, respectively. NMR spectra, at low temperatures, show that two invertomers, of similar abundance, as enantiomeric couples ∆S, ΛR and ∆R, ΛS are present. In the methylene region, four AB systems are observed that in both the species contain two non-equivalent methylene groups. Variable-temperature NMR spectra and EXSY experiments show that the sulfur inversion produces an exchange between the invertomers. The one-dimensional band-shape analysis of the exchanging methylene signals showed that the energy barriers for the process are in the 43–52 kJ mol⁻¹ range. The possible mechanisms of the sulfur inversion are discussed.     

Recent studies on chemistry of novel μ-CO-containing butterfly Fe/E (E=S,Se,Te) cluster salts

This article describes recent developments in chemical study on a series of butterfly-shaped μ-CO-containing Fe/E (E = S, Se, Te) cluster salts. These salts include eleven novel cluster anions, which are the single butterfly one μ-CO-containing [(μ-RE)(μ-CO)Fe2(CO)6]- (A), the double butterfly two μ-CO-containing {[(μ-CO)Fe2(CO)6]2(μ-EZE-μ)}2- (B, E = S; C, E = Se), the triple butterfly three μ-CO- containing {[(μ-CO)Fe2(CO)6]3[(μ-SCH2CH2)3N]}3- (D), {[(μ-CO)Fe2(CO)6]3[1,3,5-(μ-SCH2)3C6H3]}3- (E), {[(μ- CO)...     

Synthesis and crystal and molecular structures of cation-anionic complexes of five-coordinate silicon-containing disiloxane dications with lactamomethyl andN-methylacetamidomethyl C,O-chelating ligands

The reactions of bis(chloromethyl)dichlorosilane withN-trimethylsilyl lactams andN-trimethylsilyl-N-methylacetamide taken in a ratio of 1∶2 followed either by treatment with HgCl₂ in the presence of atmospheric moisture or by hydrolysis under a wet atmosphere afforded cation-anionic complexes, which contain disiloxane dications of the general formula [L₂SiOSiL₂]²⁺ (L is the lactamomethyl orN-methylacetamidomethyl bidentate ligand) and hexachlorodimercurate, tetrachloromercurate, and hydroxonium trichloride counter-ions, respectively. X-ray diffraction analysis demonstrated that the disiloxane dications in these complexes contain two five-coordinate Si atoms and occur as silicenium ions stabilized through two O→Si coordination bonds. In the case of lactamomethyl ligands, the disiloxane dications exist as diastereomers whose bischelate ligands adopt opposite configurations, whereas whenN-methylacetamidomethyl ligands are present, the bischelate ligands adopt identical configurations. The first example of the presence of a hydroxonium trichloride ion as a counter-ion in the crystal has been found. It consists of the hydroxonium cation, which holds three Cl⁻ anions through strong hydrogen bonds. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 997–1007, May, 1998     

The structure and thermochemistry of 3:4,5:6-dibenzo-2-hydroxymethylene-cyclohepta-3,5-dienenone (1) and some related compounds

Condensed and gas phase enthalpies of formation of 3:4,5:6-dibenzo-2-hydroxymethylene-cyclohepta-3,5-dienenone (1, (−199.1 ± 16.4), (−70.5 ± 20.5) kJ mol⁻¹, respectively) and 3,4,6,7-dibenzobicyclo[3.2.1]nona-3,6-dien-2-one (2, (−79.7 ± 22.9), (20.1 ± 23.1) kJ mol⁻¹) are reported. Sublimation enthalpies at T=298.15 K for these compounds were evaluated by combining the fusion enthalpies at T = 298.15 K (1, (12.5 ± 1.8); 2, (5.3 ± 1.7) kJ mol⁻¹) adjusted from DSC measurements at the melting temperature (1, (T _fus, 357.7 K, 16.9 ± 1.3 kJ mol⁻¹)); 2, (T _fus, 383.3 K, 10.9 ± 0.1) kJ mol⁻¹) with the vaporization enthalpies at T = 298.15 K (1, (116.1 ± 12.1); 2, (94.5 ± 2.2) kJ mol⁻¹) measured by correlation-gas chromatography. The vaporization enthalpies of benzoin ((98.5 ± 12.5) kJ mol⁻¹) and 7-heptadecanone ((94.5 ± 1.8) kJ mol⁻¹) at T = 298.15 K and the fusion enthalpy of phenyl salicylate (T _fus, 312.7 K, 18.4 ± 0.5) kJ mol⁻¹) were also determined for the correlations. The crystal structure of 1 was determined by X-ray crystallography. Compound 1 exists entirely in the enol form and resembles the crystal structure found for benzoylacetone.     

Ternary ion-association complexes between the indium(III) - 4-(2-pyridylazo)resorcinol anionic chelate and some tetrazolium cations

Complex formation and liquid-liquid extraction were studied in systems containing indium(III), 4-(2-pyridylazo)resorcinol (PAR), tetrazolium salt (TZS), water and chloroform. Two different TZS were used: 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT). The optimum conditions for extraction of In(III) as a ternary complex, (TT⁺)[In(PAR)₂] or (MTT⁺)[In(PAR)₂], were found: pH, extraction time, concentration of PAR and concentration of TZS. The constants of extraction (K_ex), constants of association (β), constants of distribution (K_D) and recovery factors (R%) were determined. The apparent molar absorptivities in chloroform were calculated to be ɛ′₅₂₀=6.6×10⁴ L mol⁻¹ cm⁻¹ and ɛ′₅₁₅=7.1×10⁴ L mol⁻¹ cm⁻¹ for the systems with TTC (I) and MTT (II), respectively. Beer’s law was obeyed for In(III) concentrations up to 3.4 μg mL⁻¹ in both the cases. The limits of detection (LOD=0.07 μg mL⁻¹ I and LOD=0.12 μg mL⁻¹ II), limits of quantification (LOQ=0.24 μg mL⁻¹ I and LOQ=0.41 μg mL⁻¹ II) and Sandell’s sensitivities (SS) were estimated as well.      

Kinetic and mechanism of alkene polymerization

Triphenylmethyl salts of the very weakly-coordinating borate anions [CN{B(C₆F₅)₃}₂]⁻ (1), [H₂N{(C₆F₅)₃}₂]⁻ and [M{CNB(C₆F₅)₃}₄]²⁻ (M = Ni, Pd) have been prepared in simple one-pot reactions. Mixtures of (SBI)ZrMe₂/1/AlBu ₃ ⁱ (SBI = rac-Me₂Si(Ind)₂) are 30–40 times more active in ethylene polymerizations at 60–100°C than (SBI)ZrCl₂/MAO. The quantification of anion effects on propene polymerization activity at 20°C gives the order [CN{B(C₆F₅)₃}₂]⁻ > [H₂N{(C₆F₅)₃}₂]⁻ ≈ B(C₆F₅) ₄ ⁻ ≫ [MeB(C₆F₅)₃]⁻. The highest productivities were of the order of ca. 3.0 × 10⁸ g PP (mol Zr)⁻¹ h⁻¹ [C₃H₆]⁻¹, about 1.3–1.5 times higher than with B(C₆F₅) ₄ ⁻ as the counter anion. The titanium system CGCTiMe₂/1/AlBu ₃ ⁱ gave activities that were very similar to the zirconocene catalyst. The concentration of active species [C*] as determined by quenched-flow kinetic techniques indicates typical values of around 10%, independent of the counter anion, for both the borate and MAO systems. Pulsed field-gradient spin echo and nuclear Overhauser effect NMR experiments on systems designed to be more realistic models for active species with longer polymeryl chains, (SBI)M(CH₂SiMe₃)(μ-Me)B(C₆F₅)₃ and [(SBI)MCH₂SiMe ₃ ⁺ ...B(C₆F₅) ₄ ⁻ ] (M = Zr, Hf), demonstrated the influence of bulky alkyl chains on the ion pair solution structures: while the MeB(C₆F₅)₃ compound exists as a simple inner-sphere ion-pair, the B(C₆F₅) ₄ ⁻ compound is an outer-sphere ion pair (OSIP), a consequence of the relegation of the anion into the second coordination sphere by the γ-agostic interaction with the alkyl ligand. The OSIP aggregates to ion hextuples (10 mM) or quadruples (2 mM). Implications for the polymerization mechanism are discussed; the process follows an associative interchange (I _a) pathway. The text was submitted by the authors in English.     

Liquid-crystalline CuII and PdII complexes with nonmesogenic ferrocene-containing β-aminovinyl ketone

New liquid-crystalline heteropolynuclear complexes L₂M (M=Cu²⁺ (2a), Pd²⁺ (2b)) were synthesized by the reactions of C₅H₅FeC₅H₄−C₆H₄NH−C₂H₂−(CO)−C₆H₄OC₁₂H₂₅ (1, LH) with copper(ii) and palladium(ii) acetates. Compound2b was found to possess monotropic nematic and smectic phases;2a exhibits the monotropic nematic phase and a phenomenon of “double melting”. The compositions and structures of compounds1 and2a,b were established by elemental analysis,¹H and¹³C NMR, ESR, and IR spectroscopy. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 381–383, February, 1999.     

Dihaloheptasilanes X2Si[SiMe(SiMe3)2]2 as potential precursors for silylenes, disilenes and cyclotrisilanes

The synthesis of new dihaloheptasilanes X₂Si[SiMe(SiMe₃)₂]₂ (X=Cl: 2, Br: 3, I: 4) was performed by treating dihydridoheptasilane 1 (X=H) with CCl₄, HCBr₃ or HCI₃. Difluoroheptasilane 6 (X=F) was prepared from either diphenylheptasilane 5 (X=Ph), triflic acid (HOTf), and LiF with concomitant isolation of heptasilanes 7 (X₂=Ph and OTf), 8 (X₂=F and Ph), and 9 (X₂=F and OTf), or by halogen exchange from 2 using ZnF₂. Crystal structures of 2, 3, 4, and 5 are reported. The reduction of 2 with Li, Na or KC₈ resulted in the instantaneous formation of various cyclotrisilanes, while the reduction of 3 gave exclusively the unsymmetrical cyclotrisilane (E)-1-methyl-2,3,3-tris[methylbis(trimethylsilyl)silyl]-1,2-bis(trimethylsilyl)cyclotrisilane 10, which was characterized by X-ray crystallography. A mechanism for the formation of cyclotrisilanes via a silylsilylene-to-disilene rearrangement is proposed. Attempts to prepare the tetradekasilane [(Me₃Si)₂MeSi]₂SiH–SiH[SiMe(SiMe₃)₂]₂ (by reductive dehalogenation of either HClSi[SiMe(SiMe₃)₂]₂ 13 or HISi[SiMe(SiMe₃)₂]₂ 18), or the tetradekasilane [(Me₃Si)₂MeSi]₂SiPh–SiPh[SiMe(SiMe₃)₂]₂ (by reductive dehalogenation of either PhClSi[SiMe(SiMe₃)₂]₂ 14 or PhISi[SiMe(SiMe₃)₂]₂ 19) as precursors for the disilene [(Me₃Si)₂MeSi]₂Si=Si[SiMe(SiMe₃)₂]₂ failed. 14 was characterized by X-ray crystallography. All compounds described were also characterized by multinuclear NMR spectroscopy and elemental analysis.     

Synthesis of carbosilane dendrons and dendrimers derived from 1,3,5-trihydroxybenzene

Several carbosilane wedges of generations 1-3 have been synthesized, following the divergent method, containing at the focal point a C-Br bond and as peripheral functional groups SiMeCl₂, SiMe(C₃H₅)₂, SiMe₂Cl, SiMe₂H, and ester units SiMe₂{(C₃H₆)N(C₂H₄CO₂Me)₂}. The dendrons functionalized with SiMe(C₃H₅)₂ and SiMe₂{(C₃H₆)N(C₂H₄CO₂Me)₂} groups were used to synthesize spherical dendrimers derived from 1,3,5-(HO)₃C₆H₃, leaving the outer groups unchanged. The allyl dendrimers thus obtained were used as precursors to prepare new dendrimers functionalized with SiMeCl₂, SiMe₂Cl, SiMe₂H, amine units SiMe₂{(C₃H₆)NH₂} and also ester units SiMe₂{(C₃H₆)N(C₂H₄CO₂Me)₂}.     

Catalytic transformations of oligocarbosilanes induced by AlCl3

Catalytic activation of Si−C bonds in poly(vinyltrimethylsilane) was studied using a model reaction of catalytic transformations of oligocarbosilanes Me₃Si(CH₂) _n SiMe₃ (n=2, 3) in dichlorodimethylsilane in the presence of AlCl₃ as an example. The formation of ClMe₂Si(CH₂) _n SiMe₃ was established by chromato-mass spectrometry and GLC. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2265–2266, December, 1997.     

An electroconductivity study on degree of counterion binding or dissociation of a-sulfonatomyristic acid methyl ester micelles in water as a function of temperature

 For a sodium salt of α-sulfonatomyristic acid methyl ester (14SFNa), one of the α-SFMe series surfactants, the differential conductivity (∂κ/∂C) _T , _P vs. square root of concentration (√C) was employed in order to determine not only CMC but also the limiting molar conductance (Λ⁰) and the molar conductance of micellar species (Λ^M). Based on the data of the degree of counterion binding to micelles (β) determined previously at different temperatures ranging 15–50 °C at every 5 °C, the experimental values of the degree of dissociation (ionization) of a micelle (α_EX) were calculated by regarding as α_EX=1−β. The ratio Λ^M/Λ⁰ corresponding to the ratio of slopes below and above CMC in the curve of specific conductivity (κ) vs. concentration (C), which has been often assumed to be the degree of ionization of micelles (α), was compared with the present α_EX. However, the ratio Λ^M/Λ⁰ (=α) was found to have a correlationship with α_EX (=1−β) as α_EX≈0.40×(Λ^M/Λ⁰), or strictly, α_EX=0.40 (Λ^M/Λ⁰)+0.08, indicating that the simple ratio of the slopes below and above CMC in κ vs. C curve is not true for α_EX=1−β. On the other hand, the method proposed by Evans gave a value closer to α_EX compared with the simple ratio. Received: 17 September 1996 Accepted: 8 April 1997     

Reduction of bis[(2-phosphinoethyl)tetramethyl-cyclopentadienyl]zirconium dichlorides: intramolecular C-H activation <Emphasis Type="Italic">vs.</Emphasis> stabilization of the low-valence metal center

Reduction of the R₂P-functionalized zirconocene dichlorides [C₅Me₄(CH₂)₂PR₂] (C₅Me₅)ZrCl₂ (R = Me (1) and Ph (2)) and [C₅Me₄(CH₂)₂PMe₂][C₅Me₄(CH₂)₂PR₂]ZrCl₂ (R = Me (3) and Ph (4)) with amalgamated magnesium was studied. In the reduction of compounds 1 and 2, intramolecular C-H activation highly selectively afforded the fulvene hydride complexes Zr(H)(η⁵−C₅Me₅)[η⁵:η²(C,P)−(CH₂)C₅Me₃CH₂CH₂PR₂] (R = Me (7), Ph (8)); in the case of compound 2, the aryl hydride Zr(H)(η₅:C₅Me₅)[η⁵:η¹(C)−C₅Me₄CH₂CH₂PPh(o−C₆H₄)] (9) was also formed. The reduction of complexes 3 and 4 gave the Zr^II derivatives Zr[η⁵:η¹(P)− C₅Me₄CH₂CH₂PMe₂]₂ (12) and Zr[η⁵:η₁(P)−C₅Me₄CH₂CH₂PMe₂][η⁵:η¹(P)−C₅Me₄CH₂ CH₂PPh₂] (14) stabilized by two phosphine groups. The second product in the reduction of compound 4 was the fulvene hydride complex Zr(H)(η⁵−C₅Me₄CH₂CH₂PPh₂)[η⁵:η²(C,P)−(CH₂)C₅Me₃CH₂CH₂PMe₂] (15). The reaction of compound 7 with an excess of MeI resulted selectively in replacement of the hydride ligand by iodide to give the complex ZrI(η⁵−C₅Me₅)[η⁵:η²(C,P)−(CH₂)C₅Me₃CH₂CH₂PMe₂] (10). In contrast, in the reaction of compound 7 with Me₂Si(H)Cl, the Zr-CH₂ bond underwent cleavage to give the chloride hydride complex Zr(H)Cl(η₅−C₅Me₅)[η⁵:η¹(P)−C₅Me₃(CH₂SiMe₂H)CH₂CH₂PMe₂] (11). In the reaction of complex 12 with CO, a phosphine group was replaced by CO to form the complex Zr(CO)(η5−C₅Me₄CH₂CH₂PMe₂)[η⁵:η¹(P)−C₅Me₄CH₂CH₂PMe₂] (13). The results obtained were compared with analogous reduction reactions of MeO-, MeS-, and Me₂N-functionalized zirconocene dichlorides. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 65–74, January, 2008.     

DNA-binding and nuclease activity of 1,10-phenanthroline-based thiocyanato,acetato, azido and benzoato bridged dinuclear copper(II) complexes

The mononuclear Cu(II) complex [Cu(phen)(H₂O)(NO₃)₂] (1), obtained by the reaction of 1,10-phenanthroline with Cu(NO₃)₂·3H₂O in methanol solution, reacts with anionic ligands SCN⁻, AcO⁻, N₃ ⁻ and PhCO₂ ⁻ in MeOH solution to form the stable binuclear complexes [Cu₂(H₂O)₂(phen)₂(μ-X)₂]₂ (NO₃)₂, where X = SCN⁻ (2), AcO⁻ (3), N₃ ⁻ (4) or PhCO₂ ⁻(5). The molecular structure of complex 3 was determined by single-crystal X-ray diffraction studies. These complexes were characterized by electronic, IR, ESR, magnetic moments and conductivity measurements. The electrochemical behaviour of the complexes was investigated by cyclic voltammetry. The interactions of these complexes with calf thymus DNA have been investigated using absorption spectrophotometry. Their DNA cleavage activity was studied on double-stranded pBR322 plasmid DNA using gel electrophoresis experiments in the absence and presence of H₂O₂ as oxidant.     

Reactivity of molecules with nitrogen-containing functional groups toward H+ and SiMe3 + ions

The equilibrium constants of trimethylsilyl cation transfer reactions differ from those of proton transfer reactions by many orders of magnitude. The basicity of MeCN (1), MeNO₂ (2), and Et₂NH (3) in the gas phase decreases in the series3≫1>2, whereas the affinity of the same compounds for trimethylsilyl cation decreases in the series1≫3≈2. Semiempirical quantum-chemical MNDO calculations indicate that the formation of MeCN·SiMe₃ ⁺ ions is thermodynamically more favorable than that of MeNH₂·SiMe₃ ⁺ ions. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1260–1261, June, 1998.