Synthesis and structures of the silyl bridged bis(indenyl) diruthenium complexes and a novel indenyl nonanuclear ruthenium cluster Ru9(μ6-C)(CO)14(μ3-η:η:η-C9H7)2

Thermal treatment of C₉H₇SiMe₂C₉H₇ and C₉H₇Me₂SiOSiMe₂C₉H₇ with Ru₃(CO)₁₂ in refluxing xylene gave the corresponding diruthenium complexes (E)[(η⁵-C₉H₆)Ru(CO)]₂(μ-CO)₂ [E = Me₂Si (1), Me₂SiOSiMe₂ (2)]. A desilylation product [(η⁵-C₉H₇)Ru(CO)]₂(μ-CO)₂ (3) was also obtained in the latter case. Similar treatment of C₉H₇Me₂SiSiMe₂C₉H₇ with Ru₃(CO)₁₂ gave a novel indenyl nonanuclear ruthenium cluster Ru₉(μ₆-C)(CO)₁₄(μ₃-η⁵:η²:η²-C₉H₇)₂ (5) with carbon-centered tricapped trigonal prism geometry, in addition to the diruthenium complex (Me₂SiSiMe₂)[(η⁵-C₉H₆)Ru(CO)]₂(μ-CO)₂ (4) and the desilylation product 3. Complex 4 can undergo a thermal rearrangement to form the product [(Me₂Si)(η⁵-C₉H₆)Ru(CO)₂]₂ (6). The molecular structures of 1, 2, 4, 5, and 6 were determined by X-ray diffraction.     

Vibrational spectra and structure of “staircase” carbonyl π-complexes of transition metals

FTIR spectra have been studied for staircase cyclopentadienyl complexes comprising two or three metal carbonyl fragments bound by the metal-carbon bond Cp(CO)₂Fe-CpmMn(CO)₃ (1), Cp(CO)₂Fe-CpmFe(CO)₂CH₂Ph (2), Cp(CO)₂Fe-Cpm(CO)₂Fe-CpmMn(CO)₃ (3), Cp(CO)₂Mo-Cpm(CO)₂Fe-CpmMn(CO)₃ (4), Cp(CO)₃W- Cpm(CO)₂Fe-CpmMn(CO)₃ (5), Cp(CO)₂Fe-Cpm(CO)₂Fe-BmCr(CO)₃ (6), Cr(CO)₃Bm-CpmFe(CO)₂CH₂Ph (7), where Cp = ⁵-C₅H₅, Cpm = ¹⁵-C₅H₄, Bm = ¹⁶-C₆H₅, as well as mononuclear model complexes Cp(CO)₂Fe(CH)₂Ph (8), CpMn(CO)₃ (9), and (⁶-C⁶H⁶)Cr(CO)³ (10). The spectra were interpreted on the basis of the local symmetry of each metal carbonyl center. The positions of vCOs are determined by the mutual electronic effect of each center. CpmM(CO)_n groups are strong electron acceptors and cause an increase in vCOs of adjacent M(CO)_n groups. Cp(CO)_nM groups, being electron donors, cause a decrease in the frequencies of neighboring groups. In trinuclear complexes, the frequencies of the central Fe(CO)₂ group are not changed much due to the compensation of donor and acceptor influences of two neighboring substituents.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1948–1951, November, 1994.This project was supported by the Russian Foundation for Basic Research (project code No. 93-03-18592).     

Vibrational spectra and structure of “staircase” carbonyl π-complexes of transition metals

FTIR spectra have been studied for staircase cyclopentadienyl complexes containing two or three metal carbonyl fragments bound by the metal-carbon bond Cp(CO)₂Fe-CpmMn(CO)₃ (1), Cp(CO)₂Fe-CpmFe(CO)₂CH₂Ph (2), Cp(CO)₂Fe-Cpm(CO)₂Fe-CpmMn(CO)₃ (3), Cp(CO)₂Mo-Cpm(CO)₂Fe-CpmMn(CO)₃ (4), Cp(CO)₃W-Cpm(CO)₂Fe-CpmMn(CO)₃ (5), Cp(CO)₂Fe-Cpm(CO)₂Fe-BmCr(CO)₃ (6), Cr(CO)₃Bm-CpmFe(CO)₂CH₂Ph (7), where Cp = ₅-C₅H₅, Cpm = ¹⁵-C₅H₄, Bm = ¹⁶-C₆H₅. Temperature-dependent FTIR spectra were measured inn-pentane solutions over a wide temperature range and in the low-temperature solid matrices of argon and nitrogen. Rotamers, formed due to rotation about the metal-carbon -bond, were found in solutions and matrices. A molecular mechanics calculation of1 proved the possibility of such rotation.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1952–1956, November, 1994.The authors are grateful to the Russian Foundation for Basic Research (project code No 93-03-18592) and to the International Science Foundation (project code No MEQ000).     

Reactions of dodecacarbonyltriruthenium with α,β-unsaturated ketones. Crystal and molecular structures of two reaction products

The thermal reactions of Ru₃(CO)₁₂ with RCOCH=CHPh (R=Me, p-MeC₆H₄) in hydrocarbon solvents lead to the formation of a series of complexes, several of which have been isolated as individual compounds by chromatography. The dinuclear complex Ru₂(-H)(CO)₆(-MeCOCH=CPh) and the tetranuclear complex Ru₄(-H)(-CO)(CO)₇(p-MeC ₆H₄ COCH=CPh)(-p-MeC₆H₄COCH=CPh)(₄-p-MeC₆H₃COCH=CHPh) are characterized by an X-ray structural study. The structures of other reaction products are discussed on the basis of spectral data. The reactions are accompanied by reduction of the starting enones to the corresponding unsaturated ketones.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1285–1293, July, 1993.     

Reactions of (Me2C)(Me2Si)[(η-C5H3)Mo(CO)3]2 with nitrile and subsequent cleavage of the CN bond by cooperation of molybdenum and ruthenium

Reaction of the doubly bridged dinuclear molybdenum complex (Me₂C)(Me₂Si)[(η⁵-C₅H₃)Mo(CO)₃]₂ (1) with benzonitrile in refluxing xylene afforded complexes (Me₂C)(Me₂Si)[(η⁵-C₅H₃)₂Mo₂(CO)₄(μ-η²-η²(⊥)-NCPh)] (2) (50%) and (Me₂C)(Me₂Si)[(η⁵-C₅H₃)₂Mo₂(CO)₄(μ-η¹-η²-NCPh)] (3) (6%) with different coordination of nitrile. The corresponding μ-η²-η² acetonitrile and propionitrile complexes 4 and 5 could be obtained from the reactions of (Me₂C)(Me₂Si)(C₅H₄)₂ with (RCN)₃Mo(CO)₃ (R = Me, Et) in refluxing xylene. Reactions of 1 with isonitriles generated μ-η¹-η²-CNR (R = ^tBu, Ph, C₆H₁₁) bridged complexes 6-8 in 53-63% yields. Subsequent reaction of 4 with Ru₃(CO)₁₂ yielded two CN bond cleavaged MoRu clusters (Me₂C)(Me₂Si)(η⁵-C₅H₃)₂Mo₂Ru₃(CO)₁₀(μ-CO)(μ₃-CMe)(μ₄-N) (9) (7%) and [(Me₂C)(Me₂Si)(η⁵-C₅H₃)₂]₂Mo₄Ru₆(CO)₁₆(μ-CO)(μ₄-CO)₂(μ₃-η¹-η²-η²-NCMe)(μ₃-CMe)(μ₅-N) (10) (8%). All the new complexes have been fully characterized. The molecular structures of 2, 4, 6, 9, and 10 have been determined by X-ray diffraction analysis.     

Synthesis and reactions of dicarbonyl (η2-indene)-η5-indenyl complexes of manganese and rhenium

Photochemical reactions of M(CO)₃(⁵-C₉H₇), where M=Mn (1) or Re (2), with indene have produced ²-indene complexes M(CO)₂(²-C₉H₈)(⁵-C₉H₇), where M=Mn (3) or Re (4). Deprotonation of complex3 witht-BuOK in THF at –60 °C gives the anion [Mn(CO)₂(¹-C₉H₇)(⁵-C₉H₇)^– (5), in which there occurs a rapid interchange of the Mn(CO)₂(⁵-C₉H₇) group between positions 1 and 3 in the ¹-indenyl ligand. The reaction of complex4 with Ph₃CPF₆ in CH₂Cl₂ at 0 °C leads to the complex [Re(CO)₂(³-C₉H₇)(⁵-C₉H₇)PF₆, whereas the similar reaction of complex3 gives only decomposition products even at –20 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1280–1285, July, 1993.     

Facile hydrosilylation of norbornadiene by silanes R3SiH and R2SiH2 with molybdenum catalysts

Photochemically activated [Mo(CO)₆] and [Mo(CO)₄(η⁴-nbd)] have been demonstrated to be very effective catalysts for hydrosilylation of norbornadiene (nbd) by tertiary (Et₃SiH, Cl₃SiH) and secondary (Et₂SiH₂ and Ph₂SiH₂) silanes to give 5-silyl-2-norbornene, which under the same reaction conditions transform in ring-opening metathesis polymerization (ROMP) to unsaturated polymers and to a double hydrosilylation product, 2,6-bis(silyl)norbornane. The yield of a particular reaction depends very strongly on the kind of silane involved. The reaction products were identified by means of chromatography (GC–MS) and ¹H and ¹³C NMR spectroscopy. In photochemical reaction of [Mo(CO)₄(η⁴-nbd)] and Ph₂SiH₂ in cyclohexane-d₁₂, η²-coordination of the SiH bond to the molybdenum atom is supported by ¹H NMR spectroscopy due to the detection of two equal-intensity doublets with ²J_HH = 5.4 Hz at δ 6.12 and −5.86 ppm.     

Calculation of harmonic force constants,vibrational frequencies and integrated intensities of some organic molecules using the MINDO—Forces method

The harmonic force constants, vibrational frequencies and integrated intensity ratios of CH₂, H₂O, CH₂O, C₂H₂, CO₂, HCN, CH₃, CH₄, and C₂H₄ have been calculated using the MINDO—FORCES program and the Pulay method for the calculation of the molecular force constants. The results obtained are in general quite satisfactory when compared with available literature values. The results are, however, not as satisfactory in case of molecules containing heteroatoms, due to the neglect of some dipolar repulsion integrals for the heteroatoms by the MINDO/3 method. Calculated integrated intensities for CH₃ and C₂H₄ agree well with experimental results. The calculated integrated intensities for other molecules are obtained for the first time and no comparison with published data is therefore possible.Part of the M.Sc. Thesis of K. H. A. 1978.     

π-Arene clusters of cobalt and ruthenium on the base of biphenyl

For the first time monocluster -arene derivatives of biphenyl Ph₂Co₄(CO)₉ and Ph₂Ru₆C(CO)₁₄, the shared mononuclear monocluster complex Ph₂Cr(CO)₃Co₄(CO)₉, and the bicluster derivative of cobalt Ph₂[Co₄(CO)₉]₂ have been synthesized. IR and H¹ NMR spectra of the compounds have been studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1978–1980, November, 1993.     

Comparative theoretical study of the dissociation process of the isoelectronic molecules BH3CO,CH2CO,HNCO, CO2 and BH3N2, CH2N2, HN3, N2O

Anab initio study of the electronic structure of several 22-electrons molecules is presented. The equilibrium geometries of their ground state are calculated at the SCF level using the 6–31G basis set and are found to be in good agreement with the experimental geometries. The dissociation process of these molecules leading to the isoelectronic products CO or N₂ on the one hand and BH₃, CH₂, NH and O on the other hand is studied. The least-energy dissociation paths of the ground states determined at the SCF level are compared on the basis of electron density interactions. The dissociation energies corresponding to the two lowest dissociation channels are calculated. In these calculations, the correlation energy is taken into account using a non-variational method developed previously. The calculated values of dissociation energies are in good agreement with the existing experimental values. The results permit to predict values for HNCO, BH₃CO and CH₂N₂ and to confirm the instability of BH₃N₂.Aspirant du Fonds National Belge de la Recherche Scientifique.     

A mixed Co- and Os-containingn,π-bicluster complex based on β-phenylpropionitrile

The PhCH₂CH₂CNOs₃(CO)₁₁ complex was prepared by the reaction of Os₃(CO)₁₂ with -cyanoethylbenzene, while the reaction with (CO)₃CrPhCH₂CH₂CN gave a heterometallic derivative, (CO)₃CrPhCH₂CH₂CNOs₃(CO)₁₁. A bicluster complex, Co₄(CO)₉PhCH₂CH₂CNOs₃(CO)₁₁, was synthesized for the first time by the reaction of PhCH₂CH₂CNOs₃(CO)₁₁ with Co₂(CO)₈; Co₄(CO)₉PhCH₂CH₂CN was also obtained.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 145–147, January, 1994.     

Some reactions of dimethyl tin bis-S,S′ -(O-sodium thiosulfate) and the structure of its complex with dibenzo-18-crown-6

The reactions of the title compound, Me₂Sn(S-SO₃Na · H₂O)₂, with alkyliodides and trimethyltin chloride in an aqueous medium, as well as with dibenzo-18-crown-6 (DB-18-C-6) in acetone have been studied. The iodides RI (R = Me, Et) attack both of the tin—sulfur bonds to give dimethyltin diiodide and the respective disulfides, R₂S₂. Trimethyltin chloride enters an exchange reaction which involves sodium ions and affords Me₂Sn(S-SO₃SnMe₃)₂ as the reaction intermediate; the latter decomposes to ultimately give trimethyltin sulfate, dimethyltin thiosulfite, and elemental sulfur. An ionic complex, [Me₂Sn(S-SO₃)₂]₂ ^2–[Na(DB-18-C-6)(Me₂CO)]⁺[Na(DB-18-C-6)(Me₂CO)(H₂O)]⁺, soluble in acetone and methylene chloride has been also synthesized, and its structure has been determined by means of X-ray techniques.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 962–966, May, 1993.     

Monolayer cuprous chloride dispersed on pillared clays for olefin-paraffin separations by π-complexation

New adsorbents containing cuprous chloride dispersed on pillared interlayered clays (PILC) have been prepared and studied for olefin-paraffin separations. High surface-area PILC's were synthesized with different metal oxide (Al₂O₃, Fe₂O₃, TiO₂ and ZrO₂) as the intercalating pillars. Cuprous chloride was dispersed in a submonolayer form on these PILC's. Pure-component isotherms were measured for C₂H₄, C₂H₆, C₃H₆ and C₃H₈ at 25°C and 60°C. All sorbents exhibited high C₂H₄/C₂H₆ and C₃H₆/C₃H₈ ratios with significantly high amounts of olefins adsorbed. The best sorbent was CuCl/TiO₂-PILC which showed a C₂H₄/C₂H₆ ratio of 5.3 and C₃H₆/C₃H₈=2.9 at 25°C. In all cases, olefins adsorbed by -complexation with Cu(I) ion, reflected by heats of adsorption in the range 10.7–13.7 kcal/mol, as compared to 4.8–6.9 kcal/mol for the physical adsorption of the paraffins. The -complexation was fully reversible, limited only by the rates of pore diffusion. Diffusion of C₂'s was rapid while for C₃'s the diffusion reached 60% completion in approximately 6 min. Comparing these results with those of CuCl/-Al₂O₃, the olefin/paraffin adsorption ratios were not as high as those of the later. However, the olefin isotherms on the PILC-supported CuCl displayed the desirable feature of having a steeper portion above the knee of the isotherm (the knee occurred at below 0.1 atm). This was a useful feature for separation because it yielded a larger working capacity. The steeper isotherm was attributed to a higher degree of energy heterogeneity as the PILC contained both surfaces of pillars and clay layers as opposed to only -Al₂O₃.     

The physical nature of the lone pair

Despite the large number of experimental and theoretical studies on the size, shape, and orientation of lone pairs and their resulting stereochemical character, lone pairs still remain poorly defined in terms of quantitative observable properties of a molecule. Using the conformation of saturated molecules and barriers to internal rotation, experimental chemists have arrived at conflicting sizes and orientations for lone pairs. Most theoretical attempts to define lone pair properties have centered on such non-observables as localized molecular orbitals or have been based on studies on isolated molecules.The use of observable properties to construct a consistent set of physical models to analyze the physical nature of lone pairs is discussed. Much as one probes an electric field with a test charge, probes such as H⁺, H^–, He and H could be used to probe regions of molecules such as NH₃ and H₂O where lone pairs are often postulated to exist.Ab initio quantum mechanical studies can be analyzed using electron density (and resulting changes during interaction), total pair density of electrons, the electrostatic potential about the molecule and bond energy analysis to study lone pair properties. A simple study of NH₃ using an H⁺ probe is presented to clarify the approach.     

Theoretical investigation of structure and stability of oligomers of LiH,NaH, LiF,and NaF

The molecules Li_nH_n, Na_nH_n, Li_nF_n, n=1,..., 4, and NaF and Na₂F₂ are investigated by means of extended basis set SCF and CEPA-PNO computations. In analogy to the D _2h structure of dimers, it is found that trimers have a planar cyclic D _3h equilibrium geometry. For the tetramer of LiH and NaH, the D _4h structure has about the same energy as the 3-dimensional T _d structure, whereas the latter is definitely favoured for Li₄F₄. Correlation effects are investigated for the oligomerization of LiH and the dimerization of LiF. The effect of electron correlation on corresponding E turns out to be small (<4 kJ/mol), except for the case that the T _d tetramer is involved which has a rather large correlation energy.     

Synthesis,crystal structure and conformation of N-acetyl-Cα,α-diethylglycine-N′-methylamide

Summary Synthesis and X-ray structure analysis of N-acetyl-^,-diethylglycine-N-methylamide [CH₃-Co-NH-C(C₂H₅)₂-CO-NHCH₃] are described. The compound was obtained from the corresponding N-acetyl derivative [CH₃-CO-NH-C(C₂H₅)₂-COOH] through the mixed anhydride procedure. It crystallizes as monohydrate (C₉H₁₈N₂O₂·H₂O) in space group P2₁/c,a=7.139(1),b=11.823(2),c=15.778(3) Å, =122.23(1)°,V=1126.53 ų,D _m=1.20 Mgm^–3 (room temperature),R=0.046 for 1523 reflections. The crystal packing is dominated by two strong hydrogen bonds between the water molecule and two carbonyl oxygen atoms and two weak H-bonds to two amide-N-atoms of symmetry-equivalent molecules. The molecular conformation is closer to a 3₁₀-helix then ana-helix.

---

Synthese, Kristallstruktur und Konformation von N-Acetyl-^,-diethylglycin-N-methylamid

Zusammenfassung Es wird über Synthese und die röntgenographische Strukturbestimmung von N-Acetyl-^,-diethylglycin-N-methyl-amid [CH₃-CO-NH-C(C₂H₅)₂-CO-NH-CH₃] berichtet. Die Verbindung wurde unter Anwendung der Methode der gemischten Anhydride aus dem entsprechenden N-Acetylderivat [CH₃-CO-NH-C(C₂H₅)₂-COOH] erhalten. Sie kristallisiert als Monohydrat (C₉H₁₈N₂O₂·H₂O) in der Raumgruppe P2₁/c mita=7.139(1),b=11.823(2),c=15.778(3) Å, =122.23(1)°,V=1126.53 ų,D _m=1.20 Mgm^–3,D _x=1.204 Mgm^–3 (Raumtemperatur).R=0.046 für 1523 Reflexe. Die Kristallpackung ist dominiert durch zwei starke H-Brücken vom Wassermolekül zu zwei Carbonylsauerstoffatomen sowie zwei schwachen H-Brücken zu zwei Amid-N-atomen symmetrieequivalenter Moleküle. Die Konformation des Peptidgerüstes ist näher einer 3₁₀ als einera-Helix.

     

On the affinity of cytosine towards electrophiles

Ab initio SCF computations on the intrinsic preferences of the H⁺, CH ₃ ⁺ and C₂H ₅ ⁺ cations towards the two principal sites of protonation or alkylation on cytosine, N₃ or O₂, show that this preference undergoes a continuous modification with the increase in size and complexity of the cation. N₃ is the preferred site of fixation of H⁺, O₂ the preferred site of C₂H ₅ ⁺ , while CH ₃ ⁺ has no marked preference. The exchange repulsion term of the binding energy appears responsible for the preference of C₂H ₅ ⁺ for O₂.This work was supported by the Ligue Francaise contre le Cancer and the National Foundation for Cancer Research (USA)     

β-Tricarbonyl compounds. I. 2,4-Disubstituted 1,3-cyclopentanediones

Summary Stable enolic isomers of 2-aroyl-4-aracyl-1,3-cyclopentanediones such as3 and4 were prepared by condensation of aryl methyl ketones and diethyl maleate using an excess of sodium ethoxide (Aryl=C₆H₅, 4-C₆H₄CH₃, 4-C₆H₄Br and 4-C₆H₄Cl).

---

-Tricarbonyl Verbindungen. I. 2,4-Disubstituierte 1,3-Cyclopentandione

Zusammenfassung Stabile Enol-Isomere von 2-Aroyl-4-aracyl-1,3-cyclopentandionen wie3 und4 wurden durch Kondensation von Arylmethylketonen und Diethylmaleat mit einem Überschuß von Natriumethoxid dargestellt (Aryl=C₆H₅, 4-C₆H₄CH₃, 4-C₆H₄Br und 4-C₆H₄Cl).

     

Synthesis of Co3(CO)7(μ-η3-Allyl)(μ3-X) Complexes (X=S, Se) and Structure of the Selenium Derivative

The complexes Co₃(CO)₉( ₃-X) (X=S, Se) can be reduced to the corresponding anionic species [Co₃(CO)₉( ₃-X)]^–, which react with allyl bromide to give Co₃(CO)₇(- ³-C₃H₅)( ₃-X) (X=S, Se). These are the first two cobalt complexes containing the bridging - ³-allyl ligand. The structure of the selenium complex was determined by X-ray crystallography. Crystal data for Co₃(CO)₇(- ³-C₃H₅)( ₃-Se) are as follows: space group P2₁/c, a=9.051(2) Å, b=8.102(2) Å, c=21.27(4) Å, =93.82(3)°, Z=4, and R=0.0565 for 2491 observed reflections.     

Approaching the Hartree-Fock limit for organotransition metal complexes

In theoretical studies of the electronic structure of organometallic complexes, the choice of basis set is critical, much more so than for analogous studies of molecules containing only H, C, N, and O. This problem is discussed in the light of structural predictions for the transition metal hydrides MH, MH₂, and MH₄, for the fluorides MF₂ and MF₃, and for Ni(CO)₄, Ni(C₂H₄)₃, (CO)₃NiCH₂, and Ni(C₄H₄)₂.