Palladium Clusters Pd4(SEt)4(OAc)4and Pd6(SEt)12: Structure and Properties

Palladium clusters Pd₄(SEt)₄(OAc)₄(I) and Pd₆(SEt)₁₂(II) were synthesized and studied. Their structure was determined by X-ray diffraction analysis. For I, a= 9.774(2) Å, b= 10.821(2) Å, c= 13.061(3) Å, = 92.88(3)°, V= 1379.6(5) ų, (calcd.) = 2.182 g/cm³, space group P2₁/n, Z= 4, N _ref= 1558, and R= 0.031; for II, a= 10.581(1) Å, b= 10.584(2) Å, c= 11.478(2) Å, = 101.62(1)°, = 104.95(1)°, = 106.74(1)°, V= 1135.2(4) ų, (calcd) = 2.007 g/cm³, space group P1, Z= 1, N _ref= 2828, and R= 0.022. In cluster I, four Pd atoms form a planar cycle. The neighboring palladium atoms are bound by two acetate or by two mercaptide bridges, the Pd···Pd distances being 3.036–3.195 Å. In cluster II, Pd atoms form a planar six-membered cycle with Pd···Pd distances of 3.083–3.127 Å. The neighboring palladium atoms are bound by two mercaptide bridges. The formation of analogous clusters in solution was confirmed by IR spectroscopy.     

Synthesis and X-ray structural investigation of 6-chloro-10-phenyl-1,2,3,4-tetrahydroacridine

An X-ray structural study of 6-chloro-10-phenyl-1,2,3,4-tetrahydroacridine prepared by the reaction of cyclohexanone with 2-amino-5-chlorobenzofenone was carried out. At 20°Ca=24.215(6),b=8.967(2),c=15.006(3) Å, =115.57(2)°,V= 2939(1) ų,d _calc=1.310 g cm^–3,Z=4, space groupC2/c, 1324 reflections, MoK,R=0.038. The cyclohexene ring has a half-chair conformation. The phenyl substituent is rotated 71.2° with respect to the plane of the quinoline fragment.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1467–1468, August, 1994.     

Crystal and molecular structure of nitraminotetrazole and nitramino-1,2,4-triazole. IV. 5-nitraminotetrazole sodium salt sesquihydrate

The structure of 5-nitraminotetrazole sodium salt sesquihydrate was determined by X-ray diffraction. The crystals are monoclinic, space group P2₁/c;a = 3.551(1) Å, b = 21.834(4) Å, c = 9.075(2) Å; = 110.68(3)°; V = 658.3(2) ų; Z = 4; _calc = 1.807 g/cm³. The anion is planar and has an intramolecular hydrogen bond. The negative charge of the anion is localized on one of the oxygens of the nitro group. The sodium cation (c.n.6) is coordinated by three oxygen atoms of different anions and three oxygens of crystallization water. One of the crystallization water molecules is disordered in the unit cell. The anions are hydrogen-bonded with each other and with crystallization water molecules.Original Russian Text Copyright © 2004 by A. M. Astakhov, A. D. Vasiliev, M. S. Molokeev, L. A. Kruglyakova, A. M. Sirotinin, and R. S. StepanovTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 562–565, May–June 2004.     

Synthesis,spectroscopy and thermal properties of the nickel(II), palladium(II) and copper(II) complexes of bis(aminoalkyl)-oxamides (=LH2) including the crystal structure of Cu2L(NO3)2

Summary The synthesis of the Ni^II, Pd^II and Cu^II complexes of N, N-bis(aminoalkyl)oxamides (LH₂) is described and structures are proposed on the basis of their physical and spectroscopic properties. With Ni^II and Pd^II only one complex is formed with general formula NiL or PdL, characterised by coordination through two deprotonated amide N-atoms and two terminal NH₂ groups. With Cu^II it proved possible to obtain three structurally different compounds, depending on the pH, with general formulae Cu(LH₂)X₂, Cu₂(L)X₂ and CuL in which X=Cl, Br or NO₃. The structure of [Cu₂(C₈O₂N₄H₁₆](NO₃)₂ was solved by means ofx-ray diffraction; Mr=451.33, monoclinic, space group P2₁/n, a=9.503(4), b=7.614(1), c=10.407(3) Å, =98.43(3)°, V=744.3(7)ų, Z=2, Dx=1.202 g cm^–3, =1.33 cm^–1, (MoK)=0.71073 Å, F(000)=520, room temperature, R=0.043, wR=0.047 for 1080 observed [I>-3(I)] not systematically absent reflections out of 1423 measurements and 137 variables. The compound has a conformational chair/boat disorder with 82% in the more stable chair form.     

Molecular structure of ansa-compound (η5-C5H4)CMe2(η5-C9H6)TiCl2

The structure of a new ansa compound, (⁵-C₅H₄)CMe₂(⁵-C₉H₆)TiCl₂ (1), was studied by X-ray analysis:a = 15.00(1),b =15.500(5),c = 13.032(4) Å, = 92.66°(4),V = 3025.1(1) ų, space groupP2₁/.,R = 0.038. The distorted tetrahedral coordination sphere of the Ti atom is formed by two Cl atoms and two -ligands. It was proposed that the angle () between theC-M direction and the line normal to M-Cp can be considered as one of the geometric parameters characteristic of the structure-properties correlation.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 305–308, February, 1995.     

Transition metal complexes with thiosemicarbazide-based ligands,IV: Synthesis and molecular structure of 5-nitrosalicylaldehyde S-methylisothiosemicarbazonato-piperidine-copper(II)

Summary The reaction of warmDMF solutions of Cu(II) perchlorate, 5-nitrosalicylaldehyde S-methylisothiosemicarbazone (H₂ L) and piperidine (Pip) yielded the paramagnetic (_eff=2.19 B.M.) Cu(L)Pip complex, whereL is the dianionic form of H₂ L, formed as a result of deprotonation of the phenolic hydroxyl and NH₂ group. Crystal data of the complex are: monoclinic P2₁,a=11.902(4),b=6.765(3),c=11.343(4)Å; =112.92°,V=841.20(8)ų,M=400.9,Z=2,d ₀=1.60 gcm^–3,d _c =1.58 gcm^–3,F(000)=424. The structure was refined to a residualR=0.047. The copper(II) ion is coordinated in a square-planar arrangement by the piperidine nitrogen and the NNO set of donor atoms ofL.

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Komplexe der Übergangsmetalle mit Thiosemicarbazid-Liganden, IV. Synthese und molekulare Struktur von 5-Nitrosalicylaldehyd-S-methylisothiosemicarbazonato-piperidin-kupfer(II)

Zusammenfassung Durch die Reaktion in warmenDMF-Lösungen von Cu(II) Perchlorat, 5-Nitrosalicylaldehyd-S-methylisothiosemicarbazon (H₂ L) und Piperidin (Pip) wurde ein paramagnetischer Komplex (_eff=2.19 B.M.) Cu(L)Pip erhalten, wobeiL nach doppelter Deprotonierung (NH₂- und Phenolhydroxyl-Gruppe) als dianionische Form von H₂ L vorliegt. Die kristallographischen Daten des Komplexes sind: monokline Raumgruppe P2₁,a=11.902(4),b=6.765(3),c=11.343(4)Å, =112.92°;V=841.20ų,M=400.9,Z=2,d ₀=1.60 gcm^–3,d _c =1.58 gcm^–3,F(000)=424. Die struktur wurde bis zu einemR-Wert von 0.047 verfeinert. Die Koordination des Kupfers wird quadratisch-planar über den Piperidin-Stickstoff und die NNO-Donorhülle der Chelatliganden gebildet.

     

Oligodienyl compounds of d- and f-transition metals: synthesis and stability

The results of investigations performed in the Laboratory of Organometallic Catalysis of the A. V. Topchiev Institute of Petrochemical Synthesis of the RAS are reviewed. The oligodienyl compounds of a series of transition metals, R _n ^olM and R _n ^olMX_m (R^ol= R(diene)_3–10, where R is an alkyl, allyl, alkenyl, or H; (diene)_3–10 is an oligodienyl group with 3–10 monomeric diene units; M = Ti³⁺, Cr²⁺, Mn²⁺, Co²⁺, Ni²⁺, Nd³⁺, Pr³⁺, Sm³⁺, and Gd³⁺; X is a halogen or an electronegative group), have been synthesized for the first time and some of their properties have been studied. The stability of oligodienyl compounds is much higher than that of the corresponding -alkenyl derivatives. The IR spectra of the compounds synthesized allowed us to conclude that their stability and some peculiarities of the reactions of these compounds can be explained by -coordination of the isolated double bond of the oligodienyl chain to the transition metal.Deceased in 1994.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 15–23, January, 1995.     

Coordination chemistry of alkali and alkaline earth cations. Barium-crown encapsulation studies: The synthesis and crystal structure of barium(picrate)2(benzo-15-crown-5) monohydrate

The interaction of barium with benzo-15-crown-5 (B15C5) has been followed under the competitive effect of various chelating organic anions (L), nitrophenolates and nitrobenzoates, in ethanol and ethanol-water (9:1). The rather heavily hydrated BaL₂ salts yield novel 1:1 stoichiometric products in monohydrated or anhydrous states. Use of excess crown does not under any condition lead to the formation of 1:2 charge separated complexes, expected in view of the cavity and the cation sizes. The 1:1 Ba–B15C5 interaction is counteracted by L in accordance with its nucleophilicity, i.e., the pK _a value of its parent acid, HL. The complex Ba(picrate)₂(B15C5)·H₂O (BaC₂₆H₂₆N₆O₂₀, FW=879.0), is monoclinic,P2₁/c,a=11.43(1),b=16.31(3),c=17.38(2) Å, =92.265(3)°,Z=4,D _c=1.77 g/cm³,D ₀=1.73 g/cm³, MoK, =0.71069 Å, 2 (4.0–50°), =13.5 cm^–1,F(000)=1752,T=–32°C. FinalR for the 5926 reflections was 0.049. The structure reveals barium to be 10-coordinated through all the five crown oxygens (Ba–O, 2.800 to 3.002 Å), the two bidentate picrates (Ba–O, 2.642 and 2.666 Å; Ba–ONO, 2.825 and 2.994 Å), and the water molecule (2.711 Å) so that the cation constitutes a pseudo-sandwich of the crown on one side and the anionic species on the other. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82007 (50 pages). To obtain copies, see page ii of this issue.     

Die Kristallstruktur von Dikalium-trikobalt(II)-dihydroxid-trisulfat-dihydrat,K2Co3(OH)2(SO4)3·2H2O

Crystals of K₂Co₃(OH)₂(SO₄)₃·2H₂O were synthesized under hydrothermal conditions. The crystal structure [a=17.945 (4) Å,b=7.557 (2) Å,c=9.760 (3) Å, space group Cmc2₁,Z=4] was determined by direct methods and refined with single crystal X-ray data. The H atoms were located byFourier syntheses. Their structural parameters were refined, too. The finalR-values areR=0.025 andR _w =0.028 (w=1/) for 612 reflections withF ₀>3 (F ₀). Both Co(II) atoms are octahedral six coordinated and form zigzag chains running parallel [001]. These chains are connected via sulfate groups to built up sheets parallel (100). The KO₉ polyhedron and one of the four hydrogen bonds link these sheets.

     

Synthetic and kinetic studies on copper(II), nickel(II) and cobalt(III) complexes of 1,4,7,10,13-pentaazacyclohexadecane ([16]aneN5)

Summary The pentadentate macrocycle 1,4,7,10,13-penta-azacyclo-hexadecane [16]aneN₅=(3)=L} has been prepared and a variety of copper(II), nickel(II) and cobalt(III) complexes of the ligand characterised. The copper complex [CuL](ClO₄)₂, on the basis of its d-d spectrum, appears to be square pyramidal, while [NiL(H₂O)](ClO₄)₂ is octahedral. The copper(II) and nickel(II) complexes dissociate readily in acidic solution and these reactions have been studied kinetically. For the copper(II) complex, rate=k_H[complex][H⁺]² with k_H =4.8 dm⁶ mol^–2s^–1 at 25 °C and I=1.0 mol dm^–3 (NaClO₄) with H=43 kJ mol^–1 and S ₂₉₈ =–89 JK^–1 mol^–1. Dissociation rates of the copper(II) complexes increase with ring size in the order: [15]aneN₅ < [16]aneN₅ < [17]aneN₅. For the dissociation of the nickel(II) complex, rate=k_H[Complex][H⁺] with k_H=9.4×10^–3 dm³mol^–1 s^–1 at 25 °C and I =1.0 mol dm^–3 (NaClO₄) with H=71 kJ mol^–1 and S ₂₉₈ =–47 JK^–1mol^–1.The cobalt(III) complexes, [CoLCl](ClO₄)₂, [CoL(H₂O)]-(ClO₄)₃, [CoL(NO₂)](ClO₄)₂, [CoL(DMF)](ClO₄)₃ (DMF=dimethylformamide) and [CoL(O₂CH)](ClO₄)₂ have been characterised. The chloropentamine [CoCl([16]aneN₅)]²⁺ undergoes rapid base hydrolysis with k_OH=1.1× 10⁵dm³ mol^–1s^–1 at 25°C and I=0.1 mol dm^–3 (H=73 kJ mol^–1 and S ₂₉₈ =98 JK^–1 mol^–1). Rapid base hydrolysis of [CoL(NO₂)]²⁺ is also observed and the origins of these effects are considered in detail.     

Copper(I) Complexes with N-Allylquinolinium Bromide [C9H7N(C3H5)]CuBr2 and [C9H7N(C3H5)]Cu2Br3: Synthesis and Crystal Structure

Crystals of [₉₇N(₃₅)]uBr₂ (IV) and [₉₇N(₃₅)][u₂Br₃] (V) were prepared by ac electrochemical synthesis from uBr₂, N-allylquinolinium bromide, on copper electrodes in the ethanol–benzene medium. X-ray diffraction study has shown that crystals IV and V are monoclinic: space group A2₁/a, a = 13.776(3) Å, b = 14.304(3) Å, c = 13.147(2) Å, = 107.90(1) Å, V = 2465(2) ų, Z = 8 for IV and space group P2₁/n, a = 13.881(2) Å, b = 15.446(2) Å, c = 7.111(1) Å, = 104.64(1)°, V = 1475.0(8) ų, Z = 4 for V. Structures IV and V are built of the N-allylquinolinium cations and different anions i.e., (CuBr₂) ^n- _n forming infinite chains in IV and peculiar {[Cu^I ₄Br₆]^2–} _n arranged in polymeric chains in V. In the latter case, two independent metal atoms have trigonal–pyramidal and trigonal–planar environments. In the structures of both compounds, the C=C bond of the allyl group is not involved in coordination with the Cu(I) atom.     

Crystal Structure of Ammonium Undecafluorotriantimonate(III) (NH4)2Sb3F11

The crystal structure of a novel antimony(III) fluoride complex, ammonium undecafluorotriantimonate(III) (NH₄)₂Sb₃F₁₁, was determined. The crystals are triclinic: a = 7.780(2) Å, b = 8.370(2) Å, c = 10.620(1) Å, = 71.06(1)°, = 89.03(1)°, = 63.58(1)°, V = 579.1(2) ų, Z = 2, (calcd) = 3.500 g/cm³, (exp) = 3.51 g/cm³, F(000) = 548.0, space group P . The structure consists of anionic [Sb₃F₁₁]^2– chains and ammonium cations combined into a framework by the N–H···F hydrogen bonds.     

Kristallstruktur von Trimethylisocyanursäure, (CH3NCO)3, und von Trichlorisocyanursäure-1/2-Ethylenchlorid, (ClNCO)3·1/2C2H4Cl2

X-ray crystal structure analyses of (CH₃NCO)₃ (M) and (ClNCO)₃·1/2C₂H₄Cl₂ (C) were carried out at room temperature (MoK, graphite monochromator, =0.71069 Å): 1.M=171.16, monochlinic, P2₁/c,a=14.848 (1) Å,b=13.400 (2) Å,c=8.149 (1) Å, =100.87 (1)°,V=1 592.3 ų,Z=8,F(000)=720,d _x =1.428 Mgm^–3, =76m^–1,R=6.51%,R _w =7.01% (964 reflections, 218 parameters). 2.M=281.89, monochlinic, P 2₁/c,a=9.416 (3) Å,b=5.728 (1) Å,c=18.199 (8) Å, =98.64 (2)°,V=970.4 Å₃,Z=4,F(000)=556,d _x =1.929 Mgm^–3, =1.11 mm^–1,R=3.96%,R _w =3.44% (605 reflections, 132 parameters). The ring systems together with the C atoms of the methyl groups in (M) and with the Cl atoms in (C) are planar and have D_3h-symmetry. Bond lengths and bond angles are discussed with regard to¹⁴N-NQR,³⁵Cl-NQR and vibrational spectroscopic data.

     

Thiourea N- and S-Derivatives as Ligands: Synthesis and Crystal Structure of 4CuCl · 6All–NHCSNH2 and [(All–NH)2C–SC2H5]Cu2ClxBr3 – x (x = 0.765, All is Allyl)

Crystals of the compounds 4CuCl · 6CH₂=CH–CH₂–NHCSNH₂ (I) and [(CH₂=CH–CH₂–NH)₂C–SC₂H₅]Cu₂Cl _x Br_{3 – x} (x = 0.765) (II) were synthesized by the ac electrochemical method, and their crystal structures were determined (CuK and MoK radiation, 2575 and 1090 unique reflections with F 4(F), R = 0.050 and 0.028 for I and II, respectively). Complex I crystallizes in space group C2/c, a = 17.230(7) Å, b = 12.258(5) Å, c = 42.95(2) Å, = 97.48(4)°, V = 8994(7) ų, Z = 8. The structure of -complex II is described by space group P2₁/n, a = 10.633(5) Å, b = 9.280(5) Å, c = 16.024(4) Å, = 102.16(3)°, V = 1546(1) ų, Z = 4. Complex I is built from isolated units of the aforementioned composition; every allylthiourea molecule coordinates two metal atoms through the sulfur atom. The distorted tetrahedral surrounding of every Cu(I) atom involves three S atoms and one Cl atom. The N,N"-diallyl-S-ethylisotiouronium cation coordinates two copper atoms through the C=C bonds, 1.32(1) and 1.35(1)Å, uniting the cuprohalide chains in layers. The structure of complex II is very close to the structure of the previously studied -complex of diallylammonium [H⁺L]Cu₂Cl₃.     

Darstellung und Kristallstruktur von Pb2(NO2)(NO3)(SeO3)

Crystals of Pb₂(NO₂)(NO₃)(SeO₃) were synthesized by partial reduction of nitrate ions with native copper under hydrothermal conditions. The crystal structure [a=5.529 (2) Å,b=10.357 (3) Å,c=6.811 (2) Å, space group Pmn2₁,Z=2] was determined from 1 707 independent X-ray data up to sin /=0.81 Å^–1 and was refined toR _w =0.028. The Pb(1) atom is ten coordinated to O atoms [Pb(1)-O from 2.51 Å to 2.96 Å], the Pb(2) atom has three nearest O atoms [Pb(2)-O=2.41 Å (1 ×) and 2.45 Å (2 ×)] and six next-nearest O atoms [Pb(2)-O from 2.80 Å to 3.22 Å].

Herrn Prof. Dr.K. Komarek zum 60. Geburtstag gewidmet.     

Crystal structure of LiFe3+(SeO3)2

Summary Single crystals of LiFe³⁺(SeO₃)₂ were prepared by hydrothermal synthesis. The crystal structure of LiFe³⁺(SeO₃)₂ is reported: tetragonal, space group I 2d,a=10.649(2) Å,c=9.959(2) Å,V=1129.4 ų,Z=8, 1268 unique reflections,R=0.037. The structure contains LiFeO₈ groups, built up by FeO₆ octahedra edgesharing with strongly distorted LiO₄ tetrahedra. These LiFeO₈ groups share corners with trigonal pyramidal SeO₃ groups to form a three dimensional network. The mean bondlengths are 1.994 Å, 2.006 Å and 1.699 Å for Li-O, Fe-O and Se(IV)-O, respectively.

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Die Kristallstruktur von LiFe³⁺(SeO₃)₂

Zusammenfassung Einkristalle von LiFe³⁺(SeO₃)₂ wurden auf hydrothermalem Weg dargestellt und ihre Kristallstruktur bestimmt: tetragonal, Raumgruppe I 2d,a=10.649(2) Å,c=9.959(2) Å,V=1129.4 ų,Z=8, 1268 unabhängige Reflexe,R=0.037. Kennzeichnend für die Atomanordnung sind LiFeO₈ Gruppen, die aus FeO₆ Oktaedern und mit ihnen kantenverknüpften, stark verzerrten LiO₄ Tetraedern aufgebaut sind. Diese LiFeO₈ Baueinheiten bilden, mit trigonal pyramidalen SeO₃ Gruppen über Ecken verbunden, ein dreidimensionales Netzwerk. Die Mittelwerte der Li-O, Fe-O and Se(IV)-O Abstände sind 1.994 Å, 2.006 Å und 1.699 Å.

     

Structure of Complexes Formed in the CuX2–Cu–N-Allylisoquinolinium Chloride System (X = Cl,Br)

The crystals of N-allylisoquinolinium chlorides of the compositions [C₉H₇N(C₃H₅)]₂Cu^IICl₄ (I), [C₉H₇N(C₃H₅)]Cu^ICl₂ · H₂O (II), and [C₉H₇N(C₃H₅)]Cu^ICl_1.43Br_0.57 · H₂O (III) were prepared by alternating-current electrosynthesis. X-ray diffraction analysis (using diffractometer models DARCH1 for I, STOE for II, and KUMA/CCD for III, MoK radiation) showed that the crystals of I are monoclinic, space group P2₁/n, a = 14.91(1) Å, b = 10.41(1) Å, c = 16.90(1) Å, = 109.73(8)°, V = 2470(8) ų, Z = 4. The crystals of isostructural compounds II and III are triclinic, space group P, Z = 2; crystals II: a = 7.2446(6) Å, b = 7.4379(6) Å, c = 12.110(1) Å, = 80.95(1)°, = 85.55(1)°, = 86.60(1)°, V = 641.8(2) ų; crystals III: a = 7.253(2) Å, b = 7.459(4) Å, c = 12.151(5) Å, = 80.82(4)°, = 83.73(3)°, = 86.81(4)°, V = 644.6(9) ų. The structure of I is composed of Cu^IICl₄ ^2– tetrahedra and N-allylisoquinolinium cations united by C–H···Cl hydrogen bonds in corrugated layers. The crystal structures of -complexesII and III are built of [C₉H₇(C₃H₅)]₂Cu₂ ^IX₄ dimers, which form layers along the c axis due to the C–H···X hydrogen bonds. An important role in the structure formation is played by water molecules, which crosslink the organometallic layers to form a three-dimensional framework through the O–H···X contacts.     

Synthesis and crystal structure of a new paramagnetic complex salt of diprotonated dioxocyclam with PtCl 2− 4 and water (1:1:1)

The paramagnetic complex salt of diprotonated dioxocyclam (1,11-dihydro-5,7-dioxo-1,4,8,11tetra-azacyclotetradecane), Pt(II) tetrachloride and water has been synthesized in strongly acidic medium and identified by X-ray structure analysis. The crystals of [(C₁₀H₂₂N₄O₂)²⁺(PtCl₄)^2–]·H₂O are monoclinic, space groupP2₁ c,M _r=585.23,a=9.516(1) Å,b=11.926(1) Å,c=16.622(2) Å,=102.88(2)°,V=1839(1)ų,Z=4,D _x=2.114 g cm^–3, (MoK )=0.70930 Å,=83.1 cm^–1,F(000)=1128,T=292 K,R=0.019 for 2808 observed reflections withI > 3(I). Alternating moieties of diprotonated dioxocyclam and a PtCl _2– ⁴ anion form columns running down the c axis. Water molecules are localized in the intercolumnar space and contribute to the extensive hydrogen bond network. The macrocycle conformation is characterized by two sequences of torsional angles, corresponding to two different subunits. The shorter sequence idealized as (-sc, ap, -ac, + ac, ap, +sc) [sc( ±60°), ac( ±120°), ap(180°)], describing the C pseudosymmetric part of the molecule, is centered on a -CH₂ group between the two peptide O-C-N-H fragments. The opposite C pseudosymmetric subunit has a nearly (-sc, ac, -SC, ap)₂ conformation. Pt is square planar coordinated by four Cl atoms, Pt-Cl_ve = 2.306(8) Å. The shortest Pt ... Pt distance is 7.200(1) Å.     

A CoMFA Study of Dopamine D2 Receptor Agonists and X-Ray Crystal Structure of Quinelorane Dihydrochloride Dihydrate,R(−)-Apomorphine Hydrochloride and R(−)-<Emphasis Type="Italic">N</Emphasis>-<Emphasis Type="Italic">n</Emphasis>-Propylnorapomorphine Hydrochloride

A QSAR and CoMFA study of 33 agonists of the dopamine D2 receptor has been completed. These analogs belong to different chemical classes of compounds and include varied functional groups and stereoisomers. The CoMFA program was used to calculate the steric and electrostatic interaction energies as a probe atom or probe charge interacts with the molecules. Color contour maps show that bulky substituents with low electronegativity on the fused piperidine ring nitrogen are favored for enhanced activity. The maps also showed that small substituents with low electronegativity on the aromatic ring are favored for enhanced activity. The X-ray crystal structures of quinelorane dihydrochloride (1), R-(–)-apomorphine hydrochloride (2), and R-(–)-N-n-propylnorapomorphine hydrochloride (3) showed the three-dimensional structures and the hydrogen bonding interactions of these molecules in the crystal. Since many of the dopamine agonists are mostly rigid, conformationally restrained structures, these crystal structures are reasonable representations for the solution structures. Crystallographic data: (1) C₁₄H₂₂N₄2HCl2H₂O, orthorhombic space group P2₁2₁2₁, a = 7.223 (1) Å, b = 18.705 (2) Å, c = 13.465 (2) Å, Z = 4, final R = 0.045 for 4586 observed reflections (I > 3 (I)); (2) C₁₇H₁₇NO₂ HCl, orthorhombic space group P2₁2₁2₁, a = 11.535 (2) Å, b = 13.251 (1) Å, c = 20.348 (2) Å, Z = 8, final R = 0.08 for 1806 observed reflections (I > 3 (I)); (3) C₁₉H₂₁NO₂HCl, triclinic space group P1, a = 7.133 (1) Å, b = 11.247 (1) Å, c = 11.112 (2) Å, Z = 2, final R = 0.054 for 3779 observed reflections (I > 3(I)).     

Charge control in the formation of complexes of phenol with unsaturated compounds containing organometallic substituents from group IV

The resonance donor effect of the , conjugation of R₃M and R₃MCH₂ (M = Si, Ge, Sn; R is an alklyl group) substituents with the triple bond in compounds R₃MC=CX and R₃MCH₂CCX (X = H, R) changes on passing from isolated molecules to their H-complexes. A partial ⁺ charge on the triple bond enhances , conjugation; a partial ^– charge on the triple bond has practically no effect on the resonance properties of R₃M substituents, whereas the , conjugation of R₃MCH₂ substituents diminishes owing to the effect of negative direct resonance interaction. The effect of , conjugation on the effective negative charges of the carbon atoms in the -CC- fragments was estimated quantitatively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1041–1046, June, 1994.This work was supported by the Russian Fundation for Basic Research (Grant 93-03-18372).