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An improved synthesis of platinum acetate is reported in detail. This tetrameric complex reacts with PPh3 or P � /n-Bu3 at room temperature to give the thermodynamically unstable bis-substituted trans -[Pt(OAc)2L2] complexes, which are not easily accessible via other routes. The structure of the new compound trans -[Pt(OAc)2(PPh3)2] has been determined by X-ray analysis. # 2003 Elsevier B.V. All rights reserved.

The silicon compounds SiMe2(NRR′)2 [NRR′ = NMe2 (1), NEt2 (2), NC4H8 (3), NHEt (4), NHiPr (5), NHtBu (6), NMeBu (7)] have been synthesised via aminolysis of the dichloro species SiMe2Cl2 and their ligating ability has been investigated towards zirconium(IV). The dimer zirconium compound {Zr[(NiPr)2SiMe2]2}2 (8) has been synthesised by reacting ZrCl4 with the lithium salt Li2[(NiPr)2SiMe2] and its molecular structure has been determined in the solid state by X-ray diffraction analysis. The reaction of ZrCl4 with SiMe2(NRR′)2 yields the Lewis adducts ZrCl4[(NRR′)2SiMe2] [NRR′ = NMe2 (10), NC4H8 (11), NHEt (12), NHiPr (13), NHtBu (14), NMeBu (15)]. On the other hand, the mixed amido derivative Zr(NMe2)3(NHMe)[(NtBu)SiMe2(NHtBu)] (9) has been obtained from the reaction of Zr(NMe2)4 with SiMe2(NHtBu)2. The solution molecular structure and dynamics of the zirconium derivatives have been elucidated by 1D and 2D multinuclear NMR spectroscopy.

The synthesis and the X-ray structure of the two pseudotetrahedral Zn(II) zwitterionic complexes: trichloro(1-methylpiperazin-1-ium-N4)zinc(II), [ZnCl3(H2Meppz)], and trichloro(1,4-dimethylpiperazin-1-ium-N4)zinc(II), [ZnCl3(HMe2ppz)], are described [(H2Meppz)+=1-methylpiperazin-1-ium monocation and (HMe2ppz)+=1,4-dimethylpiperazin-1-ium monocation]. [ZnCl3(H2Meppz)] and [ZnCl3(HMe2ppz)] complexes are isomorphous and isostructural, respectively, to the [CoCl3(H2Meppz)] and [CoCl3(HMe2ppz)] complexes, already reported in literature by us. Both complexes present a very uncommon and distorted tetrahedral aminotrichlorozinc(II), NZnCl3, group, where N is a nitrogen atom of an aliphatic amine. So far this group has been found only in the (1,3,5,7-tetraazaadamantane)trichloro-zincate(II) anion [{(CH2)6N4}ZnCl3]−. The bulky ZnCl3 group present in [ZnCl3(HMe2ppz)], is coordinated to the axial position of the piperazine ring instead of the less hindered equatorial position, as found in the analogous [CoCl3(HMe2ppz)] complex. An extended hydrogen bond network is present in the crystals of both the complexes but, while the [ZnCl3(H2Meppz)] complex shows nearly linear N+H⋯Cl intermolecular hydrogen bonds, the [ZnCl3(HMe2ppz)] complex shows a perfectly symmetrical (imposed by space group symmetry) Download : Download full-size image ZnNCl three-centre intermolecular hydrogen bond. The solid state infrared spectra of both the compounds are discussed in agreement with the hydrogen bond network present in the crystals.

Lanthanide(III) complexes of six-nitrogen-donor macrocyclic ligands carrying a benzyl-type group, CH2C6H4X (X=H, OH, or NH2), at each di-imine side chain were synthesized by the metal-templated, cyclic Schiff-base condensation of 2,6-diacetylpyridine with substituted S- or R,S-1,2-diaminopropanes. The complexes were obtained as mixtures of constitutional isomers and stereoisomers, which were identified by 1H NMR spectra and separated by fractional crystallization. The molecular structure of the 11-coordinate complex [La(NO3)2(H2O)(C36H38N6)](NO3)(H2O) was established by X-ray crystallography.

Complexes of Ca(II) and Sr(II) with six-nitrogen-donor macrocyclic ligands carrying a methyl group at each diimine side-chain were synthesized by the metal-templated condensation of 2,6-diacetylpyridine with R-, S-, or R,S-1,2-diaminopropane. The complexes exist as stereoisomers as well as constitutional isomers, which can be identified by 1H NMR spectra and separated by fractional crystallization. The molecular structure of the eight-coordinate complex [Sr(CF3SO3)2(C24H30N6)] was established by X-ray crystallography.

The complex [CrCl 3 (THF) 3 ] reacts with Li(CH 2 CH 2 CH 2 NMe 2 ) in THF at room temperature (r.t.) to form the tetranuclear complex [Cr 4 (CH 2 CH 2 CH 2 NMe 2 ) 4 (μ 4 -O)(μ-Cl) 6 ] ( 1 ) where each chromium atom has a distorted octahedral coordination geometry with an oxygen atom shared among the four metal ions.

The crystal and molecular structures of [(phenH)2Cl][Cr2(CO)10(μ-H)] (1) and [K(phen)2][Cr2(CO)10(μ-H)] (2) have been determined by single crystal X-ray diffraction. The availability of the potassium cation for the carbonyl oxygens coordination influences the conformation of the anion in 2 as demonstrated by the comparison with the non-coordinating [(phenH)2Cl] cation in 1 and with literature data.

The crystal structures of two stereoisomers of tetraphenyl- and pentaphenyl-substituted cyclopentenes 1 and 2 have been determined by X-ray analysis. An envelope conformation 1E has been ascertained for the cis isomer 1a, whereas the cis, cis isomer 2a, which crystallizes in two different space groups, P1¯ and P21/n, displays a twisted 2T1 conformation. The phenyl substituents are all tilted with respect to the cyclopentene ring in both structures. Compound 1a crystallizes in the space group P21/a with a = 18.553(3), b = 6.006(2), c = 19.355(5), β = 102.67(4)°, and V = 2104.2(g) A3 for Z = 4; compound 2a I crystallizes in P21/n with a = 10.064(2), b = 20.756(5), c = 12.245(3) A, β = 95.21(2)°, and V = 2547(1) A3 for Z = 4; compound 2aII crystallizes in P1¯ with a = 10.117(3), b = 11.750(2), c = 12.359(2) A, α = 111.25(2), β = 94.84(2), γ = 108.78(2)°, and V = 1262.3(6) A3 for Z = 2.

The cyanoguanidine complex cis-[Pt(NCNC(NH2)2)2(PPh3)2][BPh4]2, prepared by reacting cis-[PtCl2(PPh3)2] with cyanoguanidine in the presence of Na[BPh4], readily reacts with methanol to give cis-[(PPh3)2PtNHC(OMe) = NC(NH2) = NH)] [BPh4] containing a novel type of azametallcycle whose molecuar structure is established by X-ray crystallography. Its formation involves metal-promoted nucleophilic addition of the alcohol to the cyano group of a cyanoguanidine ligand, combined with deprotonation of the guanidine unit which then chelates the Pt(II) centre.

The syntheses of the ligand bis(benzylamide)diethylenetriaminepentaacetic acid (BBA-DTPA) and its Gd(III) and Lu(III) complexes are reported. The solid state structure of Lu(III) BBA-DTPA was determined in a single crystal X-ray diffraction study. The lutetium ion adopts a mine-coordinate geometry, which is best described as a distorted tricapped prism. Eight coordination sites are occupied by the ligand (three nitrogen atoms, two carboxamide oxygens and three carboxylate oxygens) and the ninth site is occupied by the oxygen atom of a water molecule. The VT 13 C NMR spectra of Lu(III) BBA-DTPA are consistent with the presence of three isomers in solution. Water proton relaxation rates have shown that Gd(III) BBA-DTPA displays an analogous behaviour to that observed for other Gd(III) complexes of related bisamide derivatives of DTPA. The solubility of Gd(III) BBA-DTPA has been markedly improved by the presence of an excess of hydroxypropyl-β-cyclodextrin. The thermodynamic stability of the inclusion complex has been evaluated by measuring the proton relaxation enhancement upon addition of β-cyclodextrin.

White prismatic crystals of formula Sb(dpk.OCH 3 )(O 2 C 6 H 4 ) were synthesized from the reaction of Sb(O 2 C 6 H 4 )F and dpk in methanol solution. The complex has been characterized by X-ray crystallography and Mossbauer spectroscopy. The crystal structure is characterized by a previously unknown O⊃N coordinating mode of the dpk. OCH 3 ligand. The Sb ion coordination geometry is of the AX 4 Y 2 E type, with four primary bonds due to the chelation of the dpk. OCH 3 and of the catecholato ligands, while the two secondary contacts with the oxygens of a catecholate and two dpk. OCH 3 ligands of adjacent molecules determine the chain formation.

In the β form of tris(thiocyanato-N)[2,7,13,18-tetramethyl-3,6,14,17,23,24-hexaazatricyclo[17.3.1.1 8,12 ]-tetracosa-1(23),2,6,8(24),9,11,13,17,19,21-decaene-N 3 ,N 6 ,N 14 ,N 17 ,N 23 ,N 24 ]europium, the nine-coordinate Eu III ion is bound to the N atoms of three monodentate isothiocyanate ligands and to the six N atoms of the macrocyclic ligand L (C 22 H 26 N 6 ), which has an 18-membered six-N-atom donor cavity, with a coordination geometry analogous to that of the α form.

The crystal and molecular structure of the [5S,15S] isomer of the [LaL(NCS)3] complex (L=C26H30N6) was determined by single crystal X-ray diffraction analysis. The compound crystallizes in the orthorhombic space group P212121 witha=13.647(4),b=19.504(4),c=11.606(4)A. The 9-coordinate La(III) is bound to the N atoms of three monodentate isothiocyanates and to the six N atoms of the macrocycle ligand L, which has an 18-membered, six-nitrogen donor cavity and two peripheral −CH3 substituents.

3,3′(1,2-Ethanediyl)bis(2-halophenyl-thiazolidin-4-one) derivatives display different pharmacological activities depending on the configuration of the 2,2′ centers and on the oxidation state of the sulfur atoms. Quantum-chemical calculations on the 3-fluorophenyl-substituted configurational isomers are reported here, together with the X-ray structure of the 1∶1 dioxide derivative. This crystallizes in the monoclinic space group P21/c, with four molecules per unit cell and cell dimensions:a=18.917(3),b=9.003(2),c=12.062(2)A, β=96.20(3)°. The compound, which has an approximate center of symmetry in the middle of the ethylene chain and two asymmetric carbon atoms of opposite chiralities, is the (2R,2′S-meso) (or 2S,2′R-meso) stereoisomer.

A number of adducts of InCl3 with selected Lewis bases have been synthesized and characterized. The complex of InCl3 with 1,2-dimethoxyethane (DME  CH3OCH2CH2OCH3) is characterized by two centrosymmetrically related InCl3·DME·0.5DME units, where the indium is six-coordinated to three chlorine atoms, two oxygen atoms of one chelating DME unit and one oxygen atom of the bridging DME ligand in a fac-octahedral arrangement. The suitability and limits of using InCl3·3/2DME for the synthesis of InMe3 (Me  CH3) are discussed.

1,3,5-Triscubstituted hexahydro-1,3,5-trazin-2-ones 3 are easily obtained by the reaction of 1,3,5-trisub-stituted hexahydro-1,3,5-triazines 1 with organic isocyanates 2. The reaction is believed to occur by the sequential addition to 2 of two molecules of the monomeric N-methyleneamines in thermal equilibrium with 1. Substituent scrambling at the operating temperature (120°) was negligible. The crystal structure of 1,3,5-triphenylhexahydro-1,3,5-triazin-2-one (3a) has been determined by X-ray diffraction methods.

The stereochemistry of the 3,3′-(1,2-ethanediyl)bis[2-(3-fluorophenyl)-1,3-thiazolidine-4-one] configurational isomers ( 2R,2′R 2S,2′ S and 2R,2′S meso ) has been investigated by 1 H-NMR techniques in solution, by X-ray diffraction methods in the solid state and by quantum chemical methods as the free molecule. The racemic compound, which has antagonistic activity at both H 1 and H 2 receptors, is found to prefer a gauche conformation in CDCl 3 solution, in the solid state and in the free molecule. The inactive meso stereoisomer is centrosymmetric in the crystalline state with an antiperiplanar conformation of the ethylene chain, whereas in CDCl 3 solution it exists as a rapidly interconverting mixture of 3 rotamers. The free molecule presents 2 gauche and 1 anti -periplanar conformations (differing by 1.3–2.4 kcal/mol). Some relationships between stereochemistry and activity are discussed.

Yellow crystals of formula [La(CH3COO)(NCS)2(C26H18N6)] were synthesized by the condensation of 1,2-diaminobenzene and 2,6-pyridinedicarboxyaldehyde in the presence of lanthanum(III) acetate, followed by partial acetate-thiocyanate metathesis. The complex has been characterized by X-ray crystallography. The LaIII ion is 10-coordinate, being linked to the six nitrogen atoms of the macrocyclic ligand, to the nitrogen atoms of two isothiocyanates situated on opposite sides of the macrocycle and to a bidentate chelating acetate. The IR and NMR spectra (1H and 13C) of the complex were recorded and assigned.

The results of a X-ray structure determination and of a quantum-chemical Conformational analysis on the title compound are reported. The crystals belong to the triclinic system, space groupP¯1 (after structure determination), with two molecules in the unit cell, whose parameters are:a=11.966(2),b=8.118(2),c=7.693(2)A,α=97.03(2),β=92.98(2), γ=106.15(2)°: observed density (by flotation) 1.49, calculated 1.503 g cm−3. The structure was solved from 1815 diffractometer-measured intensities, withI≥2.5σ(I) and refined by full-matrix least-squares to a final conventional indexR=0.035 (R w =0.043). The most relevant feature of the molecular structure is the orientation of the dichlorophenyl ring with respect to the planar indazole group, the dihedral angle being 83.1(1)°. A very close conformation corresponds to one of the minima calculated by the semiempirical AMI method.

The interaction of the paramagnetic complex [Eu(CH3COO)2L]Cl·4H2O, where L is the six N-donor macrocyclic ligand C22H26N6, with a series of organic substrates having potential O-donor atoms has been investigated. The 1H NMR resonances of anionic or acidic substrates were greatly shifted in the presence of the europium complex, whereas those of uncharged substrates remained essentially unchanged. The 5D0 → 7F2 emission of the europium complex was considerably enhanced in the presence of certain heteroaromatic carboxylates; new complexes of the formula [Eu(RCOO)2L]Cl·nH2O, where R is C6H5, C4H3O, C4H3S, C4H3NH or C5H4N and n = 2–4, were isolated in the solid state. The crystal and molecular structure of the triacetate, [Eu(CH3COO)2L](CH3COO)·9H2O, was established by single-crystal X-ray crystallography. The structure is ionic, with a 10-coordinate europium(III) linked to the six N-donor atoms of the macrocyclic ligand and to wo bidentate chelating acetates situated on opposite sides of the macrocycle. An ionic acetate and a network of hydrogen-bonded H2O molecules (nine per complex unit) completed the crystal lattice.

The interaction of the new, potentially binucleating, ligand 2,6-diacetylpyridine-bis(1′-phthalazinylhydrazone) (H 2 dapz), containing only nitrogen donor atoms, towards nickel(II), copper(II) and zinc(II) salts is reported. Depending on the nature of the counteranions, Ni II and Cu II ions selectively enter in one of the two ‘compartments’ present in the ligand. Analytical and spectroscopic characterizations of five series of mononuclear complexes [dapzM], [H 2 dapzMCl 2 ], [HdapzMCl], [(H 2 dapz) 2 M][ClO 4 ] 2 , [HdapzM][ClO 4 ], coming from reactions of metal acetates, metal chlorides and metal perchlorates, respectively, and the ligand in the bisdeprotonated, monodeprotonated and undeprotonated forms, are reported together with some interconversion reactions. Some tentative stereochemical assignments of these compounds are reported on the basis of their physicochemical properties. Different behaviour has been observed in the case of zinc(II) chloride and perchlorate. Crystal structure analysis on the bisdeprotonated complex [dapzNi] 2 , shows that the compound is dimeric, with the metal ions octahedrally coordinated into the upper compartment, and the pyridine nitrogens bridging the two nickel atoms.

The X-ray crystal structures of [Th(NCS) 4 (DIPIBA) 3 ] ( 1 ) [DIPIBA Me 2 CH CON(CHMe 2 ) 2 ] and [Th(NCS) 2 Cl 2 (DCA) 3 ]( 2 ) [DCA MeCON(cycloC 6 H 11 ) 2 ] have been determined from three-dimensional X-ray diffraction data. The different steric constraints of the ligand are not sufficient for different coordination geometries. In 1 and 2 the coordination polyhedron about the seven-coordinate thorium atom is a pentagonal bipyramid geometry which is becoming rather common for thorium(IV) compounds. In these compounds two chlorine ( 2 ) and two thiocyanate ( 1 ) anions are in axial positions with a significant shortening of the axial Th—NCS bonds with respect to the equatorial ones, while in the equatorial plane a neutral ligand lies between two anionic ligands, the remaining coordination positions being occupied by two other neutral ligands. The average bonding distances are Th O = 2.34(1)A, Th N ax = 2.42(1) and Th N eq = 2.46(1)Ain 1 , and Th O = 2.357(5), Th N eq = 2.479(6) and Th Cl ax = 2.695(3)Ain 2.

Complexes with formula [LnL8](ClO4)3 (LnLaHo) and [LnL7](ClO4)3 (LnErLu, Y; Lδ-valerolactam) were synthesized and characterized by conductance measurements, IR spectra, X-ray powder diffraction patterns, electronic absorption spectra of the neodymium and emission spectrum of the europium compounds. X-ray single crystal structural analysis of the neodymium compound showed that it forms monoclinic crystals, space group P21/n with a=25.491(4), b=16.074(3), c=13.051(3) A and β=90.15(3)°. Neodymium ions are coordinated in a square-antiprismatic arrangement to eight oxygen atoms of the δ-valerolactam ligands. The average NdO bond length is 2.45(1) A. The non-coordinated ClO4− ions are partially disordered.

Reaction of the new disodium salt: Na2[2,6-C5H3N(CH2C5H4)2 (2; 2,6-C5H3N = 2,6-pyridyl) with UCl4 in THF affords the reddish-green, mononuclear Cp2UIVCl2-derivative (Cp  η5-C5H5): μ-{2,6-CH2C5H3NCH2}(η5-C5H4)2UIVCl2 (1. According to a single-crystal X-ray study, 1 involves a notably strong UN bond (UNav: 2.62(1) A) along with two nonequivalent Cl ligands (UCl: 2.615(3) and 2.636(3) A). The low-temperature 1H NMR spectrum of the paramagnetic complex is in full accord with the solid state structure 1. Up to room temperature, the dissolved molecules of 1 show no fluxionality on the NMR time scale, although the two CH2 proton resonances appear to undergo coalescence.

The crystal and molecular structures of two configurational isomers (hereinafter HM and LM) of the title compound have been determined from single-crystal X-ray diffraction data. The HM isomer has crystallographically imposed ¯1 symmetry; then, the two asymmetric carbon atoms must have opposite chirality and the product is the 2R2′S-meso (or 2S2/t'r-meso) stereoisomer. The ethylenediamine group assumes the anti-periplanar conformation, the two phenyl rings are strictly planar, and the two thiazolidine rings present the same envelope conformation. The LM isomer is characterized by a-syn-clinal conformation of the ethylenediamine group, by the same envelope conformation of the two thiazolidine rings, and by the same chirality of the two asymmetric carbons atoms. Nevertheless in the crystal structure both enantiomers, 2R2′R and 2S2′S, are present.

A series of complexes of formula ML 3 X 3 •nS, in which M is La(III)-Yb(III), L 3 is C 26 H 18 N 6 , X is a mononegative ion, and S is water or methanol, were obtained by metal-templated condensation from 2,6-diformylpyridine and 1,2-diaminobenzene, as well as by metal exchange from Ba(L 3 ) 2 (ClO 4 ) 2 . The spectral properties of the complexes (IR and 1 H and 13 C NMR spectra for the diamagnetic species) closely resembled those of the Sr(II) analogue, the structure of which was established by X-ray analysis

The interaction of unchanged N-donor ligands with the complex [Eu(CH3COO)2L]Cl·4(H2O), where L is the macrocyclic ligand C22H26N6, was investigated in solution by NMR spectroscopy and luminescence titration. Both experiments indicated little or no interaction of the N-donor ligands with the metal centre of the macrocyclic complex. Attempts to isolate a 1,10-phenanthroline complex of the europium macrocycle produced instead {[Eu(CH3COO)L]2(μ-CO3)}(OH)2·7H2O, which incorporated atmospheric carbon dioxide. The X-ray crystal structure showed a bis-chelating carbonato group linking two europium macrocycles, each of which was folded in a butterfly configuration towards the external bidentate chelating acetates. Ionic hydroxides and clathrated water molecules completed the structure.

PA, C18H14C12N20282, Mr=425.36, tri- clinic, P1 (after structure determination), a-- 11.232(2), b=10.465(2), c=8.386(2) A, a= 107-07 (3), fl = 83-63 (4), y = 98.90 (3) °, V= 928.7 (4)/~3, Z = 2, Dx = 1.521 g cm -3, ,~(Mo Ka) = 0.71069 A,/1, = 5.27 cm -~, F(000)= 436, room tem- perature. Final conventional R value is 0.033 (wR = 0.041) for 2716 diffractometer-measured intensities with I___ 3tr(l). The molecular structure is charac- terized by the different conformations of the two thiazolidine rings, one of which is an envelope, and by opposite chirality of the two asymmetric C atoms. In the crystal structure both the enantiomers 2S,2'R and 2R,2'S are present. PB, CI8HI4C12N20282, Mr = 425.36, orthorhombic, Pbcn, a=7.759(2), b= 19.625 (4), c = 12.504 (3) A, V= 1904.0 (6) A 3, Z = 4, Dx = 1.483 g cm -3, a(Mo Ka) = 0.71069 A, /1, = 5.14cm -I, F(000)= 872, room temperature. Final conventional R value is 0.049 (wR = 0.067) for 1334 diffractometer-measured intensities with I_> 3tr(l). Because the molecular structure has exact C2 sym- metry, the two phenyl rings are strictly parallel and the conformations (half chair) of the two thiazolidine rings are the same as well as the chirality of the two asymmetric C atoms. Nevertheless both enantiomers 2R,2"R and 2S,2"S are in the crystal.

A novel polynuclear lanthanum complex of the DOTA ligand has been prepared and its X-ray crystal structure determined. This complex provides the first evidence of an “inverted square antiprismatic”...

Reaction of thallium(I) cyclopentadienide with InCl3 and InI3 led to the stepwise replacement of halide ions by cyclopentadienides. The complex [In(C5H5)Cl2 {O(CH2CH2)2}2] was isolated and its solid-state structure was established by single-crystal X-ray diffraction. In this pentacoordinated complex, the central indium(III) ion is bonded to two tetrahydrofuran molecules in the axial position, one cyclopentadienide ligand and two chloride ions in the equatorial positions in a trigonal bipyramidal arrangement.

The Al(III)-binding abilities of two aldaric acids, D-saccharic acid and mucic acid (the neutral form is denoted as H(2)L), were studied in solution by means of pH potentiometric, (1)H and (13)C NMR, and ESI-MS techniques. The most probable conformations and isomeric binding modes of the complexes formed in solution were determined by density functional theory (DFT) calculations. A solid D-saccharic acid complex K(2)[[Al(LH(-2))(H(2)O)](2)].H(2)O was isolated and crystallographically characterised. The two alcoholic hydroxy groups alpha to the terminal COO(-) groups were found to take part in the coordination, but in different ways. One of them coordinates in a bridging mode. Detailed ESI-MS and NMR studies proved that the complex retains its structure in solution. However, depending on the ligand and the pH, such complexes may exist in two isomeric forms. DFT calculations on the ion [[Al(LH(-2))(H(2)O)](2)](2-) revealed that several orbitals participate in stabilizing the dimeric arrangement.

New data on some cyclic dimethyl- and diethylindium-amides were obtained. X-ray structure of pyrrolidinodimethylindium was determined. The molecule is centrosymmetric with square–planar In 2 N 2 base and distorted tetrahedral metal environment similar to that of known dialkylindium amides, the cyclic amido-ligands are present in an envelope conformation. A novel material- and energy-saving procedure for sorption ultra-purification of highly sensitive organometallic compounds in absolute non-polar media was developed. Advanced inorganic and inorgano–organic crystalline layered materials possessing enhanced affinity towards selected ions or molecules were applied for the sorption treatment.

C 8 H 6 N 2 O 2 , M r =162.15, monoclinic, P2 1 /n, a=10.402 (2), b=15.025 (3), c=9.467 (2) A, β=96.24 (3) o , V=1470.8 (5) A 3 , Z=8, D m (flotation in heptane/carbon tetrachloride)=1.45, D x =1.46 Mg m -3 , λ(Mo Kα)=0.71069 A, μ=0.102 mm -1 , F(000)=672, T=295 K, R=0.041 (wR=0.048) for the 2105 observed reflections with I≥2.5σ(I). In both molecules of the asymmetric unit the carboxy group prefers a near coplanar [4.8 (1) and 5.4 (1) o ] and transoid orientation with respect to the strictly planar heterocyclic ring

The complex [Pt(Me)(dppe){η 1 -CH(PPh 3 )(COOEt)}]BF 4 has been synthesized and characterized spectroscopically and structurally. It crystallizes in the space group P 2 1 / n , with lattice constants a =14.525(3) A, b =14.931(3) A, c =21.921(4) A, β =103.47(3)°. The X-ray analysis revealed a particularly overcrowded molecular structure containing high stereochemical constraints. The structural features account for specific chemical and physical properties of this compound, thus representing an interesting example of applied crystallography.

The X-ray data on La, Nd, Er complexes ([Ln(TFA) (HMPA) ]) show that they crystallize in different forms depending on the solvent 3 3 1 content. Er is six and seven coordinated in the two complex cations coexisting in the crystal cell: [Er(TFA) (HMPA) ] and 2 4 1 1 [Er(TFA) (HMPA) (H O) ] . The trifluoroacetate anions are monodentate in both coordination polyhedra. In the [Nd(TFA) (HMPA) ] 2 2 2 3 2 4 cations, Nd is eight coordinated with bidentate trifluoroacetate ligands. Ó 2001 Elsevier Science B.V. All rights reserved.

In solution, the complex trans -[PdCl(C 5 H 4 N C 2 )(PMe 2 Ph) 2 ] ( 1 ) is in equilibrium with a small amount of the binuclear species [{PdCl(μ-C 5 H 4 N C 2 , N )(PMe 2 Ph)} 2 ] ( 2 ), which can be isolated upon recrystallization. The compound 1 is easily N-protonated by HClO 4 to the 2-pyridylium product trans -[PdCl(C 5 H 5 N C 2 )(PMe 2 Ph) 2 ]ClO 4 ( 3 ), which crystallizes in the orthorhombic space group P2 1 2 1 2 1 , with cell parameters a =15.761(3), b =14.369(2), c =11.132(2) A and Z =4. The X-ray crystal structure analysis of 3 , using 3744 observed reflections in the refinement and resulting in a final R value of 0.0298, shows that the coordination around palladium is essentially square-planar with PdC=1.970(5), PdCl=2.368(2), PdP(1)=2.317(1) and PdP(2)=2.318(1) A. The planar pyridine ring is perpendicular to the coordination plane, and the NH group is involved in hydrogen bonding with an oxygen of the perchlorate anion, at a contact distance of 2.08(6) A. Extensive hydrogen bonding occurs also in dichloromethane solution and accounts for the hindered rotation of the 2-pyridylium ligand around the PdC 2 bond.

1,3,5-Trisubstituted 1,3,5-triazinane-2-thiones 8 were obtained in high yields by the uncatalysed reaction between 1,3,5-triaryl or -trialkyl 1,3,5-triazinanes 1 with aryl or alkyl isothiocyanates 4 at 130 °C. Only the reaction of 1,3,5-triaryl-1,3,5-triazinanes 1 with alkyl isothiocyanates 4 failed. Although no other type of cyclization was detected, the systems in which the substituent in 4 was different from that in 1 exhibited more or less extensive random redistribution of the substituents, according to a retrocyclization–recyclization mechanism. X-Ray crystallographic data were obtained for two derivatives 8f and 8m. 1H and 13C NMR data, as well as electron impact fragmentations, were collected and are discussed.

Ba(thd)2 (1) (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) has been synthesized by reacting Hthd both with barium metal and with barium isopropoxide. Compound 1 readily forms the solvated complex [Ba(thd)2·Et2O]2 (2), which has been isolated and characterized by elemental analysis, mass spectrometry, IR, 1H and 13C NMR spectroscopy, and single-crystal X-ray structural studies. Compound 2 is a dimeric species in which the two barium atoms are bridged through four oxygen atoms of two β-diketonato ligands, while the other ligands, the remaining two thd− and two Et2O ligands are coordinated in a terminal mode.

The interaction of dimethyldiaminosilane ligands of general formula SiMe2(NR2)(NR′2) (NR2, NR′2 = NiHPr, NHtBu, NC4H8, NHCH2CH2NMe2) with AlX3 (X = Cl, Me) has been investigated and the synthesis of novel aluminium derivatives is reported, namely AlMe3[SiMe2(NR2)(NR′2)], AlX2[SiMe2(NR)(NR′2)] and AlMe[SiMe2(NR)2], containing the silane ligand as neutral, monoanionic and dianionic species, respectively. Moreover, the solution molecular structures and dynamics have been elucidated via 1D/2D variable temperature NMR spectroscopy showing the influence of the N-substituents of the silane ligand and of the aluminium ancillary ligands.

The title compound crystallizes in the triclinic system, space group P1 with a = 11.512(3), b = 9.387(3), c = 6.757(2) A, α = 105.6(4), β = 96.8(4) and γ = 107.0(4)° and Z = 2. The structure is built up from two distinct coordination polyhedra, one is formed by the uranium which is at a centre of a pentagonal bipyramid, the other by the potassium cations heptacoordinate to oxygen atoms either belonging to the maleic ligands or to the uranyl group. The uranium polyhedra are connected through bridging maleato groups. The maleato-U-maleato chains in the direction of the c axis are held together through the potassium coordination polyhedra.

The synthesis, thermal behaviour and crystal structure of lithium glutaratehydrogenglutaratedioxouranate(VI) tetrahydrate is described. The compound crystallizes in the monoclinic system, space group P21/n with a = 9.143(3), b = 26.825(11), c = 7.776(2) A, β = 101.2°(2) and Z = 4. The two glutarato ligands behave differently; one is bridging the uranyl groups in infinite chains running approximately in the a axis direction, the second is bridging the uranyl and the lithium ions. The carboxylic groups are chelated on the uranium and monodentate on the lithium. The structure is linked through a network of hydrogen bonding involving water molecules and oxygen atoms from the carboxylato groups. The geometry around the uranium is approximately hexagonal bipyramidal while the lithium is tetrahedrally coordinated with one glutarate oxygen and 3 water oxygens.

SrUO2(C3H2O4)2 · 3H2O and BaUO2 (C3H2O4) · 3H2O are isostructural. They crystallize in the orthorhombic system space group Pbca with eight molecules in cells of dimensions a = 16.729 (8), b = 23.247 (11) and c = 6.848 (5) A and a = 17.063 (9), b = 23.604 (12) and c = 6.885 (5) A, respectively. The structures were solved by the heavy-atom technique and refined with full-matrix least-squares to the R values of 0.043 and 0.046, respectively. The coordination geometry around the uranium atom is a pentagonal bipyramid with the malonates behaving as bidentate or terdentate ligands to the uranium atoms forming polymeric chains [UO2(C3H2O4)2]n2n− parallel to c. The space between the uranyl dimalonate chains is occupied by the oxygen atoms belonging either to the water molecules or to the carboxylic groups. Each polyhedron shares two edges forming columns running in the same direction as the uranyl chains and connecting them four by four.

Thorium tetrachloride forms a 1:3 complex, ThCl 4 ·3L, with N,N -diethyl N ′, N ′-dimethylurea (dedmu); and 1:2 complexes with dedmu, N,N -diisopropyl N ′, N ′-dimethyl (dibdmu), N,N -diisobutyl- N ′, N ′-dimethyl (dibdmu), N,N -diisopropyl N ′, N ′-diphenyl (dipdpu), N,N,N ′, N ′-tetramethyl (tmu) and N,N,N ′, N ′-tetraethylurea (teu) have been obtained. A dichloromethane solvate, ThCl 4 ·3L·CH 2 Cl 2 , where L= N,N ′-dimethyl- N ′, N -diphenylurea (dmdpu), has also been obtained. The crystal and molecular structure of ThCl 4 (dmdpu) 3 ·n-pentane has been determined from three dimensional X-ray diffraction data. The cell is triclinic, space group P 1 , with a =16.826(3), b =16.019(3), c =12.131(2) A, α=11O.4(1), β=106.6(1) and γ=59.4(1)° and Z =2. Full matrix least-squares refinement with 7963 intensity observations reached convergency with R =0.053 and R w =0.058. The coordination polyhedron about the seven-coordinate thorium atom is a pentagonal bipyramid with two chlorine atoms in apical positions. The average bonding distances are ThO=2.392(5), ThCl eq =2.743(3) and ThCl ax =2.696(3) A. The IR spectra of the complexes are also reported.

The crystal structures of the titlke compounds have been determined by X-ray diffraction. Urea, I crystallizes in the triclinic PI space group with cell dimensions a = 8.336(2), b = 11.009(2), c = 13.313(2) A, α = 105.55(3), β = 103.62(3), γ = 104.63(3)° and Z = 2 final R value 0.072 for 2105 observations. Urea, II crystallizes in the orthorhombic P212121 space group with cell dimensions a = 8.750(2), b = 10.844(3) and c = 21.215(3) A and Z = 4, final R value 0.083 for 599 observations. All the hydrogen atoms were located in the complex urea, I; urea molecules form hydrogen bonded dimers about centers of symmetry, these dimers are sandwiched between macrocyclic rings forming one simple and one bifurcated hydrogen bond from the “endo” hydrogen atoms to the ether oxygen atoms. These units are held by hydrogen bonding between the urea molecules and carboxylic acids in two other units; these hydrogen bonds are cyclic involving eight atoms -(N-H(exo)…O(keto)-C-O-H…O(urea)-C)-. Only one carboxylic acid group per molecule takes part in these hydrogen bonds, the other forms a short, 2.490(7) A, internal bond to the acceptor keto oxygen atom. N(H)…O bonds range from 2.930(7) to 3.206(7) A, O(H)…O is 2.475(6) A. In the complex urea, II each urea is hydrogen bonded to three different host molecules and vice versa; the urea “endo” hydrogen atoms bond to the ether oxygen atoms, while both “exo” hydrogen atoms take part in cyclic hydrogen bonds to carboxylic acids. There is not internal hydrogen bond. N(H)…O bonds range from 2.83 to 3.26(2) A and the O-…O bonds are 2.55 and 2.56(2) A.

Reactions of aliphatic branched aldehydes with proline in dimethyl sulfoxide or acetonitrile solution afford oxazolidin-5-ones with high diastereoselection. Linear aldehydes afford aldolic/crotonic condensation products; with short reaction times, the presence of Oxazolidinones can be detected in the pmr spectra. Acyclic aminoacids and branched aldehydes yield a reaction mixture the pmr and ir spectra of which give evidence for iminic-oxazolidinone equilibria. The structure of (2R,5S)-2-trichloromethyl-1-aza-3-oxabiciclo-[3.3.0]octan-4-one has been confirmed by X-ray diffraction analysis.

The compounds of the formula CuCl2(4-aminobenzophenone) (hereinafter L) 0.5S (S = ethanol or methanol) were synthesized and characterized by means of thermogravimetric electronic, IR spectra and magnetic susceptibility measurements. For the ethanol derivative, the structure was determined by a single crystal X-ray diffraction analysis. It crystallizes in the monoclinic system, space group P21/awith Z = 4 in a unit cell having a = 29.903(4), b = 6.202(2), c = 8.195(2) A, β = 92.88(4)°. The structure is polymeric and consists of infinite chains of chlorine bridged copper(II) ions along the b axis: the repeating unit is (LCuCl2EtOHCuCl2L)n. Although the two coppers are related through crystallographic inversion centres, they have different coordination geometries owing to the statistical positioning of the ethanol molecule. One is octahedrally coordinated to three chlorines in the square plane and to the nitrogen of L, while in the apical positions are the ethanol oxygen and a fourth chlorine atom; the second has a pyramidal coordination geometry, because of the missing ethanol oxygen in one apical position. (The same structure has been deduced for the methanol derivative.) Relevant bond distances are CuCl(1), 2.593(5); CuCl(1)′, 2.294(4); CuCl(2)″, 2.450(4); CuN, 2.03(1); CuO, 2.06(2) A.

The synthesis, thermal behaviour and crystal structure of fumarate dioxouranium(VI) dihydrate are described. The compound crystallizes in the monoclinic system, space group P 2 1 /n with a = 9.952(3), b = 7.502(2), c = 5.571(2) A, β = 98.6(3)° and Z = 2.555 observed reflections (I > 3σ( I )) were refined to a final R = 0.0235. The fumarate ligands bridge the uranyl groups in chains. The geometry around the uranium is approximately hexagonalbipyramidal, with the two water molecules coordinated to the uranyl group.

C13H10ClO2NS, Mr = 279.75, monoclinic, P2(1)/a, a = 14.490 (3), b = 22.598 (5), c = 7.336 (2) A, beta = 92.4 (1) degree, U = 2400 (1) A3, Z = 8, D chi = 1.548 g cm-3, lambda(Mo K alpha) = 0.71069 A, mu = 2.07 cm-1, F(000) = 1152, room temperature, R = 0.037 for 2423 independent reflections with I greater than or equal to 3 sigma(I). Each unit cell contains two independent molecules which differ mainly in the orientation of their N(CH3)2 groups. The two tricyclic moieties of each molecule are not coplanar, the pyran ring being tilted by 7.9 (1) degree with respect to the benzene ring in molecule 1 and by 8.7 (1) degree in molecule 2. There are weak interactions between the molecules involving the carboxylic O atoms and the H atoms of the phenyl moieties.