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Two novel Cd(II) and Zn(II) complexes with the condensation product of 2-formylpyridine and selenosemicarbazide were synthesized. The structure of Cd(II) complex was determined by X-ray crystallography. The ligand is coordinated in a neutral form via pyridine and azomethine nitrogen atoms and the selenium donor. The cadmium ion completes its five-coordination by two chloride ligands, forming a square-pyramidal geometry. The structure of Zn(II) complex was established by analysis of spectroscopic data, which indicated coordination of the ligand as a bidentate via the selenium and the azomethine nitrogen atoms. The cytotoxic activity of the newly synthesized complexes, as well as if five structurally related complexes and the ligand evaluated against eight tumor cell lines. The new Cd(II) complex showed the highest activity similar to cisplatin with IC50 less than 10muM for all cell lines. Cell cycle distribution and apoptosis study showed that Cd(II) complex and cisplatin might have some similarity in anticancer activity, which was not the case for cisplatin and other studied complexes. Effects of the complexes on matrix metalloproteinases (MMPs) MMP-9 and MMP-2 was also studied. Cd(II) and Zn(II) complexes and cisplatin increased MMP-2 activity in supernatants of tested cells, while Ni(II) complex with the same ligand decreased the activity, implying a possible activity in preventing tumor invasion and metastasis processes.

Trichlorostannyl complexes M(SnCl3)(Tp)L(PPh3) (1, 2) and M(SnCl3)(Cp)L(PPh3) (5, 6) [M = Ru, Os; L = P(OMe)3 (a), P(OEt)3 (b), PPh(OEt)2 (c), PPh3 (d)] were prepared by allowing chloro complexes MCl(Tp)L(PPh3) and MCl(Cp)L(PPh3) to react with an excess of SnCl2·2H2O in ethanol. Treatment of trichlorostannyl complexes 1, 2, 5, and 6 with NaBH4 in ethanol yielded tin trihydride derivatives M(SnH3)(Tp)L(PPh3) (3, 4) and M(SnH3)(Cp)L(PPh3) (7, 8). Reaction of these complexes with CCl4 gave the trichlorostannyl precursors 1, 2, 5, and 6. Hydridochlorostannyl intermediates Os(SnH2Cl)(Tp)[P(OMe)3](PPh3) (9a) and Os(SnHCl2)(Tp)[P(OMe)3](PPh3) (10a) were also obtained. Reaction of trihydridostannyl complexes M(SnH3)(Tp)L(PPh3) (3, 4) with CO2 (1 atm) led to hydridobis(formate) derivatives M[SnH{OC(H)═O}2](Tp)L(PPh3) (11). In contrast, reaction of the related complexes M(SnH3)(Cp)L(PPh3) (7, 8) with CO2 (1 atm) led to the binuclear OH-bridging bis(formate) derivatives [M[Sn{OC(H)═O}2(μ-OH)](Cp)L(PPh3)]2 (12, 13). ...

New complexes of Cd(II), Zn(II) and Ni(II) with 2-quinolinecarboxaldehyde selenosernicarbazone (Hqasesc) were synthesized and structurally characterized. The structure of the ligand, Cd(II) and Zn(II) complexes was determined by NMR and IR spectroscopy, elemental microanalysis and molar conductivity measurements. Both complexes occur in solution in two forms, the major tetrahedral and minor octahedral. In the major Cd(II) complex one qasesc(-) ligand is coordinated as a tridentate, the fourth coordination site being occupied by acetate, while in the major Zn(II) complex two qasesc- ligands are coordinated as bidentates. In both minor complexes two qasesc- ligands are coordinated as tridentates forming the octahedral geometry around the central metal ion. The only paramagnetic complex in the series is Ni(II) complex for which X-ray structure analysis was performed. The complex has the angularly distorted octahedral geometry with two qasesc- ligands coordinated as tridentates, in a similar way as in the minor complexes of Cd(11) and Zn(11). (c) 2007 Elsevier Ltd. All rights reserved.

Complexes of Pt(II), Pd(II), and Ni(II) with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and semioxamazide were synthesized, characterized, and their antimicrobial activity was evaluated. The ligand and the complexes were characterized by spectroscopic methods with the particular accent on NMR spectral analysis. For the palladium(II) complex, the crystal structure was determined by X-ray analysis. In all the complexes the ligand is coordinated as a tridentate via a P, N, O donor set. The Pd(II) and Pt(II) complexes have a square planar geometry, whereas the geometry of the Ni(II) complex is tetrahedral. The ligand showed antibacterial and antifungal activity, which was enhanced upon complexation.

Four Co(III), Zn(II), Pd(II) and Cd(II) complexes with ligands derived in situ from acetylpyridine and ethyl hydrazinoacetate or hydrolysed ethyl hydrazinoacetate were prepared. An X-ray structural analysis showed that the Co(III) complex is octahedral with two tridentate (E)-2-[N′-(1-pyridin-2-yl-ethylidene)hydrazino]acetate (apha) ligands, each forming two five-membered rings with the metal ion. In the tetrahedral Zn(II) complex, only a single apha ligand was coordinated, in the same way as that in the Co(III) complex. In the case of the tetrahedral Cd(II) complex the non-hydrolysed form of (E)-2-[N′-(1-pyridin-2-yl-ethylidene)hydrazino]acetic acid ethyl ester (aphaoet) coordinated as a bidentate and the two remaining coordination sites were occupied by Cl− and CH3COO− ions. In addition, the square-planar neutral Pd(II) complex was synthesized, having the same bidentate as in the Cd(II) complex and two Cl− ions in the remaining coordination sites. Due to their being diamagnetic, all four complexes were ...

In this paper, we report the synthesis and the characterization of a novel series of lanthanide (III) complexes with two potentially hexadentate ligands. The ligands contain a rigid phenanthroline moiety and two flexible hydrazonic arms with different donor atom sets (NNN 0 N 0 OO and NNN 0 N 0 N 00 N 00 , respectively for H2L 1 (2,9-diformylphenanthroline)bis(benzoyl)hydrazone and H2L 2 (2,9-diformylphenanthroline)bis(2-pyridyl)hydrazone). Both nitrate and acetate complexes of H2L 1 with La, Eu, Gd, and Tb were prepared and fully characterized, and the X-ray crystal structure of the complex [Eu(HL 1 )(CH3 COO)2] AE 5H2O is presented. The stability constants of the equilibria Ln 3+ +H 2L 1 = [Ln(H2L 1 )] 3+ and Ln 3+ +( L 1 ) 2� = [Ln(L1)] + (Ln = La(III), Eu(III), Gd(III), and Tb(III)) are determined by UV spectrophotometric titrations in DMSO at t =2 5� C. The nitrate complexes of H2L 2 with La, Eu, Gd and Tb were also synthesized, and the X-ray crystal structures of [La(H2L 2 )(NO3)2(H2O)](NO3), [Eu(H2L 2 )(NO3)2](NO3) and [Tb(H2 L 2 )(NO3)2](NO3) are discussed.

A family of organic-inorganic wheel-and-axle diols (Pd(LOH)(2)Cl(2), Pd(LOH)(2)(CH(3))Cl, Pd(LOH)(2)(CH(3)COO)(2), LOH = alpha-(4-pyridyl)benzhydrol) and several corresponding solvates are synthesized and characterized by single-crystal X-ray diffraction analysis. Their structures are compared to investigate the factors governing the modes of solid state association, the propensity to clathration, and the structural basis of guest inclusion. In all the complexes, the palladium coordination is a slightly distorted square. The LOH ligands coordinate Pd(2+) by means of the 4-pyridyl ring. In the chloride complexes solvation occurs with a 1:2 host/guest ratio by hydrogen bonding between the terminal -OH groups of the complex diol and one acceptor atom on the guest, and it is further assisted by guest stacking between host aryl rings. All solvates are organized in layers with practically invariant metrics, while the layers may be assembled in different arrangements. The structures of the nonsolvate compounds are related to the metrics of the solvate forms by rotation of the complex molecules within the layer plane. In all cases the nonsolvates are completely converted into the corresponding crystalline solvate forms by exposure to the vapor of the guest, and conversely they are quantitatively recovered from the solvate upon removal of the guest by mild conditions. On the basis of the structural data, it is proposed that the solvation/desolvation process proceeds by a concerted rotation of the complex molecules in the layer plane. The structural analysis of Pd(LOH)(2)(CH(3)COO)(2) and of its tetrahydrofuran monosolvate form suggests that the first step of the solid/gas solvation process may imply the clathration of 1 mol of guest between the aryl rings, which successively triggers the collective reorientation of the host molecules.

The reaction of [ReCl2(OCH3)(NO)(PPh3)2] with phosphane in the presence of NaBH4 gives different dihydride [ReH2(NO){PPh2(OEt)}3] (1) and alkoxy-hydride [ReH(OR1)(NO)P3] (2, 3) [R1 = CH3, C2H5; P = PPh(OEt)2, P(OEt)3] derivatives depending on the nature of the phosphane and the solvent used. The protonation reactions of the new hydrides with Bronsted acid were performed and led to thermally unstable [Re(OR1)(η2-H2)(NO)P3]+ (2*, 3*) dihydrogen cations. Hydrazine complexes [ReH(RNHNH2)(NO){PPh2(OEt)}3]BPh4 (4) (R = H, CH3,C6H5) and [Re(OR1)(RNHNH2)(NO)P3]BPh4 (5, 6) [R1 = CH3, C2H5; R = H, CH3,C6H5; P = PPh(OEt)2] were prepared by allowing the hydrides [ReH2(NO)P3] and [ReH(OR1)(NO)P3] to react first with triflic acid and then with hydrazine. The complexes were characterized spectroscopically and by the X-ray crystal structure determination of [Re(OC2H5)(NH2NH2)(NO){PPh(OEt)2}3]BPh4 (5a). Oxidation of the hydrazine complexes 4−6 was studied with Pb(OAc)4 at −30 °C and, depending on the nature of the hydrazine and the stoichiometry of the complexes, led to aryldiazene [ReH(C6H5N=NH)(NO){PPh2(OEt)}3]BPh4 (7c), [Re(OC2H5)(C6H5N=NH)(NO){PPh(OEt)2}3]BPh4 (8c), methyldiazene [ReH(CH3N=NH)(NO){PPh2(OEt)}3]BPh4 (7b) and a mixture of methyldiazene [Re(OCH3)(CH3N=NH)(NO){PPh2(OEt)}3]BPh4 (9b) and methyleneimine [Re(OCH3)(η1-NH=CH2)(NO){PPh2(OEt)}3]BPh4 (9*b) derivatives. Mono- and binuclear aryldiazene complexes [ReH(ArN=NH)(NO){PPh2(OEt)}3]BPh4 (10), [{ReH(NO)[PPh2(OEt)]3}2(µ-HN=NAr−ArN=NH)](BPh4)2 (11), [Re(OR1)(ArN=NH)(NO)P3]BPh4 (12, 14, 16) and [{Re(OR1)(NO)P3}2(µ-HN=NAr−ArN=NH)](BPh4)2 (13, 15) [R1 = CH3, C2H5; P = PPh(OEt)2, P(OEt)3; Ar = C6H5, 4-CH3C6H4; Ar-Ar = 4,4′-C6H4-C6H4] were also prepared by allowing hydrides [ReH2(NO)[PPh2(OEt)}3] and [ReH(OR1)(NO)P3] to react with mono- and bis-aryldiazonium cations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The new potentially hexadentate ligand (2,9-diformylphenanthroline) bis(benzoyl)hydrazone (H 2 L) is synthesised and spectroscopically characterised. It reacts with dibutyltin diacetate and diphenyllead dichloride giving the complexes [(C 4 H 9 ) 2 SnL] and [(C 6 H 5 ) 2 PbL], respectively; their X-ray structure and spectroscopic characterization are reported.

Palladium(II) and nickel(II) complexes with tetradentate ligands derived from pyrrole 2-carboxaldehyde and various diamines have been synthesized and characterized. The complexes are neutral and the coordination around the metal is square-planar; they are able to activate the molecular hydrogen and to catalyse the homogenous hydrogenation of phenylacetylene. The X-ray structures of N,N′-cycloexylenebis(pyrrol-2-ylmethyleneamine) (H2L4), PdL4 and PdL3 (H2L3, N,N′-propylenebis(pyrrol-2-ylmethyleneamine)) are discussed.

The octahedral copper(II) complex with two 2′-[1-(2-pyridinyl)ethylidene]oxalohydrazide molecules was synthesized from bis(acetylacetonato)copper(II) and 2′-[1-(2-pyridinyl)ethylidene]oxamohydrazide (Hapsox). The complex is unstable when not in solution. X-ray analysis confirmed the tridentate coordination of the ligands in the monoanionic form. In addition, the stable tetrahedral copper(II) complex with one ligand molecule coordinated as a tridentate in the dianionic form was prepared by direct synthesis from Cu(NO3)2·3H2O and Hapsox, and characterized by elemental analysis, magnetic measurements and by i.r. and u.v./vis. spectrophotometry.

A variety of prop-2-ynylamides have been carbonylated under oxidative conditions to give oxazolines, oxazolines with chelating groups, and bisoxazolines bearing an (alkoxycarbonyl)methylene chain at the 5 position in good yields. The cyclization-alkoxycarbonylation process was carried out in alcoholic media at 50-70 degrees C and under 24 bar pressure of 3:1 carbon monoxide/air in the presence of catalytic amounts of 10% Pd/C or PdI2 in conjunction with KI. Cyclization occurred by anti attack of an oxygen function on the palladium-coordinated triple bond, followed by stereospecific alkoxycarbonylation, strictly resulting in E-stereochemistry. The structures of representative oxazolines and bisoxazolines have been determined by X-ray diffraction analysis.

Metal complexes of general formula M(L)X2 and M(L)X3 [L = (4S,5S)-2,2-dimethyl-4,5-bis{6-[(4,5-dihydro-4-(S)-(1-methylethyl)oxazol-2-yl)pyridin-2-yl]}-1,3-dioxolane] were obtained by reacting, respectively, CoII, CuII, NiII, and ZnII nitrate salts and the RhIII chloride salt, with a chiral C2-symmetric bis(oxazolinylpyridinyl)dioxolane (L) ligand, in MeOH/CHCl3 solution. A single crystal X-ray analysis was carried out on [Ni(L)(OH2)2](NO3)2 · 2H2O and the molecular structure of L was also determined. In the free ligand the two symmetric arms are essentially planar and oriented nearly perpendicular to the dioxolane average plane. In the Ni complex one seven-membered and two five-membered chelation rings are formed. The metal atom also lies on the C2 axis, and two symmetry-related water molecules complete the octahedral coordination environment. Both compounds crystallize in chiral space groups; the ligand crystallizes in orthorhombic system, space group C 2 2 21, Z = 4; the nickel complex crystallizes in tetragonal system, space group P 43 21 2, Z = 4.

The title compound was prepared by a template synthesis from 2,6-diacetylpyridine, dioxamohydrazide and Fe(ClO4)3·6H2O(mol ratio 1:2:1) in MeOH/H2O(3:1) solution and its structure determined by single-crystal X-ray diffraction; triclinic, space group P1, a = 7.5186(7), b = 10.9730(9), c = 14.6110(10) A, α = 95.866(1), β = 100.252(1), γ = 92.895(1), z = 2. The polydentate ligand is coordinated as a dianionic pentadentate while water molecules occupy apical positions in the structure. This is the first example of a monomeric, pentagonal bipyramidal structure of an Fe(III) complex with a dianionic bis(acylhydrazone) derivative of 2,6-diacetylpyridine.

The crystalline ternary inclusion complex terfenadine/ g -cyclodextrin/tartaric acid (TFN/ g CD/TA, 2:4:1) has been prepared from a aqueous solution (terfenadine, TFN, rac - f -[4-(1,1-dimethylethy...

The mono- and binuclear aryldiazene complexes [Re(C6H5N=NH)(CO)5-nPn]BY4 (1-5) and [(Re(CO)5-nPn)2-(mu-HN=NAr-ArN=NH)](BY4)2 (6-12) [P = P(OEt)3, PPh(OEt)2, PPh2OEt; n = 1-4; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-(2-CH3)C6H3-C6H3(2-CH3), 4,4'-C6H4-CH2-C6H4; Y = F, Ph) were prepared by reacting the hydride species ReH(CO)5-nPn with the appropriate mono- and bis(aryldiazonium) cations. These compounds, as well as other prepared compounds, were characterized spectroscopically (IR; 1H, 31P, 13C, and 15N NMR data), and 1a was also characterized by an X-ray crystal structure determination. [Re(C6H5N=NH)(CO)(P(OEt)3)4]BPh4 (1a) crystallizes in space group P1 with a = 15.380(5) A, b = 13.037(5) A, c = 16.649(5) A, alpha = 90.33(5) degrees, beta = 91.2(1) degrees, gamma = 89.71(9) degrees, and Z = 2. The "diazene-diazonium" complexes [M(CO)3P2(HN=NAr-ArN identical to N)](BF4)2 (13-15, 17) [M = Re, Mn; P = PPh2OEt, PPh2OMe, PPh3; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-C6H4-CH2-C6H4] and [Re(CO)4(PPh2OEt)(4,4'-HN=NC6H4-C6H4N identical to N)](BF4)2 (16b) were synthesized by allowing the hydrides MH(CO)3P2 or ReH(CO)4P to react with equimolar amounts of bis(aryldiazonium) cations under appropriate conditions. Reactions of diazene-diazonium complexes 13-17 with the metal hydrides M2H2P'4 and M2'H(CO)5-nP"n afforded the heterobinuclear bis(aryldiazene) derivatives [M1(CO)3P2(mu-HN=NAr-ArN=NH)M2HP'4](BPh4)2 (ReFe, ReRu, ReOs, MnRu, MnOs) and [M1(CO)3P2(mu-HN=NAr-ArN=NH)M2'(CO)5-nP"n](BPh4)2 (ReMn, MnRe) [M1 = Re, Mn; M2 = Fe, Ru, Os; M2' = Mn, Re; P = PPh2OEt, PPh2OMe; P',P" = P(OEt)3, PPh(OEt)2; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-C6H4-CH2-C6H4; n = 1, 2]. The heterotrinuclear complexes [Re(CO)3(PPh2OEt)2(mu-4,4'-HN=NC6H4-C6H4N=NH)M(P(OEt)3)4(mu-4,4'-HN=NC6H4- C6H4N=NH)Mn(CO)3(PPh2OEt)2](BPh4)4 (M = Ru, Os) (ReRuMn, ReOsMn) were obtained by reacting the heterobinuclear complexes ReRu and ReOs with the appropriate diazene-diazonium cations. The heterobinuclear complex with a bis(aryldiazenido) bridging ligand [Mn(CO)2(PPh2OEt)2(mu-4,4'-N2C6H4-C6H4N2)Fe(P(OEt)3)4]BPh4 (MnFe) was prepared by deprotonating the bis(aryldiazene) compound [Mn(CO)3(PPh2OEt)2(mu-4,4'-HN=NC6H4-C6H4N=NH)Fe(4- CH3C6H4CN)(P(OEt)3)4](BPh4)3. Finally, the binuclear compound [Re(CO)3(PPh2OEt)2(mu-4,4'-HN=NC6H4-C6H4N2)Fe(CO)2(P(OPh)3)2](BPh4)2 (ReFe) containing a diazene-diazenido bridging ligand was prepared by reacting [Re(CO)3(PPh2OEt)2(4,4'-HN=NC6H4-C6H4N identical to N)]+ with the FeH2(CO)2(P(OPh)3)2 hydride derivative. The electrochemical reduction of mono- and binuclear aryldiazene complexes of both rhenium (1-12) and the manganese, as well as heterobinuclear ReRu and MnRu complexes, was studied by means of cyclic voltammetry and digital simulation techniques. The electrochemical oxidation of the mono- and binuclear aryldiazenido compounds Mn(C6H5N2)(CO)2P2 and (Mn(CO)2P2)2(mu-4,4'-N2C6H4-C6H4N2) (P = PPh2OEt) was also examined. Electrochemical data show that, for binuclear compounds, the diazene bridging unit allows delocalization of electrons between the two different redox centers of the same molecule, whereas the two metal centers behave independently in the presence of the diazenido bridging unit.

Depending on experimental conditions and the nature of the hydrazine, the reactions of ReCl3P3 [P = PPh(OEt)2] with RNHNH2 (R = H, CH3, tBu) afford the bis(dinitrogen) [Re(N2)2P4]+ (2+), dinitrogen ReClN2P4 (3), and methyldiazenido [ReCl(CH3N2)(CH3NHNH2)P3]+ (1+) derivatives. In contrast, reactions of ReCl3P3 [P = PPh(OEt)2, PPh2OEt] with arylhydrazines ArNHNH2 (Ar = Ph, p-tolyl) give the aryldiazenido cations [ReCl(ArN2)(ArNHNH2)P3]+ (4+) and [ReCl(ArN2)P4]+ (7+) and the bis(aryldiazenido) cations [Re(ArN2)2P3]+ (5+, 6+). These complexes were characterized spectroscopically (IR; 1H and 31P NMR), and the BPh4 complexes 1, 2, and 7 were characterized crystallographically. The methyldiazenido derivative [ReCl(CH3N2)(CH3NHNH2){PPh(OEt)2}3][BPh4] (1) crystallizes in space group P1 with a = 15.396(5) A, b = 16.986(5) A, c = 11.560(5) A, α = 93.96(5)°, β = 93.99(5)°, γ = 93.09(5)°, and Z = 2 and contains a singly bent CH3N2, group bonded to an octahedral central metal. One methylhydrazine ligand, one Cl- trans...

Carbamato displacement from the hydrocarbon soluble N,N-diisopropylcarbamato derivative Ti(O2CNiPr2)4, 1, by triphenylsilanol led to the bis(silanolato)bis(carbamato) complex Ti(O2CNiPr2)2(OSiPh3)2, 2. X-Ray diffraction showed the mononuclear compound 1 to contain eight-co-ordinated titanium with slightly asymmetric bidentate carbamato groups in a distorted dodecahedral geometry. Titanium is six-co-ordinated in 2 to six oxygen atoms belonging to two bidentate carbamato groups and to two cis-arranged silanolato ligands in a distorted octahedral geometry. Exhaustive carbamato displacement from titanium, carried out with a silanol∶titanium molar ratio > 4∶1, afforded the mononuclear tetrasilanolato complex Ti(OSiPh3)4, 3, containing a tetrahedral titanium centre.

Several potentially tridentate hydrazonic ligands containing a PNO donor atom set were synthesised and used to prepare the corresponding acetato palladium(II) complexes. These were used as catalysts in the homogeneous hydrogenation of styrene and other unsaturated C–C bonds under mild conditions. Depending on the basicity of the hydrazonic nitrogen of the ligand, a different catalytic activity of the complexes was observed. This substantiates a heterolytic activation of the molecular hydrogen, which leads to the protonation of the ligand and formation of a palladium(II) hydride complex. Kinetic studies of the hydrogenation of styrene in methanol were performed, using complex 1a as catalyst. A dependence, approximately of first order in hydrogen and catalyst concentrations and zero order in styrene concentration, was found. Two kinetic equations derived from a statistic processing are compared. The X-ray crystal structure of complex 1a is also reported.

The antibiotic activity (via inhibition of DNA-dependent RNA polymerase, DDRP) of rifamycins has been correlated to the conformation of the ansa chain, which can be described by means of 17 torsion angles defined along the ansa backbone. It has been shown that favourable or unfavourable conformations of the ansa chain in rifamycin crystals are generally diagnostic of activity or inactivity against isolated DDRP. The principles of structure correlation suggest that the torsional variety observed in rifamycin crystals should mimic the dynamic flexibility of the ansa chain in solution. Twenty-six crystal structures of rifamycins are grouped into two classes (active and non-active). For each class the variance of the 17 ansa backbone torsion angles is analysed. Active compounds show a well-defined common pattern, while non-active molecules are more scattered, mainly due to steric constraints forcing the molecules into unfavourable conformations. The experimental distributions of torsion angles are compared to the torsional freedom of the ansa chain simulated by molecular dynamics calculations performed at different temperatures and conditions on rifamycin S and rifamycin O, which represent a typical active and a typical sterically constrained molecule, respectively. It is shown that the torsional variety found in the crystalline state samples the dynamic behaviour of the ansa chain for active compounds. The methods of circular statistics are illustrated to describe torsion angle distributions.

Chelating properties of C2-symmetric chiral bipyridine ligands are discussed. In particular we report the syntheses of the cobalt(II), nickel(II), zinc(II) and copper(II) complexes of (4S,5S)-2,2-dimethyl-4,5-bis(2-pyridyl)-1,3-dioxolane. All compounds have been characterized by IR spectroscopy, and an X-ray diffraction analysis has been carried out on one of them: Co(L)(NO3)2. The ligand coordinates the cobalt atom by the two nitrogen donors N(1) and N(2). A seven-membered chelation ring is formed, presenting a remarkable non-crystallographic twofold pseudosymmetry around the axis connecting Co and the midpoint of the C(6)–C(7) bond. The metal also binds two monodentate nitrates, thus completing a distorted coordination tetrahedron.

The synthesis of complexes of the type trans -[RhL 4 X 2 ] + {L = N -alkylimidazoles ( N -RIm) [R = methyl (Me), ethyl (Et), n-propyl (Pr 0 , n-butyl (Bu n )], 4(6)-hydroxypyrimidine (4(6)-hydPm); X = Cl − or Br − ) is achieved by the general catalytic method involving the use of ethanol. The formation of complexes with L = N -Melm was reexamined and a new procedure has been established. The distribution of the trans -[RhL 4 X 2 ] + and [RhL 5 X] 2+ ions as reaction products strongly depends on the nature of the solvent and the structure of the ligand. We proposed that the initial product trans -[RhL 4 X(sol)] 2+ produced by catalytic action of ethanol, undergoes nucleophilic substitution reactions either by halogenide anions X or by ligand molecules L, thus giving rise to the formation of trans -[RhL 4 X 2 ] + or [RhL 3 X] 2+ complexes. The direction of the nucleophilic substitution is determined by the concentration of ethanol, the L ligand and the X halogen. IR, Raman, electronic absorption and 1 H NMR spectra were used to characterize the complexes. The prepared complexes show significant antifungal activity. The crystallographic structure of rans -[Rh( N -Melm) 4 Cl 2 ]Cl·2H 2 O has been determined. The octahedron is slightly distorted since it has, in a square plane, four nitrogen ligands and two Cl atoms at the two apical sites. The octahedral bond angles are very close to the ideal values and are in the range of 88.1(1)–89.6(1)°. The Rh atom is located on the two-fold rotation axis which relates two pairs of N -methylimidazole molecules and Cl atoms.

The mechanism of action of rifamycins against bacterial DNA-dependent RNA polymerase has been explained on the basis of the spatial arrangement of four oxygens which can form hydrogen bonds with the enzyme. Structural descriptors are derived from X-ray diffraction crystal structures of 25 active and nonactive rifamycins. Principal component analysis is used to find the combination of structural parameters which better discriminate between active and nonactive rifamycins. Two possible mechanisms of molecular rearrangement are described which can convert nonactive into active conformations. The energy involved for conformational rearrangements is studied by molecular modeling techniques. Methyl C34 is found to play a key role for determining the geometry of the pharmacophore. Rifamycin O, reported to be active, is obtained by oxidation of rifamycin B and is studied by X-ray single-crystal diffractometry, by solution IR and NMR spectroscopy, and by thermal analysis. Surprisingly the oxidation process is totally stereospecific, and an explanation is given based on solution spectroscopic evidence. The conformation found in the solid state is typical of nonactive compounds, and molecular mechanics calculations show that a molecular rearrangement to the active conformation would require about 15 kcal/mol. Thermal analysis confirms that rifamycin O has a sterically constrained conformation. Therefore, it is likely that the antibiotic activity of rifamycin O is due either to chemical modification prior to reaching the enzyme or to conformational activation.

The solid state structure of delapil hydrochloride was determined by single-crystal X-ray diffraction analysis (monoclinic, P21, a=16.098(5), b=10.712(3), c=7.856(2) A , β=97.85(2)° . The comparison between delapril and other ACE inhibitors of the same family is discussed with regard to the geometry of the phenomenological active site of the enzyme. In the solid state the amide bond conformation resulted in being trans, whereas, in solution, NMR spectra indicate that the molecule exists as a mixture of rotational isomers trans and cis (approximately 70:30). The free energy of activation for the hindered rotation about the amide bond was determined by line-shape analysis. The attempt to isolate possible conformational polymorphs failed, indicating that the trans conformation is favored when molecules pack together in the crystal.

Mono- and bimetallic organotin complexes with pyrrole-2,5-dicarboxaldehyde bis(2-hydroxybenzoylhydrazone) (H 5 dfps) and pyrrole-2,5-dicarboxaldehyde bis(2-picolinoylhydrazone) (H 3 dfpp) were synthesized and characterized by IR, 1 H and 119 Sn NMR spectroscopy. X-ray analysis of the complex [Sn(H 3 dfps)(C 6 H 5 ) 2 ] · (CH 3 ) 2 SO revealed a pentacoordination around tin through a N,N,O terdentate ligand behaviour of the hydrazone. This complex is the most active compound, exhibiting MIC values of 3 and 12 μg/ml against Gram positive and Gram negative bacteria, respectively. None of the ligands or complexes produced DNA-damage in the Bacillus subtilis rec -assay or showed mutagenic activity in the Salmonella -microsome test.

Ni(II) complexes of hydrazonic ligands derived from 2, 6-disubstituted pyridines and alkyl or aryl hydrazides are synthesized and characterized. The coordination geometry depends on the type of R' substitutents of the ligand. When R' is alkyl, stable complexes with square planar geometry are obtained with an E,Z induced configuration of the hydrazonic arms. These complexes are not mesogenic. For R = aryl two different Ni(II) complexes are formed: the monomeric square planar and a dimeric one with octahedral coordination. In solution the monomer slowly interconverts to the dimer, which is the thermodynamically more stable product. The X-ray structure of the dimer 12a and its magnetic properties are reported. The mesogenic properties of these Ni(II) derivatives depend on the coordination geometry. The monomeric complex 11b forms a metastable meso phase. After the clearing point dimerization takes place and the corresponding dimer 12b does not present liquid crystalline properties.

Palladium(II) complexes of the type Pd(PNO)Y (PNO = 2-(diphenylphosphino)benzaldehyde picolinhydrazone, nicotinhydrazone, isonicotinhydrazone; Y = CH3CO2, Cl, I) and Pd(PNS)Y (PNS = 2-(diphenylphosphino)benzaldehyde thiosemicarbazone; Y = CH3CO2, Cl, I) were synthesised and characterised by spectroscopic methods. The X-ray structure of an iodo complex was also determined. The catalytic activity of all the complexes in the homogeneous hydrogenation of terminal double and triple bonds was tested with particular regards to the chemoselectivity from triple to double bond. A correlation between the catalytic activity and the nature of the ligand and Y group was established. In the hydrogenation of phenylacetylene using acetato complexes as catalysts, stable phenylethynylpalladium(II) complexes were recovered and characterised by spectroscopic methods. A facile route of synthesis of alkynyl complexes was also determined.

Aryldiazene complexes [Mn(CO)(3)(ArN=NH)P(2)]BF(4) (1, 2) and [{Mn(CO)(3)P(2)}(2)(m-HN=NArArN=NH)](BF(4))(2) (3, 4) [P = PPh(OEt)(2), PPh(2)OEt; Ar = C(6)H(5), 2-CH(3)C(6)H(4), 4-CH(3)C(6)H(4), 4-CH(3)OC(6)H(4); ArAr = 4,4'-C(6)H(4)C(6)H(4), 4,4'-(2-CH(3))C(6)H(3)C(6)H(3)(2-CH(3)), 4,4'-C(6)H(4)CH(2)C(6)H(4)] were prepared by reacting hydride species MnH(CO)(3)P(2) with the appropriate aryldiazonium cations in CH(2)Cl(2) or acetone solutions at -80 degrees C. The compounds were characterized by IR, (1)H and (31)P NMR spectra (with (15)N isotopic substitution), and a single-crystal X-ray structure determination. The complex [Mn(CO)(3)(4-CH(3)C(6)H(4)N=NH){PPh(OEt)(2)}(2)]BF(4) (1c) crystallizes in the space group C2/c with a = 31.857(5) A, b = 11.119(2) A, c = 22.414(3) A, beta = 97.82(1) degrees, and Z = 8. Treatment of aryldiazene compounds 1-4 with NEt(3) gave the pentacoordinate aryldiazenido [Mn(CO)(2)(ArN(2))P(2)] (5, 6) and [{Mn(CO)(2)P(2)}(2)(m-N(2)ArArN(2))] (7, 8) [P = PPh(OEt)(2), PPh(2)OEt; Ar = C(6)H(5), 4-CH(3)C(6)H(4); ArAr = 4,4'-C(6)H(4)C(6)H(4), 4,4'-(2-CH(3))C(6)H(3)C(6)H(3)(2-CH(3))] derivatives. Protonation reactions of these aryldiazenido complexes 5-8 with HCl afforded the aryldiazene [MnCl(CO)(2)(ArN=NH)P(2)] (9) and [{MnCl(CO)(2)P(2)}(2)(m-HN=NArArN=NH)] (10) derivatives. Hydrazine complexes [Mn(CO)(3)(RNHNH(2))P(2)]BPh(4) (11, 12) [P = PPh(OEt)(2), PPh(2)OEt; R = H, CH(3), C(6)H(5), 4-NO(2)C(6)H(4)] were prepared by allowing hydride species MnH(CO)(3)P(2) to react first with triflic acid and then with the appropriate hydrazine. Their characterization by IR, (1)H and (31)P NMR spectra, and an X-ray crystal structure determination is reported. The compound [Mn(CO)(3)(NH(2)NH(2)){PPh(OEt)(2)}(2)]BPh(4) (11a) crystallizes in the space group Po with a = 13.772(3) A, b = 14.951(4) A, c = 13.319(3) A, alpha = 104.47(1) degrees, beta = 100.32(1) degrees, gamma = 111.08(1) degrees, and Z = 2. Oxidation reactions of hydrazine compounds 11 and 12 with Pb(OAc)(4) at -40 degrees C gave stable aryldiazene [Mn(CO)(3)(RN=NH)P(2)]BPh(4) and thermally unstable (upon reaching -40 degrees C) diazene [Mn(CO)(3)(HN=NH)P(2)]BPh(4) derivatives.

Benzotriazole and its 5-methyl-and 5-nitro derivatives react with diethyl ethoxymethylenemalonate by ethylation at each of the ring N-atoms and through Michael addition, to give the isomeric esters ethyl (E/Z) 3-[5(6)-R-benzotriazol-1-yl]propenoates. Benzotriazole and its 5-nitro derivative react similarly with ethyl acetoacetate but N-ethyl derivatives are obtained in lower yields. Other 1,2,3-triazoles derivatives and indole were ineffective in this reaction while benzimidazole produced similar results but accompanied with a small amount of a benzimidazoline addition product, whose structure has been determined by crystallo-graphic analysis.

The crystal structure of a glycopeptide antibiotic A–40926 aglycone was investigated by X-ray analysis at −120°. A-40926 crystallises in the orthorhombic space group P212121 with two monomers in the asymmetric unit, a = 21.774(4), b = 28.603(7), c = 29.757(4) A. ‘Conventional’ direct methods approach failed to solve the structure, but a novel iterative real/reciprocal space procedure was successful. Refinement against 11248 F2 data led to R1 = 13.3% for 6770 F > 4σ (F). The two monomers of A-40926 have similar conformations and are bound by antiparallel H-bonds to form a ‘chain’ structure of connecting dimers. The antibiotic molecule possesses a ‘binding pocket’ for the C-terminal carboxy group of the cell-wall protein, which is consisten with suggestions based on NMR data and the recently reported crystal structure of ureido-balhimycin. In A-40926 the monomers are polymerically linked by H-bonds, quite unlike the tight dimer formation observed in ureido-balhimycin.

Chemical implantation of tin on a commercial silica has been carried out by using the hydrocarbon soluble Sn(O 2 CN i Pr 2 ) 4 as precursor, the N,N -dialkylcarbamato group is chemically displaced by the silanol groups of the support under mild conditions.

A new hydrazonic ligand, 2,6-diacetylpyridine bis(octanoylhydrazone) (H 2 dapo), has been prepared and examined as chelating agent towards iron(II), cobalt(H), nickel(II) and palladium(II) ions. All the compounds have been characterized by IR and 1 H and 13 C NMR spectroscopies. The X-ray diffraction analysis carried out on [Ni(H 2 dapo)(OH 2 ) 2 ]Cl 2 showed a pentagonal bipyramidal stereochemistry which can be also assumed for the Fe and Co chloro complexes, while for Ni(dapo) and Pd(dapo) the spectroscopic investigation suggests a square planar coordination and a different configuration ( E and Z ) for the two hydrazonic chains.

Manganese(II), nickel(II), and copper(II) complexes of 2,6-diacetylpyridine bis (acetylhydrazone) (H2dapac) have been synthesized and structurally characterized by X-ray diffraction methods. [Mn(H2dapac) (OH2)2](NO3)2 crystallizes in the monoclinic space groupP21/c witha=11.145(3),b=10.723(4),c=17.189(2) A, β=92.81(2)° andZ=4; [Ni(H2dapac)(OH2)2] (NO3)2·H2O crystallizes in the monoclinic space groupP21 witha=9.994(3),b=14.423(4),c=7.697(2)A, β=100.37(2)°, andZ=2; [Cu(H2dapac)(OH2)2](NO3)2·H2O crystallizes in the orthorhombic space groupPbcn witha=20.986(5),b=14.552(3),c=6.905(1)A andZ=4. In each case the metal atom has a slightly distorted pentagonal bipyramidal environment, the equatorial positions being occupied by three nitrogen and two oxygen atoms from the hydrazone ligand and the apices by two water molecules. The crystalline cohesion in ensured by a three-dimensional network of hydrogen bonds involving the complex cations, the nitrate anions, and, where present, the uncoordinate water molecules.

The ligand behavior of di-2-pyridylketone 2-aminobenzoylhydrazone (Hdpa), and phenyl(2-pyridyl)ketone 2-aminobenzoylhydrazone (Hdpa) towards organotin derivatives was investigated. The synthesis and the IR and 119Sn NMR spectroscopic characterization of the compounds is reported, together with the X-ray crystal structures of Hdpa and Sn(C6H5)3Cl(OH2)·Hdpa, which are discussed and compared. The in vitro evaluation of antimicrobial properties revealed the strong activity of Sn(C6H5)2(Hdpa)Cl2 and Sn(C6H5)3Cl(OH2)·Hdpa complexes. None of the compounds showed genotoxicity in the Bacillus subtilis rec-assay and in the Salmonella-microsome test.

Two paramagnetic octahedral nickel(II) complexes containing the tetradentate 1,3-propanediamine-N,N′-diacetate (1,3-pdda) or ethylenediamine-N,N′-propionate (eddp) anions and water in the remaining two coordination positions were prepared and characterized. In both cases, only one (uns-cis) of the three geometrical isomers, was found to dominate. The 1,3-pdda and eddp ligands prefer the uns_cis configuration, indicating that six-membered chelate rings have a profound effect on the distribution of geometrical isomers. The infrared and electronic absorption spectra of these complexes are discussed in comparison with those of an edda-Ni(II) complex (eedda=ethylenediamine-N,N′-diacetate ion) of known s-cis configuration. The electronic absorption spectra have been treated in terms of Oh symmetry but the splitting of the 3T2g(Oh) bands of the complexes indicates that the tetragonal field is enhanced. The splitting patterns are assigned with the D4h model: 3B1g→3B2gand 3B1g→3Eg. The magnetic measurements are also reported for the complexes studied. The uns-cis-[Ni(1,3-pdda)(H2O)2] complex crystallizes in the space group P212121 of the orthorhombic crystal system with a=15.982(4), b=8.502(2), c=8.032(2) (A) and Z=4. The six-membered diamine ring assumes the stable ‘chair’ conformation. The five-membered glycinate rings show a relatively small puckering resembling an ‘envelope’ conformation.

2,6-Diacetylpyridine bis{[dl-hydroxy(phenyl)acetic]hydrazone} (H4dapm) has been synthesized and spectroscopically characterized (IR and NMR) along with six metal (Cu, Ni, Fe) complexes. The crystal structure of [Ni(H4dapm)(H2dapm)]·13H2O has been determined by X-ray diffraction methods. It crystallizes in the monoclinic space group C2c with a=20.977(6), b=20.040(6), c=14.328(3) A, β=100.67(2)° and Z=4. The complex has twofold crystallographically imposed symmetry with the nickel atom in a distorted octahedral environment consisting of six nitrogen atoms from two ligand molecules.

The amino/imino equilibrium is studied in free bases and hydrochloride salts of amidinobenzisothiazole derivatives by IR and 1H-NMR spectroscopy. The X-ray crystallographic analysis of two of these compounds shows that the free base exists as amino form whereas the hydrochloride as imino form. Untersuchungen des Amidin-Systems in Amidinobenzisothiazol-Derivaten Das Amin/Imin-Gleichgewicht der Titelverbindungen als freie Basen und als Hydrochloride wurde durch IR- und 1H-NMR-Spektroskopie untersucht. Die Rontgenstrukturanalyse von zwei Derivaten zeigt, das die freien Basen als Amine, die Hydrochloride als Imine vorliegen.

Cobalt(II), nickel(II), and copper(II) complexes of 2-[(2S)-2-pyrrolidinyllpyridine (L) have been synthesized and characterized. The crystal structure of the complex [Cu(L)2(NO3)]NO3 has been determined by X-ray diffraction. Crystals are monoclinic, space groupP2+, witha=10.766(3).b=7.525(2),c=13.447(4) A. β=104.64(2)°. and Z=2. The structure consists of [Cu(L)2(NO3)]+ cations and NO 3 t- anions. The copper atom has a distorted trigonal bipyramidal coordination geometry with the two pyrrolidine nitrogens and one nitrate oxygen occupying the equatorial positions and the two pyridine nitrogens at the apices. The crystalline cohesion is ensured by a network of hydrogen bonds involving the pyrrolidine groups as donors and both coordinate and uncoordinate nitrates as acceptors.

The new potentially tetradentate aroylhydrazone ligands, Hbitp and Hsitp, produced by condensation of 5-acetyl-2,2′- pyridylthiophene with benzoyl- and salicyloylhydrazine, respectively, have been reacted with several metal(II) acetates. Deprotonation at the amide nitrogen occurs and neutral complexes of the type [M(bitp)2L2] and [M(sitp)2L2] are obtained, where L is a solvent molecule. An X-ray crystal structure determination carried out on [Co(bitp)2(dmso)2] (I) revealed that these ligands behave as bidentate through the (O)CNN hydrazide moiety, assuming the Z configuration around the CN hydrazone bond. The coordination environment is distorted octahedral, the solvent molecules occupying the axial positions. The crystal structure of the Ligand Hbitp (II) has also been determined for comparison.

The conformational and packing properties of two encapsulated cobalt(III) complexes containing cyclo-triphosphate have been investigated. Compound (I), (1,3,6,8,10,13,16,19-octaazabicyclo[6.6.6]icosane)cobalt(III) cyclo-triphosphate-water (2/7) has the trivial name cobalt(III) sepulchrate cyclo-triphosphate-water (2/7) and chemical formula [Co(sep)](P 3 O 9 ).3.5H 2 O. The cation shows an lel 3 geometry very similar to those found in other sepulchrate complexes

2-(2′-Thienyl)pyridine (pyth) and its acetylated derivative (apyth) ( III ) react with copper chloride to give compounds of formulae [Cu(pyth) 2 Cl 2 ] ( I ) and [Cu(apyth) 2 Cl 2 ] ( II ). The crystal structures of I , II and III have been determined by X-ray methods. In both copper complexes the metal atom is surrounded by two N atoms (CuN, 2.025(5) A in I and 2.021(2) A in II ) from two ligands molecules and two Cl atoms (2.265(2) A in I and 2.264(1) A in II ) in a typical square planar environment. Two thiophene S atoms (CuS, 2.968(2) A in I and 2.904(1) A in II ) complete the coordination sphere, making the complex elongated octahedral. By contrast, in all complexes of general formula [Cu(bipy) 2 X]X, (bipy= 2,2′-bipyridyl) the coordination environment around copper is quasi- trigonal bipyramidal, the pyridine rings in each bidentate ligand being almost coplanar, and one anion does not participate to coordinative bonding.

The complex (1,3,6,8,10,13,16,19-octaazabicyclo[6.6.6]-icosane)cobalt(III) perchlorate thiosulfate, [Co(C 12 H 30 N 8 )](ClO 4 )(S 2 O 3 ), crystallizes in the hexagonal space group P6 3 22. Cations and anions occupy special-site positions with the anions disordered as a result of symmetry requirements. Co(sep) 3+ (sep=C 12 H 30 N 8 ) adopts the optically active D 3 crystallographic geometry. The packing consists of layers of interacting Co(sep) 3+ and S 2 O 3 2- ions, intercalated by isolated ClO 4 - anions. The second complex, rac-(1,3,6,8,10,13,16,19-octaazabicyclo[6.6.6]icosane)cobalt trichloride monohydrate, rac-[Co(C 12 H 30 N 8 )]Cl 3 .H 2 O, crystallizes in themonoclinic space group P2 1 /a.

From the reaction of di-2-pyridylketone 2-aminobenzoylhydrazone (Hdpa) with SnPh 2 Cl 2 two complexes, [SnPh 2 (Hdpa)Cl 2 ] ( 1 ) and [SnPh(dPa)Cl 2 ] ( 2 ), were isolated as yellow and red crystalline products, respectively. In compound 1 the Hdpa coordinates very weakly to tin through O (2.434(7) A), N(1) (2.695(8) A) and N(3) (2.749(9) A); on the contrary, in 2 the Hdpa is deprotonated and binds much more strongly to tin through the same atoms (2.200(16), 2.162(19) and 2.140(18) A, respectively). 119 Sn NMR data in dimethyl sulphoxide suggest that the solid state structure of 2 is retained, whereas that of 1 breaks down in solution.

The synthesis and structural characterization by IR, ESR, 119 Sn and 57 Fe Mossbauer spectroscopy, X-ray powder diffraction, and TG and DSC methods of a new series of organotin hexacyanoferrates are reported.

Anhydrous [Au2Br6] and Aul can be obtained by halide exchange from [Au2Cl6] with RX (X = Br or I, R = H or alkyl). The addition of [Au2Cl6] to CPh3Cl produces the ionic derivative [CPh3][AuCl4] whose crystal and molecular structure has been determined by X-ray diffraction. Crystal data: space group P21/c, a= 8.225(3), b= 14.671(6), c= 16.738(8)A, β= 97.85(2)° and Z= 4. Other organic chlorides RCl (R = Pr, SiMe3 or But) react with [Au2Cl6] with a partial reduction to the mixed-valence chloride [Au4Cl8]. Addition of [Au2Cl6] to anhydrous iron(III) chloride produced a mass-spectrometrically active mixed iron–gold species.