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An unprecedented study on the inhibitory activities of a class of phosphane gold(I) complexes on E. coli dihydrofolate reductase (DHFR) is reported. The gold(I) complexes considered in this work consist of azolate or chloride ligands and phosphane as co-ligands. The ligands have been functionalized with polar groups (–COOH, –COO−, NO2, Cl, CN) to obtain better solubility in polar media. Neutral, anionic and cationic gold(I) complexes have been tested as DHFR inhibitors by means of a continuous direct spectrophotometric method. X-ray structural characterizations were performed on ((triphenylphosphine)-gold(I)-(4,5-dicyanoimidazolyl-1H-1yl) and on the analog (triphenylphosphine)-gold(I)-(4,5-dichloroimidazolyl-1H-1yl). The inhibition constants obtained from the enzyme tests range from 20 μM to 63 nM (auranofin) and are conducive to promoting these compounds as potential DHFR inhibitors.

The crystal structures of [NiCl2(PMePh2) · (PNMe2)] · 1/2 CH2Cl2 (1), C33H33Cl2NNiP2 · ½ CH2Cl2, and [NiCl(PMePh2)(PNMe2)][PF6] (2), C33H34ClF6NNiP3, have been determined by X-ray diffraction. Complex 1 crystallises in the monoclinic space group P21/n, a = 11.305(6) Å, b = 17.620(9) Å, c = 18.061(9) Å, β = 90.48(4)°, V = 3597(3) Å3 and Z = 4. Refinement of 2508 observed reflections and 275 parameters converges to a conventional R of 0.051. The coordination around the Ni(II) centre is distorted trigonal bipyramidal with the two axial positions occupied by the phosphorus atom of the monodentate phosphine and the tertiary amine nitrogen of the bidentate PNMe2 chelate. The equatorial sites accommodate the remaining phosphorus of the amino-phosphine and two chlorine donors. Complex 2 crystallites in the orthorhombic space group Pbca, a = 18.61(1) Å, b = 15.42(1) Å, c = 23.25(2) Å, V = 6673(7) Å3 and Z = 8. Refinement of 2351 observed reflections and 347 parameters yields R = 0.051. A square planar geometry describes the coordination around the metal with the two phosphorus donors located in a mutual cis-arrangement. As expected on the basis of the different coordination number, all of the metal-donor distances decrease on going from 1 to 2, as evidenced, in particular, by the Ni–N bond which contracts from 2.325(8) Å to 2.056(8) Å.

Chemical preparation and structural characterization of technetium oxide anion and rhenium oxide anion complexes with tetradentate phosphino-amido ligands is presented here. X-ray crystallography was used to elucidate the structures of various salts of the Tc and Re oxo complexes.

Following an increasing interest in the gold drug therapy field, nine new neutral azolate gold(I) phosphane compounds have been synthesized and tested as anticancer agents. The azolate ligands used in this study are pyrazolates and imidazolates substituted with deactivating groups such as trifluoromethyl, nitro or chloride moieties, whereas the phosphane co-ligand is the triphenylphosphane or the more hydrophilic TPA (TPA = 1,3,5-triazaphosphaadamantane). The studied gold(I) complexes are: (3,5-bis-trifluoromethyl-1H-pyrazolate-1-yl)-triphenylphosphane-gold(I) (1), (3,5-dinitro-1H-pyrazolate-1-yl)-triphenylphosphane-gold(I) (2), (4-nitro-1H-pyrazolate-1-yl)-triphenylphosphane-gold(I) (5), (4,5-dichloro-1H-imidazolate-1-yl)-triphenylphosphane-gold(I) (7), with the related TPA complexes (3), (4), (6) and (8) and (1-benzyl-4,5-di-chloro-2H-imidazolate-2-yl)-triphenylphosphane-gold(I) (9). The presence of deactivating groups on the azole rings improves the solubility of these complexes in polar media. Compounds 1-8 contain the N-Au-P environment, whilst compound 9 is the only one to contain a C-Au-P environment. Crystal structures for compounds 1 and 2 have been obtained and discussed. Interestingly, the newly synthesized gold(I) compounds were found to possess a pronounced cytotoxic activity on several human cancer cells, some of which were endowed with cis-platin or multidrug resistance. In particular, among azolate gold(I) complexes, 1 and 2 proved to be the most promising derivatives eliciting an antiproliferative effect up to 70 times higher than cis-platin. Mechanistic experiments indicated that the inhibition of thioredoxin reductase (TrxR) might be involved in the pharmacodynamic behavior of these gold species.

The solid-state structures of four 1,2,3,4-tetrahydroacridines [tacrine hydrochloride monohydrate (1), 7-methoxytacrine hydrochloride monohydrate (2), velnacrine hydrogenmaleate (3) and suronacrine hydrogenmaleate (4)] were determined from single-crystal X-ray diffraction analysis. (1): monoclinic,P21/n, a=8.778(1),b=8.521(1),c=17.603(2)A, β=101.34(1)°. (2): monoclinic,C2/c, a=12.326(7),b=18.050(9),c=13.822(8)A, β=113.70(4)°. (3): triclinic,\(P\bar 1\),a=7.349(2),b=9.417(3),c=12.557(4)A, α=109.62(2), β=98.12(2), γ=101.18(2)°. (4): monoclinic,P21/n, a=8.513(6),b=18.74(1),c=13.401(6)A, β=91.21(5)°. FinalR factors for compounds(1)–(4) are 0.047, 0.057, 0.057, 0.11, respectively. The overall arrangement of the common aminotetrahydroacridine skeleton looks similar in all derivatives. However, whereas enantiomerization of the unsubstituted cyclohexenyl rings occurs in (1) and (2), onlyquasi-axially hydroxyl substituted diastereomers are found for (3) and (4). This is presumably due to the different propensities for hydrogen bonding of axially vs. equatorially disposed hydroxyl groups with the hydrogenmaleate anions. Empirical and semiempirical calculations were performed to examine the conformational behavior of the four compounds, bothin vacuo and in solution.

The crystalline adduct of formula (DPK·H)+[{ReOCl2(DPK·OH)}2Cl]− was prepared by the reaction of trans- ReOCl3(PPh3)2 with di-(2-pyridyl)ketone (DPK) in THF or dichloromethane. The compound was characterized by elemental analysis, vibrational, optical and 1H NMR spectroscopy. The evidence suggests that the coordinated DPK ligands have undergone addition of water at the carbonylic carbon atom, and that the (C5H4N)2C(O)(OH) moiety acts as a uninegative, terdentate N,O,N-donor ligand. The X-ray crystal structure of the compound is also reported. Crystal data: C33H27Cl5N6O7Re2, triclinic, space group P 1 ; a=9.483(3), b=14.399(5), c=15.413(7) A, α=110.68(3), β=104.73(3), γ=92.66(3)° and U=1879.9(9) A3 to give Z=2 for Dcalc=2.07 Mg/m3.

The synthesis and characterization of the cationic complex [Pd(η 3 -C 3 H 5 )(2-((4-phenyl-1 H -1,2,3-triazol-1-yl)methyl)pyridine)](BF 4 ) ( 2 ) are reported. The solid-state structure of 2 has been unambiguously confirmed by single-crystal X-ray diffraction analysis. 1 H NMR spectroscopy reveals that in solution complex 2 is dynamic and that syn – syn , anti – anti exchange of the allyl protons occurs. Complex 2 exhibits good activity in the Suzuki–Miyaura coupling of aryl bromides with phenyl boronic acid.

In the metallacycle 1-chloro-2,5-dithiastibolane, [Sb(SCH 2 ) 2 Cl], antimony(III) conserves a residual coordination ability. Adducts with monodentate (dimethyl sulfoxide) and chelating (2,2′-bipyridine and 1,10-phenanthroline) ligands were obtained and characterized by IR spectra. The X-ray crystal structure of chloro(1,10-phenanthroline)(ethane-l,2-dithiolato[2−]− S , S ′)antimony(III) has shown that two independent molecules are contained in asymmetric units. The coordination geometry about the antimony is distorted rectangular pyramidal without any intermolecular association.

The condensation of one primary amino group of the appropriate triamine: bis(2-aminoethyl)-amine (DET), bis(3-aminopropyl)-amine (DPT) or bis(3-aminopropyl)-methylamine (MeDPT), with the appropriate aldehyde: pyridine-2-carboxaldehyde (pya), 3-formylisoquinoline (iqa) or 2-aminobenzaldehyde (aba), has yielded six new quadridentate N4-type ligands: pyaDET, pyaDPT, pyaMeDPT, iqaMeDPT, abaDET and abaDPT. The ligands have been isolated as corresponding copper (II) complexes of the general formula [CuLI]I or [CuLI]I·MeOH. The crystal structures of [Cu(pyaDPT)I]I·MeOH, [Cu(pyaMeDPT)I]I·MeOH and [Cu(iqaMeDPT)I]I complexes have been determined by single crystal X-ray diffraction techniques. The geometry around the copper center is intermediate between idealized square-pyramidal and trigonal-bipyramidal symmetry, with the trigonality increasing on going from [Cu(pyaDPT)I]I·MeOH to [Cu(iqaMeDPT)I]I. Crystallographic data: [Cu(pyaDPT)I]I·MeOH: triclinic, P1, a=8.398(3), b=9.503(3), c=12.191(5) A, α=86.96(3), β=85.68(3), γ=78.73(3)°, R=0.076; [Cu(pyaMeDPT)I]I·MeOH: monoclinic, P21/c, a=9.670(4), b=12.351(6), c=17.074(5) A, β=95.60(3)°, R=0.058; [Cu(iqaMeDPT)I]I: monoclinic, P21//n, a=11.210(3), b=10.920(4), c=17.323(5) A, β=96.11(2)°, R=0.045.

The reaction of trans -[PtCl 2 (NCMe) 2 ] with a 5-fold excess of MeNH 2 in CH 2 Cl 2 at −10°C affords in high yield the bis-amidine complex trans -[PtCl 2 { Z -N(H)C(NHMe)Me} 2 ] ( 1 ), where both the amidine ligands assume the Z configuration corresponding to the trans addition of the amine along the CN triple bond. Compound 1 has been fully characterized by spectroscopic techniques and also by X-ray diffraction analysis.

The molecular structures of the cognition activators (±)1-benzenesulphonyl-2-oxo-5-ethylthiopyrrolidine (1) and (±)1-benzenesulphonyl-2-oxo-5-isopropylthiopyrrolidine (2) were determined by means of X-ray diffraction and semi-empirical quantum mechanical methods. The conformational properties of the compounds, in the solid state andin vacuo (free molecule), were compared with those of the corresponding oxygenated derivatives bearing, in position 5, ethoxy and isopropyloxy substituents, respectively. The molecular arrangements of (1) and (2) in the solid state are similar, with the exception of the side chain on C(5), and they are retained alsoin vacuo. Both present an “envelope” conformation of the five-membered ring, and the relative positions of the five- and six-membered rings look similar and parallel those of their oxygenated parents. Fromin vacuo calculations another low-energy arrangement seems to be possible, and a detailed examination of the side-chain freedom in (1) and (2) gives more insight in the conformational properties of the compounds.

The crystal and molecular structures of the nootropic agents RU-47001 ((±) 1-(4-nitrobenzenesulphonyl)-2-oxo-5-ethoxypyrrolidine) and RU-47064 ((±) 1-(4-nitrobenzenesulphonyl)-2-oxo-5-isopropyloxypyrrolidine) have been determined by X-ray analysis and their solution conformation has been investigated using 1 H NMR spectroscopy. The conformations of these molecules together with those of their analogues RU-35929 ((±) 1-benzenesulphonyl-2-oxo-5-ethoxypyrrolidine), RU-47010 ((±) 1-(3-pyridinylsulphonyl)-2-oxo-5-ethoxypyrrolidine) and RU-35965 ((±) 1-benzenesulphonyl-2-oxo-5-isopropyloxypyrrolidine) have been deduced from semi-quantitative PM3 type theoretical calculations. The main feature of all compounds consists of a common envelope conformation with C (4) at the flap of the pyrrolidinone ring in the solid, that in solution changes into the analogous, but opposite, possible puckered conformational isomer. The 5-alkoxy groups were found rather flexible in solution. Theoretical preferred conformations about NS and SC bonds were in acceptable agreement with those of the solid state. The calculated torsional energetics suggested that 1 – 5 do not undergo conformational interconversion.

The crystal and molecular structures of the cognition activators 1-(4-methoxybenzoyl)-5-oxo-2-pyrrolidinepropanoic acid (CI-933) ( 1 ) and 4-hydroxymethyl-1-benzyl-pyrrolidin-2-one (WEB-1868) ( 2 ) have been determined by X-ray analysis. The conformations of the isolated molecules 1 and 2 have been deduced from AM1-type theoretical calculations. Whilst in 1 there are no hydrogen bonds, in 2 stabilization of the crystal occurs through effective inter- and intramolecular bonds. The five-membered ring in both 1 and 2 adopts an envelope conformation in the solid with C(3) at the flap displaced from the C(1), C(2), C(4), N(5) mean plane. Bond distances and angles are normal and comparable with previously known similar structures. In the crystal, the torsion angles C(1)-N(5)-C(6)-C(7) and N(5)-C(6)-C(7)-C(8) in 1 are 43.1° and 44.8°, respectively; the same torsion angles in 2 are −101° and 42°, respectively. Results of theoretical calculations correlate well with the conformation of 1 in the solid, whilst in the case of 2 these indicate that the conformation in the crystal should not be retained by the isolated molecule. The complete analysis of the very high field (600 MHz) 1 H NMR spectra of both compounds in CDCl 3 , gives results well in line with the above established conformational features.

This paper provides an overview of the about 80 crystal structures of technetium complexes described in the past 5 years and exhibiting some peculiar structural features. In almost 90% of the compounds, technetium shows an odd oxidation number, and by a large majority the revised complexes are mononuclear and neutral. The review especially focuses on nitrido-Tc(V), oxo-Tc(V) and fac-[Tc(CO)3]+ complexes, which cover approximately one-half of the X-ray structural reports.

The interactions between zinc(II) and the two ligands 2-hydroxynicotinic acid (HNic) and 3-hydroxypicolinic acid (HPic) have been investigated by means of potentiometric titrations in aqueous 0.6 m (Na)Cl at 25 °C. In both cases, only mononuclear complexes are formed. The qualitative and quantitative results obtained have been confirmed in part by UV–Vis spectrophotometry and 1H NMR spectroscopy. The complex trans-diaqua-bis-(3-hydroxypicolinato)zinc(II) was obtained as a crystal and examined by X-ray crystallography. The thermodynamic results allow drawing some conclusions regarding the extent of Zn(II) interference in a hypothetical chelation therapy treatment of aluminium or iron overload with these two ligands.

The PN(2)S chelate N-[N-(3-diphenylphosphinopropionyl)glycyl]-S-tritylcysteine methyl ester [PN(2)S(Trt)-OMe] was synthesized and reacted with ReOCl(3)(PPh(3))(2) and Ph(4)P[ReOCl(4)]. The reactions of both tritylated and detritylated ligands with Re(V)O precursors gave two diastereomers, 9a and 9b, of the ReO(PN(2)S-OMe) complex. The two isomers, produced in a 1:1 molar ratio, are stable and do not interconvert. They were separated by reverse-phase HPLC and characterized by NMR, FT-IR, and UV-visible spectroscopy and electrospray mass spectrometry. X-ray analysis established for 9a the presence in the solid of the syn isomer. Compound 9a, C(21)H(23)N(2)O(5)PSRe, crystallized from warm acetonitrile in the triclinic space group Ponemacr;, a = 9.828(2) A, b = 11.163(2) A, c = 11.641(2) A, alpha = 106.48(3) degrees, beta = 109.06(3) degrees, gamma = 102.81(3) degrees, V = 1085.7(4) A(3), Z = 2. The PN(2)S coordination set is in the equatorial plane, and the complex shows a distorted square pyramidal coordination. The anti configuration assigned to 9b is consistent with all the available physicochemical data. Follow-up of the reaction of the detritylated ligand with Ph(4)P[ReOCl(4)] in ethanol or acetonitrile indicated that the phosphorus atom of the chelate binds first to the metal and that this bond acts as the driving force for coordination.

Monooxo complexes of rhenium(V) with 2-aminophenol and some of its derivatives (H2nod), containing the N,O donor-atom set, have been synthesized. Square-pyramidal complexes [ReO(nod)2]− were isolated by reaction with (n-Bu4N) [ReOCl4] in ethanol. In benzene the neutral species [ReOCL(Hnod)2] were obtained. In the presence of hydrochloric acid in ethanol, the anionic complexes (n-Bu4N) [ReOCl3(Hnod)] were produced. Trans-[ReOCl3(PPh3)2] was also reacted with some of the H2nod ligands to yield [ReOCL2(Hnod)(PPh3]. The crystal structure of [ReOCl2(Hmap)(PPh3)] (H2map = 2-aminobenzylalcohol) was determined; crystals are monoclinic, P21/n, with a = 15.065(6), b = 11.253(7), c = 15.850(7) A, β = 94.27(4)°, U = 2680(2) A and Z = 4. The structure was solved by the Patterson method and refined by full-matrix least-squares techniques to R = 0.042. The monoanionic Hmap− ligand is coordinated as a bidentate through a neutral amino nitrogen and an anionic alcoholate oxygen atom, with the latter trans to the ...

The complex cis-[ReO2(Hdab)(py)2] (1) (H2dab=1,2-diaminobenzene) has been prepared by reacting trans-[ReO2(py)4]I with H2dab in ethanol. This is the first example of a neutral hexacoordinate rhenium(V) complex with a cis arrangement of the two oxo groups. The compound also provides the first example of a bidentate monoanionic monoimino coordination mode of H2dab. Crystal data for 1·(H3dab)I·H2O: C22H26IN6O2Re·H2O, triclinic, space group P1, a=9.570(2), b=12.493(3), c=12.851(3) A, α=61.60(3), β=70.56(3), γ=78.68(4)°, V=1273.1(4) A3 and Z=2.

The reactions of the nitrile complexes cis- and trans-[PtCl2(NCR)2] with S(+)-2-chloro-1-propanol in the presence of 2 equiv. of n-BuLi afford the chiral oxazoline complexes cis- and trans-[PtCl2{(R)- NC(R)OCH 2 C H(Me)}2] [cis, R=Me (1), cis, R=Ph (2); trans, R=Ph (3)]. The structures of 1 and 2 were determined by X-ray analysis which allowed to establish the R configuration of the oxazoline rings. The reactions of cis- and trans-[PtCl2(NCR)2] with S(+)-2-chloro-1-phenylethanol and R(−)-2-chloro-1-phenylethanol in the presence of 2 equiv. of n-BuLi afford the oxazoline complexes cis- and trans-[PtCl2{(S)- NC(R)OCH(Ph)C H2}2] [cis, R=Me (4), cis, R=Ph (5); trans, R=Ph (6)] and cis- and trans-[PtCl2{(R)- NC(R)OCH(Ph)C H2}2] [cis, R=Me (7), trans, R=Me (8); trans, R=Ph (9)]. The structure of 6 was determined by an X-ray investigation which allowed to establish the S configuration of the oxazoline rings. The proposed mechanism for the nitrile to chiral oxazoline conversion entails nucleophilic attack of the alkoxide, generated by deprotonation reaction of the corresponding alcohol with n-BuLi, followed by intramolecular cyclization. This latter step proceeds with complete inversion of configuration at the chiral carbon atom for 1–3, while with retention of configuration for 4–9.

In the crystal of the title compound, C(10)H(12)O(2), there are two symmetry-independent molecules, which are essentially superimposable. Each molecule exhibits an intramolecular O-H.O hydrogen bond, with O.O separations of 2.483 (4) and 2.468 (4) A.

The reaction of 2 equiv. of 3-nitro-1,2-diaminobenzene (H2L1) with trans-ReOCl3(PPh3)2 in ethanol gave the oxo-free rhenium(V) complex [ReCl(PPh3)(L1)2] (1) in good yield. IR, 1H NMR and X-ray crystallographic results indicate that the diamine ligand L1 coordinates in a dianionic bidentate diamido form to the metal, and that the complex has the unusual skew-trapezoidal bipyramidal geometry. With 4-nitro-1,2-diaminobenzene (H2L2) as ligand the complex [Re(L2)Cl3(PPh3)2] (2) was characterized, in which L2 coordinates in a dianionic monodentate imido form through one nitrogen only. Crystal data for 1·EtOH: C32H31ClN6O5PRe, monoclinic P21/c, a=14.937(11), b=15.017(8), c=15.394(12) A, β=112.12(6)°, V=3198.7(38) A3, Z=4, Dcalc=1.728 g cm−3, structure solution and refinement based on 3151 reflections converged at R=0.0807.

Trans-ReOCl3(PPh3)2 reacts with 2,3- and 2,6-dihydroxybenzoic acid (H2dhb) in an equimolar ratio in benzene to give the products [ReOCl(2,3-dhb)(PPh3)2] (1) and [ReOCl(2,6-dhb)(PPh3)2] (2), respectively. Elemental analysis, infrared, NMR and X-ray crystallographic results indicate that the ligand 2,3-dhb coordinates via the catecholato mode to the metal centre in 1, but 2,6-dhb functions as a salicylato-type chelate in 2.

The co-ordination geometry of the monomeric rhenium complexes mer-[ReIIICl3(L)3] (L = py 1, 3,5-lut 2, 4-pic 3) has been determined in the solid state by single X-ray diffraction of the representative complex 2 and in solution by proton NMR spectroscopy. Only a single stable conformation has been found in the solid state and in solution, under the experimental conditions utilised. The NMR spectra of the related complexes mer-[ReIIICl3(L)2(PPh3)] (L = py 4, 3,5-lut 5, 4-vinpy 6) have also been reported for comparison purposes.

The co-ordination of dipeptides modified with a phosphine group to the ReO 3+ core has been studied, and the new donor sets PN 2 X (X = O or S) achieved. N-{N-[3-(Diphenylphosphino)propionyl]glycyl }-L-S-benzylcysteine (H 3 L 2 ) and its methyl ester derivative (H 2 L 1 ) have been used for preparing six-co-ordinated oxorhenium(V) complexes, providing a new chelating system for targeting 186/188 Re to protein bioactive molecules. The complexes have been characterized by means of UV/VIS, IR, FAB and 1 H NMR spectroscopy. The crystal structures of [ReO(L 2 )(OH 2 )]·H 2 O·MeOH and [ReO(L 1 )Cl] have been established. In both the complexes the co-ordination geometry is distorted octahedral. The ligands are tetradentate, co-ordinating the ReO 3+ moiety through the phosphine phosphorus, the two deprotonated amide nitrogens and the O or S atom from the carboxylate or thioether groups. When the cysteine carboxylic moiety is free, it can replace, in organic solvents, the thioether sulfur to give a stable complex, the fourth donor atom in the equatorial plane being a carboxylate oxygen. In basic medium [ReO(L 1 )Cl] underwent substitution of Cl - by OH - , evidence for the high stability of the PN 2 S donor set.

The structure of the title compound, trichloro-2κ 3 Cl-(5,10,15,20-tetraphenylporphyrinato-1κ 4 N 21,22,23,24 )rhodium (III)tin(II)(Rh-Sn), [RhSnCl 3 (C 44 H 28 N 4 )], consists of well separated units in which the Rh atom is five-coordinate at the center of a square-pyramidal polyhedron with the Sn atom at the top. The macrocylic unit is planar with the Rh atom displaced by only 0.02 A from the ring plane. The Rh-Sn bond length is 2.450 (1) A

The crystal structures of two cocrystallized complexes of MgCl2 with 2,4-pentanedione have been determined. The conglomerate crystallizes in the monoclinic system, space groupP 21/c (No. 14);a=7.835(2),b=18.169(4),c=13.303(3) A, β=90.70(2)°,Z=4. The former complex is a dimer which consists of two octahedra sharing one edge by two chlorine bridges between the metal atoms. The chelate ring in the equatorial plane and two apical water molecules realize the coordination polyhedron around each Mg atom. In the latter complex the metal lies at the center of a slightly distorted octahedron formed by six oxygens, four from two chelate ligands and two from apical water molecules.

A X-ray crystal structure determination of the title compound was carried out. A comparison of the relevant bond distances and angles in the ring system with other published structures showed that protonation has an influence on the ring geometry.

The dinuclear complexes cis-[(PMe 3 ) 2 Pt(1-MeCy(-H))] 2 X 2 (X=NO 3 - (1A), ClO 4 - (1B)), containing NH 2 -deprotonated 1-methylcytosine (1-MeCy(-H)) ligands, in aqueous or DMSO solution, at 80 o C convert quantitatively into the corresponding trinuclear derivatives cis-[(PMe 3 ) 2 Pt(1-MeCy(-H))] 3 X 3 (2A,B) which have been characterized in the solid state by single-crystal X-ray analysis and in solution by multinuclear ( 1 H, 31 P, 195 Pt, 13 C, and 15 N) NMR spectroscopy. The nitrate salt (2A) crystallizes from ethanol in the triclinic system, space group P1

The title compound, [Re(C 18 H 15 NP) 2 (C 2 H 5 O)O], was synthesized by the oxidation-substitution reaction of [Re III (PNH) 2 (PNH 2 )]Cl, where PNH 2 is 2-(diphenylphosphino)phenylamine, with NEt 3 in EtOH. The X-ray diffraction study of this new triclinic phase, designated β, confirms the molecular structural details for the monoclinic α isomer, which crystallized in space group P2 1 /c with a=12.056 (3), b=26.303 (6), c=11.005 (3) A, β=102.32 (2) o [Refosco, Tisato, Bandoli, Bolzati, Dolmella, Moresco & Nicolini (1993). J. Chem. Soc. Dalton Trans. pp. 605-618]

Reduction-substitution reactions of [TcO4]- with (o-aminophenyl)diphenylphosphine (HL) at a strictly controlled stoichiometric metal/ligand ratio gave neutral oxotechnetium(V) complexes of the type [TcOL2(OR)] (R = Me 1 or Et 2): Analogous [ReOL2(OR)] species (R = H 3, Me 4, Et 5, Pr 6, Bu 7, C2H4OH 8, C3H6OH 9, Ph 10 or OCMe 11) are instead produced via ligand-exchange reactions in basic media starting from (ReOCl4]-. Compounds 1-11 are referred to as 'equatorial' because the co-ordination of both bidentate L- chelates occurs symmetrically in the equatorial plane orthogonal to the M=O moiety, with a mutual cis-phosphorus configuration. The site trans to the oxo group is always occupied by an oxygen-containing monodentate ligand the co-ordination of which determines the stability of this class of octahedral complexes. Nevertheless the -OR group is easily exchangeable with other nucleophiles available in the reaction mixture by the mass effect and/or donor ability of the incoming ligand. The crystal structures of complexes 1 and 5 have been determined: 1, monoclinic, space group P2(1)/c, Z = 4, a = 12.156(3), b = 26.005(6), c =1 0.953(2) angstrom, beta = 102.49(2)-degrees, R' 0.0611 using 1766 observed reflections; Tc-O(1) 1.700(8), Tc-O(2) 1.999(8), Tc-P 2.511(3) and 2.503(4), Tc-N 1.972(10) and 1.976(8) angstrom; O(1)-Tc-N 105.8(4) and 103.6(4), 0(l)-Tc-P 88.1(3) and 88.9(2), 0(l)-Tc-O(2) 158.3(3)-degrees; 5, monoclinic, space group P2(1)/c, Z = 4, a = 12.056(3), b 26.303(6), c = 11.005(3) angstrom, beta = 102.32(2)-degrees, R' 0.0614 using 4752 observed reflections; Re-O(1) 1.692(7), Re-O(2) 2.004(7), Re-P 2.495(2) and 2.493(3), Re-N 1.990(8) and 2.003(7) angstrom; O(1)-Re-N 104.6(3) and 102.6(3), O(1)-Re-P 89.1(2) and 88.8(2), 0(l)-Re-0(2) 160.8(3)-degrees. By treatment of [MOL,(OR)] solutions with HX (X = halide), further reduction to lower-oxidation-state species occurs when M = Tc, while another class of stable and neutral oxo complexes, termed 'twisted', is produced when M = Re. Two mutually orthogonal L- chelates co-ordinate the metal while still preserving the cis-phosphorus configuration, one ligand bridging an equatorial and an apical position (with the phosphinoamido nitrogen trans to the Re-O linkage) and the other two equatorial positions. The equatorial plane is completed by a halide atom. The chloro derivative [ReOL2Cl] exhibits two crystalline forms, alpha (12) and beta (13), the crystal structures of which have been determined: 12, monoclinic, space group P2(1)/n, Z = 4, a = 9.594(l), b =18.565(4), c = 17.656(2) angstrom, beta = 91.00(1)-degrees, R' 0.0477 using 2979 observed reflections; Re-0 1.767(7), Re-Cl 2.436(3), Re-P(1) 2.429(3), Re-P(2) 2.479(3), Re-N(1) 1.986(9), Re-N(2) 2.029(8) angstrom; O-Re-N(2) 162.8(3), O-Re-N(l) 108.6(3)-degrees; 13, orthorhombic, space group P2(1)2(1)2(1), Z = 4, a = 10.196(5), b = 14.047(6), c = 21.987(8) angstrom, R' 0.0671 using 2501 observed reflections; Re-0 1.69(l), Re-Cl 2.422(6), Re-P(1) 2.434(5), Re-P(2) 2.476(5), Re-N(l) 2.01(l), Re-N(2) 2.04(1) angstrom; O-Re-N(2) 162.7(6), O-Re-N(l) 109.0(7)-degrees. The interconversion between 'equatorial' and 'twisted' species is discussed. Elemental analyses, FAB mass, IR, electronic, H-1 and P-31 NMR spectra are reported. The P-31 NMR signal is diagnostic for both classes of complexes in solution, being a singlet for the 'equatorial' and two doublets for the 'twisted' species, respectively.

The preferred crystalline, solution and in vacuo arrangements of the title compound were investigated by means of single crystal X-ray diffraction, H-1 NMR spectroscopy and molecular mechanics calculations, respectively, and the findings were compared with those obtained for two similar compounds. The X-ray powder pattern diffraction was also collected.

The X-ray structural determination of the manganese(I)–rhenium(I) complex [(OC)3Mn{(η5-C5H4)(Z)CHCHCC(η5-C5H4)}Re(CO)3]1 has been carried out. The structural data show that the (Z)-enyne linkage between the two cyclopentadienyl rings, despite the conjugation that would keep the ligand framework coplanar, allows twisting of the two cyclopentadienylmetal units. Because of this characteristic the Mn ⋯ Re interatomic distance (6.1 A) is much shorter than in similar bis(cyclopentadienyl)-linked heterobimetallic complexes. Reaction of 1 with [Co2(CO)8] affords quantitatively the corresponding dicobalt tetragonal pyramidal adduct [(OC)3Mn{(η5-C5H4)(Z)CHCH[graphic omitted]–(η5-C5H4)}Re(CO)3]2 the X-ray structure of which has been determined. The presence of the dicobalt unit on the triple bond heavily affects the carbon chain connecting the two cyclopentadienyl rings, and the metal centres are at a larger distance than in 1. Crystal data: 1, triclinic, space group P, a= 6.546(1), b= 11.066(2), c= 13.451(3)A, α= 96.06(2), β= 100.46(2), γ= 96.31(1)°, R(F)= 0.0466, R′(F)= 0.0542 for 2710 observed reflections with F > 4.0σ(F); 2, triclinic, space group P, a= 9.825(3), b= 11.853(4), c= 13.662(3)A, α= 109.41(2), β= 104.36(2), γ= 99.16(2)°, Z= 2, R(F)= 0.0325, R′(F)= 0.0352 for 5913 observed reflections with F > 4.0σ(F).

Spirocyclic bis(ethane-1,2-dithiolato[2−]-S,S′)tin(IV) forms hexacoordinate crystalline complexes with pyridine and 2-(2-pyridyl)ethylamine. The compounds have been prepared by conventional methods and the crystal structures have been determined by an X-ray diffraction study. In the parent compound the tin is tetracoordinate in a highly distorted tetrahedral structure, with a weak intermolecular Sn···S interaction. On the contrary, the adducts are essentially octahedral about the tin, with longer SnS bonds in the five-membered rings SnS 2 C 2 . The 2-(2- pyridyl)ethylamine ligand is bonded to the metal through the aminic nitrogen.

The condensation of one primary amino group of the appropriate triamine: bis(2-aminoethyl)-amine (DET), bis(3-aminopropyl)-amine (DPT) or bis(3-aminopropyl)-methylamine (MeDPT), with the appropriate aldehyde: pyridine-2-carboxaldehyde (pya), 3-formylisoquinoline (iqa) or 2-aminobenzaldehyde (aba), has yielded six new quadridentate N4-type ligands: pyaDET, pyaDPT, pyaMeDPT, iqaMeDPT, abaDET and abaDPT. The ligands have been isolated as corresponding copper (II) complexes of the general formula [CuLI]I or [CuLI]I·MeOH. The crystal structures of [Cu(pyaDPT)I]I·MeOH, [Cu(pyaMeDPT)I]I·MeOH and [Cu(iqaMeDPT)I]I complexes have been determined by single crystal X-ray diffraction techniques. The geometry around the copper center is intermediate between idealized square-pyramidal and trigonal-bipyramidal symmetry, with the trigonality increasing on going from [Cu(pyaDPT)I]I·MeOH to [Cu(iqaMeDPT)I]I. Crystallographic data: [Cu(pyaDPT)I]I·MeOH: triclinic, P1, a=8.398(3), b=9.503(3), c=12.191(5) A, α=86.96(3), β=85.68(3), γ=78.73(3)°, R=0.076; [Cu(pyaMeDPT)I]I·MeOH: monoclinic, P21/c, a=9.670(4), b=12.351(6), c=17.074(5) A, β=95.60(3)°, R=0.058; [Cu(iqaMeDPT)I]I: monoclinic, P21//n, a=11.210(3), b=10.920(4), c=17.323(5) A, β=96.11(2)°, R=0.045.

The reaction of pertechnetate with 1,2-diaminobenzene (H2pda) in the presence of the reducing agent sodium dithionite in alkaline aqueous solution led to the formation and isolation of (n-Bu4N)[TcO(pda)2] (1). If the reaction is performed without reducing agent in methanol, the green compound [Tc(pda)3](TcO4) (2) is formed. Both complexes are diamagnetic, and a single NH stretching frequency in both indicates that each pda ligand contains one hydrogen per nitrogen, and is dianionic. X-ray crystal structures of both compounds are also reported. Crystal data for complex 1, C28H48N5OTc: orthorhombic, space group P212121, a=11.644(3), b=15.303(4), c=16.950(5) A and U=3020.3(1.5) A3 to give Z=4 for Dcalc=1.25 g cm−3. Crystal data for 2, C18H18N6O4Tc2: orthorhombic, Pna21, a=13.869(4), b=12.799(5), c=10.851(3) A and U=1926.2(1.1) A3 to give Z=4 for Dcalc=1.99 g cm−3. The structures have been solved by Patterson and Fourier methods and refined by least-squares methods to R=0.058 for 1 and 0.090 for 2. Complex 2 represents the first tris-bidentate cationic complex of technetium to be structurally characterized. Complex 1, with an unexpectedly low ν(TcO) of 891 cm−1, has a TcO bond distance of 1.668(7) A, that is typical for monooxotechnetium(V) square-pyramidal complexes.

Reaction of pertechnetate with the two bidentate functionalized phosphines (2-diphenylphosphino)-thiopheenol and -phenol; X-ray structure.

The conformational features of three tetrahydropyridinyl oxime cognition activators 1-(1-methyl-1,2,5,6-tetrahydro-3-pyridinyl)ethanone oxime·HCl (I), 1-(1-methyl-1,2,3,6-tetrahydro-4-pyridinyl)ethanone oxime·HCl (II), and 1-(1,2,5,6-tetrahydro-3-pyridinyl)ethanone O-methyloxime HCl(III) were analyzed by X-ray diffraction and the quantum mechanical semiempirical PM3 methods. Results indicate that in the solid state the drugs exhibit “anti-syn” isomerism, with the substituent at the oxime oxygen atomanti oriented in respect to C=N. This arrangement also represents a low-energy situationin vacuo, as confirmed at the PM3 level, although another low-energy conformation (“clinal-anti”) could be of significance in the conformational energetics of the drugs.

The reactions of (o-aminophenyl)diphenylphosphine (HL) with ammonium pertechnetate have been investigated. The complexes [TcL3] 1 and [TcL2(HL)]+ 2, with [TcO4]-, [ClO4]- and [CF3CO2]- as counter anions, were isolated from the reaction mixture depending on the pH. The transformation of 1 into 2, and vice versa, was identified as an acid-base equilibrium by UV/VIS spectrophotometric measurements. The products have been characterized by means of the usual physicochemical determinations. Compound 2, as its perchlorate salt, has been studied by means of X-ray analysis. It exhibits a distorted-octahedral configuration in a monoclinic crystal system: space group P2(1)/n, a = 11.009(2), b = 19.361 (3), c = 24.473(3) angstrom, beta = 100.76(1)-degrees and Z = 4. The structure was solved by Patterson and Fourier methods and refined by least-squares methods to R = 0.052 using 5096 observed reflections. Relevant bond lengths and angles are: Tc-P(1) 2.483(2), Tc-P(2) 2.430(2), Tc-P(3) 2.436(2), Tc-N(1) 2.048(5), Tc-N(2) 1.948(5), Tc-N(3) 1.979(5) angstrom; P(2)-Tc-P(3) 160.2(1), P(1)-Tc-N(3) 164.3(2), N(1)-Tc-N(2) 163.6(2)-degrees.

The ligand o-(dipheny1phosphino)benzaldehyde (Ph2P-C6H4CHO) is one of the simplest possible bidentate 0,P-chelating phosphine ligands. We have studied the reaction of this ligand with oxotetrachlorotechnetate(V) and observed an unexpected Tc(IV) product containing an 2P2-tetradentate ligand. The synthesis and X-ray structural characterization of this unusual product are now reported. .....

A new series of five-co-ordinate rhenium(III) complexes containing the mixed S,P-bidentate 2-(diphenylphosphino)ethanethiolate ligand together with a monothiol RSH [R = Ph2PCH2CH2, Ph2P(O)CH2CH2, PhCH2, Ph or Prn] have been synthesized and characterized. This ReIIIP2S3 series was prepared by substitution reactions of [ReIIICl3(MeCN)(PPh3)2], a pre-reduced rhenium(III) precursor, by addition of 2-(diphenylphosphino)ethanethiol and the corresponding monothiol. Formation of these compounds was verified by elemental analysis and 1H and 31P NMR and positive-ion fast atom bombardment mass spectroscopy. The complexes were found to be diamagnetic, neutral and stable. They exhibit a trigonal-bipyramidal geometry, where three sulfur atoms occupy the equatorial plane and two phosphorus atoms are positioned at the apices. The X-ray structural analysis of bis[2-(diphenylphoshino)ethanethiolato-κS,κP](phenylmethanethiolato-κS)rhenium(III) revealed that this compound crystallizes in the monoclinic space group P21/c with Z= 8, a= 21.011(9), b= 20.397(9), c= 16.289(7)A, β= 107.13(5)°, R= 0.050, R′= 0.063, by using 5644 observed reflections. The above data further demonstrate the preference of a five-co-ordinate configuration when the P2S3 donor-atom set is available for co-ordinating rhenium(III).

Crystals of the title compound, C11H18N2O2·HBr, are monoclinic, space groupP21, witha=7.339(3),b=13.246(7),c=7.340(4) A,β=116.94(5)°, andZ=2. The structure was solved by direct methods and refined by fullmatrix least-squares calculations to anR value of 0.046 for 1218 observed reflections. The piperidine ring, in a chair conformation, is perpendicular (90.6°) to the strictly planar pyrrolidine-2,5-dione ring. Br− is hydrogen bonded to the positively charged piperidine N1 atom. Bond lengths and valence angles are comparable to those of various related compounds.

Ligand-exchange reactions of potential quinquedentate Schiff base ligands derived from salicylaldehyde and 1,3-diamino-2-hydroxypropane (H3L) with [MOCl4]− (M = Tc and Re) have been investigated. The complexes [MOCl2(ROH)(H2L·HCl)] (I) (R = Me, Et), [ReOCl(HL)] (II) and μ-O[MO(HL)]2 (III) were synthesized and characterized by the usual physicochemical measurements. Cyclic voltammetries for both III complexes reveal two separate and single-electron redox processes. The crystal structure of μ-O[TcO(HL)]2 was determined by single-crystal X-ray diffraction methods. Crystals are monoclinic, space group P21/c, with a = 9.423(6), b = 19.666(9), c = 22.785(11) A, β = 99.41(4)° and Z = 4. X-ray diffraction provides 2842 observed reflections (up to θ = 40°) and the structure has been refined by full-matrix least-squares methods to R = 0.10. The ‘dimeric’ structure of μ-O[TcO(HL)]2 consists of two distorted octahedral TcO(HL) moieties bridged by an oxygen atom which occupies the sixth coordination site of each moiety with the TcOTc angle nearly linear (173°).