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Over the last three decades, the chemistry of zirconium has facilitated antibody development and the clinical management of disease in the precision medicine era. Scientists have harnessed its reactivity, coordination chemistry, and nuclear chemistry to develop antibody-based radiopharmaceuticals incorporating zirconium-89 (89Zr: t1/2 = 78.4 h, β+: 22.8%, Eβ+max = 901 keV; EC: 77%, Eγ = 909 keV) to improve disease detection, identify patients for individualized therapeutic interventions. and monitor their response to those interventions. However, release of the 89Zr4+ ion from the radiopharmaceutical remains a concern, since it may confound the interpretation of clinical imaging data, negatively affect dosimetric calculations, and hinder treatment planning. In this report, we relate our novel observations involving the use of polyazamacrocycles as zirconium-89 chelators. We describe the synthesis and complete characterization of zirconium 2,2',2″,2‴-(1,4,7,10-tetraazacyclotridecane-1,4,7,10-tetrayl)tetraacetic acid (Zr-TRITA), zirconium 3,6,9,15-Tetraazabicyclo[9.3.1] pentadeca-1(15),11,13-triene-3,6,9-triacetic acid (Zr-PCTA), and zirconium 2,2',2″-(1,4,7-triazacyclononane-1,4,7-triyl)triacetic acid (Zr-NOTA). In addition, we elucidate the solid-state structure of each complex using single-crystal X-ray diffraction analysis. Finally, we found that [89Zr]Zr-PCTA and [89Zr]Zr-NOTA demonstrate excellent stability in vitro and in vivo and provide a rationale for these observations. These innovative findings have the potential to guide the development of safer and more robust immuno-PET agents to improve precision medicine applications.

This paper describes the synthesis and characterization of RP­(o-biphenyl)2 phosphine ligands (where R = PhO, Ph, and t-Bu), corresponding gold­(I) chloride precatalysts, gold­(I) triflate catalysts, and gold­(I) π-complexes. All ligands and gold chlorides and three π-complexes were characterized in the solid state. The most significant differences between complexes in the solid state were varying P–Au bond lengths, a consistent reflection of the different electronic character of each phosphine. NMR spectroscopic data on enol ether π-complexes is consistent with increasing cationic character in the alkene fragment, from R = t-Bu to R = Ph and OPh. The intermolecular alkene exchange process for [LAu­(methoxypropene)]­SbF6 (L = PhO­(o-biphenyl)2P) is faster than that of the analogous complex with t-Bu2(o-biphenyl)­P, presumably due to the higher electrophilicity of the former complex. Examination of a series of vinyl silane π-complexes with triaryl phosphine ligands reveals increasing stability and ease of preparation (Ph3P < Ph2P­(o-biphenyl) < PhP­(o-biphenyl)2). These results reveal that incorporation of a second biphenyl substituent into ligand architectures allows preparation of a series of gold π-complexes with increased stability over a range of phosphine donicity.

Three new derivatives of a platinum–acridine hybrid anticancer agent were synthesized using nitrile–amine coupling (amidination) chemistry. In the new structures, the nonleaving group propane-1,3-diamine (pn) of a previously optimized analogue (hybrid 1) was replaced with 2,2-dimethylpropane-1,3-diamine (Me2pn, hybrid 2), (1R,2R)-1,2-diaminocyclohexane (R,R-dach, hybrid 3), or (1S,2S)-1,2-diaminocyclohexane (S,S-dach, hybrid 4). The cytotoxicity of the four compounds was determined in two non-small cell lung cancer (NSCLC) cell lines, NCI-H460 and A549. The IC50 values extracted from cell proliferation assays span a range of two orders of magnitude, with the highest activity established for compound 1 in NCI-H460 (8 nM) and the lowest for compound 4 in A549 (825 nM). Partitioning coefficients (log D, based on compound distribution in 1-octanol/saline) and levels of cellular accumulation (by inductively coupled plasma mass spectrometry, ICP-MS) were determined for the hybrids. The results suggest that efficient cellular uptake by an active transport mechanism, which depends on the nature of the nonleaving group, is a modulator of chemosensitivity and a prerequisite for the high nanomolar cytotoxicity observed for the most active platinum–acridines.

Di(2-thienyl)imide, 1, has been shown to chemically polymerize, and, if metal complexes of 1 could be synthesized, the polymer could have potential applications as an ion sensor and environmental remediation agent. As a first step towards this goal, di(2-thienyl)imide is shown to form complexes with Mn (II), Co (II), and Zn (II) perchlorates. The complexes of Mn2+ and Co2+ are isostructural with two di(2-thienyl)imide ligands in equatorial positions and two perchlorate ions axial. The Zn2+ complex has two water molecules in the axial positions and the thiophene rings in the two equatorial ligands are tilted in the same direction from the median plane due to intra- and intermolecular contacts. The crystal structures and infrared spectra, as well as an improved synthesis and polymerization of di(2-thienyl)imide, are reported and discussed.

It was found that methyl-2-thienylimide ( L 1 ), C 4 H 3 SC(O)NHC(O)CH 3 , could act as a ligand and combine with metal(II) perchlorates (Ni 2+ , Mn 2+ , and Co 2+ ) to produce complexes for potential use as metal ion uptake and release agents in polymer form. Methyl-3-thienylimide ( L 2 ) formed a similar complex with Co 2+ . The synthesis and structures obtained from single crystal X-ray diffraction data are reported. The carbonyl groups in the ligands are cis / trans with respect to the N-H group in the solid state but are necessarily trans-trans in the complex. The ligands are bidentate, forming bonds to the metal ions through the imide oxygen atoms; the imide ligands are protonated. The cobalt and nickel complexes have two bidentate ligands in the equatorial positions and two water molecules in the apical positions with the ligands cis to each other in the case of methyl-2-thienylimide while they are trans in the cobalt complex formed by methyl-3-thienylimide. The manganese complex is seven coordinate with three bidentate ligands and one water molecule. Significant hydrogen bonding is present in all of the complexes leading to the formation of 2D networks in two cases and an infinite chain in one. IR, and UV–Visible spectroscopy along with elemental analyses are also presented.

Cationic gold(I) enamine complexes with the (t-Bu)2(o-biphenyl)phosphine ligand were isolated and characterized by NMR spectroscopy and X-ray crystallography. The complexes display highly distorted coordination modes that are consistent with characterization as α-metalated iminium ions. The barrier to rotation around the formal enamine C–C double bond has been measured in a geminally disubstituted enamine complex, and it is comparable to the barrier to C–C single-bond rotation in electronically restricted alkanes. With additional substitution on the enamine double bond, the complexes remain highly distorted, and the reaction of a mixture of E and Z enamines results in formation of a stereochemically pure gold complex. A survey of binding constants reveals enamines to be significantly stronger donors than any alkenes examined to date, and in the case of a geminally disubstituted enamine, the coordination is stronger even than that of triethylamine. The high stability drives the isomerization of an internal...

A thin film of a RuII(bpy)2(dcbpy)Cl2, RuDCBPY, doped metal–organic framework of Zr6O4(OH)4(bpdc)6, RuDCBPY-UiO67 (where bpy is 2,2′-bipyridine, dcbpy is 5,5′-dicarboxyphenyl-2,2′-bipyridine, and bpdc is 4,4′-biphenyldicarboxylic acid), has been prepared on fluorine-doped tin oxide and glass slides solvothermally. The film is shown to be isostructural with UiO-67 and similarly doped RuDCBPY-UiO67 powders. The photophysical properties of the film show significant line broadening of the diffuse reflectance spectra, a successive red shift of the emission maxima, and biphasic kinetics with increased RuDCBPY doping of UiO-67 films above 10 mm. The two lifetime components are consistent with a dual population of RuDCBPY within the UiO-67 material: a population of RuDCBPY incorporated into the framework of UiO-67 replacing a bpdc ligand and a second population of RuDCBPY encapsulated within the octahedral cavities. The RuDCBPY dopant within the UiO-67 films interact with each other and undergo self-quenching via...

As a result of explorations into the solution chemistry of silver/gold mixtures, a unique diphosphine trimetallic chloronium dication was discovered that incorporates silver-arene chelation and a triangular mixed gold/silver core in the solid state. Notably, it was isolated from a Celite prefiltered solution initially thought to be silver-free. The crystal structure also incorporates the coordination to silver of one fluorine atom of one SbF6(-) counterion. The structure was compared to two new, but well-precedented, phosphine digold chloride cations. DFT calculations supported significant silver-halide and silver-arene interactions in the mixed gold/silver complex and metallophilic interactions in all three complexes. Comparison of computed data revealed that the ωB97X-D functional, which has a long-range corrected hybrid with atom-atom dispersion corrections, gave a better fit to the experimental data compared with the PBE0 functional, which has previously failed to capture aurophilic interactions. Preliminary studies support the presence of the mixed gold/silver structure in solution.

Cationic {[(t-Bu)2(o-biphenyl)P]Au(enol ether)}+SbF6– and {[(t-Bu)3P]Au(enol ether)}+SbF6– complexes were isolated and characterized by NMR spectroscopy and X-ray crystallography. For three of the four complexes characterized in the solid state, gold coordinates to the electron-rich bond in a η1 fashion, while a 2,3-dihydrofuran complex displays η2 coordination.

Five new isostructural two-dimensional lanthanide-based coordination polymers with the formula Ln 2 (F 4 BDC) 3 (DEF) 2 (EtOH) 2 -2(DEF) (Ln = Tb, 1 ; Gd, 2 ; Eu, 3 ; La, 4 ; Nd, 5 ; F 4 BDC 2− = 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylate ligands; DEF = N,N′-diethylformamide), have been synthesized by reaction of Ln(NO 3 ) 3 and F 4 BDC in a DEF/EtOH solvent mixture. The compounds were characterized by single-crystal and powder X-ray diffraction. In all cases, the metal ion is coordinated by nine oxygen atoms from two bidentate μ 2 -F 4 BDC 2− ligands, two bridging μ 2 -F 4 BDC 2− ligands, one μ 3 -F 4 BDC 2− ligand, one DEF molecule and one EtOH molecule forming a tri-capped trigonal prism. The Ln(1) metal ion is linked to an adjacent Ln(1) metal ion through the oxygen atoms of two bridging μ 2 -F 4 BDC 2− ligands and two μ 3 -F 4 BDC 2− bridging ligands to form a Ln 2 O 18 dimer. The Ln 2 O 18 polyhedra building units are linked to each other through four F 4 BDC 2− ligands to form 2D sheets that are held together by hydrogen bonding to form a 3D framework. Compounds 1–5 were further characterized using thermogravimetric analysis and infrared spectroscopy. Studies of the photoluminescence properties of compounds 1 and 3 , as well as the catalytic activity of compounds 3 – 5 in the Biginelli reaction, are presented.

1,3-Dien-2-yl(Rpyr)bis(dimethylglyoximato) cobalt(III) complexes (R = H, NMe2) have been shown to participate in cycloaddition reactions with a variety of tropones. In general, tropones that do not contain electron-withdrawing substituents react with dienyl complexes via [6 + 4] cycloaddition and tropones that are substituted with at least one additional electron-withdrawing group react via [4 + 2] cycloaddition. Both types of metal-substituted cycloadducts ([6 + 4] and [4 + 2]) presented here have also been characterized by X-ray crystallography.

The reaction of TpRu(CO)(NCMe)(Me) (1) and pyrrole forms TpRu(CO){κ2-N,N-(H)NC(Me)(NC4H3)} (2). The formation of complex 2 involves the cleavage of the N−H bond and 2-position C−H bonds of pyrrole as well as a C−C bond forming step between pyrrole and the acetonitrile ligand of 1. Mechanistic studies indicate that the most likely reaction pathway involves initial metal-mediated N−H activation of pyrrole to produce TpRu(CO)(N-pyrrolyl)(NCMe) (3) followed by C−C bond formation and proton transfer. Complex 3 has been independently prepared and demonstrated to convert to 2. Computational studies support the suggested selectivity for initial N−H bond cleavage in preference to C−H bond activation.

A series of new thiophene amides containing a pyridine ring has been synthesized and characterized. Single crystal X-ray structures have been determined for four of the new substances which show two distinct patterns of hydrogen-bonding. The crystal structure of the copper (II) complex of one of the ligands shows that the bonding is O,N in a square planar geometry with perchlorate ions in the axial positions. The new compounds do not undergo electropolymerization due to primary oxidation of the amide function but tuning of the amide group by introduction of an electron-withdrawing group on the pyridine ring allows electropolymerization to occur.

Three novel coordination polymers built of octahedral niobium cyanochloride clusters [Nb6Cl12(CN)6] and alkaline earth metal complexes have been prepared by reaction of aqueous solutions of (Me4N)4Nb6Cl18 and KCN with solutions of alkaline earth metal salts and 1,10-phenanthroline (phen) (1:2 molar ratio) in H2O/EtOH. The structures of [Ca(phen)2(H2O)3]2[Nb6Cl12(CN)6] x (phen)(EtOH)1.6 (1), [Ca(phen)2(H2O)2]2[Nb6Cl12(CN)6] x (phen)2 x 4H2O (2), and [Ba(phen)2(H2O)]2[Nb6Cl12(CN)6] (3) were determined by single-crystal X-ray diffraction. The three compounds were found to crystallize in the monoclinic system (space group Pn) with a = 11.5499(6) A, b = 17.5305(8) A, c = 21.784(1) A, beta = 100.877(1) degrees for 1; triclinic system (P1) with a = 12.609(4) A, b = 13.262(4) A, c = 16.645(5) A, alpha = 69.933(6) degrees, beta = 68.607(6) degrees, gamma = 63.522(5) degrees for 2; and a = 16.057(1) A, b = 16.063(1) A, c = 16.061(1) A, alpha = 86.830(1) degrees, beta = 64.380(1) degrees, gamma = 67.803(1) degrees for 3. Compounds 1 and 2 are built of cluster anions [Nb6Cl12(CN)6]4- trans-coordinated by two Ca2+ complexes via CN ligands to form neutral macromolecular units [Ca(phen)2(H2O)3]2[Nb6Cl12(CN)6] in 1 and [Ca(phen)2(H2O)2]2[Nb6Cl12(CN)6] in 2. Water of coordination and cyanide ligands form hydrogen bonded 3D and 2D frameworks for 1 and 2, respectively. The structure of 3 consists of [Nb6Cl12(CN)6]4- cluster anions and [Ba(phen)2(H2O)]2+ complexes linked through bridging cyanide ligands to form a neutral three-dimensional framework in which each barium complex is bound to three neighboring Nb6 clusters and each Nb6 cluster is linked to six Ba complexes.

The octahedral edge-bridged niobium cyano-chloride cluster [Nb6Cl12(CN)6]4- and the [Mn(salen)]+ metal complex have been used as building units to prepare solid-state materials with extended frameworks at room temperature through self-assembly processes. Three materials with different dimensionalities were prepared and characterized: (Me4N)4[Nb6Cl12(CN)6]·2MeOH (1) (0D), (Me4N)2[Mn(salen)]2[Nb6Cl12(CN)6] (2) (2D), and (Et4N)2[Mn(salen)(MeOH)]2[Nb6Cl12(CN)6]·2MeOH (3) (1D). 1 was used as cluster precursor for the preparation of 2 and 3. The framework dimensionality seems to be affected by the size of the template-counterion used. Single-crystal X-ray analysis revealed that 1 is based on discrete [Nb6Cl12(CN)6]4- separated by (Me4N)+ and MeOH molecules. 2 has a two-dimensional framework, in which each layer is formed by [Nb6Cl12(CN)6]4- clusters connected through four cyanide ligands to four different [Mn(salen)]+. Each manganese complex connects two clusters through Nb−CN−Mn−NC−Nb bridges, leading to the ...

The synthesis, cytotoxicity, and nucleoside binding of some platinum-acridinylthiourea conjugates derived from the prototypical compound [PtCl(en)(ACRAMTU)](NO3)2 ("PT-ACRAMTU"; en=ethane-1,2-diamine, ACRAMTU=1-[2-(acridin-9-ylamino)ethyl]-1,3-dimethylthiourea, protonated form) are reported. To establish structure-activity relationships within this class of compounds, systematic changes were made to the thiourea nonleaving group, which links the intercalator to platinum. Three new derivatives of ACRAMTU, one di-, one tri-, and one tetraalkylated, were generated, where the degree of alkylation indicates the number of alkyl groups attached to the SCN2 framework. Subsequent reaction of the tri- and tetraalkylated derivatives with activated [PtCl2(en)] yielded the corresponding platinum conjugates. The dialkylated thiourea gave an unstable complex, which was not included in the studies. The crystal structure of PT-ACRAMTU x MeOH has been determined. In the solid state, one axial position of the square-planar platinum coordination sphere is partially shielded by the bulky thiourea group, providing a strong rationale for the kinetic inertness of the compound. The cytotoxicity of the prototype, the two new conjugates, and cisplatin was assessed in ovarian (A2780, A2780/CP), lung (NCI-H460), and colon (RKO) cancer cell lines using clonogenic survival assays. The derivatives containing trialkylated thiourea groups showed activity similar or superior to cisplatin, with IC50 values in the low micromolar concentration range. The complex modified with the tetraalkylated (bulkiest) thiourea was significantly less active, possibly due to the greatly decreased rate of binding to nucleobase nitrogen (1H NMR spectroscopy), but was most efficient at overcoming cross resistance to cisplatin in A2780/CP. Possible consequences of the reported structural modifications for the mechanism of action of these agents are discussed.

New niobium oxychloride cluster compounds corresponding to the general formula, A 5 Ti 8 Nb 18 Cl 53 O 12 (A = K, In), have been prepared in sealed quartz tubes from a mixture containing NbCl 5 , Nh 2 O 5 , Nb, Ti, and KCl or In by solid-state reactions at 750°C. Their structure was determined using single-crystal X-ray diffraction; Crystal data: trigonal, P3m1 (No. 164) (for K: a = 16.8303(11) A, c = 9.0510(8) A, V = 2220.3(3) A 3 and Z = 1; for In: a = 16.889(2) A, c = = 9.0684(2) A, V = 2240.0(6) A 3 and Z = 1). The full-matrix least-squares refinement of all data against F 2 converged to R 1 = 0.044, wR 2 = 0.088 for K, and R 1 = 0.050, wR 2 = 0.140 for In. The structure consists of octahedral (Nb 5 Cl i 8 O i 4 )Cl a 6 cluster units that share four outer chloride ligands with four adjacent clusters to form a two-dimensional framework that generates six- and three-member rings similar to those found in hexagonal tungsten bronze. Additional linkages within the same layer are provided by Ti 3 Cl 7 O 6 trimers. Adjacent layers are stacked in registry with each other leading to the formation of six-member ring openings channels parallel to the [001] direction in which a disordered [A 5 (Ti 2 Cl 9 )] 2+ species are located. Magnetic susceptibility studies show paramagnetic behavior with a magnetic moment of 3.74 μR per formula unit.

A new method for the synthesis of cobaloxime dienyl complexes (cobaloxime=pyridine(dimethylglyoxime) 2 Co) which involves a zinc-mediated hydrocobaltation of enynes is reported. Use of this dienyl complex synthesis method allows subsequent Diels–Alder reactions of these complexes to be accomplished without isolation of the dienyl complexes. A new silane-based cobaloxime-substituted cycloadduct demetallation protocol is then reported which provides Diels–Alder cycloadducts and cobalt complexes which have been recycled into the zinc-mediated dienyl complex synthesis.

In the course of our investigation aimed at the preparation of anisotropic cluster materials using a combination of oxide and chloride ligands to induce directional bonding preferences in the cluster unit, a series of niobium oxychloride cluster compounds AxNb6Cl12O2 (A=K, x=0.72(2); A=Rb, x=0.736(7); A=Cs, x=0.938(4); A=In, x=0.634(8)) was obtained by solid state synthesis. The cluster framework is based on (Nb6Cl10iO2i)Cl4aO2a clusters connected via oxide ligands in the a → direction with two Nb–O linkages between adjacent clusters, which resembles intercluster bonding in Chevrel–Sergent phases, while in the other two directions, the linkages occur through single Cla–a bridges. The framework generates channels where the cations A+ are located. The electronic band structure of the series features a narrow partially occupied band originating from a Nb–Nb bonding state. Magnetic and ESR measurements show the presence of localized unpaired electrons, and resistivity measurements indicate a semiconducting behavior.

Reaction of dichloro(1,2-dimethoxyethane)nickel with 2 equiv of (tris(2,4,6-trifluoromethyl)phenyl)lithium, generated in situ, produced bis(2,4,6-tris(trifluoromethyl)phenyl)(1,2-dimethoxyethane)ni...

Cyclopentadienylmolybdenumtricarbonyl anion reacts with a variety of allenic electrophiles to produce η3-2-alkylidene cyclobutanonyl and/or η3-butadienyl complexes. The 2-alkylidene cyclobutanone can be synthetically modified, while still complexed to molybdenum, by nucleophilic addition to the carbonyl or via enolate chemistry. The cyclobutanone can then be removed from the metal via oxidative demetalation. Several of the new complexes reported here have been characterized by X-ray crystallography.

The reaction of tris(pentafluorophenyl)boron trihydrate, B(C6F5)3·3H2O (1), with the nickel dimer [(PPh2CHC(O)Ph)Ni(Ph)]2 (3) (synthesized by phosphine abstraction from (PPh2CHC(O)Ph)Ni(Ph)(PPh3) (2)) yields (PPh2CH2C(O)Ph)Ni(C6F5)2 (4). In this reaction a number of processes occur: fragmentation of the dimer 3, transfer of two protons from 1, and transfer of two C6F5 groups from boron to nickel. In solution, 4 loses one C6F5 ligand as pentafluorobenzene due to proton transfer from the chelating ligand, forming the dimer [(PPh2CHC(O)Ph)Ni(C6F5)]2 (5). Compounds 4 and 5 were characterized by NMR and MS techniques. Compound 4 was independently synthesized by the reaction of PPh2CH2C(O)Ph and (η6-toluene)Ni(C6F5)2. The crystal structure of 4 was determined using single-crystal X-ray diffraction methods. Details concerning the synthesis and characterization of 1−3 are also given.

Reduced cobaloxime (cobaloxime = [(pyridine)(dimethylglyoxime)2cobalt]) compounds react with a variety of oxygen-substituted allenic and propargyl electrophiles to produce cobaloxime-substituted α,β- or β,γ-unsaturated ketones and aldehydes. Two of the new unsaturated acyl complexes prepared have been characterized by X-ray crystallography. Several of the α,β-unsaturated acyl complexes were subsequently converted into 1-cobaloxime-1,3-dienyl complexes using Peterson or Petasis olefinations. One of these new dienyl complexes has also been characterized by X-ray crystallography.

We have investigated the possibility of altering the electronic configuration of the niobium oxochloride cluster compound Ti2Nb6Cl14O4 (I) by doping this material with monovalent cations that can fit into cavities present in its cluster framework. The doping of I with In+ and Tl+ ions resulted in the formation of MxTi2Nb6Cl14-xO4+x (M = In, x = 0.10, 0.20, 0.27; M = Tl, x = 0.10, 0.20) in which the M+ ions partially occupy these cavities. The crystal structure analysis indicated that the additional charge provided by M+ ions is compensated by substitution of chlorine by oxygen, which leads to the cluster electronic configuration being intact. Crystal data: In0.272Ti2Nb6Cl13.728O4.272, space group C2/c (No. 15), a = 12.679(2) A, b = 14.567(2) A, c = 12.632(3) A, beta = 95.26(2) degrees, Z = 4; Tl0.196Ti2Nb6Cl13.804O4.196, space group C2/c (no. 15), a = 12.732(1) A, b = 14.607(2) A, c = 12.662(2) A, beta = 95.28(1) degrees, Z = 4.

The syntheses of two optically active Co(salen)-1,3-butadien-2-yl complexes are reported. One of the dienyl complexes was characterized by X-ray crystallography. The dienyl complexes underwent Diels−Alder reactions with high enantioselectivity with dimethyl fumarate. A highlight of this chemistry is that Diels−Alder cycloadduct cobalt complexes were cleanly cleaved at the cobalt−carbon bond with concomitant optically active cobalt complex starting material and optically active cyclohexene cycloadduct recovery.

The preparation of several cyclopentadienyl iron dicarbonyl and triphenylphosphine manganese tetracarbonyl η1-2-alkynyl complexes are reported. The [3+2] cycloaddition reactions of these complexes with sulfur dioxide and sulfur trioxide yielded transition-metal substituted 1,2-oxathiolene-2-oxides and 1,2-oxathiolene-2,2-dioxides, respectively. One of the η1-propargyl complex SO3 cycloadducts has been characterized by X-ray crystallography. The transition metal can subsequently be cleaved from the oxathiole-oxide and dioxide containing complexes to produce a variety of new sulfur containing heterocycles.

The previously known, but not well-characterized, fluorinated imides, trifluoroacetyltrifluoroacetimide, HN(C(O)CF3)2 (1), acetyltrifluoroacetimide, HN(C(O)CH3)C(O)CF3 (2), and dichlorophosphoryltrifluoroacetimide, HN(P(O)Cl2)C(O)CF3 (3), have been shown to be moderately strong acids in aqueous solution; the first two compounds have pKa’s of 2.0 and 2.1 while the last compound consumes three equivalents of base per mole of imide owing to the hydrolyzable chlorine atoms. All three imides show a window of electrochemical inactivity on platinum from 0 to near +2.0 V. On vitreous carbon, (1) and (2) are inactive from –1.0 to +1.5 V and (3) from –1.0 to +1.0 V (vs. SCE). (1) crystallizes in a body-centered tetragonal unit cell while (2) and (3) crystallize in monoclinic unit cells. Hydrogen-bonded chains are formed in (1) and (2) and hydrogen-bonded dimers are formed in (3). The compounds were further characterized by 1H, 19F, and 13C NMR, FTIR, and elemental analysis.

2-Cobaloxime- E -1,3-pentadienyl complexes (cobaloxime=pyridine(dimethyl or diphenylglyoxime) 2 Cobalt (III)) react with cyclohexenone in enantioselective Lewis acid catalyzed [4+2] cycloaddition reactions. These cycloaddition reactions produce octalones with cis ring junctions through exo transition states. The octalones are removed from the cobalt via demetallation reactions which replace the cobalt with a hydrogen and provide pyr(dmg) 2 CoMe which can be recycled into the synthesis of the starting dienyl complex. The enantiomeric purity of the demetallated octalones was determined by gas chromatographic analysis.

The ability of the fungal carcinogen ochratoxin A (OTA, 1) to bind Cu(II) in a stepwise fashion to produce a nonsymmetric dinuclear complex (2) is described. Structural changes in 1 induced by Cu coordination are discussed, as is the catalytic activity of Cu in the lactone hydrolysis of 1 in aqueous media (pH 7.8) at 37 °C.

The preparation of several cyclopentadienyliron dicarbonyl η1-2-alkynyl and η1-allenyl complexes is reported. The 3 + 2 cycloaddition reactions of these complexes with sulfur dioxide yielded regioisomeric transition-metal-substituted 1,2-oxathiolen-1-yl oxides (sulfenate esters). One of the η1-allenyl complex SO2 cycloadducts has been characterized by X-ray crystallography. The transition metal can subsequently be cleaved from the sulfenate ester containing complexes under oxidative and nonoxidative reaction conditions to produce a variety of new sulfur-containing heterocycles.

Treatment of allenic electrophiles with Mo-(CO) 3 (py) 3 followed by potassium hydrotris(1-pyrazolyl)-borate (KTp) or treatment of an enyne with TpMo(CO) 3 H followed by decarbonylation cleanly produced stable, new η 3 -dienyl complexes.

It is reported how the N-H-Cl hydrogen bonding in anilinium chloride and trichlorostannate (II) derivatives is affected by methyl and methoxy substitutions in the phenyl ring of an aniline group. Such hydrogen bonding has been confirmed by close N-Cl contacts in an X-ray structure determination on 2-methylanilinium trichlorostannate (II). Crystals are orthorhombic: space group P2121; a = 0.7290(3) nm, b = 1.9096(7) nm, c = 0.8233(4) nm, = β = = 90°; V = 1.1461(8) nm3, Z = 4. The degree of hydrogen bonding manifests itself in changes in the core electron binding energies of the N and Cl atoms as observed by X-ray photoelectron spectroscopy (XPS), and also by the characteristic shift in the N-H stretching frequency measured by diffuse reflectance infrared spectroscopy. Correlations are observed between changes in the anilinium v(N-H) force constants and changes in the corresponding N(1s) and Cl(2p) binding energies. The varying degrees of hydrogen bonding depend on the positions and types of substituents on the aniline aromatic ring and correlate with their dissociation constants, pKa: but, theoretical analysis of one of the methylaniline hydrochlorides shows that the position of the H atom in the hydrogen bond, N H Cl, is a significantly stronger influence on the fractional charge on nitrogen, suggesting that overall crystal structure may be the determining factor on N charge.

We have investigated the possibility of altering the electronic configuration of the niobium oxochloride cluster compound Ti2Nb6Cl14O4 (I) by doping this material with monovalent cations that can fit into cavities present in its cluster framework. The doping of I with In+ and Tl+ ions resulted in the formation of MxTi2Nb6Cl14-xO4+x (M = In, x = 0.10, 0.20, 0.27; M = Tl, x = 0.10, 0.20) in which the M+ ions partially occupy these cavities. The crystal structure analysis indicated that the additional charge provided by M+ ions is compensated by substitution of chlorine by oxygen, which leads to the cluster electronic configuration being intact. Crystal data: In0.272Ti2Nb6Cl13.728O4.272, space group C2/c (No. 15), a = 12.679(2) A, b = 14.567(2) A, c = 12.632(3) A, beta = 95.26(2) degrees, Z = 4; Tl0.196Ti2Nb6Cl13.804O4.196, space group C2/c (no. 15), a = 12.732(1) A, b = 14.607(2) A, c = 12.662(2) A, beta = 95.28(1) degrees, Z = 4.

The new niobium oxychloride cluster compound, Cs2Ti4Nb6Cl18O6, was obtained by solid-state synthesis techniques in the course of our systematic investigation of metal oxychloride systems aimed at the preparation of low-dimensional cluster compounds. Cs2Ti4Nb6Cl18O6 crystallizes in the trigonal system, with unit cell parameters a= 11.1903(7), c = 15.600(2) A, space group P3bar1c, Z = 2. Its crystal structure was determined by single-crystal X-ray diffraction techniques. The full-matrix least-squares refinement against F(2) converged to R(1) = 0.048 (F(o) > 4sigma(F(o))), wR(2) = 0.069 (all data). The structure is based on an octahedral cluster unit (Nb6Cl(i)6O(i)6)Cl(a)6 in which the six edge-bridging oxide ligands are arranged in two sets of three on opposite sides of the Nb6 octahedron. Ti(3+) ions link the clusters through O(i) and Cl(a) ligands to form linear chains running along the c axis. The location of titanium ions correlates with the arrangement of oxide ligands around the Nb6 metal core. The chains interact with each other through additional Ti(3+) and Cs(+) ions. Interchain interactions are significantly weaker than intrachain interactions, resulting in a quasi-one-dimensional character of the overall structure.

Cyclopentadienylmolybdenumdicarbonyl anion reacts with a variety of allenic electrophiles to produce η3-2-alkylidene cyclobutanoyl complexes. Three of these complexes have been characterized by X-ray crystallography, and the 2-alkylidene cyclobutanone has been removed and recovered from one complex via oxidative demetalation.

Complexes of Zn(II), Cu(II) and Co(II) with either N-(2-methylpyridyl)-3-thienyl-alkyl-carboxamide or N-(2-pyridyl)-3-thienylalkyl-carboxamide groups have been prepared and characterized. Crystal structures of ten new complexes are reported and discussed. N-(2-Methylpyridyl)-3-thienyl-alkyl-carboxamide exhibits both uni- and bidentate behavior. With all ligands, bidentate complexation is through the carbonyl oxygen and pyridine nitrogen atoms (O, N) and the amide nitrogen atom remains protonated. The electrochemical behavior and the infrared spectra of selected complexes are discussed.

The unusual dinucleating properties of a simple bidentate Schiff base (LH, 1) in the presence of weakly coordinating methanol solvent lead to the self-assembly of [ Fe 2 II ( L b ) 2 ( L t ) 2 ( μ - MeOH ) ] (2) (b and t refer to bridging and terminally bound ligands, respectively). Complex 2 is the first diiron(II) species in which the two metal centers are triply bridged by single atoms in an asymmetric fashion, involving both μ-OPh and μ-OHMe bridges. This binding mode produces an Fe⋯Fe distance of 3.139(1) A. Dinucleation appears to be driven by a combination of ligand deficiency and solvent-mediated chemistry reminiscent of host–guest interactions. The presence of a μ-MeOH ligand is unprecedented in iron chemistry. Parallel-mode EPR spectra of complex 2 recorded at 4 K show an intense negative signal at g ∥ ≈ 16 , suggesting the dimeric form exists in solution.

Three complexes containing the novel, sterically hindered ligand 6-(methylpyridin-2-yl)acetate (PICAC) have been synthesized and characterized: [Pt(NH 3 ) 2 (PICAC- N , O )]NO 3 ( 1 ), [Pt(en)(PICAC- N , O )]NO 3 ( 2 ), and [Pd(en)(PICAC- N , O )]NO 3 ( 3 ) (en = ethane-1,2-diamine). The crystal structures of 2 and 3 have been determined. The two complexes are isostructural and exhibit a mixed [N 3 O] coordination. In both cases, PICAC forms a sterically crowded six-membered chelate. Signal multiplicities in 1 H NMR spectra of 1 – 3 indicate that the N,O chelates are conformationally rigid on the NMR timescale as a result of the steric bulk of the pyridine derivative. Complex 2 undergoes facile ring opening in 0.1 M NaCl solution at neutral pH, resulting in a zwitterionic species in which carboxylate oxygen has been replaced with chloride. The complex was identified by X-ray crystallography as [PtCl(en)(PICAC- N )] · H 2 O ( 4 ), which contains a “dangling” carboxylate group. In 4 , the pyridine moiety adopts an almost perpendicular orientation relative to the platinum coordination plane. Likewise, complex 2 reacts rapidly with 5′-guanosine monophosphate (5′-GMP) to form the monofunctional adduct [Pt(en)(PICAC)(5′-GMP)] ( 5 ) (NMR, 25 °C, t 1/2 ≈ 24 min). 2-D nuclear Overhauser enhancement spectroscopy (NOESY) and double quantum-filtered correlated spectroscopy (dqf-COSY) experiments (500 MHz) and variable temperature NMR spectroscopy confirm that adduct 5 exists as a 1:1 mixture of rotamers in solution as a result of the mutual repulsion between the cis -oriented pyridine and guanine bases. While 2 readily reacts with DNA nitrogen, its monofunctional adducts show no significant effect on the conformation of native DNA. Circular dichroism (CD) spectra recorded of platinum-modified calf-thymus DNA suggest that the structural damage produced by complex 2 does not mimic that produced by the clinical agent. Both the unusual reactivity and the inability to induce cisplatin-like DNA conformational changes are proposed to be responsible for the marginal biological activity of the new complexes.

The recent discovery of the promising tumor cell kill by a novel platinum-acridine conjugate [Martins, E. T.; et al. J. Med. Chem. 2001, 44, 4492] has prompted us to explore the utility of analogous light-activatable rhodium(III) compounds as photocytotoxic agents. Here, the design and synthesis of [Rh(NH(3))(5)L](n)(+) complexes are described with L = 1,1,3,3-tetramethylthiourea (tmtu) or 1-[2-(acridin-9-ylamino)ethyl]-1,3,3-trimethylthiourea (2). The intercalator-based DNA-affinic carrier ligand 2 was synthesized from N-acridin-9-yl-N'-methylethane-1,2-diamine and dimethylthiocarbamoyl chloride and isolated as the hydrotriflate salt 2(CF(3)SO(3)). [Rh(NH(3))(5)(tmtu)](3+) (1) and [Rh(NH(3))(5)(2)](4+) (3) were obtained from the reactions of the trifluoromethanesulfonato complex [Rh(NH(3))(5)(OSO(2)CF(3))](CF(3)SO(3))(2) with the appropriate thiourea in noncoordinating solvents. All compounds were characterized by (1)H NMR and UV-vis spectroscopies and by elemental analyses. The single-crystal X-ray structures of 1(CF(3)SO(3))(3) x 2MeOH, 2(CF(3)SO(3)), and 3(CF(3)SO(3))(4) x H(2)O have been determined. Ligand-field photolysis of thermally inert 1 (lambda(max) = 378 nm) resulted in the aquation of 2 equiv of ammine ligand without noticeable release of sulfur-bound tmtu ((1)H NMR spectroscopy, NH(3)-sensitive electrode measurements). This was confirmed by (15)N[(1)H] NMR spectroscopy using (15)N-labeled [Rh((15)NH(3))(5)(tmtu)](3+) (1), which also indicated photoisomerization of the [RhN(5)S] moiety. Despite greatly accelerated ligand exchange, rhodium in 1 and 3 did not show light-enhanced formation of covalent adducts in calf thymus DNA. "Dark binding" levels of 3 in native DNA were slightly higher than for nontargeted 1, but significantly lower than those observed for analogous platinum-acridine. Agarose gel electrophoresis revealed photocleavage of supercoiled pUC19 plasmid DNA in the presence of hybrid 3 and its individual constituents 1 and 2. Simple 1 induced single-strand breaks while 3 produced complete degradation of the DNA after 24 h of continuous irradiation. Acridine 2 alone produced double-strand breaks. The extent of DNA damage observed for 1-3 correlates with the photocytotoxicity of the compounds in human leukemia cells, suggesting that DNA might be the cellular target of these agents.

Interest in mixed metals titanium phosphates, both in glass and crystalline forms, for their properties as ionic conductors or non-linear optical materials, has led to large number of studies of these materials [1-3]. Our investigation of Na2O – Li2O – CaO – TiO2 – P2O5 system led to the discovery of NaxLiyCazTit(PO4)3 solid solutions which exist in both glassy and crystalline forms. Here the preparation of NaxLiyCazTit(PO4)3 will be described. The compounds were structurally characterized by PXRD, and their chemical and physical characterization were completed using DTA, XRD, UV-visible, Raman spectroscopy and ionic conductivity measurements. NaxLiyCazTit(PO4)3 glasses have been prepared by heating stochiometric amounts of Na2CO3, Li2CO3, CaCO3, TiO2 and NH4H2PO4 in a platinum crucible at 10500C. The microcrystalline samples were obtained by crystallization of the corresponding glasses at 6400C or by standard solid state preparation at 7000C. The values of the characteristic temperatures Tg (glass transition), Tc (crystallization) and Tf (fusion) of the glasses are found in the following ranges: 400 – 5000C for Tg, 440 – 6500C for Tc and 780 – 8300C for Tf. Rietveld refinements of powder X ray diffraction data collected on crystalline samples of NaxLiyCazTit(PO4)3 shows the existence of a solid solution in the domain 0 ≤ X ≤ 0.5 and the presence of a mixture of phases in the domain 0.5 < X ≤ 1.5. The crystalline phases belong to the Nasicon family, space group R32. Their structure, determined from refinement of powder diffraction patterns , consists of a 3D network of AO6 (A = Ti, Na, Li, and Ca) octahedra and PO4 tetrahedra linked by corners. Sodium atoms fully occupy the M(1) sites and partially the M(2) sites.

The new niobium oxychloride cluster compound, Cs2Ti4Nb6Cl18O6, was obtained by solid-state synthesis techniques in the course of our systematic investigation of metal oxychloride systems aimed at the preparation of low-dimensional cluster compounds. Cs2Ti4Nb6Cl18O6 crystallizes in the trigonal system, with unit cell parameters a= 11.1903(7), c = 15.600(2) A, space group P3bar1c, Z = 2. Its crystal structure was determined by single-crystal X-ray diffraction techniques. The full-matrix least-squares refinement against F(2) converged to R(1) = 0.048 (F(o) > 4sigma(F(o))), wR(2) = 0.069 (all data). The structure is based on an octahedral cluster unit (Nb6Cl(i)6O(i)6)Cl(a)6 in which the six edge-bridging oxide ligands are arranged in two sets of three on opposite sides of the Nb6 octahedron. Ti(3+) ions link the clusters through O(i) and Cl(a) ligands to form linear chains running along the c axis. The location of titanium ions correlates with the arrangement of oxide ligands around the Nb6 metal core. The chains interact with each other through additional Ti(3+) and Cs(+) ions. Interchain interactions are significantly weaker than intrachain interactions, resulting in a quasi-one-dimensional character of the overall structure.

The asymmetric arrangement of chloride and oxide ligands around the octahedral Nb6 cluster core and their electrostatic interaction with Ti3+ counterions play an important role in the formation of a novel 2D framework with cluster connectivity unprecedented in compounds containing octahedral clusters.

(CH 3 C 5 H 4 ) 2 V 2 S 4 Fe(CO) 3 , (CH 3 C 5 H 4 )V 2 S 3 Fe(CO) 3 et (CH 3 C 5 H 4 ) 2 V 2 S 4 Fe(NO 2 ) cristallisent dans le systeme monoclinique, groupe d'espace P2 1 /c. Leur structure affinee respectivement jusqu'a R=0,028; R=0,038; R=0,031 et forme un triangle isocele d'atomes metalliques. (CH 3 C 5 H 4 ) 4 V 4 S 8 Ni cristallise dans le systeme orthorhombique, groupe d'espace Pbcn avec R=0,081. La molecule forme un tetraedre d'atomes Ni

C 32 H 26 N 4 Br 2 , M = 626.4, triclic P 1 C 1 ; (No. 2) with a = 13.530(5) A, b = 10.781(5) A, c = 10.444(5) A, β = 97.62(3), V = 1493(1) A 3 , Z = 2, μ = 27.1 cm −1 , F = (000) = (600), D c = 1.84 g cm −3 . Several molecular conformations are possible for the title compound. Although free rotation of the bipyridyl moieties around the CC bonds is possible, the bulky 4,4′-bipyridyls impose steric hindrance and restrict the free rotation. Examination of the Drieding model of the molecule eliminated those arrangements where considerable overlapping of the bipyridyls occurred. NMR results were not useful in choosing the most likely candidate for the structure from the remaining possibilities. Three-dimensional diffraction data was collected at 20+1 C on a computer-controlled four circle Nicolet audiodiffractometer using graphite crystal monochromated Mo α -radiation. The most probable conformation where the hydrogen—hydrogen and bipyridyl—bipyridyl interactions are minimum is shown in Fig. 1.

Die Titelverbindung (II), in der U(III) durch Pentamethylcyclopentadienyl-Liganden komplexiert ist, ist eine ausgezeichnete Ausgangsverbindung fur weitere U(III)-Verbindungen.