(S)-(2-(2'-Pyridyl)ethyl)cysteamine and (S)-(2-(2'-pyridyl)ethyl)-d,l-homocysteine as ligands for the "fac-[M(CO)(3)](+)" (M = Re, (99m)Tc) core

The reaction of fac-[NEt(4)](2)[Re(CO)(3)Br(3)] with (S)-(2-(2'-pyridyl)ethyl)cysteamine, L(1), in methanol leads to the formation of the cationic fac-[Re(CO)(3)(NSN)][Br] complex, 1, with coordination of the nitrogen of the pyridine, the sulfur of the thioether, and the nitrogen of the primary amine. When fac-[NEt(4)](2)[Re(CO)(3)Br(3)] reacts with the homocysteine derivative (S)-(2-(2'-pyridyl)ethyl)-d,l-homocysteine, L(2), the neutral fac-Re(CO)(3)(NSO) complex, 2, is produced with coordination of the nitrogen of the primary amine, the sulfur of the thioether, and the oxygen of the carboxylate group, while the pyridine ring remains uncoordinated. The analogous technetium-99m complexes, 1' and 2', were also prepared quantitatively by the reaction of L(1) and L(2) with the fac-[(99m)Tc(CO)(3)(H(2)O)(3)](+) precursor at 70 degrees C in water. Given that both (S)-(2-(2'-pyridyl)ethyl)cysteamine and homocysteine can be easily N- or S-derivatized by a bioactive molecule of interest, both the NSN or NSO ligand systems could be used to develop target-specific radiopharmaceuticals for diagnosis and therapy.     

A new type of tweezer complex involving a rhenium-rhenium multiple bond that enforces an unusual structure in a dipalladium(II) unit

The substitution of the mu-acetato ligands in cis-Re(2)(mu-O(2)CCH(3))(2)Cl(2)(mu-dppm)(2) (1, dppm = Ph(2)PCH(2)PPh(2)) and trans-Re(2)(mu-O(2)CCH(3))(2)Cl(2)(mu-dppE)(2) (2, dppE = Ph(2)PC(=CH(2))PPh(2)) by [4-Ph(2)PC(6)H(4)CO(2)](-) occurs with retention of stereochemistry to give cis-Re(2)(mu-O(2)CC(6)H(4)-4-PPh(2))(2)Cl(2)(mu-dppm)(2) (3) and trans-Re(2)(mu-O(2)CC(6)H(4)-4-PPh(2))(2)Cl(2)(mu-dppE)(2) (6), respectively. The uncoordinated phosphine groups in complexes 3 and 6 have been used to form mixed-metal assemblies with Au(I) and Pd(II), including the Re(2)Pd(2) complex cis-Re(2)(mu-O(2)CC(6)H(4)-4-PPh(2))(2)Cl(2)(mu-dppm)(2)(Pd(2)Cl(4)) (5), in which the planar [(P)ClPd(mu-Cl)(2)PdCl(P)] unit has the unusual cis structure. The crystal structures of 3 and 5 have been determined.     

Spectro- and electrochemical studies of some ruthenium and osmium complexes of 2-(2'-pyridyl)benzimidazole; complexes with intra-molecular charge transfer

Reaction of Ru3(CO)12, with 2-(2'-pyridyl)benzimidazole (HPBI) resulted in the formation of Ru(CO)3(HPBI) (I) complex. In presence of pyridine or dipyridine, the two derivatives [Ru(CO)3(HPBI)].Py (II) and [Ru(CO)3(HPBI)].dpy (III) were isolated. The corresponding reactions of Os3(CO)12 yielded only one single product; Os(CO)2(HPBI)2 (IV). Spectroscopic studies of these complexes revealed intramolecular metal to ligand CT interactions. Reactions of RuCl3 with HPBI gave three distinct products; [Ru(HPBI)2Cl2]Cl (V), [Ru(HPBI)(dipy)Cl2]C1 (VI) and [Ru(PBI)2(py)2]Cl (VII). The UV-vis studies indicated the presence of intramolecular ligand to metal CT interactions. Electrochemical investigation of the complexes showed some irreversible, reversible and quasi-reversible redox reactions due to tautomeric interconversions through electron transfer.     

New dirhenium(III) compounds bridged by carboxylate ligands: N(C(4)H(9))(4)[Re(2)(OOCCF(3))Cl(6)] and Re(2)(OOCCCHCo(2)(CO)(6))(4)Cl(2)

The solvothermal reaction of (N(C(4)H(9))(4))(2)[Re(2)Cl(8)] with trifluoroacetic acid and acetic anhydride leads to the new rhenium trifluoroacetate dimer N(C(4)H(9))(4)[Re(2)(OOCCF(3))Cl(6)] (1) and to the rhenium carbonyl dimer Re(2)(mu(2)-Cl)(2)(CO)(8) as the rhenium-reduced byproduct. The reaction of the precursor complex, N(C(4)H(9))(4)[Re(2)(OOCCF(3))Cl(6)] (1), with the organometallic carboxylic acid (CO)(6)Co(2)HCCCOOH leads to the cluster of clusters compound Re(2)(OOCCCHCo(2)(CO)(6))(4)Cl(2) (2), which has the dimer structure of Re(2)(OOCR)(4)Cl(2). Cyclic voltammetric measurements show that Re(2)(OOCCCHCo(2)(CO)(6))(4)Cl(2) (2) has one reduction centered on the dirhenium core and a reduction centered on the cobalt atoms. DFT calculations have been used to rationalize the observed displacements of the voltammetric signals in Re(2)(OOCCCHCo(2)(CO)(6))(4)Cl(2) (2) compared to the parent ligand (CO)(6)Co(2)HCCCOOH and rhenium pivalate.     

New Group 6 metal carbonyl derivatives of 2-(2'(-pyridyl)benzimidazole: synthesis and spectroscopic studies

Reaction of Cr(CO)(6) with 2-(2'-pyridyl)benzimidazole (pbiH) under reduced pressure resulted in the formation of the dinuclear complex [Cr(2)(CO)(6)(pbiH)(2)]. Infra-red (IR) spectroscopy revealed the presence of terminal and bridge Cr-CO bonds. Interaction of M(CO)(6), M=Cr, Mo and W, with pbiH in the presence of 2,2'-bipyridine (bpy) gave the tetracarbonyl complexes [M(CO)(4)(pbiH)].bpy. Spectroscopic studies of the complexes indicated the presence of hydrogen bonding between the bpy nitrogen and the NH group of pbiH. Reactions of M(CO)(6) with pbiH in the presence of PPh(3) gave the tricarbonyl monosubstituted derivatives [M(CO)(3)(PPh(3))(pbiH)]. The spectroscopic studies of the complexes suggested the proposed structures.     

Concerning the photophysical properties of Re2(4+) and Re2(6+) carboxylate compounds

The preparation and structure of Re(2)(dppm)(2)(O(2)CC(6)H(4)-p-NO(2))(2)Cl(2), where dppm = Ph(2)PCH(2)PPh(2), is reported together with its photophysical properties (absorption, steady state emission, fs- and ns-transient absorption spectroscopy) and electrochemistry. These data are compared with photophysical studies on the previously reported Re(2)(dppm)(2)(O(2)CCH(3))(2)Cl(2). The preparation of the complex Re(2)(O(2)CC(6)H(4)-p-NO(2))(4)Cl(2) is also reported together with its photophysical properties which allows for a comparison of the electronic structures and photophysical states of Re(2)(4+) and Re(2)(6+) containing complexes having MM configurations σ(2)π(4)δ(2)δ(*2) and σ(2)π(4)δ(2), respectively. An interesting comparison is also made with the related MM quadruply bonded complexes of molybdenum and tungsten.     

Complexation of the triply-bonded dirhenium(II) complex Re(2)Cl(4)(mu-dppm)(2) (dppm = Ph(2)PCH(2)PPh(2)) by up to three acetylene molecules

The triply bonded dirhenium(II) synthons Re(2)X(4)(mu-dppm)(2) (X = Cl, Br; dppm = Ph(2)PCH(2)PPh(2)) react with acetylene at room temperature in CH(2)Cl(2) and acetone to afford the bis(acetylene) complexes Re(2)X(4)(mu-dppm)(2)(mu:eta(2),eta(2)-HCCH)(eta(2)-HCCH) (X = Cl (3), Br(4)). Compound 3 has been derivatized by reaction with RNC ligands in the presence of TlPF(6) to give unsymmetrical complexes of the type [Re(2)Cl(3)(mu-dppm)(2)(mu:eta(2),eta(2)-HCCH)(eta(2)-HCCH)(CNR)]PF(6) (R = Xyl (5), Mes (6), t-Bu (7)), in which the RCN ligand has displaced the chloride ligand cis to the eta(2)-HCCH ligand. The reaction of 3 with an additional 1 equiv of acetylene in the presence of TlPF(6) gives the symmetrical all-cis isomer of [Re(2)Cl(3)(mu-dppm)(2)(mu:eta(2),eta(2)-HCCH)(eta(2)-HCCH)(2)]PF(6) (8). The two terminal eta(2)-HCCH ligands in 8 are very labile and can be displaced by CO and XylNC to give the complexes [Re(2)Cl(3)(mu-dppm)(2)(mu:eta(2),eta(2)-HCCH)(L)(2)]Y (L = CO when Y = PF(6) (9); L = CO when Y = (PF(6))(0.5)/(H(2)PO(4))(0.5) (10); L = XylNC when Y = PF(6) (11)). These substitution reactions proceed with retention of the all-cis stereochemistry. Single-crystal X-ray structure determinations have been carried out on complexes 3, 5, 8, 10, and 11. In no instance have we found that the acetylene ligands undergo reductive coupling reactions.     

Reactions of the Dirhenium(II) Complexes Re(2)X(4)(&mgr;-dppm)(2) (X = Cl, Br; dppm = Ph(2)PCH(2)PPh(2)) with Isocyanides. 11.(1) A Triply Bonded Dirhenium Complex Containing a Labile Acetonitrile Ligand. Synthesis, Structural Characterization, and Reactivity of [(XylNC)(CH(3)CN)ClRe(&mgr;-dppm)(2)ReCl(2)(CO)]O(3)SCF(3)

The reaction of the open bioctahedral form of Re(2)Cl(4)(&mgr;-dppm)(2)(CO)(CNXyl) (1), where XylNC = 2,6-dimethylphenyl isocyanide, with TlO(3)SCF(3) in the presence of acetonitrile proceeds with retention of stereochemistry at the dirhenium unit to afford the complex [Re(2)Cl(3)(&mgr;-dppm)(2)(CO)(CNXyl)(NCCH(3))]O(3)SCF(3) (3). The single-crystal X-ray structure determination of 3 shows that a Re&tbd1;Re bond is retained (the Re-Re distance is 2.378(3) ?) and that it is the chloride ligand trans to the XylNC ligand of 1 which is labilized. Complex 1 reacts with TlO(3)SCF(3) in a noncoordinating solvent to produce the unsymmetrical complex [Re(2)Cl(3)(&mgr;-dppm)(2)(CO)(CNXyl)]O(3)SCF(3) (2), through loss of this same chloride ligand of 1 and CO transfer from the adjacent Re center. The acetonitrile ligand of 3 is very labile and is readily displaced by XylNC and t-BuNC, with retention of stereochemistry, to produce complexes of stoichiometry [Re(2)Cl(3)(&mgr;-dppm)(2)(CO)(CNXyl)(CNR)]O(3)SCF(3) (R = Xyl, 4a; R = t-Bu, 4b). In a noncoordinating solvent, the nitrile ligand of 3 is lost and 2 is formed following CO transfer; this conversion is reversed upon the reaction of 2 with acetonitrile. When 3 is treated with CO, the acetonitrile ligand is again displaced, but in this instance the reaction is accompanied by a structure change to produce an edge-sharing bioctahedral complex of the type [Re(2)(&mgr;-CO)(&mgr;-Cl)(&mgr;-dppm)(2)Cl(2)(CO)(CNXyl)]O(3)SCF(3) (5).     

Substitution reactions with [ReBr(2)(CO)(2)(NCCH(3))(2)](-): a convenient route to complexes with the cis-[Re(CO)(2)](+) core

Water- and air-stable complexes comprising the cis-[Re(CO)(2)](+) core can be synthesized from the (Et(4)N)[ReBr(2)(NCCH(3))(2)(CO)(2)] precursor . Complex showed distinctly different chemical and electronic behaviour compared to [ReBr(3)(CO)(3)](2-). Substituting the two bromides in with imidazole-like ligands or alpha,alpha'-diimines gave new complexes with potential applications in bioinorganic chemistry and photochemistry. The two acetonitrile ligands are very stably bound and could not be replaced. Under CO pressure, the uncommon complex mer-[ReBr(NCCH(3))(2)(CO)(3)] was formed from . The reaction of with the tetradentate ligand bis(2-pyridylmethyl)glycine (BPG) finally induced a four fold substitution at the metal center to form a [Re(CO)(2)(L(4))](+)-type complex.     

Synthesis and characterization of the dimercury(I)-linked compound [PPn]4[(Re7C(CO)21Hg)2]. Oxidative cleavage of the mercury-mercury bond leading to carbidoheptarhenate complexes of mercury(II), including [PPN][Re7C(CO)21Hg(S=C(NME2)2)

The reaction of [PPN](3)[Re(7)C(CO)(21)] with Hg(2)(NO(3))(2).2H(2)O in dichloromethane formed the complex [PPN](4)[(Re(7)C(CO)(21)Hg)(2)] ([PPN](4)[1]), isolated in 60% yield. Analogous salts of [1](4-) with [PPh(4)](+) and [NEt(4)](+) were also prepared. The crystal structure of [PPN](4)[1] showed that two carbidoheptarhenate cores are linked by a dimercury(I) unit (d(Hg-Hg) = 2.610(4) A), with each individual mercury atom face-bridging. Oxidative cleavage of the Hg-Hg bond in [1](4-) was effected by 4-bromophenyl disulfide to form [Re(7)C(CO)(21)HgSC(6)H(4)Br](2-) ([4](2-)), by I(2) to form [Re(7)C(CO)(21)HgI](2-) ([5](2-)), and by Br(2) to form [Re(7)C(CO)(21)HgBr](2-) ([6](2-)). Oxidation of [1](4-) by ferrocenium ion (2 equiv) in the presence of tetramethylthiourea resulted in the derivative [Re(7)C(CO)(21)HgSC(NMe(2))(2)](-) ([7](-)). The molecular structure of [PPN][7] was determined by X-ray crystallography. This is the first example of a carbidoheptarhenate-mercury complex with a neutral ligand on mercury, and ligand exchange was demonstrated by displacement with triethylphosphine. Complex [7](-) can also be prepared by protonating [Re(7)C(CO)(21)HgO(2)CCH(3)](2-) in the presence of tetramethylthiourea. Cyclic voltammetry data to calibrate and compare the redox properties of compounds [1](4-) and [7](-) have been measured.     

Novel concentration-driven structural interconversion in shape-specific solids supported by the octahedral [Re(6)(mu3-Se)8]2+ cluster core

A complex containing the face-capped octahedral [Re(6)(mu(3)-Se)(8)](2+) cluster core, cis-[Re(6)(mu(3)-Se)(8)(PPh(3))(4)(4,4'-dipyridyl)(2)](SbF(6))(2) (1), is used as a ditopic ligand with an enforced right angle between the two 4,4'-dipyridyl moieties for the coordination of Cd(2+) ion. Two coordination polymers, [[Re(6)(mu(3)-Se)(8)(PPh(3))(4)(4,4'-dipyridyl)(2)](2)[Cd(NO(3))(2)]](SbF(6))(4).21C(4)H(10)O.21CH(2)Cl(2) (2) and [[Re(6)(mu(3)-Se)(8)(PPh(3))(4)(4,4'-dipyridyl)(2)][Cd(NO(3))(3)]](NO(3)).2C(4)H(10)O.CH(2)Cl(2) (3), are obtained. The relative concentration of Cd(2+) determines which species is isolated, and the conversion of the first structure into the second is demonstrated experimentally.     

New phosphorescent polynuclear Cu(I) compounds based on linear and star-shaped 2-(2'-pyridyl)benzimidazolyl derivatives: syntheses, structures, luminescence, and electroluminescence

Four dinuclear and trinuclear Cu(I) complexes that contain 2-(2'-pyridyl)benzimidazolyl derivative ligands including 1,4-bis[2-(2'-pyridyl)benzimidazolyl]benzene (1,4-bmb), 1,3-bis[2-(2'-pyridyl)benzimidazolyl]benzene (1,3-bmb), 1,3,5-tris[2-(2'-pyridyl)benzimidazolyl]benzene (tmb), and 4,4'-bis[2-(2'-pyridyl)benzimidazolyl]biphenyl (bmbp) have been synthesized. The formulas of these complexes are [Cu(2)(1,4-bmb)(PPh(3))(4)][BF(4)](2) (1), [Cu(2)(1,3-bmb)(PPh(3))(4)][BF(4)](2) (2), [Cu(3)(tmb)(PPh(3))(6)][BF(4)](3) (3), and [Cu(2)(bmbp)(PPh(3))(4)][BF(4)](2) (4), respectively. The crystal structures of 2-4 have been determined by single-crystal X-ray diffraction analyses. The Cu(I) ions in the complexes have a distorted tetrahedral geometry. For 3, two structural isomers (syn and anti) resulted from two different orientations of the three 2-(2'-pyridyl)benzimidazolyl chelating units were observed in the crystal lattice. Variable-temperature (1)H NMR experiments established the presence of syn and anti isomers for 1-3 in solution which interconvert at ambient temperature. Complexes 1-4 have a weak MLCT absorption band in the 350-450 nm region and display a yellow-orange emission when irradiated by UV light. One unexpected finding is that the yellow-orange emission of complexes 1-4 has a very long decay lifetime (approximately 200 micros) at 77 K. An electroluminescent (EL) device using 4 as the emitter and PVK as the host was fabricated. However, the long decay lifetime of the copper complexes may limit their applications as phosphorescent emitters in EL devices.     

Syntheses and crystal structures of dinuclear complexes containing d-block and f-block luminophores. Sensitization of NIR luminescence from Yb(III), Nd(III), and Er(III) centers by energy transfer from Re(I)- and Pt(II)-bipyrimidine metal centers

Mononuclear complexes [Re(bpym)(CO)(3)Cl] and [Pt(bpym)(CC-C(6)H(4)CF(3))(2)] (bpym = 2,2'-bipyrimidine), in which one of the bipyrimidine sites is vacant, have been used as "complex ligands" to prepare heterodinuclear d-f complexes in which a lanthanide tris(1,3-diketonate) unit is attached to the secondary bipyrimidine site to evaluate the ability of d-block chromophores to act as antennae for causing sensitized near-infrared (NIR) luminescence from adjacent lanthanide(III) centers. The two sets of complexes so prepared are [Re(CO)(3)Cl(mu-bpym)Ln(fod)(3)] (abbreviated as Re-Ln; where Ln = Yb, Nd, Er) and [(F(3)C-C(6)H(4)-CC)(2)Pt(mu-bpym)Ln(hfac)(3)] (abbreviated as Pt-Ln; where Ln = Nd, Gd). Members of both series have been structurally characterized; the metal-metal separation across the bipyrimidine bridge is approximately 6.3 A in each case. In these complexes, the (3)MLCT (MLCT = metal to ligand charge-transfer) luminescences of the mononuclear [Re(bpym)(CO)(3)Cl] and [Pt(bpym)(CC-C(6)H(4)CF(3))(2)] complexes are quenched by energy transfer to those lanthanides (Ln = Yb, Nd, Er) that have low-lying f-f states capable of NIR luminescence; as a result, sensitized NIR luminescence is seen from the lanthanide center following excitation of the d-block unit. In the solid state, quenching of the luminescence from the d-block chromophore is complete, indicating efficient d --> f energy transfer, as a result of the short metal-metal separation across the bipyrimidine bridge. In a CH(2)Cl(2) solution, partial dissociation of the dinuclear complexes into the mononuclear units occurs, with the result that some (3)MLCT luminescence is observed from mononuclear [Re(bpym)(CO)(3)Cl] or [Pt(bpym)(CC-C(6)H(4)CF(3))(2)] present in the equilibrium mixture. Solution UV-vis and luminescence titrations, carried out by the addition of portions of Ln(fod)(3)(H(2)O)(2) or Ln(hfac)(3)(H(2)O)(2) to the d-block complex ligands, indicate that binding of the lanthanide tris(1,3-diketonate) unit at the secondary bipyrimidine site to give the d-f dinuclear complexes occurs with an association constant of ca. 10(5) M(-)(1).     

Generation of AuPd22/Au2Pd21 analogues of the high-nuclearity Pd23(CO)20(PEt3)10 cluster containing 19-atom centered hexacapped-cuboctahedral (nu 2-octahedral) metal fragment: structural-to-synthesis approach concerning formation of Au2Pd21(CO)20(PEt3)10

Reactions of Pd(PEt(3))(2)Cl(2) and Au(PPh(3))Cl in DMF with NaOH under CO atmosphere gave rise to the unique capped three-shell homopalladium Pd(145)(CO)(x)(PEt(3))(30)(x approximately 60) and two neutral Au-Pd clusters: Au(2)Pd(21)(CO)(20)(PEt(3))(10) (1) and Au(2)Pd(41)(CO)(27)(PEt(3))(15)(following article). Similar reactions with Pd(PMe(3))(2)Cl(2) being used in place of Pd(PEt(3))(2)Cl(2) afforded Au(2)Pd(21)(CO)(20)(PMe(3))(10) (2), the trimethylphosphine analogue of, and the electronically equivalent [AuPd(22)(CO)(20)(PPh(3))(4)(PMe(3))(6)](-) monoanion (3) as the [PPh(4)](+) salt. Each of these three air-sensitive 23-atom heterometallic Au-Pd clusters was obtained in low yields (7-25%); however, their geometrical similarities with the known cuboctahedral-based homopalladium Pd(23)(CO)(20)(PEt(3))(10) (4), recently obtained in good yields from Pd(10)(CO)(12)(PEt(3))(6), suggested an alternative preparative route for obtaining. This "structure-to-synthesis" approach afforded 1 in 60-70% yields from reactions of Pd(10)(CO)(12)(PEt(3))(6) and Au(PPh(3))Cl in DMF with NaOH under N(2) atmosphere. Both the compositions and atomic arrangements for 1, 2 and 3 were unambiguously established from low-temperature single-crystal CCD X-ray crystallographic determinations in accordance with their nearly identical IR carbonyl frequencies. Cluster 1 was also characterized by (31)P[(1)H] NMR, cyclic voltammetry (CV) and elemental analysis. The virtually identical Au(2)Pd(21) core-architectures of 1 and 2 closely resemble that of 4, which consists of a centered hexa(square capped)-cuboctahedral Pd(19) fragment of pseudo-O(h) symmetry that alternatively may be viewed as a centered Pd(19)nu(2)-octahedron (where nu(n) designates (n + 1) equally spaced atoms along each edge). [AuPd(22)(CO)(20)(PPh(3))(4)(PMe(3))(6)](-) (3) in the crystalline state ([PPh(4)](+) salt) consists of two crystallographically independent monoanions 3A and 3B; a superposition analysis ascertained that their geometries are essentially equivalent. A CV indicates that reversibly undergoes two one-electron reductions and two one-electron oxidations; these reversible redox processes form the basis for an integrated structural/electronic picture that is compatible with the existence of the electronically-equivalent 1-3 along with the electronically-nonequivalent 4 (with two fewer CVEs) and other closely related species.     

Cytotoxic gold compounds: synthesis, biological characterization and investigation of their inhibition properties of the zinc finger protein PARP-1

The new gold(III) complexes: [Au{2-(2'-pyridyl)imidazolate}Cl(2)] and [Au{2,6-bis(2'-benzimidazolate)pyridine}(OCOCH(3))] and the mono- and binuclear gold(I) complexes: [Au{2-(2'-pyridyl)imidazole}(PPh(3))](PF(6)), [Au(2-phenylimidazolate)(DAPTA)] (DAPTA = 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane), [(PPh(3)Au)(2)(2-R-imidazolate)](PF(6)) (R = 2-C(5)H(4)N, Ph) have been synthesized and characterized. The structure of the [(PPh(3)Au)(2){2-(2'-pyridyl)imidazolate)](PF(6)) complex was also characterized by X-ray crystallography. The antiproliferative properties of the complexes were assayed against human ovarian carcinoma cell lines, either sensitive (A2780) or resistant to cisplatin (A2780cisR), human mammary carcinoma cells (MCF7) and non-tumorigenic human kidney (HEK293) cells. Most of the studied compounds showed important cytotoxic effects. Interestingly, the compounds containing the 2-(2'-pyridyl)imidazolate ligand showed selectivity towards cancer cells with respect to the non-tumorigenic ones, with the dinuclear compound [(PPh(3)Au)(2){2-(2'-pyridyl)imidazolate)](PF(6)) being the most active. Some compounds were also screened for their inhibitory effect of the zinc-finger protein PARP-1, essential for DNA repair and relevant to the mechanisms of cancer cell resistance to cisplatin. Interaction studies of the compounds with the model protein ubiquitin were undertaken by electrospray ionization mass spectrometry (ESI MS). The results are discussed in relation to the putative mechanisms of action of the cytotoxic gold compounds.     

Syntheses and structures of dinuclear gold(I) dithiophosphonate complexes and the reaction of the dithiophosphonate complexes with phosphines: diverse coordination types

The dinuclear gold(I) dithiophosphonate complex, [Au(2)(dtp)(2)] (1), where dtp = [S(2)P(R)(OR')](-) with R = p-C(6)H(4)OCH(3); R'= c-C(5)H(9), has been synthesized and its reaction studied with the phosphine ligands PPh(3) and Ph(2)P(CH(2))(n)PPh(2) (n = 1-4). Compound 1 contains two gold atoms homobridged by the anionic dithiophosphonate ligand, forming an eight-membered ring complex in a chair form. After the reaction of 1 with diphosphine ligands, the dinuclear open-ring complexes Au(2)(dppm)(dtp)(2) (2), Au(2)(dppe)(dtp)(2) (3), Au(2)(dppp)(dtp)(2) (4), Au(2)(dppb)(dtp)(2) (5) were formed (dppm = diphenylphosphinomethane; dppe = diphenylphosphinoethane; dppp = diphenylphosphinopropane; dppb = diphenylphosphinobutane). The reaction with dppm is stoichiometry-dependent. Thus, when 1 reacts with 2 equiv of dppm, the ionic complex [Au(2)(dppm)(2)(dtp)]dtp forms. This dtp counterion was exchanged with tetrafluoroborate to yield [Au(2)(dppm)(2)(dtp)]BF(4), the crystallization of which afforded two interconvertible isomers, 6-yellow and 7-white. Reaction of 1 with PPh(3) affords the tetracoordinate mononuclear complex [Au(dtp)(PPh(3))(2)] (8). The molecular structures of 1-8 were confirmed by X-ray crystallography and show multiple coordination modes and geometries. The crystal structures of 1 and its reaction products with dppm (2, 6, 7) show short intramolecular Au.Au aurophilic bonding interactions of 2.95-3.10 A while no intermolecular interactions were discernible. However, reaction products of 1 with longer-chain Ph(2)P(CH(2))(n)PPh(2) ligands, n = 2-4, exhibit structures that lack both intra- and intermolecular Au.Au interactions.     

Polycarbide nickel clusters containing interstitial Ni(eta2-C2)4 and Ni2(micro-eta2-C2)4 acetylide moieties: mimicking the supersaturated Ni-C solutions preceding the catalytic growth of CNTs with the structures of [HNi25(C2)4(CO)32]3- and [Ni22(C2)4(CO)28Cl]3-

Reaction of [Ni(6)(CO)(12)](2-) with CCl(4) in CH(2)Cl(2) gives the [HNi(25)(C(2))(4)(CO)(32)](3-) and [Ni(22)(C(2))(4)(CO)(28)Cl](3-) carbonyl clusters containing interstitial Ni(eta(2)-C(2))(4) and Ni(2)(micro-eta(2)-C(2))(4) acetylide moieties.     

Transition metal complexes of the chelating phosphine borane ligand Ph2PCH2Ph2P.BH3

Chromium and ruthenium complexes of the chelating phosphine borane H(3)B.dppm are reported. Addition of H(3)B.dppm to [Cr(CO)(4)(nbd)](nbd = norbornadiene) affords [Cr(CO)(4)(eta1-H(3)B.dppm)] in which the borane is linked to the metal through a single B-H-Cr interaction. Addition of H(3)B.dppm to [CpRu(PR(3))(NCMe)(2)](+)(Cp =eta5)-C(5)H(5)) results in [CpRu(PR(3))(eta1-H(3)B.dppm)][PF(6)](R = Me, OMe) which also show a single B-H-Ru interaction. Reaction with [CpRu(NCMe)(3)](+) only resulted in a mixture of products. In contrast, with [Cp*Ru(NCMe)(3)](+)(Cp*=eta5)-C(5)Me(5)) a single product is isolated in high yield: [Cp*Ru(eta2-H(3)B.dppm)][PF(6)]. This complex shows two B-H-Ru interactions. Reaction with L = PMe(3) or CO breaks one of these and the complexes [Cp*Ru(L)(eta1-H(3)B.dppm)][PF(6)] are formed in good yield. With L = MeCN an equilibrium is established between [Cp*Ru(eta2-H(3)B.dppm)][PF(6)] and the acetonitrile adduct. [Cp*Ru (eta2-H(3)B.dppm)][PF(6)] can be considered as being "operationally unsaturated", effectively acting as a source of 16-electron [Cp*Ru (eta1-H(3)B.dppm)][PF(6)]. All the new compounds (apart from the CO and MeCN adducts) have been characterised by X-ray crystallography. The solid-state structure of H(3)B.dppm is also reported.     

Complexes of substituted derivatives of 2-(2-pyridyl)benzimidazole with Re(I), Ru(II) and Pt(II): structures, redox and luminescence properties

N,N'-Chelating ligands based on the 2-(2-pyridyl)benzimidazole (PB) core have been prepared with a range of substituents (phenyl, pentafluorophenyl, naphthyl, anthracenyl, pyrenyl) connected to the periphery via alkylation of the benzimidazolyl unit at one of the N atoms. These PB ligands have been used to prepare a series of complexes of the type [Re(PB)(CO)(3)Cl], [Pt(PB)(CCR)(2)](where -CCR is an acetylide ligand) and [Ru(bpy)(2)(PB)][PF(6)](2)(bpy = 2,2'-bipyridine). Six of the complexes have been structurally characterised. Electrochemical and luminescence studies show that all three series of complexes behave in a similar manner to the analogous complexes with 2,2'-bipyridine in place of PB. In particular, all three series of complexes show luminescence in the range 553-605 nm (Pt series), 620-640 nm (Re series) and 626-645 nm (Ru series) arising from the (3)MLCT state, with members of the Pt(II) series being the most strongly emissive with lifetimes of up to 500 ns and quantum yields of up to 6% in air-saturated CH(2)Cl(2) at room temperature. In the Re and Ru series there was clear evidence for inter-component energy-transfer processes in both directions between the (3)MLCT state of the metal centre and the singlet and triplet states of the pendant organic luminophores (naphthalene, pyrene, anthracene). For example the pyrene singlet is almost completely quenched by energy transfer to a Re-based MLCT excited state, which in turn is completely quenched by energy transfer to the lower-lying pyrene triplet state. For the analogous Ru(II) complexes the inter-component energy transfer is less effective, with (1)anthracene --> Ru((3)MLCT) energy transfer being absent, and Ru((3)MLCT)-->(3)anthracene energy transfer being incomplete. This is rationalised on the basis of a greater effective distance for energy transfer in the Ru(II) series, because the MLCT excited states are localised on the bpy ligands which are remote from the pendant aromatic group; in the Re series in contrast, the MLCT excited states involve the PB ligand to which the pendant aromatic group is directly attached, giving more efficient energy transfer.     

Syntheses,reactivity, and crystal structures of molybdenum complexes with pyridine-2-thionate (pyS)-containing ligands: crystal structures of [Mo(eta(3)-C(3)H(5))(CO)(2)](2)(mu-eta(1),eta(2)-pyS)(2), exo-[Mo(eta(3)-C(3)H(5))(CO)(eta(2)-pyS)(eta(2)-dppe)], [Mo(CO)(3)(eta(1)-SC(5)H(4)NH)(eta(2)-dppm)], and [Mo(CO)(eta(2)-pyS)(2)(eta(2)-dppm)

The doubly bridged pyridine-2-thionate (pyS) dimolybdenum complex [Mo(eta(3)-C(3)H(5))(CO)(2)](2)(mu-eta(1),eta(2)-pyS)(2) (1) is accessible by the reaction of [Mo(eta(3)-C(3)H(5))(CO)(2)(CH(3)CN)(2)Br] with pySK in methanol at room temperature. Complex 1 reacts with piperidine in acetonitrile to give the complex [Mo(eta(3)-C(3)H(5))(CO)(2)(eta(2)-pyS)(C(5)H(10)NH)] (2). Treatment of 1 with 1,10-phenanthroline (phen) results in the formation of complex [Mo(eta(3)-C(3)H(5))(CO)(2)(eta(1)-pyS)(phen)] (3), in which the pyS ligand is coordinated to Mo through the sulfur atom. Four conformational isomers, endo,exo-complexes [Mo(eta(3)-C(3)H(5))(CO)(eta(2)-pyS)(eta(2)-diphos)] (diphos = dppm, 4a-4d; dppe, 5a-5d), are accessible by the reactions of 1 with dppm and dppe in refluxing acetonitrile. Homonuclear shift-correlated 2-D (31)P((1)H)-(31)P((1)H) NMR experiments of the mixtures 4a-4d have been employed to elucidate the four stereoisomers. The reaction of 4 and pySK or [Mo(CO)(3)(eta(1)-SC(5)H(4)NH)(eta(2)-dppm)] (6) and O(2) affords allyl-displaced seven-coordinate bis(pyridine-2-thionate) complex [Mo(CO)(eta(2)-pyS)(2)(eta(2)-dppm)] (7). All of the complexes are identified by spectroscopic methods, and complexes 1, 5d, 6, and 7 are determined by single-crystal X-ray diffraction. Complexes 1 and 5d crystallize in the orthorhombic space groups Pbcn and Pbca with Z = 4 and 8, respectively, whereas 6 belongs to the monoclinic space group C2/c with Z = 8 and 7 belongs to the triclinic space group Ponemacr; with Z = 2. The cell dimensions are as follows: for 1, a = 8.3128(1) A, b = 16.1704(2) A, c = 16.6140(2) A; for 5d, a = 17.8309(10) A, b = 17.3324(10) A, c = 20.3716(11) A; for 6, a = 18.618(4) A, b = 16.062(2) A, c = 27.456(6) A, beta = 96.31(3) degrees; for 7, a = 9.1660(2) A, b = 12.0854(3) A, c = 15.9478(4) A, alpha = 78.4811(10) degrees, beta = 80.3894(10) degrees, gamma = 68.7089(11) degrees.