Synthesis and DNA-binding properties of cationic 2,2':6',2' '-terpyridineplatinum(II) complexes containing 1,2- and 1,7-dicarba-closo-dodecaborane(12)

The first examples of DNA metallointercalators containing a dicarba-closo-dodecaborane(12) (carborane) moiety are presented. Treatment of the labile platinum(II) complex [Pt(OTf)(terpy)](+) (terpy = 2,2':6',2' '-terpyridine) with the 1,2-carborane monothiol derivatives 1-HS(CH(2))(n)-1,2-C(2)B(10)H(11) (n = 0, 1) or the novel 1,7-carborane ligand, 1-HSCH(2)-1,7-C(2)B(10)H(11), affords the stable, brightly colored species [Pt(1-S(CH(2))(n)-1,Z-C(2)B(10)H(11))(terpy)](+) (Z = 2, n = 0, 1; Z = 7, n = 1) in good yield and purity. Preliminary DNA-binding experiments with calf-thymus DNA indicate an intercalative interaction by the platinum(II) complexes at high r(f) values.     

Selective complexation of uranium(III) over lanthanide(III) triflates by 2,2':6',2"-terpyridine. X-Ray crystal structures of [M(OTf)3(terpy)2] and [M(OTf)2(terpy)2(py)][OTf](M = Nd, Ce, U) and of polynuclear mu-oxo uranium(IV) complexes resulting from hydrolysis

Reactions of Ln(OTf)3(Ln = Ce, Nd) or [U(OTf)3(dme)2](OTf = OSO2CF3, dme = dimethoxyethane) with 2 mol equivalents of 2,2':6',2"-terpyridine (terpy) in pyridine or acetonitrile led to the quantitative formation of the bis(terpy) complexes which crystallized as the discrete cation-anion pairs [M(OTf)2(terpy)2(py)][OTf] x 0.5py from pyridine or neutral derivatives [M(OTf)3(terpy)2] x nMeCN from acetonitrile (M = Ce, Nd, U). The crystal structures of these complexes show the differences in the M-O bond lengths to follow the variation of the ionic radii of the metals, while the U-N(terpy) and U-N(py) bonds are shorter than those expected from a purely ionic bonding model. The better affinity of terpy for U(III) over Ce(III) and Nd(III) was evidenced by the thermodynamic parameters (K, DeltaH, DeltaS) corresponding to the equilibrium between the bis- and tris(terpy) complexes in acetonitrile. Hydrolysis of the bis(terpy) compounds followed different courses; whereas the aquo compound [Ce(OTf)2(terpy)2(H2O)][OTf] crystallized readily from pyridine, the uranium complexes [UX2(terpy)2(py)]X (X = I, OTf) were oxidized into the tri- and tetranuclear mu-oxo U(IV) compounds [{UI(terpy)2(mu-O)}2{UI2(terpy)}]I4 x 2MeCN x H2O and [{U(OTf)(terpy)2(mu-O)(mu-OTf)U(terpy)}2(mu-OTf)2(mu-O)][OTf]4 x py x MeCN. The crystal structures of these first examples of uranium(IV) compounds with terpy ligands show the almost linear arrangement of the metal atoms.     

Two new terpyridine dimanganese complexes: a manganese(III,III) complex with a single unsupported oxo bridge and a manganese(III,IV) complex with a dioxo bridge. Synthesis, structure, and redox properties

Two new terpyridine dimanganese oxo complexes [Mn(2)(III,IV)(mu-O)(2)(terpy)(2)(CF(3)CO(2))(2)](+) (3) and [Mn(2)(III,III)(mu-O)(terpy)(2)(CF(3)CO(2))(4)] (4) (terpy = 2,2':6,2' '-terpyridine) have been synthesized and their X-ray structures determined. In contrast to the corresponding mixed-valent aqua complex [Mn(2)(III,IV)(mu-O)(2)(terpy)(2)(H(2)O)(2)](3+) (1), the two Mn atoms in 3 are not crystallographically equivalent. The neutral binuclear monooxo manganese(III,III) complex 4 exhibits two crystallographic forms having cis and trans configurations. In the cis complex, the two CF(3)CO(2)(-) ligands on each manganese adopt a cis geometry to each other; one CF(3)CO(2)(-) is trans to the oxygen of the oxo bridge while the second is cis. In the trans complex, the two coordinated CF(3)CO(2)(-) have a trans geometry to each other and are cis to the oxo bridge. The electrochemical behavior of 3 in organic medium (CH(3)CN) shows that this complex could be oxidized into its corresponding stable manganese(IV,IV) species while its reduced form manganese(III,III) is very unstable and leads by a disproportionation process to Mn(II) and Mn(IV) complexes. Complex 4 is only stable in the solid state, and it disproportionates spontaneously in CH(3)CN solution into the mixed-valent complex 3 and the mononuclear complex [Mn(II)(terpy)(2)](2+) (2), thereby preventing the observation of its electrochemical behavior.     

Multinuclear platinum(II)-amine complexes containing bis(aminopropyl)dicarba-closo-dodecaborane(12) ligands

Treatment of the bridging bidentate 1,Z-bis(aminopropyl)-1,Z-dicarba-closo-dodecaborane(12)(1,Z-bis(aminopropyl)-1,Z-carborane) ligands of the type 1,Z-[H(2)N(CH(2))(3)](2)-1,Z-C(2)B(10)H(10)(L(1), Z= 7, 5) or (L(2), Z= 12, 6) with two equivalents of trans-[PtClI(2)(NH(3))](-), followed by halogen ligand metathesis with AgOTf and HCl((aq)) afforded the novel diplatinum(II)-amine species cis-[[PtCl(2)(NH(3))](2)L(n)](7(n= 1) or 8(n= 2), respectively). Similarly, the reaction of L(1) or L(2) with the labile trans-[PtCl(dmf)(NH(3))(2)](+) afforded trans-[[PtCl(NH(3))(2)](2)L(n)](OTf)(2)(9(n= 1) or 10(n= 2), respectively) in good yield and purity. However, isolation of the analogous 1,2-carborane complexes was not possible owing to decomposition reactions that led to extensive degradation of the carborane cage and reduction of the metal centre. The mixed dinuclear complex [cis-[PtCl(2)(NH(3))]-L(1)-trans-[PtCl(NH(3))(2)]]OTf (19) was prepared by treatment of the Boc-protected amine ligand 1-[(Boc)(2)N(CH(2))(3)]-7-[H(2)N(CH(2))(3)]-1,7-C(2)B(10)H(10)(L(3), 15) with trans-[PtCl(dmf)(NH(3))(2)](+) to yield trans-[PtCl(NH(3))(2)L(3)]OTf (16), followed by acid deprotection of the pendant amine group, complexation with trans-[PtClI(2)(NH(3))](-), and halogen ligand metathesis using AgOTf and HCl((aq)). A novel trinuclear species containing 5 was prepared by the addition of two equivalents of 15 to the labile precursor cis-[Pt(dmf)(2)(NH(3))(2)](2+) followed by acid deprotection of the pendant amine groups. Further complexation with two equivalents of trans-[PtClI(2)(NH(3))](-) followed by halogen ligand metathesis using AgOTf and HCl((aq)) afforded the triplatinum(II)-amine species [cis-[Pt(NH(3))(2)(L(1))(2)]-cis-[PtCl(2)(NH(3))](2)](OTf)(2)(23). Complexes 7-10, 19 and 23 represent the first examples of multinuclear platinum(ii)-amine derivatives containing carborane cages. Preliminary in vitro cytotoxicity studies for selected complexes are also reported.     

New [Mo(eta3-allyl)(CO)2L3]+ complexes with monodentate or tridentate nitrogen-donor ligands

Cationic complexes [Mo(eta(3)-allyl)(CO)2L3]+ (L3 = either nitrogen-donor tridentate ligand or three monodentate ligands) were prepared in high yield and under mild conditions using as precursors either the triflato complex [Mo(eta(3)-allyl)(OTf)(CO)2(NCMe)2] or the combination of the chloro complex [Mo(eta(3)-allyl)Cl(CO)2(NCMe)2] and the salt NaBAr'(4)(Ar'= 3,5-bis(trifluoromethyl)phenyl). The tridentate ligands employed were 2,2':6',2'-terpyridine (terpy) and cis,cis-1,3,5-cyclohexanetriamine (CHTA), whereas the monodentate ligands imidazole (im) and 3,5-dimethylpyrazole (dmpz) were chosen. In order to stabilize the labile intermediates, an excess of acetonitrile was used in most of the syntheses. However, the pyrazole complex was prepared through a nitrile-free route to avoid reactions at the coordinated nitrile. The solid state structures of [Mo(eta(3)-methallyl)(CO)2(terpy)]OTf (2), [Mo(eta(3)-methallyl)(CO)2(CHTA)]BAr'4 (3), [Mo(eta(3)-methallyl)(CO)2(NCMe)3]BAr'4 (4), [Mo(eta(3)-allyl)(CO)2(im)3]OTf (5) and [Mo(eta(3)-allyl)(CO)2(dmpz)3]BAr'4 (6) were determined by means of single-crystal X-ray diffraction.     

(2,2':6',2' '-Terpyridine)platinum(II) complexes containing (thioalkyl)dicarba-closo-dodecaborane(12) ligands

A series of novel platinum(II)-2,2':6',2' '-terpyridine (trpy) complexes containing (thioalkyl)dicarba-closo-dodecaborane(12) (closo-carborane) derivatives were prepared by treatment of the labile precursor species [Pt(MeCN)(trpy)](OTf)2 with R(CH2)nSH (R = closo-1,2-carborane, n = 0-3; R = closo-1,7-carborane, n = 1; R = closo-1,12-carborane, n = 1) in the presence of NEt3 to afford brightly colored complexes of the type [PtS(CH2)nR(trpy)]OTf. All products were characterized by means of multinuclear (1H, 13C, 11B, and 195Pt) 1D- and 2D-NMR spectroscopy, ESI-MS, and, for the 1,7-carborane derivative, X-ray crystallography. Preliminary in vitro cytotoxicity studies of selected complexes against human ovarian carcinoma cells are also reported.     

From model compounds to protein binding: syntheses, characterizations and fluorescence studies of [RuII(bipy)(terpy)L]2+ complexes (bipy = 2,2'-bipyridine; terpy = 2,2':6',2''-terpyridine; L = imidazole, pyrazole and derivatives, cytochrome c)

Compounds [RuII(bipy)(terpy)L](PF6)2 with bipy = 2,2'-bipyridine, terpy = 2,2':6',2"-terpyridine, L = H2O, imidazole (imi), 4-methylimidazole, 2-methylimidazole, benzimidazole, 4,5-diphenylimidazole, indazole, pyrazole, 3-methylpyrazole have been synthesized and characterized by 1H NMR, ESI-MS and UV/Vis (in CH3CN and H2O). For L = H2O, imidazole, 4,5-diphenylimidazole and indazole the X-ray structures of the complexes have been determined with the crystal packing featuring only few intermolecular C-H...pi or pi-pi interactions due to the separating action of the PF6-anions. Complexes with L = imidazole and 4-methylimidazole exhibit a fluorescence emission with a maximum at 662 and 667 nm, respectively (lambdaexc= 475 nm, solvent CH3CN or H2O). The substitution of the aqua ligand in [Ru(bipy)(terpy)(H2O)]2+ in aqueous solution by imidazole to give [Ru(bipy)(terpy)(imi)]2+ is fastest at a pH of 8.5 (as followed by the increase in emission intensity). Coupling of the [Ru(bipy)(terpy)]2+ fragment to cytochrome c(Yeast iso-1) starting from the Ru-aqua complex was successful at 35 degrees C and pH 7.0 after 5 d under argon in the dark. The [Ru(bipy)(terpy)(cyt c)]-product was characterized by UV/Vis, emission and mass spectrometry. The location where the [Ru(bipy)(terpy)] complex was coupled to the protein was identified as His44 (corresponding to His39 in other numbering schemes) using digestion of the Ru-coupled protein by trypsin and analysis of the tryptic peptides by HPLC-high resolution MS.     

Dimer-of-dimers model for the oxygen-evolving complex of photosystem II. Synthesis and properties of [MnIV4O5(terpy)4(H2O)2](ClO4)6

A dimer-of-dimers model compound for the oxygen-evolving complex of photosystem II, [[(H(2)O)(terpy)Mn(IV)(micro-O)(2)Mn(IV)(terpy)](2)(micro-O)](ClO(4))(6) (terpy = 2,2':6',2' '-terpyridine), has been prepared and characterized by X-ray crystallography and ESI-MS. Low pH was found to promote the disproportionation of [Mn(III/IV)(2)O(2)(terpy)(2)(OH(2))(2)](3+) to Mn(2+) and a Mn(IV/IV)(2)O(2)(terpy)(2) species; the latter complex slowly dimerizes to form the title complex. Protonation of a micro-oxo bridge is proposed to initiate the disproportionation, based on analogy with the [Mn(III/)(IV)(2)O(2)(bpy)(4)](3+) system.     

Reactivity at the beta-diketiminate ligand Nacnac- on titanium(IV) (Nacnac- = [Ar]NC(CH3)CHC(CH3)N[Ar], Ar = 2,6-[CH(CH3)2]2C6H3). Diimine-alkoxo and bis-anilido ligands stemming from the Nacnac- skeleton

The reaction of ketene OCCPh(2) with the four-coordinate titanium(IV) imide (L(1))Ti[double bond]NAr(OTf) (L(1)(-) = [Ar]NC(CH(3))CHC(CH(3))N[Ar], Ar = 2,6-[CH(CH(3))(2)](2)C(6)H(3)) affords the tripodal dimine-alkoxo complex (L(2))Ti[double bond]NAr(OTf) (L(2)(-) = [Ar]NC(CH(3))CHC(O)[double bond]CPh(2)C(CH(3))N[Ar]). Complex (L(2))Ti[double bond]NAr(OTf) forms from electrophilic attack of the beta-carbon of the ketene on the gamma-carbon of the Nacnac(-) NCC(gamma)CN ring. On the contrary, nucleophiles such as LiR (R(-) = Me, CH(2)(t)Bu, and CH(2)SiMe(3)) deprotonate cleanly in OEt(2) the methyl group of the beta-carbon on the former Nacnac(-) backbone to yield the etherate complex (L(3))Ti[double bond]NAr(OEt(2)), a complex that is now supported by a chelate bis-anilido ligand (L(3)(2)(-) = [Ar]NC(CH(3))CHC(CH(2))N[Ar]). In the absence of electrophiles or nucleophiles, the robust (L(1))Ti[double bond]NAr(OTf) template was found to form simple adducts with Lewis bases such as CN(t)Bu or NCCH(2)(2,4,6-Me(3)C(6)H(2)). Complexes (L(2))Ti[double bond]NAr(OTf), (L(3))Ti[double bond]NAr(OEt(2)), and the adducts (L(1))Ti[double bond]NAr(OTf)(XY) [XY = CN(t)Bu and NCCH(2)(2,4,6-Me(3)C(6)H(2))] were structurally characterized by single-crystal X-ray diffraction studies.     

Substitution reactions of [Ru(dppe)(CO)(H(2)O)(3)][OTf](2)

The labile nature of the coordinated water ligands in the organometallic aqua complex [Ru(dppe)(CO)(H(2)O)(3)][OTf](2) (1) (dppe = Ph(2)PCH(2)CH(2)PPh(2); OTf = OSO(2)CF(3)) has been investigated through substitution reactions with a range of incoming ligands. Dissolution of 1 in acetonitrile or dimethyl sulfoxide results in the facile displacement of all three waters to give [Ru(dppe)(CO)(CH(3)CN)(3)][OTf](2) (2) and [Ru(dppe)(CO)(DMSO)(3)][OTf](2) (3), respectively. Similarly, 1 reacts with Me(3)CNC to afford [Ru(dppe)(CO)(CNCMe(3))(3)][OTf](2) (4). Addition of 1 equiv of 2,2'-bipyridyl (bpy) or 4,4'-dimethyl-2,2'-bipyridyl (Me(2)bpy) to acetone/water solutions of 1 initially yields [Ru(dppe)(CO)(H(2)O)(bpy)][OTf](2) (5a) and [Ru(dppe)(CO)(H(2)O)(Me(2)bpy)][OTf](2) (6a), in which the coordinated water lies trans to CO. Compounds 5a and 6a rapidly rearrange to isomeric species (5b, 6b) in which the ligated water is trans to dppe. Further reactivity has been demonstrated for 6b, which, upon dissolution in CDCl(3), loses water and coordinates a triflate anion to afford [Ru(dppe)(CO)(OTf)(Me(2)bpy)][OTf] (7). Reaction of 1 with CH(3)CH(2)CH(2)SH gives the dinuclear bridging thiolate complex [[(dppe)Ru(CO)](2)(mu-SCH(2)CH(2)CH(3))(3)][OTf] (8). The reaction of 1 with CO in acetone/water is slow and yields the cationic hydride complex [Ru(dppe)(CO)(3)H][OTf] (9) via a water gas shift reaction. Moreover, the same mechanism can also be used to account for the previously reported synthesis of 1 upon reaction of Ru(dppe)(CO)(2)(OTf)(2) with water (Organometallics 1999, 18, 4068).     

Spectroelectrochemistry and DFT analysis of a new {RuNO}n redox system with multifrequency EPR suggesting conformational isomerism in the {RuNO}7 state

The compound [Ru(NO)(bpym)(terpy)](PF6)3, bpym = 2,2'-bipyrimidine and terpy = 2,2':6',2"-terpyridine, with a {RuNO}6 configuration (angle Ru-N-O 175.2(4) degrees ) was obtained from the structurally characterized precursor [Ru(NO2)(bpym)(terpy)](PF6), which shows bpym-centered reduction and metal-centered oxidation, as evident from EPR spectroscopy. The relatively labile [Ru(NO)(bpym)(terpy)](3+), which forms a structurally characterized acetonitrile substitution product [Ru(CH3CN)(bpym)(terpy)](PF6)2 upon treatment with CH3OH/CH3CN, is electrochemically reduced in three one-electron steps of which the third, leading to neutral [Ru(NO)(bpym)(terpy)], involves electrode adsorption. The first-two reduction processes cause shifts of nu(NO) from 1957 via 1665 to 1388 cm(-1), implying a predominantly NO-centered electron addition. UV-vis-NIR Spectroscopy shows long-wavelength ligand-to-ligand charge transfer absorptions for [Ru(II)(NO(-I))(bpym)(terpy)]+ in the visible region, whereas the paramagnetic intermediate [Ru(NO)(bpym)(terpy)](2+) exhibits no distinct absorption maximum above 309 nm. EPR spectroscopy of the latter at 9.5, 95, and 190 GHz shows the typical invariant pattern of the {RuNO}7 configuration; however, the high-frequency measurements at 4 and 10 K reveal a splitting of the g1 and g2 components, which is tentatively attributed to conformers resulting from the bending of RuNO. DFT calculations support the assignments of oxidation states and the general interpretation of the electronic structure.     

Luminescent platinum(II) terpyridyl complexes: effect of counter ions on solvent-induced aggregation and color changes

A series of platinum(II) terpyridyl complexes [Pt(tpy)(C triple bond C-C triple bond CH)]X, 1-X (X=OTf-; PF6-; ClO4-; BF4-; BPh4-); [Pt(tpy)(C triple bond CC6H5)]X, 2-X (X=OTf-; PF6-; ClO4-; BF4-); [Pt(tpy)(C triple bond CC6H4OCH3-4)]OTf, 3-OTf, and [Pt(4'-CH3O-tpy)(C triple bond CC6H5)]OTf, 4-OTf (tpy=2,2':6',2'-terpyridine, OTf=trifluoromethanesulfonate) were synthesized and their photophysical properties determined. Electronic absorption and emission studies showed the formation of a new band upon increasing the diethyl ether content in an acetonitrile/diethyl ether mixture. This was ascribed to the formation of complex aggregates, the solution color of which is dependent on the nature of the anions. This indicates that counter ions play an important role in governing the degree of aggregation and the extent of interactions within these aggregates. Addition of various anions to solutions of 1-OTf and 1-PF6 produced anion-induced color changes upon solvent-induced aggregation, indicating that these complexes may serve as potential colorimetric anion probes.     

Substitution reactions of [Pt(terpy)X]2+ with some biologically relevant ligands. Synthesis and crystal structure of [Pt(terpy)(cyst-S)](ClO4)2.0.5H2O and [Pt(terpy)(guo-N7)](ClO4)2.0.5guo.1.5H2O

Substitution reactions of the complexes [Pt(terpy)(H(2)O)](2+), [Pt(terpy)(cyst-S)](2+) and [Pt(terpy)(guo-N(7))](2+), where terpy = 2,2':6',2"-terpyridine, cyst = L-cysteine and guo = guanosine, with some biologically relevant ligands such as inosine (INO), inosine-5'-monophosphate (5'-IMP), guanosine-5'-monophosphate (5'-GMP), l-cysteine, glutathione, thiourea, thiosulfate and diethyldithiocarbamate (DEDTC), were studied in aqueous 0.10 M NaClO(4) at pH 2.5 and 6.0 using variable-temperature and -pressure stopped-flow spectrophotometry. The reactions of [Pt(terpy)(H(2)O)](2+) with INO, 5'-IMP and 5'-GMP showed that these ligands are very good nucleophiles. The second order rate constants varied between 4 x 10(2) and 6 x 10(2) M(-1) s(-1) at 25 degree C. The [Pt(terpy)(cyst-S)](2+) complex is unreactive towards nitrogen donor nucleophiles, and cysteine cannot be replaced by N(7) from INO, 5'-IMP and 5'-GMP. However, sulfur donor nucleophiles such as thiourea, thiosulfate and diethyldithiocarbamate could displace the Pt-cysteine bond. Diethyldithiocarbamate is the best nucleophile and the order of reactivity is: thiourea < thiosulfate < DEDTC with rate constants of 0.936 +/- 0.002, 5.99 +/- 0.02 and 8.88 +/- 0.07 M(-1) s(-1) at 25 degree C, respectively. The reactions of [Pt(terpy)(guo-N(7))](2+) with sulfur donor ligands showed that these nucleophiles could substitute guanosine from the Pt(ii) complex, of which diethyldithiocarbamate and thiosulfate are the strongest nucleophiles. The tripeptide glutathione is also a very efficient nucleophile. Activation parameters (Delta H(++), Delta S(++) and Delta V(++)) were determined for all reactions. The crystal structures of [Pt(terpy)(cyst-S)](ClO(4))(2).0.5H(2)O and [Pt(terpy)(guo-N(7))](ClO(4))(2).0.5guo.1.5H(2)O were determined by X-ray diffraction. Crystals of [Pt(terpy)(cyst-S)](ClO(4))(2).0.5H(2)O are orthorhombic with the space group P2(1)2(1)2(1), whereas [Pt(terpy)(guo-N(7))](ClO(4))(2).0.5guo.1.5H(2)O crystallizes in the orthorhombic space group P2(1)2(1)2. A typical feature of terpyridine complexes can be found in both molecular structures: the Pt-N (central) bond distance, 1.982(7) and 1.92(2) A, respectively, is shorter than the other two Pt-N distances, being 2.043(7) and 2.034(7) A in [Pt(terpy)(cyst-S)](ClO(4))(2).0.5H(2)O and 2.03(2) and 2.04(2) A in [Pt(terpy)(guo-N(7))](ClO(4))(2).0.5guo.1.5H(2)O, respectively. In both crystal structures two symmetrically independent cations representing different conformers are present in the asymmetric unit. The results are analysed in reference to the antitumour activity of Pt(II) complexes, and the importance of the rescue agents are discussed.     

Hydride ion transfer from ruthenium(II) complexes in water: kinetics and mechanism

Reactions of hydride complexes of ruthenium(II) with hydride acceptors have been examined for Ru(terpy)(bpy)H(+), Ru(terpy)(dmb)H(+), and Ru(η(6)-C(6)Me(6))(bpy)(H)(+) in aqueous media at 25 °C (terpy = 2,2';6',2'-terpyridine, bpy = 2,2'-bipyridine, dmb = 4,4'-dimethyl-2,2'-bipyridine). The acceptors include CO(2), CO, CH(2)O, and H(3)O(+). CO reacts with Ru(terpy)(dmb)H(+) with a rate constant of 1.2 (0.2) × 10(1) M(-1) s(-1), but for Ru(η(6)-C(6)Me(6))(bpy)(H)(+), the reaction was very slow, k ≤ 0.1 M(-1) s(-1). Ru(terpy)(bpy)H(+) and Ru(η(6)-C(6)Me(6))(bpy)(H)(+) react with CH(2)O with rate constants of (6 ± 4) × 10(6) and 1.1 × 10(3) M(-1) s(-1), respectively. The reaction of Ru(η(6)-C(6)Me(6))(bpy)(H)(+) with acid exhibits straightforward, second-order kinetics, with the rate proportional to [Ru(η(6)-C(6)Me(6))(bpy)(H)(+)] and [H(3)O(+)] and k = 2.2 × 10(1) M(-1) s(-1) (μ = 0.1 M, Na(2)SO(4) medium). However, for the case of Ru(terpy)(bpy)H(+), the protonation step is very rapid, and only the formation of the product Ru(terpy)(bpy)(H(2)O)(2+) (presumably via a dihydrogen or dihydride complex) is observed with a k(obs) of ca. 4 s(-1). The hydricities of HCO(2)(-), HCO(-), and H(3)CO(-) in water are estimated as +1.48, -0.76, and +1.57 eV/molecule (+34, -17.5, +36 kcal/mol), respectively. Theoretical studies of the reactions with CO(2) reveal a "product-like" transition state with short C-H and long M-H distances. (Reactant) Ru-H stretched 0.68 ?; (product) C-H stretched only 0.04 ?. The role of water solvent was explored by including one, two, or three water molecules in the calculation.     

Dinuclear palladium(ii) complexes with bridging amidate ligands

New homonuclear dimeric Pd(ii) complexes have been synthesized by the reaction of Pd(en)(2+) or Pd(bipy)(2+) (where en = ethylenediamine and bipy = 2,2'-bipyridine) units with acetamide or by the Pd(ii) mediated hydrolysis of CH(3)CN. In these dimers the two metal centers are bridged by either two amidates or by the combination of one hydroxo group and one amidate ligand. The crystal structures of complexes {[Pd(bipy)](2)(micro-1,3-CH(3)CONH)(2)}(NO(3))(2).H(2)O.1/2(CH(3))(2)CO.1/2CH(3)CN () and {[Pd(bipy)](2)(micro-1,3-CH(3)CONH)(2)}(OTf)(2) () showed intrametallic Pd-Pd distances of 2.8480(8) A () and 2.8384(7) A (), respectively, in accordance with the accepted values for a strong Pd-Pd interaction. The presence of pi[dot dot dot]pi interactions between the bipyridine ligands on the di-micro-amidate complexes of Pd(bipy)(2+) shortens the distance between the two Pd centers and allows the formation of the metal-metal interaction. By contrast, the crystal structure of complex {[Pd(en)](2)(micro-1,3-CH(3)CONH)(2)}(OTf)(2).H(2)O (), (where OTf = triflate) where there is no pi[dot dot dot]pi interaction between the ligands on the metal centers, is also reported, and no Pd-Pd interaction is observed. Additionally, one of the complexes, {[Pd(en)](2)(micro-OH)(micro-CH(3)CONH)}(NO(3))(2) (), presents an interesting hydrogen bonded 3-D network formed by nitrate ions and water molecules. All complexes have been characterized by infrared and (1)H NMR spectroscopy.     

Deprotonation of cationic tungsten(IV) aqua-oxo-alkyne complexes to form dioxo-vinyl tungsten(VI) complexes

Chiral tungsten(IV) aqua-oxo-alkyne complexes, [Tp'W(O)(H2O)(RC identical to CR)][OTf] (R = H (1); R = Me (2)); (Tp' = hydridotris(3,5-dimethylpyrazolyl)borate; OTf = trifluoromethanesulfonate), have been prepared by halide abstraction from iodide precursors. These cationic complexes have been characterized with triflate as the counteranion. The tautomeric dihydroxo isomer has not been observed. The neutral triflate adduct Tp'W(O)(OTf)(HC identical to CH) (3) has also been isolated. Cationic complexes 1 and 2 undergo deprotonation and isomerization when exposed to Al2O3 to give the dioxo-vinyl compounds Tp'W(O)2(CH=CH2) (6) and Tp'W(O)2[C(Me)=C(H)(Me)] (7), reflecting the conversion of the WIV(OH)(RC identical to CR) fragment to WVI(=O)(RC=CHR). The presumed intermediates, neutral oxo-hydroxo compounds Tp'W(O)(OH)(RC identical to CR) (R = H (9); R = Me (10)), can be accessed by deprotonation of 1 or 2 with NaOH. Conversion of 9 to 6 was achieved thermally upon heating at 100 degrees C for 2 days. X-ray structural data have provided solid-state structures of both the cationic aqua complex 2 and the dioxo-vinyl complex 6.     

Platinum(II) hydrazido complexes

Reaction of 1,2-dimethylhydrazine with the platinum hydroxo complex [(dppp)Pt(mu-OH)](2)(BF(4))(2) gives the bridging 1,2-dimethylhydrazido(-2) product [(dppp)(2)Pt(2)(mu-eta(2):eta(2)-MeNNMe)](BF(4))(2) 1. Crystals of 1.CH(2)Cl(2) from CH(2)Cl(2)/Et(2)O are monoclinic (C/2) with a = 19.690(1), b = 18.886(1), c = 17.170 (1) A, and beta = 92.111(1) degrees. Treatment of [(dppp)Pt(mu-OH)](2)(OTf)(2) with 1,1-dimethylhydrazine gives [(dppp)(2)Pt(2)(mu-OH)(mu-NHNMe(2))](OTf)(2) 2. Crystals of 2.CH(2)Cl(2) from CH(2)Cl(2)/Et(2)O are triclinic (P-1) with a = 12.910 (3), b = 13.927(3), c = 17.5872 (3) A, alpha = 87.121(3), beta = 89.997(4), and gamma = 84.728(3) degrees. Reaction of [(dppp)Pt(mu-OH)](2)(OTf)(2) with 1 equiv of phenylhydrazine in CH(2)Cl(2) gives [(dppp)(2)Pt(2)(mu-OH)(mu-NHNHPh)](OTf)(2) 3. Two equivalents of phenylhydrazine with [(dppp)Pt(mu-OH)](2)(X)(2) gives [(dppp)Pt(mu-NHNHPh)](2)(X)(2) 4 (X = BF(4), OTf). Crystals of 3.ClCH(2)CH(2)Cl from ClCH(2)CH(2)Cl/(i)()Pr(2)O are monoclinic (P2(1)/n) with a = 20.990(2), b = 13.098(1), c = 25.773 (2) A, and beta = 112.944(2) degrees. Crystals of 4(X = BF(4)).ClCH(2)CH(2)Cl(.)()2((t)()BuOMe) from ClCH(2)CH(2)Cl/(t)()BuOMe are monoclinic (C2/m) with a = 30.508(1), b = 15.203(1), c = 19.049 (1) A, and beta = 118.505(2) degrees.     

Osmabenzenes from the reactions of a dicationic osmabenzyne complex

Treatment of the osmabenzyne Os([triple bond]CC(SiMe(3))=C(Me)C(SiMe(3))=CH)Cl(2)(PPh(3))(2) (1) with 2,2'-bipyridine (bipy) and thallium triflate (TlOTf) produces the thermally stable dicationic osmabenzyne [Os([triple bond]CC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)](OTf)(2) (2). The dicationic osmabenzyne 2 reacts with ROH (R = H, Me) to give osmabenzene complexes [Os(=C(OR)CH=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf, in which the metallabenzene ring deviates significantly from planarity. In contrast, reaction of the dicationic complex 2 with NaBH(4) produces a cyclopentadienyl complex, presumably through the osmabenzene intermediate [Os(=CHC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf. The higher thermal stability of [Os(=C(OR)CH=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf relative to [Os(=CHC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf can be related to the stabilization effect of the OR groups on the metallacycle. A theoretical study shows that conversion of the dicationic osmabenzyne complex [Os([triple bond]CC(SiMe(3))=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)](OTf)(2) to a carbene complex by reductive elimination is thermodynamically unfavorable. The theoretical study also suggests that the nonplanarity of the osmabenzenes [Os(=C(OR)CH=C(Me)C(SiMe(3))=CH)(bipy)(PPh(3))(2)]OTf is mainly due to electronic reasons.     

Mononuclear and dinuclear complexes with a [Ru(tBu2PCH2CH2PtBu2)(CO)] core

Thermolysis of solid [Ru(d(t)bpe)(CO)2Cl2](2, d(t)bpe =(t)Bu2PCH2CH2P(t)Bu2) under vacuum affords the five-coordinate complex [Ru(d(t)bpe)(CO)Cl2] (4), which was shown by X-ray crystallography to contain a weak remote agostic interaction. In solution, 4 can be readily trapped by CO, CH3CN or water to give [Ru(d(t)bpe)(CO)(L)Cl2](L = CO, 2; L = CH3CN, 6; L = H2O, 7). Reaction of 4 with AgOTf/H2O yields the tris-aqua complex [Ru(d(t)bpe)(CO)(H2O)3](OTf)2 (8), which has been structurally characterised and probed in solution by pulsed-gradient spin echo (PGSE) NMR spectroscopy. The water ligands in 8 are labile and easily substituted to give [Ru(d(t)bpe)(CO)(NCCH3)3](OTf)2 (10) and [Ru(d(t)bpe)(CO)(DMSO)3](OTf)2 (11). In the presence of CO, the tris-aqua complex undergoes water-gas shift chemistry with formation of the cationic hydride species [Ru(d(t)bpe)(CO)3H](OTf) (12) and CO2. X-Ray crystal structures of complexes 2, 4, 6, 8 and 11-12 are reported along with those for [{Ru(d(t)bpe)(CO)}2(mu-Cl)2(mu-OTf)](OTf) (3), [{Ru(d(t)bpe)(CO)}2(mu-Cl)3][Ru(d(t)bpe)(CO)Cl3](5) and [Ru(d(t)bpe)(CO)(H2O)2(OTf)](OTf)(9).     

Solid state coordination chemistry of the copper(ii)-terpyridine/oxovanadium organophosphonate system: hydrothermal syntheses, structural characterization and magnetic properties

The hydrothermal reactions of CuSO4.5H2O, Na3VO4, 2,2':6':2'-terpyridine (terpy), and the appropriate organophosphonate ligand yield a series of materials of the Cu(ii)-terpy/oxovanadium organophosphonate family. The complexes exhibit distinct structures spanning one-, two- and three-dimensions and exhibiting diverse oxovanadium building blocks. Thus, [{Cu(terpy)}(V2O4)(O3PPh)(HO3PPh)2] (1) is one-dimensional and constructed from binuclear units of corner-sharing V(v) square pyramids. While [{Cu(terpy)}VO(O3PCH2PO3)] (2), [{Cu(terpy)}2(V4O10)(O3PCH2CH2PO3)] (3), and [{Cu(terpy)}(V2O4){O3P(CH2)3PO3}].2.5H(2)O (4.2.5H2O) are similarly one-dimensional, the V/O structural components consist of isolated V(iv) square pyramids, tetranuclear V(v) units of three tetrahedra and one square pyramid in a corner-sharing arrangement, and isolated V(v) tetrahedra and square pyramids, respectively. The second propylenediphosphonate derivative, [{Cu(terpy)}(V2O4){O3P(CH2)3PO3}] (5) is three-dimensional and exhibits isolated V(v) tetrahedra as the vanadate component. The two-dimensional structure of [{Cu(terpy)(H2O)}(V3O6){O3P(CH2)4PO3}] (6) is mixed valence with isolated V(iv) square pyramids and binuclear units of corner-sharing V(v) tetrahedra providing the V/O substructures.