Toward functional carboxylate-bridged diiron protein mimics: achieving structural stability and conformational flexibility using a macrocylic ligand framework

A dinucleating macrocycle, H(2)PIM, containing phenoxylimine metal-binding units has been prepared. Reaction of H(2)PIM with [Fe(2)(Mes)(4)] (Mes = 2,4,6-trimethylphenyl) and sterically hindered carboxylic acids, Ph(3)CCO(2)H or Ar(Tol)CO(2)H (2,6-bis(p-tolyl)benzoic acid), afforded complexes [Fe(2)(PIM)(Ph(3)CCO(2))(2)] (1) and [Fe(2)(PIM)(Ar(Tol)CO(2))(2)] (2), respectively. X-ray diffraction studies revealed that these diiron(II) complexes closely mimic the active site structures of the hydroxylase components of bacterial multicomponent monooxygenases (BMMs), particularly the syn disposition of the nitrogen donor atoms and the bridging μ-η(1)η(2) and μ-η(1)η(1) modes of the carboxylate ligands at the diiron(II) centers. Cyclic voltammograms of 1 and 2 displayed quasi-reversible redox couples at +16 and +108 mV vs ferrocene/ferrocenium, respectively. Treatment of 2 with silver perchlorate afforded a silver(I)/iron(III) heterodimetallic complex, [Fe(2)(μ-OH)(2)(ClO(4))(2)(PIM)(Ar(Tol)CO(2))Ag] (3), which was structurally and spectroscopically characterized. Complexes 1 and 2 both react rapidly with dioxygen. Oxygenation of 1 afforded a (μ-hydroxo)diiron(III) complex [Fe(2)(μ-OH)(PIM)(Ph(3)CCO(2))(3)] (4), a hexa(μ-hydroxo)tetrairon(III) complex [Fe(4)(μ-OH)(6)(PIM)(2)(Ph(3)CCO(2))(2)] (5), and an unidentified iron(III) species. Oxygenation of 2 exclusively formed di(carboxylato)diiron(III) compounds, a testimony to the role of the macrocylic ligand in preserving the dinuclear iron center under oxidizing conditions. X-ray crystallographic and (57)Fe M?ssbauer spectroscopic investigations indicated that 2 reacts with dioxygen to give a mixture of (μ-oxo)diiron(III) [Fe(2)(μ-O)(PIM)(Ar(Tol)CO(2))(2)] (6) and di(μ-hydroxo)diiron(III) [Fe(2)(μ-OH)(2)(PIM)(Ar(Tol)CO(2))(2)] (7) units in the same crystal lattice. Compounds 6 and 7 spontaneously convert to a tetrairon(III) complex, [Fe(4)(μ-OH)(6)(PIM)(2)(Ar(Tol)CO(2))(2)] (8), when treated with excess H(2)O.     

Formation of N-heterocyclic diphosphine ligands from Ag(I)-assisted condensation reactions between bdppeda and formaldehyde and their binuclear silver(I) complexes

The reaction of [Ag(MeCN)(4)]ClO(4) with N,N,N',N'-tetra(diphenylphosphanylmethyl)ethylenediamine (dppeda) in CH(2)Cl(2)/MeOH afforded an unexpected cationic binuclear complex [Ag(2)(L(1))(2)(η,η-μ-ClO(4))(2)](ClO(4))(2) (L(1) = N,N'-bis(diphenylphosphanylmethyl)-3H-4,5-dihydroimidazole-1-ium) (1). Compound 1 was also prepared in high yield from reactions of [Ag(MeCN)(4)]ClO(4) with N,N'-bis(diphenylphosphanylmethyl)ethylenediamine (bdppeda) in the presence of formaldehyde (HCHO) or formic acid (HCOOH). Analogous reactions of AgCl with bdppeda and HCHO resulted in the formation a neutral binuclear complex [Ag(2)(L(2))(2)(μ-Cl)(2)] (L(2) = N,N-bis(diphenylphosphanylmethyl)-tetrahydroimidazole) (2). Treatment of 1 with concentrated HCl gave rise to a partially anion-exchanged product [Ag(2)(L(1))(2)(μ-Cl)(2)](ClO(4))(2) (3). Compounds 1 and 3 have a similar cationic binuclear structure, in which a [Ag(2)(η,η-μ-ClO(4))(2)] or [Ag(2)(μ-Cl)(2)] ring is sandwiched by two in situ-formed cationic L(1) ligands. The L(1) ligand may be generated by the Ag(I)-assisted condensation reaction between bdppeda and HCHO or HCOOH. Compound 2 holds a neutral binuclear structure, in which a [Ag(2)(μ-Cl)(2)] ring is connected by two in situ-formed L(2) ligands from its top and bottom sites. The neutral ligand L(2) may be produced from another Ag(I)-assisted condensation reaction between bdppeda and HCHO. The in situ formation of the L(1) and L(2) ligands provides a new route to the N-heterocyclic diphosphine ligands, and an interesting insight into the coordination chemistry of their metal complexes.     

Structural motifs in phenylbismuth heterocyclic carboxylates--secondary interactions leading to oligomers

The reaction of triphenylbismuth [BiPh(3)] with several heterocyclic carboxylic acids was explored. Seven crystalline compounds, [PhBi(2-O(2)C-3-(OH)C(5)H(3)N)(2)(2-O(2)C-3-(OH)C(5)H(3)NH)] (5), [(Bi(2-O(2)C-3-(OH)C(5)H(3)N)(4))(C(5)H(5)NH)(C(5)H(5)N)] (7), [PhBi(2-O(2)C-C(4)H(3)N(2))(2)(2-O(2)C-C(4)H(4)N(2))·H(2)O] (8), [PhBi(2-O(2)C-C(9)H(6)N)(2)·H(2)O] (9), [Ph(2)Bi(O(2)C-C(4)H(3)O)] (10), [Ph(2)Bi(O(2)C-C(4)H(3)S)] (11) and [PhBi(O(2)C-C(4)H(3)S)(2)](2) (12), were prepared by simple reactions using BiPh(3) and the corresponding acids, 3-hydroxypicolinic acid, pyrazine-2-carboxylic acid, quinoline-2-carboxylic (quinaldic) acid, furan-2-carboxylic acid and thiophene-2-carboxylic acid. Compound 5 primarily exhibits a coordination number of six with pentagonal pyramidal geometry at bismuth, but an additional weak Bi···O interaction in the direction of the lone pair of electrons is present. This feature leads to a weakly bound dimer. The use of pyridine as the solvent in a similar reaction, however, led to 7, in which all of the Bi-Ph bonds are cleaved. In this compound, bismuth exhibits a coordination number of eight and distorted dodecahedral geometry. In compound 8, the geometry around bismuth is primarily a pentagonal pyramid, however, clear-cut but weak secondary Bi···N interactions leading to a dimeric formulation are discernible in the structure. The quinaldate compound 9 exhibits a lower formal coordination number of five for bismuth, with square pyramidal geometry, but again two secondary Bi···O interactions for each bismuth in the direction of the lone pair lead to a dimer. A similar secondary Bi···O interaction involving furan oxygen is present in the furoate compound 10, which is a polymeric chain (one dimensional coordination polymer). Although the thiophene carboxylate 11 is also a polymeric chain, no Bi···S interactions are present. Unlike the previously reported tetrameric biscarboxylate [PhBi(2-O(2)C-C(5)H(3)N)(2)](4), the thiophene carboxylate [PhBi(O(2)C-C(4)H(3)S)(2)](2) (12) is a dimer considering only primary interactions. However, these dimers are arranged in such a way that there are secondary Bi···S interactions in the structure in the expected direction of the lone pair of electrons on bismuth. Thus, these studies suggest that the stereochemical activity (or inactivity) of the bismuth lone pair of electrons need to be judged more cautiously. TGA studies are consistent with the presence of Bi-Ph groups in all of the compounds, except 7, as indicated by their formulae.     

Synthesis and structure of a bismuth(III)/chromium(VI) oxo cluster containing a Bi4Cr4O12 core

Bismuth(III) compounds containing the Kl?ui's oxygen tripodal ligand [CpCo{P(O)(OEt)(2)}(3)](-) (L(OEt)(-)) have been synthesized, and their interactions with dichromate in aqueous media were studied. The treatment of Bi(5)O(OH)(9)(NO(3))(4) with NaL(OEt) in water afforded [L(OEt)Bi(NO(3))(2)](2) (1), whereas that of BiCl(3) with NaL(OEt) in CH(2)Cl(2) yielded L(OEt)BiCl(2) (2). Chloride abstraction of 2 with AgX afforded [L(OEt)BiX(2)](2) [X(-) = triflate (OTf(-)) (3), tosylate (OTs(-)) (4)]. In aqueous solutions at pH > 4, 4 underwent ligand redistribution to give the bis(tripod) complex [(L(OEt))(2)Bi(H(2)O)][OTs] (5). The treatment of 4 with Na(2)Cr(2)O(7) in acetone/water afforded the Bi(III)/Cr(VI) oxo cluster [(L(OEt))(4)Bi(4)(μ(3)-CrO(4))(2)(μ(3)-Cr(2)O(7))(2)] (6) containing a unique Bi(4)Cr(4)O(12) oxometallic core. Compound 6 oxidized benzyl alcohol to give ca. 6 equiv of benzaldehyde. The reaction between 2 and CrO(3) yielded [L(OEt)Bi(OCrO(2)Cl)](2)(μ-Cl)(2) (7). The crystal structures of complexes 4-7 have been determined.     

Self-assembly of a series of novel metal-organic compounds containing ferrocenecarboxylate components

Using FcCOONa (Fc = (eta(5)-C(5)H(5))Fe(eta(5)-C(5)H(4))) as starting material, we obtained an unprecedented metal-organic coordination polymer containing ferrocenecarboxylate components [[Pb(2)(FcCOO)(eta(2)-FcCOO)(mu(2)-eta(2)-FcCOO)(mu(3)-eta(2)-FcCOO)(CH(3)OH)].1.5CH(3)OH.H(2)O](n) (1), tetramer [Zn(4)(mu(2)-FcCOO)(6)(mu(4)-O)] (2), and coordination polymers [Pb(FcCOO)(mu(2)-FcCOO)(bpe)](n) (3) (bpe = 1,2-bis(4-pyridyl)ethene), [[Zn(FcCOO)(2)(bpt)].2.5H(2)O](n) (4) (bpt = N,N'-bis(3-pyridylmethyl)thiourea), and [Zn(FcCOO)(eta(2)-FcCOO)(bbp)](n) (5) (bbp = 4,4'-trimethylene-dipyridine). Compounds 1 and 2 are formed by ferrocenecarboxylate units coordinating with Pb(II) or Zn(II). In polymer 1, ferrocenecarboxylate units have four kinds of coordinate modes; just these novel coordinate modes lead to the unprecedented one-dimensional polymer where two kinds of rhomboids are arranged alternatively along the chain. Compound 2 is a tetramer, in which a distinct connectivity of the six ferrocene units is established through the four Zn atoms. Compounds 3-5 are obtained by organic ligands bridging Pb(II) or Zn(II), leading to a new type of metal-organic coordination polymer.     

Co-complexation of Lithium Gallates on the Titanium Molecular Oxide {[Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CH)

Amide and lithium aryloxide gallates [Li(+){RGaPh(3)}(-)] (R = NMe(2), O-2,6-Me(2)C(6)H(3)) react with the μ(3)-alkylidyne oxoderivative ligand [{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CH)] (1) to afford the gallium-lithium-titanium cubane complexes [{Ph(3)Ga(μ-R)Li}{Ti(η(5)-C(5)Me(5))(μ-O)}(3)(μ(3)-CH)] [R = NMe(2) (3), O-2,6-Me(2)C(6)H(3) (4)]. The same complexes can be obtained by treatment of the [Ph(3)Ga(μ(3)-O)(3){Ti(η(5)-C(5)Me(5))}(3)(μ(3)-CH)] (2) adduct with the corresponding lithium amide or aryloxide, respectively. Complex 3 evolves with formation of 5 as a solvent-separated ion pair constituted by the lithium dicubane cationic species [Li{(μ(3)-O)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-CH)}(2)](+) together with the anionic [(GaPh(3))(2)(μ-NMe(2))](-) unit. On the other hand, the reaction of 1 with Li(p-MeC(6)H(4)) and GaPh(3) leads to the complex [Li{(μ(3)-O)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-CH)}(2)][GaLi(p-MeC(6)H(4))(2)Ph(3)] (6). X-ray diffraction studies were performed on 1, 2, 4, and 5, while trials to obtain crystals of 6 led to characterization of [Li{(μ(3)-O)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-CH)}(2)][PhLi(μ-C(6)H(5))(2)Ga(p-MeC(6)H(4))Ph] 6a.     

Lewis base character of the phosphorus atom in phosphanido-niobocene complexes. Synthesis of new early-early homo- and heterobimetallic entities

The reaction of phosphanido complexes [Nb(η(5)-C(5)H(4)SiMe(3))(2)(L)(PPh(2))] [L = CO (1), CNXylyl (2)] with early transition metal halides in high oxidation states has been carried out. New bimetallic niobocene complexes [{Nb(η(5)-C(5)H(4)SiMe(3))(2)(L)}(μ-PPh(2))(MCl(5))] [M = Nb, L = CO (3), L = CNXylyl (4); M = Ta, L = CO (5), L = CNXylyl (6)] have been successfully synthesized by the reaction with [MCl(5)](2) (M = Nb or Ta). In a similar way [{Nb(η(5)-C(5)H(4)SiMe(3))(2)(L)}(μ-PPh(2))(MCl(4))] [M = Ti, L = CO (13), CNXylyl (14); M = Zr, L = CO (15), CNXylyl (16)] were synthesized using MCl(4) (M = Ti or Zr). Solutions of complexes 4-6 in chloroform produced new ionic derivatives [Nb(η(5)-C(5)H(4)SiMe(3))(2)(P(H)Ph(2))(L)] [MCl(6)] [M = Nb, L = CO (7), L = CNXylyl (8); M = Ta, L = CO (9), L = CNXylyl (10)]. Ionic complexes [Nb(η(5)-C(5)H(4)SiMe(3))(2)(P(Cl)Ph(2))(L)] [NbCl(4)O(thf)] [L = CO (11), CNXylyl (12)] were formed from solutions in thf - rapidly in the case of 3 but more slowly for 4. New heterometallic complexes [Nb(η(5)-C(5)H(4)SiMe(3))(2)(L)(μ-PPh(2)){(Ti(η(5)-C(5)R(5))Cl(3)}] [R = H, L = CO (17), CNXylyl (18); R = CH(3), L = CO (19), CNXylyl (20)] were synthesized by the reaction of 1 or 2 with [Ti(η(5)-C(5)R(5))Cl(3)] (R = H or CH(3)). All of these compounds were characterized by IR and multinuclear NMR spectroscopy, and the molecular structures of 9 and 12 were determined by single-crystal X-ray diffraction.     

Synthetic entry into polynuclear bismuth-manganese chemistry: high oxidation state Bi(III)2Mn(IV)6 and Bi(III)Mn(III)10 complexes

The first high nuclearity, mixed-metal Bi(III)/Mn(IV) and Bi(III)/Mn(III) complexes are reported. The former complexes are [Bi(2)Mn(IV)(6)O(9)(O(2)CEt)(9)(HO(2)CEt)(NO(3))(3)] (1) and [Bi(2)Mn(IV)(6)O(9)(O(2)CPh)(9)(HO(2)CPh)(NO(3))(3)] (2) and were obtained from the comproportionation reaction between Mn(O(2)CR)(2) and MnO(4)(-) in a 10:3 ratio in the presence of Bi(NO(3))(3) (3 equiv) in either a H(2)O/EtCO(2)H (1) or MeCN/PhCO(2)H (2) solvent medium. The same reaction that gives 2, but with Bi(O(2)CMe)(3) and MeNO(2) in place of Bi(NO(3))(3) and MeCN, gave the lower oxidation state product [BiMn(III)(10)O(8)(O(2)CPh)(17)(HO(2)CPh)(H(2)O)] (3). Complexes 1 and 2 are near-isostructural and possess an unusual and high symmetry core topology consisting of a Mn(IV)(6) wheel with two central Bi(III) atoms capping the wheel on each side. In contrast, the [BiMn(III)(10)O(8)](17+) core of 3 is low symmetry, comprising a [BiMn(3)(μ(3)-O)(2)](8+) butterfly unit, four [BiMn(3)(μ(4)-O)](10+) tetrahedra, and two [BiMn(2)(μ(3)-O)](7+) triangles all fused together by sharing common Mn and Bi vertices. Variable-temperature, solid-state dc and ac magnetization data on 1-3 in the 1.8-300 K range revealed that 1 and 2 possess an S = 0 ground state spin, whereas 3 possesses an S = 2 ground state. The work offers the possibility of access to molecular analogs of the multifunctional Bi/Mn/O solids that are of such great interest in materials science.     

Bismuth coordination chemistry with allyl, alkoxide, aryloxide, and tetraphenylborate ligands and the {[2,6-(Me2NCH2)2C6H3]2Bi}+ cation

A series of bis(aryl) bismuth compounds containing (N,C,N)-pincer ligands, [2,6-(Me(2)NCH(2))(2)C(6)H(3)](-) (Ar'), have been synthesized and structurally characterized to compare the coordination chemistry of Bi(3+) with similarly sized lanthanide ions, Ln(3+). Treatment of Ar'(2)BiCl, 1, with ClMg(CH(2)CH═CH(2)) affords the allyl complex Ar'(2)Bi(η(1)-CH(2)CH═CH(2)), 2, in which only one allyl carbon atom coordinates to bismuth. Complex 1 reacts with KO(t)Bu and KOC(6)H(3)Me(2)-2,6 to yield the alkoxide Ar'(2)Bi(O(t)Bu), 3, and aryloxide Ar'(2)Bi(OC(6)H(3)Me(2)-2,6), 4, respectively, but the analogous reaction with the larger KOC(6)H(3)(t)Bu(2)-2,6 forms [Ar'(2)Bi][OC(6)H(3)(t)Bu(2)-2,6], 6, in which the aryloxide ligand acts as an outer sphere anion. Chloride is removed from 1 by NaBPh(4) to form [Ar'(2)Bi][BPh(4)], 5, which crystallizes from THF in an unsolvated form with tetraphenylborate as an outer sphere counteranion.     

Substituent size effects in lewis base induced reductions in organolanthanide chemistry

The reaction of the tripodal 1,3,5-trialkyl-1,3,5-triazacyclohexanes (L=cyclo-[N(R)CH(2)](3) , R=Et, iPr, tBu), with [Sm(AlMe(4))(3)] resulted in the formation of divalent samarium complexes of the constitution [{L(n)Sm(AlMe(4))(2)}(m)] (n, m=1,2) under ethane extrusion. These compounds were characterised by single-crystal X-ray diffraction and elemental analyses. Simultaneous occurrence of Lewis base induced reduction and C--activation reactions is observed. The ratio of products depends on the bulkiness of the N-alkyl substituent R. The reaction of [Sm(AlMe(4))(3)] with 1,3,5-triisopropyl-1,3,5-triazacyclohexane (TiPTAC) in benzene afforded the inversion-symmetric dimer [{(TiPTAC)(η(3)-AlMe(4))Sm}(2)(μ(2)-AlMe(4))(2)], whereas in toluene the pseudo-samarocene [(TiPTAC)(2)Sm(η(1)-AlMe(4))(2)] was obtained. The trisaluminate [(TiPTAC)Sm{(μ(2)-Me)(Me(2) l)}(2)(μ(3)-CH(2))(2)AlMe(2))] was found to be the C--activation product. In the case of the particular bulky 1,3,5-tri-tert-butyl-1,3,5-triazacyclohexane (TtBuTAC), the reaction led to the formation of the dimeric [{(TtBuTAC)(η(3)-AlMe(4))Sm}(2)(μ(2)-AlMe(4))(2)] even in toluene in comparably high yields. The decrease of the steric demand to ethyl groups in 1,3,5-triethyl-1,3,5-triazacyclohexane (TETAC) afforded the samarocene-like [(TETAC)(2) Sm(η(1)-AlMe(4))(2)] in lower yields. The resulting divalent samarium compounds are found to be stable with respect to reagents like dinitrogen, conjugated olefins and polycyclic aromatic systems.     

Reactions of in situ generated hydrated organotin cations with chelating O,O- or O,N-ligands: a possible structure-directing influence of the organic substituent on tin

The reaction of [n-Bu(2)SnO](n) with 1,5-naphthalenedisulfonic acid tetrahydrate in a 1:1 stoichiometry followed by reaction with 2,2'-bipyridine-N,N'-dioxide (BPDO-I) afforded a 1D-coordination polymer [n-Bu(2)Sn(BPDO-I)(1,5-C(10)H(6)(SO(3))(2))](n) (1) where the disulfonate ligand acts as a bridging ligand between two tin centers. An analogous reaction involving [Ph(2)SnO](n) afforded a trihydrated O,O'-chelated diorganotin cation [{Ph(2)Sn(BPDO-I)(H(2)O)(3)}(2+)][C(10)H(6)(SO(3)(-))(2)]·2CH(3)OH (2·2CH(3)OH). Utilizing two equivalents of BPDO-I in this reaction resulted in the ionic complex [{Ph(2)Sn(BPDO-I)(2)(H(2)O)}(2+)][C(10)H(6)(SO(3)(-))(2)]·3H(2)O (3·3H(2)O). In 2 and 3 the sulfonate ligands are not present in the coordination sphere of tin. Reaction of [n-Bu(2)SnO](n) and 1,5-naphthalenedisulfonic acid tetrahydrate, followed by reaction with [bis(diphenylphosphoryl)methane (DPPOM)] resulted in the formation of, [{n-Bu(2)Sn(DPPOM)(2)(H(2)O)(1,5-C(10)H(6)(SO(3))(SO(3)(-))}]·H(2)O (4·H(2)O). Of the two coordinating groups present in DPPOM, only one P=O group is coordinated to the tin atom. The remaining P=O motif is free and is involved in intramolecular H-bonding with the tin-bound water molecule. Using [Ph(2)SnO](n) instead of [n-Bu(2)SnO](n) afforded the ionic complex [{Ph(2)Sn(DPPOM)(2)}(2+){1,5-C(10)H(6)(SO(3)(-))(2)}] (5) where the DPPOM functions as a chelating ligand. The reaction of [n-Bu(2)SnO](n) with 1,5-naphthalenedisulfonic acid tetrahydrate followed by addition of one equivalent of 8-hydroxyquinoline (8-HQ) in presence of triethylamine afforded the neutral dinuclear complex, [(H(2)O)(8-Q)n-Bu(2)Sn(μ-1,5-C(10)H(6)(SO(3))(2))n-Bu(2)Sn(8-Q)(H(2)O)] (6) where the two tin atoms are bridged by the disulfonate ligand. Compounds 1-6 are thermally stable as shown by their thermogravimetric analyses.     

Allyl strontium compounds: synthesis, molecular structure and properties

The synthesis and attempted isolation of neutral bis(allyl)strontium [Sr(C(3)H(5))(2)] (1) resulted in the isolation of potassium tris(allyl)strontiate K[Sr(C(3)H(5))(3)] (2). In situ generated 1 shows a pronounced Br?nsted basicity, inducing polymerisation of THF. Ate complex 2 crystallises as [K(THF)(2){Sr(C(3)H(5))(3)}(THF)](∞) (2·(THF)(3)). The salt-like solid state structure of 2·(THF)(3) comprises a two-dimensional network of (μ(2)-η(3):η(3)-C(3)H(5))(-) bridged potassium and strontium centres. Synthesis of allyl complexes 1 and 2 utilised SrI(2), [Sr(TMDS)(2)] (3) (TMDS = tetramethyldisilazanide), and [Sr(HMDS)(2)] (HMDS = hexamethyldisilazanide) as strontium precursors. The solid state structure of previously reported [Sr(TMDS)(2)] (3) was established by X-ray single crystal analysis as a dissymmetric dimer of [Sr(2)(TMDS)(4)(THF)(3)] (3·(THF)(3)) with multiple Si-HSr agostic interactions. The presence of ether ligands (THF, 18-crown-6) influenced the Si-HSr resonances in the NMR spectra of the amido complex 3.     

Synthesis and characterization of nickel inverse 9-metallacrown-3, palladium-silver, and dinuclear platinum complexes containing pyrazole-functionalized NHC ligands

Three metallacrown nickel complexes [Ni(3)(μ-OH)(L1)(3)](PF(6))(2) (1, L1 = 3-((N-methylimidazolylidenyl)methyl)-5-methylpyrazolate), [Ni(3)(μ-OH)(L2)(3)](PF(6))(2) (2, L2 = 3-((N-mesitylimidazolylidenyl)methyl)-5-methylpyrazolate), and [Ni(3)(μ-OH)(L3)(3)](PF(6))(2) (3, L3 = 3-((N-pyrimidin-2-ylimidazolylidenyl)methyl)-5-methylpyrazolate) were obtained by the reactions of corresponding silver-NHC complexes with Raney nickel powder at 45 °C. The same reaction at 80 °C afforded [Ni(3)(L2)(4)](PF(6))(2) (4). The carbene-transfer reaction of the silver-carbene complex with [(η(3)-C(3)H(5))PdCl](2) yielded the heterotrimetallic complex [AgPd(2)(η(3)-C(3)H(5))(2)(L2)(2)](PF(6)) (5), whereas the carbene-transfer reaction with Pt(cod)Cl(2) gave [Pt(2)(L3)(2)](PF(6))(2) (6). All of these complexes have been fully characterized by ESI-MS, NMR spectroscopy, and elemental analysis. The molecular structures of 1-6 were also studied by X-ray diffraction analysis. In 1-3, three nickel centers are bridged together by three pyrazole-NHC ligands and a hydroxide group, forming a 9-metallacrown-3 topology. Complex 4 is paramagnetic, consisting of two square-planar nickel(II) ions and one tetrahedral nickel ion in which three Ni ions are bridged by four pyrazolate units. In the mixed Pd-Ag complex 5, two palladium and one silver centers are bridged by two pyrazole-NHC ligands. Complex 5 showed good catalytic activity in the Sonogashira coupling reaction of aryl bromides and phenylacetylene under mild conditions typically catalyzed by Pd-Cu systems.     

Electrophilic arene hydroxylation and phenol O-H oxidations performed by an unsymmetric μ-η(1):η(1)-O2-peroxo dicopper(II) complex

Reactions of the unsymmetric dicopper(II) peroxide complex [Cu(II)(2)(μ-η(1):η(1)-O(2))(m-XYL(N3N4))](2+) (1?O(2), where m-XYL is a heptadentate N-based ligand), with phenolates and phenols are described. Complex 1?O(2) reacts with p-X-PhONa (X = MeO, Cl, H, or Me) at -90?°C performing tyrosinase-like ortho-hydroxylation of the aromatic ring to afford the corresponding catechol products. Mechanistic studies demonstrate that reactions occur through initial reversible formation of metastable association complexes [Cu(II)(2)(μ-η(1):η(1)-O(2))(p-X-PhO)(m-XYL(N3N4))](+) (1?O(2)?X-PhO) that then undergo ortho-hydroxylation of the aromatic ring by the peroxide moiety. Complex 1?O(2) also reacts with 4-X-substituted phenols p-X-PhOH (X = MeO, Me, F, H, or Cl) and with 2,4-di-tert-butylphenol at -90?°C causing rapid decay of 1?O(2) and affording biphenol coupling products, which is indicative that reactions occur through formation of phenoxyl radicals that then undergo radical C-C coupling. Spectroscopic UV/Vis monitoring and kinetic analysis show that reactions take place through reversible formation of ground-state association complexes [Cu(II)(2)(μ-η(1):η(1)-O(2))(X-PhOH)(m-XYL(N3N4))](2+) (1?O(2)?X-PhOH) that then evolve through an irreversible rate-determining step. Mechanistic studies indicate that 1?O(2) reacts with phenols through initial phenol binding to the Cu(2)O(2) core, followed by a proton-coupled electron transfer (PCET) at the rate-determining step. Results disclosed in this work provide experimental evidence that the unsymmetric 1?O(2) complex can mediate electrophilic arene hydroxylation and PCET reactions commonly associated with electrophilic Cu(2)O(2) cores, and strongly suggest that the ability to form substrate?Cu(2)O(2) association complexes may provide paths to overcome the inherent reactivity of the O(2)-binding mode. This work provides experimental evidence that the presence of a H(+) completely determines the fate of the association complex [Cu(II)(2)(μ-η(1):η(1)-O(2))(X-PhO(H))(m-XYL(N3N4))](n+) between a PCET and an arene hydroxylation reaction, and may provide clues to help understand enzymatic reactions at dicopper sites.     

Hydrolysis studies on bismuth nitrate: synthesis and crystallization of four novel polynuclear basic bismuth nitrates

Hydrolysis of Bi(NO(3))(3) in aqueous solution gave crystals of the novel compounds [Bi(6)O(4)(OH)(4)(NO(3))(5)(H(2)O)](NO(3)) (1) and [Bi(6)O(4)(OH)(4)(NO(3))(6)(H(2)O)(2)]·H(2)O (2) among the series of hexanuclear bismuth oxido nitrates. Compounds 1 and 2 both crystallize in the monoclinic space group P2(1)/n but show significant differences in their lattice parameters: 1, a = 9.2516(6) ?, b = 13.4298(9) ?, c = 17.8471(14) ?, β = 94.531(6)°, V = 2210.5(3) ?(3); 2, a = 9.0149(3) ?, b = 16.9298(4) ?, c = 15.6864(4) ?, β = 90.129(3)°, V = 2394.06(12) ?(3). Variation of the conditions for partial hydrolysis of Bi(NO(3))(3) gave bismuth oxido nitrates of even higher nuclearity, [{Bi(38)O(45)(NO(3))(24)(DMSO)(26)}·4DMSO][{Bi(38)O(45)(NO(3))(24)(DMSO)(24)}·4DMSO] (3) and [{Bi(38)O(45)(NO(3))(24)(DMSO)(26)}·2DMSO][{Bi(38)O(45)(NO(3))(24)(DMSO)(24)}·0.5DMSO] (5), upon crystallization from DMSO. Bismuth oxido clusters 3 and 5 crystallize in the triclinic space group P1? both with two crystallographically independent molecules in the asymmetric unit. The following lattice parameters are observed: 3, a = 20.3804(10) ?, b = 20.3871(9) ?, c = 34.9715(15) ?, α = 76.657(4)°, β = 73.479(4)°, γ = 60.228(5)°, V = 12021.7(9) ?(3); 5, a = 20.0329(4) ?, b = 20.0601(4) ?, c = 34.3532(6) ?, α = 90.196(1)°, β = 91.344(2)°, γ = 119.370(2)°, V = 12025.8(4) ?(3). Differences in the number of DMSO molecules (coordinated and noncoordinated) and ligand (nitrate, DMSO) coordination modes are observed.     

New coordination polymers with extended arm cyclotriguaiacyclene ligands: 1D chains, and interpenetrating or polycatenating 2D (4(2).6(2))(4.6(2))2 networks

A series of new 1D chain and 2D coordination polymers with cyclotriguaiacylene-type ligands are reported. A zig-zag 1D coordination chain is found in complex [Cd(2)(4ph4py)(NO(3))(3)(H(2)O)(2)(DMA)(2)]·(NO(3))·(DMA)(4), where 4ph4py = tris[4-(4-pyridyl)benzoyl]-cyclotriguaiacylene and DMA = dimethylacetamide, while complex [Zn(4ph4py)(2)(CF(3)COO)(H(2)O)]·(CF(3)COO)(NMP)(7), where NMP = N-methylpyrrolidone, has a doubly bridged coordination chain structure. Complexes [M(3ph3py)(NO(3))(2)]·(NMP)(4) where M = Co or Zn, 3ph3py = tris[3-(3-pyridyl)benzoyl]cyclotriguaiacylene, are isostructural and feature 1D ladder coordination chains. Complexes [Cd(2)(4ph4py)(2)(NO(3))(4)(NMP)]·(NMP)(9)(H(2)O)(4) and [Co(4ph4py)(H(2)O)(2)]·(NO(3))(2)·(DMF)(2), where DMF = dimethylformamide, both have (3,4)-connected 2D coordination polymers with a rare (4(2).6(2))(4.6(2))(2) topology. A 2D coordination polymer with this topology is also found in complex [Co(2)(3ph4py)(2)(NO(3))(H(2)O)(5)]·(NO(3))(3)·(DMF)(9) where 3ph4py = tris[3-(4-pyridyl)benzoyl]cyclotriguaiacylene. All 2D coordination polymer complexes are interpenetrating or polycatenating. [Co(2)(3ph4py)(2)(NO(3))(H(2)O)(5)](3+)polymers form a 2D→3D polycatenation showing self-complementary "hand-shake" interactions between the host-type ligands.     

Reactions of phthalazine, quinazoline, 4,7-phenanthroline and 2,3'-bipyridine with ruthenium carbonyl

The reactions of [Ru(3)(CO)(12)] with four aromatic diazines have been studied in THF at reflux temperature. With phthalazine (L(1)), the compound [Ru(3)(μ-κ(2)N(2)N(3)-L(1))(μ-CO)(3)(CO)(7)] (1), which contains an intact phthalazine ligand in an axial position bridging an Ru-Ru edge through both N atoms, is initially formed but it reacts with more phthalazine to give [Ru(3)(κN(2)-L(1))(μ-κ(2)N(2)N(3)-L(1))(μ-CO)(3)(CO)(6)] (2), in which a π-π stacking interaction between the aromatic rings of both ligands determines their position in cluster axial sites on the same face of the Ru(3) triangle. With quinazoline (HL(2)), the cyclometalated hydrido decacarbonyl derivative [Ru(3)(μ-H)(μ-κ(2)N(3)C(4)-L(2))(CO)(10)] (3) is initially produced but it partially decarbonylates under the reaction conditions to give [Ru(6)(μ-H)(2)(μ-κ(2)N(3)C(4)-L(2))(μ(3)-κ(3)-N(1)N(3)C(4)-L(2))(CO)(19)] (4), which results from the displacement of a CO ligand of 3 by the uncoordinated N(1) atom of another molecule of 3. With 4,7-phenanthroline (H(2)L(3)), the stepwise formation of the cyclometalated derivatives [Ru(3)(μ-H)(μ-κ(2)N(4)C(3)-HL(3))(CO)(10)] (5) and two isomers of [Ru(6)(μ-H)(2)(μ(4)-κ(4)N(4)C(3)N(7)C(8)-L(3))(CO)(20)] (6a, 6b) takes place. In compounds 6a and 6b, two Ru(3)(μ-H)(CO)(10) trinuclear units are symmetrically (C(2) in 6a or C(S) in 6b) bridged by a doubly-cyclometalated 4,7-phenanthroline ligand. With 2,3'-bipyridine (HL(4)), two products have been isolated, [Ru(3)(μ-H)(μ-κ(2)N(3')C(4')-L(4))(CO)(10)] (7) and [Ru(3)(μ-H)(μ-κ(3)N(2)N(3')C(2')-L(4))(CO)(9)] (8). While compound 7 contains an N(3')C(4')-cyclometalated 2,3'-bipyridine, in compound 8 an N(3')C(2')-cyclometalation is accompanied by the coordination of the N(2) atom of the remaining pyridine fragment. The structures of compounds 2, 3, 4, 6a and 8 have been determined by X-ray diffraction crystallography.     

Remarkable in vitro bactericidal activity of bismuth(iii) sulfonates against Helicobacter pylori

Four new tris-substituted bismuth(iii) sulfonates of general formula [Bi(O(3)SR)(3)] (R = phenyl 1, p-tolyl 2, 2,4,6-mesityl 3 and S-(+)-10-camphoryl 4) have been synthesised and characterised. Their synthesis by solvent-free (SF) and solvent-mediated (SM) methods has been explored and their activity against Helicobacter pylori has been investigated. The compounds 1-4 display a remarkable in vitro activity against three laboratory strains of H. pylori (B128, 26?695 and 251) with minimum inhibitory concentration (MIC) values as low as 0.049 μg mL(-1) for the strains B128 and 26?695, and 0.781 μg mL(-1) for the clinical isolate 251. This places most MIC values in the nano-molar region and demonstrates the strong influence of the sulfonate group on the bactericidal properties. The novel solid state structure [Bi(8)(O(3)SMes)(20)(SO(4))(2)(H(2)O)(6)]·(C(7)H(8))(7)5·(C(7)H(8))(7), derived from the SM reaction under reflux conditions, is presented and the incorporation of the two inorganic sulfate anions in the centre of the wheel-like bismuth sulfonate cluster explained.     

Formation and coordination modes of the C4E4 moiety (E = COOMe) bound to two palladium(II) moieties

The transmetallation of the palladacyclopentadiene complex Pd{C(COOMe)C(COOMe)C(COOMe)C(COOMe)}(bipy) with the dicationic Pd(II) complex [Pd(bipy)(CH(3)CN)(2)][BF(4)](2) afforded a terminally σ-palladated diene complex [Pd(2){μ-η(1):η(1)-C(COOMe)C(COOMe)C(COOMe)C(COOMe)}(bipy)(2)(CH(3)CN)(2)][BF(4)](2). It was revealed by X-ray crystallographic analysis that replacement of the acetonitrile ligands in a terminally σ-palladated diene complex with PPh(3) ligands resulted in the conformation change of the σ-palladated diene moiety from skewed s-cis to planar s-trans. Treatment of a bis-triphenylphosphine dipalladium complex [Pd(2)(PPh(3))(2)(CH(3)CN)(4)][PF(6)](2) with dimethoxyacetylene dicarboxylate (DMAD) (1 equiv.) in acetonitrile resulted in the insertion of DMAD to the Pd-Pd bond to afford [Pd(2){μ-η(1):η(1)-C(COOMe)C(COOMe)}(PPh(3))(2)(CH(3)CN)(4)][PF(6)](2). Addition of the second DMAD gave the ylide-type complex [Pd(2){μ-η(2):η(3)-C(COOMe)C(COOMe)C(COOMe)C(COOMe)(PPh(3))}(PPh(3))(2)(CH(3)CN)(3)][PF(6)](2) of which the structure was determined by X-ray crystallographic analysis.     

Rhodium pyrazolate complexes as potential CVD precursors

Reaction of 3,5-(CF(3))(2)PzLi with [Rh(μ-Cl)(η(2)-C(2)H(4))(2)](2) or [Rh(μ-Cl)(PMe(3))(2)](2) in Et(2)O gave the dinuclear complexes [Rh(η(2)-C(2)H(4))(2)(μ-3,5-(CF(3))(2)-Pz)](2) (1) and [Rh(2)(μ-Cl)(μ-3,5-(CF(3))(2)-Pz) (PMe(3))(4)] (2) respectively (3,5-(CF(3))(2)Pz = bis-trifluoromethyl pyrazolate). Reaction of PMe(3) with [Rh(COD)(μ-3,5-(CF(3))(2)-Pz)](2) in toluene gave [Rh(3,5-(CF(3))(2)-Pz)(PMe(3))(3)] (3). Reaction of 1 and 3 in toluene (1?:?4) gave moderate yields of the dinuclear complex [Rh(PMe(3))(2)(μ-3,5-(CF(3))(2)-Pz)](2) (4). Reaction of 3,5-(CF(3))(2)PzLi with [Rh(PMe(3))(4)]Cl in Et(2)O gave the ionic complex [Rh(PMe(3))(4)][3,5-(CF(3))(2)-Pz] (5). Two of the complexes, 1 and 3, were studied for use as CVD precursors. Polycrystalline thin films of rhodium (fcc-Rh) and metastable-amorphous films of rhodium phosphide (Rh(2)P) were grown from 1 and 3 respectively at 170 and 130 °C, 0.3 mmHg in a hot wall reactor using Ar as the carrier gas (5 cc min(-1)). Thin films of amorphous rhodium and rhodium phosphide (Rh(2)P) were grown from 1 and 3 at 170 and 130 °C respectively at 0.3 mmHg in a hot wall reactor using H(2) as the carrier gas (7 cc min(-1)).