Chelated bis-N-heterocyclic carbene platinum and palladium units as tunable components of multinuclear complexes.

Heterometallic trinuclear M2M' complexes (M = Rh, Ir; M' = Pt, Pd) containing a platinum or palladium moiety with chelated bis-N-heterocyclic carbene ligands, [(MCp*)2{M'(bisNHC-Cn-R)}(µ3-S)2](BPh4)2 (M = Rh, Ir; M' = Pt, Pd; bisNHC-Cn-R = methylene-, ethylene-, or propylene-bridged bis(N-alkyl-imidazolylidene)), were synthesized by reacting bis(hydrosulfido)platinum(II) or palladium(II) complexs with bisNHC-Cn-R and hydroxo-bridged dinuclear complexes [(MCp*)2(µ-OH)3](BPh4), whose dinuclear structures remained intact during the formation of the trinuclear complexes, which was confirmed by using electrospray mass spectrometry and NMR spectroscopy. The heterometallic trinuclear M2M' complexes with a variety of alkylene bridges in bisNHC-Cn-R showed two reversible reduction waves in the cyclic voltammogram, and the second reduction potentials were affected by the alkylene chain lengths, which caused different dihedral angles between the imidazolylidene rings and the coordination plane of the platinum or palladium center. The M2M' complexes, except for those containing the platinum unit with the ethylene-bridged bisNHC ligands, showed dynamic behavior in solution due to the flapping wing motion of the NHC ligand moieties. Although activation parameters obtained from line-shape analyses on variable-temperature NMR spectra of the complexes suggested that the flapping wing motion occurred without bond cleavage, large negative ΔS(‡) values were obtained for the complexes with the palladium unit with the ethylene-bridged ligand, suggesting that the Pd-Ccarbene bond cleavage, accompanied by coordination of solvent molecules, occurred.

π-back-bonding interaction depending on the bridging chain lengths of chelated N-heterocyclic carbene platinum units in heterometallic trinuclear complexes affecting their electrochemical property.

Newly synthesized heterometallic trinuclear M2Pt complexes (M = Rh, Ir) containing a platinum moiety having a chelated bis-N-heterocyclic carbene (bisNHC) ligand with a variety of alkylene chain lengths of the bridging part showed two reversible reduction waves in cyclic voltammetry. Only the second reduction potentials were affected by the alkyl chain lengths, which afforded different dihedral angles between the imidazolylidene rings and the platinum coordination plane resulting in the variation of π-back-donation from the platinum center to the carbene carbon atoms.

µ2-Acetato-κ(2) O:O'-(4,4'-bipyridyl-κN)tris-(diethyl di-thio-phosphato-κ(2) S,S')-µ3-sulfido-tri-µ2-sulfido-trimolybdenum(IV) diethyl ether monosolvate.

In the title compound, [Mo3(CH3COO)(C4H10O2PS2)3S4(C10H8N2)]·C4H10O, the complex mol-ecule has a trinuclear incomplete cuboidal structure which is coordinated by three kinds of ligands, namely, diethyl di-thio-phosphate, acetate and 4,4'-bipyridyl. If Mo-Mo bonds are ignored, each Mo atom can be considered as six-coordinated in a distorted octa-hedral geometry. The Mo-Mo distance of 2.6880 (5) Šfor two the Mo atoms bridged by the acetate ligand is shorter than the other two Mo-Mo distances [2.7490 (5) and 2.7566 (5) Å]. One ethyl group is disordered between two conformations in a 0.65 (3):0.35 (3) ratio. In the crystal, weak C-H⋯O inter-actions link the trinuclear mol-ecules related by translation in [100] into chains. The crystal packing exhibits short inter-molecular S⋯S contacts of 3.1886 (13) Å. In other words, in this crystal packing, a supramolecular structure is constructed by the C-H⋯O and S⋯S interactions.

Anion-controlled assembly of four manganese ions: structural, magnetic, and electrochemical properties of tetramanganese complexes stabilized by xanthene-bridged Schiff base ligands.

The reaction of manganese(II) acetate with a xanthene-bridged bis[3-(salicylideneamino)-1-propanol] ligand, H(4)L, afforded the tetramanganese(II,II,III,III) complex [Mn(4)(L)(2)(µ-OAc)(2)], which has an incomplete double-cubane structure. The corresponding reaction using manganese(II) chloride in the presence of a base gave the tetramanganese(III,III,III,III) complex [Mn(4)(L)(2)Cl(3)(µ(4)-Cl)(OH(2))], in which four Mn ions are bridged by a Cl(-) ion. A pair of L ligands has a propensity to incorporate four Mn ions, the arrangement and oxidation states of which are dependent on the coexistent anions.

Syntheses, characterization, and antitumor activities of platinum(II) and palladium(II) complexes with sugar-conjugated triazole ligands.

Four platinum(II) and palladium(II) complexes with sugar-conjugated bipyridine-type triazole ligands, [Pt(II)Cl(2)(AcGlc-pyta)] (3), [Pd(II)Cl(2)(AcGlc-pyta)] (4), [Pt(II)Cl(2)(Glc-pyta)] (5), and [Pd(II)Cl(2)(Glc-pyta)] (6), were prepared and characterized by mass spectrometry, elemental analysis, (1)H- and (13)C-NMR, IR as well as UV/VIS spectroscopy, where AcGlc-pyta and Glc-pyta denote 2-[4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl]ethyl 2,3,4,6-tetra-O-acetyl-ß-D-glucopyranoside (1) and 2-[4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl]ethyl ß-D-glucopyranoside (2), respectively. The solid-state structure of complex 6 was determined by single-crystal X-ray-diffraction analysis. These complexes exhibited in vitro cytotoxicity against human cervix tumor cells (HeLa) though weaker than that of cisplatin.

Bis(µ(2)-4,7-dimethyl-4,7-diazadecane-1,10-dithiolato)trinickel(II) bis(perchlorate).

In the title compound, [Ni(3)(C(10)H(22)N(2)S(2))(2)](ClO(4))(2), the complex cation consists of a nickel(II) ion and two [Ni(C(10)H(22)N(2)S(2))] units with an N(2)S(2) tetra-dentate ligand, 3,3'-[1,2-ethane-diylbis(methyl-imino)]bis-(1-propane-thiol-ate). The central Ni(II) ion is located on a crystallographic inversion centre and is bound to the four S atoms of the two [Ni(C(10)H(22)N(2)S(2))] units to form a linear sulfur-bridged trimetallic moiety. The dihedral angle between the central NiS(4) plane and the terminal NiN(2)S(2) plane is 145.71 (5)°. In the [Ni(C(10)H(22)N(2)S(2))] unit, the two methyl groups on the chelating N atoms are cis to each other, and the two six-membered N,S-chelate rings adopt a chair conformation. The Ni-S bond lengths and the S-Ni-S bite angles in the central NiS(4) group are similar to those in the [Ni(C(10)H(22)N(2)S(2))] unit.

Crystal structures and electrochemical properties of nickel(II) complexes with N,N',N'',S-tetra-dentate Schiff base ligands.

The thiol-ate nickel complexes {2-[({2-[(2-amino-ethyl-κN)(meth-yl)amino-κN]eth-yl}imino-κN)meth-yl]benzene-thiol-ato-κS}nickel(II) chloride, [Ni(C12H18N3S)]Cl (1), and [2-({[2-(piperazin-1-yl-κ2 N 1,N 4)eth-yl]imino-κN}meth-yl)benzene-thiol-ato-κS]nickel(II) hexa-fluoro-phosphate di-chloro-methane monosolvate, [Ni(C13H18N3S)]PF6·CH2Cl2 (2), were synthesized by the reactions of 2-(tert-butyl-thio)-benzaldehyde, tri-amines, and nickel(II) salts. Both complexes have a nickel ion surrounded by an N,N',N'',S-tetra-dentate ligand, forming a square-planar geometry. The terminal N,N-chelating moiety is N,N-di-alkyl-ethane-1,2-di-amine for 1 and 1-alkyl-piperazine for 2. The N-Ni-N bite angle in the terminal N,N-chelate ring in 2 [76.05 (10)°] is much smaller than that in 1 [86.16 (6)°]. Cyclic voltammograms of 1 and 2 in aqueous media indicated that the reduction and oxidation potentials of 2 are more positive than those of 1. The smaller bite angle of the terminal piperazine chelate in 2 reduces the electron-donating ability of the tetra-dentate ligand, resulting in a positive shift of the redox potentials. Both complexes exhibit catalytic activity for proton reduction, and the piperazine moiety in 2 is effective in reducing the overpotential.

Redox-controlled, reversible rearrangement of a tris(2-pyridylthio)methyl ligand on nickel to an isomer with an "N,S-confused" 2-pyridylthiolate arm.

Interchange between the nickel +2 and +3 oxidation states precisely controls the reversible rearrangement of the tris(2-pyridylthio)methanide (tptm) ligand in the organometallic nickel(II) complex [{Ni(µ-Br)-(tptm)}(2)] (2). Oxidation of 2 first gives the corresponding Ni(III) complex [{Ni(µ-Br)(tptm)}(2)][PF(6)](2) (4). However, in solution the tptm ligand in 4 slowly undergoes a rearrangement, in which the N and S atoms of one of the pyridylthiolate arms exchange Ni and C bonding partners, thereby resulting in an "N,S-confused" isomer of tptm in the product, [NiBr(bpttpm)]PF(6) (5; bpttpm= bis(2-pyridylthio)(2-thiopyridinium)-methyl). Reduction of 5 reverses this ligand rearrangement and 2 is reformed quantitatively. The individual steps involved in these unusual ligand rearrangements were investigated by a number of methods, including voltammetric analysis, and a mechanism for this process is proposed. X-ray crystal structure determinations of the key compounds 2, 4 and 5 have been obtained.

(η-Benzene){2-[2-(tert-butyl-sulfan-yl)phenyl]pyridine-κN,S}chlorido-ruthenium(II) hexa-fluorido-phosphate.

In the title compound, [RuCl(C(6)H(6))(C(15)H(17)NS)]PF(6), the cation adopts a three-legged piano-stool structure around the Ru(II) atom with an η(6)-benzene ligand, a chloride ligand and a 2-[2-(tert-butyl-sulfan-yl)phen-yl]pyridine (btppy) ligand. The btppy ligand acts as a N,S-bidentate ligand, forming a six-membered ring, which has an envelope conformation. The S-Ru-N bite angle is 86.76 (9)°, and the dihedral angle between the pyridine and benzene rings in btppy is 39.8 (2)°. The unit cell contains two pairs of racemic diastereomers with (S(Ru),S(S)) and (R(Ru),R(S)) configurations, in which the tert-butyl group on the coordin-ated S atom is distant from the η(6)-benzene ligand.

Arthroplasty using a custom-made cemented total hip prosthesis for an extensive giant cell tumor of the proximal femur: report of a patient followed up for over 30 years.

We report the case of a 26-year-old man who had a pathologic transtrochanteric fracture of the left femur due to a grade II giant cell tumor affecting the neck and the trochanteric area. This patient underwent complete resection of the tumor and arthroplasty using a custom-made cemented total hip prosthesis. The good radiologic and functional results of the surgery have been maintained for over 30 years without local recurrence or lung metastasis. Moreover, new bone formation was observed at the reattachment sites of abductors, iliopsoas tendons and vastus lateralis to the femoral component of the prosthesis although local bone resorption was detected at the upper lateral part of the femoral stem and zone I of the cup side.

Tetra- and dinuclear manganese complexes of xanthene-bridged O,N,O-Schiff bases with 3-hydroxypropyl or 2-hydroxybenzyl groups: ligand substitution at a triply bridging site.

Complexation properties of U-shaped ligands, L1 and L2, which are Schiff bases of 5,5'-(9,9-dimethylxanthene-4,5-diyl)bis(salicylaldehyde) (H2xansal) with 3-amino-1-propanol or 2-hydroxybenzylamine, respectively, were investigated to construct polynuclear manganese complexes. In these ligands, two O,N,O-Schiff bases are bridged by a xanthene backbone. The reactions of H4L1 or H4L2 with manganese salts afforded tetra- and dinuclear manganese complexes, including the tetramanganese(ii,ii,iii,iii) complex [Mn4(L1)2(µ-OAc)2] with a Mn4O6 core exhibiting an incomplete double-cubane structure. In the Mn4O6 core, phenolate and alkoxide O atoms bridge the manganese ions. Deprotonated 3-hydroxypropyl groups were crucial to the assembly of four manganese ions because the phenolate-bridged dimanganese(iii,iii) complex [Mn2(H2L1)2]2+ was obtained in the absence of a base, and H4L2, which has 2-hydroxybenzyl groups instead of 3-hydroxypropyl groups in H4L1, afforded the cyclic dimanganese(iv,iv) complex [Mn2(L2)2]. We disclosed that [Mn4(L1)2(µ-OAc)2] was converted to the oxo-bridged tetramanganese(iii,iii,iii,iii) complex [Mn4(L1)(HL1)(µ3-O)(µ-OAc)2]+ by treating with NH4PF6 or NH4BF4: a triply bridging alkoxide was protonated and replaced by an oxide ligand. The cyclic voltammograms of [Mn4(L1)(HL1)(µ3-O)(µ-OAc)2]+ suggested that the reverse reaction forming [Mn4(L1)2(µ-OAc)2] occurred in the electrochemical processes and was assisted by protonation.

Synthesis and characterization of tris(2-pyridylthio)methanido Zn complex with a Zn-C bond and DFT calculation of its one-electron oxidized species.

Tris(2-pyridylthio)methane (tptmH) reacts with ZnCl(2) producing the Zn-C containing complex of [ZnCl(tptm)], whose cyclic voltammogram shows an irreversible oxidation peak at 0.2 V vs. E(0')(Fc(+/0)). DFT calculations suggested that 1e(-) oxidation should occur at the tptm ligand resulting in the cleavage of the Zn-C bond, leading to decomposition of the complex.

Structure study and luminescence thermochromism in hexanuclear 6-methyl-2-pyridinethiolato copper(I) crystals.

The structure of hexanuclear 6-methyl-2-pyridinethiolato copper(I) [Cu6(6-mpyt)(6)] crystals has been studied by the X-ray diffraction analysis. These crystals show highly efficient luminescence whose color changes drastically from red to green-blue with lowering temperature from room temperature (RT) to liquid nitrogen temperature (LNT). This is a new example of luminescence thermochromism for hexanuclear copper(I) cluster compounds. Two relaxed luminescence bands appear predominantly: one (CC-band), red luminescence appearing in the lower-energy region around 1.8 eV at higher temperature, is assigned to the transition between intramolecular orbitals (MO) of a Cu cluster center (CC), and the other (CT-band), green-blue luminescence appearing at the higher energy side of 2.6 eV than the CC-band at lower temperature, is assigned to a charge transfer (CT) transition from the CC-MO to a ligand MO. Additionally, the CT band can be deconvoluted to two subbands CT(L) and CT(H). The intensities of the CC- and the CT-bands change complementarily with temperature via a thermal activation process, giving the thermochromism. All of these band shapes can be fitted by a Gaussian function, and their widths are fairly large obeying the hyperbolic cotangent law. These features reflect our system to be a strong electron-lattice coupling one. The relaxation process of the photoexcited states is discussed in terms of a configuration coordinate model.

A two-dimensional clathrate hydrate sandwiched by planar arrays of a copper complex.

The first structurally characterised example of a 2-D clathrate hydrate spontaneously assembles when [CuF(tptm)] (tptm = tris(2-pyridylthio)methyl) crystallises from toluene/water solutions to produce a material in which planar arrays of [CuF(tptm)] sandwich and hydrogen bond to continuous 2-D sheets of water that incorporate toluene molecules at regular intervals.

Formation, reactivity and redox properties of carbon- and sulfur-bridged diiron complexes derived from dibenzothienyl Schiff bases: effect of N,N- and N,P-chelating moieties.

Dibenzothienyl Schiff bases, DBT-NN and DBT-NP, were derived from condensation of 4-formyldibenzothiophene with N,N-dimethylethylenediamine and 2-(diphenylphosphino)ethylamine, respectively. A photochemical reaction of [Fe(CO)5] with DBT-NN produced diiron complexes, [Fe2(µ-DBT-NN)(CO)6] (1) and [{Fe(µ-BPT-NN-κ(3)S,C,N)(CO)2}Fe(CO)3] (2). Complex 1 has π coordination of a Schiff base C=N bond and an N,N-chelate, while 2 has an S,C,N-tridentate ligand having an uncoordinated dimethylamino group. The corresponding reaction with DBT-NP produced a diiron complex of an S,C,N,P-tetradentate ligand, [{Fe(µ-BPT-NP-κ(4)S,C,N,P)(CO)}Fe(CO)3] (3), which has an N,P-chelate, via the DBT-NP complex [Fe(DBT-NP-κP)(CO)4] (4). Reactions of 2 and 3 with one equivalent of PMe2Ph gave the monosubstituted complexes [{Fe(µ-BPT-NN-κ(3)S,C,N)(CO)2}Fe(CO)2(PMe2Ph)] (5) and [{Fe(µ-BPT-NP-κ(4)S,C,N,P)(CO)}Fe(CO)2(PMe2Ph)] (6), respectively. The corresponding reactions with an excess of PMe2Ph produced mononuclear complexes, trans-[Fe(BPT-NN-κ(3)S,C,N)(CO)(PMe2Ph)2] (7) and [Fe(BPT-NP-κ(4)S,C,N,P)(CO)(PMe2Ph)] (8), respectively. Complexes 1-3 and 5-8 were structurally characterized by X-ray crystallography. Complexes 2, 3, 5 and 6 have similar dinuclear structures with different carbonyl/phosphine substitution patterns. Cyclic voltammograms of 2, 3 and 5 showed two one-electron reduction processes, and more negative potentials were observed for 6. The shift of the redox potentials are rationalized by the electron-donating character of the phosphine ligands, which suggests that the reduction occurs at the asymmetrically bridged diiron core.

Structure and reactivity of a novel parallel thiosulfito (SSO2-S:S') rhodium dinuclear complex.

The parallel thiosulfite ligand (SSO2) in a rhodium complex, which is formed by oxygenation of a bridging disulfide, is converted to a bridging hydrocarbyl thiolate ligand and sulfur dioxide gas by the reaction with hydrocarbyl halides.

Thia-calix[n]pyridines, synthesis and coordination to Cu(I,II) ions with both N and S donor atoms.

The novel thia-calix[n]pyridines (n = 3, 4, 6) coordinated to copper ions through nitrogen and sulfur atoms to give multinuclear complexes whose structures have been determined by X-ray crystallography and NMR spectra.

Synthesis and insulinomimetic activities of novel mono- and tetranuclear oxovanadium(IV) complexes with 3-hydroxypyridine-2-carboxylic acid.

Two chargeless VO(IV) complexes with 3-hydroxypyridine-2-carboxylic acid (H2hpic), [VO(Hhpic-O,O)(Hhpic-O,N)(H2O)].3H2O (1) and the cyclic tetramer [(VO)4(mu-(hpic-O,O',N))4(H2O)4].8H3O (2), have been synthesized and characterized by elemental analysis, mass, infrared, electronic absorption, electron spin resonance (ESR) spectroscopies, and X-ray crystallography. Their coordination structures are similar to each other (and 1 is readily transformed into 2), but are quite different from that of bis(pyridine-2-carboxylato)oxovanadium(IV). The magnetic susceptibility of 2 indicates the presence of a weak ferromagnetic intramolecular interaction between the V atoms at low temperature, in addition to a weak antiferromagnetic intermolecular interaction. The ESR signal of 2 was broad, while 1 showed an eight-line hyperfine splitting pattern due to coupling of the unpaired electron with the 51V nucleus (I=7/2). The ESR spectrum and cyclic voltammogram of 2 clearly show that the cyclic tetramer remains intact in solution. The insulinomimetic activity of 1 and 2 was evaluated by means of in vitro measurements of the inhibition of free fatty acid release from epinephrine-treated isolated rat adipocytes. While 1 exerted higher insulinomimetic activity than VOSO4, the activity of 2 was significantly lower than that of VOSO4. Hence 2 appears to retain its cyclic structure during the in vitro test. These results indicate that the rational ligand design for VO complexes might be a promising approach to obtain superior insulinomimetic activity.

Synthesis, magnetic properties and dynamic behavior of cobalt complexes with an anthracene-containing dioxolene ligand.

The anthracene-functionalized cobalt complexes [Co(L)(TPA)]PF6 (1) and [Co(L)(Me(n)TPA)]PF6 (2, n = 1; 3, n = 2; 4, n = 3) were synthesized by the combination of 9-(3,4-dihydroxyphenyl)anthracene (H2L) and tris(2-pyridylmethyl)amine (TPA) or its derivatives (Me(n)TPA, n = 1, 2, 3). Characterization of complexes 1-4 was performed by UV-vis absorption, IR, (1)H NMR, and magnetic susceptibility measurements. In the solid state, the variable-temperature magnetic susceptibility data showed that complex 1 is low-spin cobalt(III) catecholate (Co(III)(LS)-Cat), while complex 4 is high-spin cobalt(II) semiquinonate (Co(II)(HS)-SQ) in the range 4.5-400 K. The susceptibility data of complexes 2 and 3 suggested valence tautomerism between the Co(III)(LS)-Cat and Co(II)(HS)-SQ forms. Light-induced valence tautomerism was observed in complexes 2 and 3 at 5 K by photo-irradiation. In solution, the temperature dependence of (1)H NMR spectra of 1 and 2 showed an equilibrium between their geometrical isomers.

Titanium and manganese complexes supported by a xanthene-bridged bis(tripodal N2O2) ligand: isomerization, intramolecular hydrogen bonding and metal-binding ability.

A new bis(N2O2) ligand, L(4-), in which two tripodal diamine-bis(phenolate) moieties are bridged by a xanthene backbone, was prepared. The reaction of H4L with 2 equiv. of [Ti(O(i)Pr)4] produced C2 and Cs symmetrical isomers of the dititanium(IV,IV) complex [Ti2(L)(O(i)Pr)4]. The isolated C2 isomer was slowly converted to the Cs isomer via Ti-N bond cleavage to form a 3 : 2 mixture in equilibrium. A similar dimanganese(III,III) complex [Mn2(L)(OMe)2(MeOH)2] was synthesized from a 1 : 2 mixture of H4L and manganese(II) perchlorate in the presence of triethylamine. An X-ray analysis of [Mn2(L)(OMe)2(MeOH)2] revealed that two Mn-N2O4 octahedrons are connected by intramolecular hydrogen bonds as well as a xanthene bridge to form a C2 symmetrical structure. The dimanganese(III,III) complex further reacted with manganese(II) acetate to form the mixed-valence trimanganese(III,II,III) complex [Mn3(L)(µ-OMe)2(µ-OAc)2]. Electrochemical data of the trimanganese(III,II,III) complex indicated that the xanthene-bridged dimanganese(III,III) unit effectively binds a Mn(II) ion in solution.