Restriction of reaction sites on metal-sulfide cores induced by steric repulsion of bis-N-heterocyclic carbene ligands in trinuclear complexes bearing triply bridging sulfide ligands.

Mixed-ligand and mixed-metal trinuclear complexes bearing two {Pt-bisNHC-C1} moieties, [{Pt(bisNHC-C1)}(ML)(μ-S)] (ML = Pt(bisNHC-C2), = 2; ML = Pt(bisNHC-C3), = 2; ML = Rh(cod), = 1; ML = RhCp*, = 2), where bisNHC-C1, bisNHC-C2 and bisNHC-C3 represent methylene-, ethylene- and propylene-bridged bis-NHC ligands, respectively, were synthesised and structurally characterised. Reactions of these complexes with a half eq. of Ag(i) ions were examined using H and Pt NMR spectroscopy.

Electronic and steric impact of bis-NHC ligands on reactions of PtS cores in trinuclear complexes bearing bis-NHC ligands with various lengths of alkylene bridges.

Alkylene-bridged bis-N-heterocyclic carbene ligands working as strong σ-donors enhance the reactivity of the PtS core in a triplatinum complex. Although an Ag(I) ion possibly reacts with the Pt-Pt bond, one of the sulfide ligands coordinates to an Ag(I) ion due to the steric hindrance of the ligands.

Dibenzoate esters of cis-tetralin-2,3-diol as analogs of (-)-epigallocatechin gallate: synthesis and crystal structure of anticancer drug candidates.

(-)-Epigallocatechin gallate (EGCG), the main component of green tea extract, displays multiple biological activities. However, it cannot be used as a drug due to its low cellular absorption, instability and metabolic degradation. Therefore, there is a need to provide analogs that can overcome the limitations of EGCG.

Metal-metal bond formation of triplatinum cores with a silver(i) ion affording a heptanuclear cluster bearing four Pt-Ag bonds.

An N-heterocyclic carbene triplatinum complex with two triply bridging sulfide ligands reacts with a silver(i) salt and affords a heptanuclear complex. X-ray crystallographic analysis revealed that a silver(i) ion connects two triplatinum complexes with one of the three Pt-Pt bonds of each triplatinum unit.

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.

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.

Sulfur containing platinum(II) complexes with N-heterocyclic carbene ligands obtained by reactions of a hydrosulfido complex.

A hydrosulfido platinum(ii) complex with a chelated N-heterocyclic carbene (NHC) ligand was oxidised with O(2) in the presence of excess hydrogen sulfide, to give a linear tetrasulfido complex, and without hydrogen sulfide, to give a thiosulfato-bridged dinuclear complex. The hydrosulfido complex also reacted with an acetato complex containing the chelating NHC platinum unit to afford a trinuclear platinum complex with two triply bridging sulfido ligands showing an equilibrium in solution between two isomers based on the arrangement of the chelating NHC ligands.

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).

Dynamic behaviour attributed to chiral carbohydrate substituents of N-heterocyclic carbene ligands in square planar nickel complexes.

Nickel complexes having acetylated glucopyranosyl group incorporated N-heterocyclic carbene (NHC) ligands with methyl or benzyl groups as an N-substituent exhibit two kinds of dynamic behaviours in solution (1)H NMR spectroscopy. One of the dynamic behaviours is attributed to the anti- and syn-rotamers, which occur by the rotation of the unsymmetrical NHC ligands around the axes of the Ni-C bonds. The other is attributed to the diastereomers of the syn-rotamers, which occur by opposite rotation of the imidazolylidene rings and the chiral carbohydrate group incorporated into the NHC ligands.

Unprecedented diastereoselective generation of chiral-at-metal, half sandwich Ir(III) and Rh(III) complexes via anomeric isomerism on "sugar-coated" N-heterocyclic carbene ligands.

The first example of the diastereoselective synthesis induced by anomeric isomerism of sugar units in ligands of metal complexes was demonstrated. S and R configurations of chiral-at-metal Ir(III) and Rh(III) complexes were selectively obtained by using chelate-type NHC ligands with α- and β-glucopyranosyl units, respectively.

Carbon-sulfur bond cleavage reactions of dibenzothiophene derivatives mediated by iron and ruthenium carbonyls.

A thermal reaction of 6-(4''-dibenzothienyl)-2,2'-bipyridine (bpyDBT) with [Ru(3)(CO)(12)] produced a sulfur-bridged triruthenium complex via double carbon-sulfur bond cleavage and CO insertion, while a diiron(I,I) complex containing a thiametallacycle was obtained by a photochemical reaction of bpyDBT with [Fe(CO)(5)].

Carbene-carbanion equilibrium for tris(2-pyridylthio)methanido Fe(II) complexes.

A reaction of FeCl(2) with tris(2-pyridylthio)methane (tptmH) produced the carbanion complex [Fe(tptm)(CH(3)CN)(2)](FeCl(4)){(C(2)H(5))(3)NH}. When FeI(2) was used instead of FeCl(2), the carbene complex [FeI(pyt)(bptmd)] (pyt = 2-pyridinethiolate, bptmd = bis(2-pyridylthio)methylidene) was isolated. The carbene forms [FeX(pyt)(bptmd)](n+) (n = 1 for X = CH(3)CN, n = 0 for X = I) were observed for [Fe(tptm)(CH(3)CN)(2)](FeCl(4)){(C(2)H(5))(3)NH} and [FeI(pyt)(bptmd)] in chloroform, whereas the carbene-carbanion equilibrium was observed in acetonitrile by NMR measurements.

Rh(I)-catalyzed CO gas-free carbonylative cyclization reactions of alkynes with 2-bromophenylboronic acids using formaldehyde.

The rhodium(I)-catalyzed reaction of alkynes with 2-bromophenylboronic acids in the presence of paraformaldehyde resulted in a CO gas-free carbonylative cyclization, yielding indenone derivatives. [RhCl(BINAP)](2) and [RhCl(cod)](2) were responsible for the decarbonylation of formaldehyde and the subsequent carbonylation of alkynes with 2-haloboronic acids, respectively, leading to efficient whole carbonylation. Sterically bulky and electron-withdrawing groups on unsymmetrically substituted alkynes favored the alpha-position of indenones.

Photochromism of an organorhodium dithionite complex in the crystalline-state: molecular motion of pentamethylcyclopentadienyl ligands coupled to atom rearrangement in a dithionite ligand.

In the crystalline state, the rhodium dinuclear complex [(RhCp*)(2)(mu-CH(2))(2)(mu-O(2)SSO(2))] (1) with a photoresponsive dithionite group (mu-O(2)SSO(2)) and two pentamethylcyclopentadienyl ligands (Cp* = eta(5)-C(5)Me(5)) undergoes a 100% reversible unimolecular type T inverse photochromism upon interconversion to [(RhCp*)(2)(mu-CH(2))(2)(mu-O(2)SOSO)] (2). The photochromism can be followed directly by using stepwise crystal structure analysis (Angew. Chem.

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)).

Mimicking the photosynthetic system with strong hydrogen bonds to promote proton electron concerted reactions.

A Copper(2+) complex with a Cu(II)-C bond containing sp(3) configuration was used to investigate the role of strong hydrogen bonds in proton coupled electron transfer (PCET) reactions. The only example of a Cu(II)-C system realized so far is that using tris-(pyridylthio)methyl (tptm) as a tetradentate tripodal ligand. Using this ligand, [CuF(tptm)] and [Cu(tptm)(OH)] have been prepared.

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.

Thiacalix[3]pyridine produces a stable mononuclear rhodium(II) complex with mutual Jahn-Teller effect.

Thiacalix[3]pyridine (Py3S3) consists of pyridines and bridging sulfur atoms producing a stable octahedral mononuclear Rh(II) complex [Rh(II)(Py3S3)2]2+ showing mutual Jahn-Teller effect, a metal based reversible redox couple of Rh(III/II) at 0.02 V vs. SCE and a g(perpendicular) > g(||) relationship in EPR measurements.

A complete series of copper(II) halide complexes (X = F, Cl, Br, I) with a novel Cu(II)-C(sp3) bond.

A complete series of copper(ii) halide complexes [CuX(tptm)](X = F (), Cl (), Br (), I (); tptm = tris(2-pyridylthio)methyl) with a novel Cu(II)-C(sp(3)) bond has been prepared by the reactions of [Cu(tptm)(CH(3)CN)]PF(6)(.PF(6)) with corresponding halide sources of KF or n-Bu(4)NX (X = Cl, Br, I), and the trigonal bipyramidal structures have been confirmed by X-ray crystallography and/or EPR spectroscopy. The iodide complex easily liberates the iodide anion in acetonitrile forming the acetonitrile complex as a result.

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.

Selective oxygenation of amphiphilic thiacalix[3]pyridine Rh(I) diene complexes in both water and organic solvents.

Thiacalix[3]pyridine (Py3S3) reacted with [Rh(diene)(mu-Cl)]2(diene = 1,5-cyclooctadiene (cod), 2,5-norbornadiene (nbd)) to give amphiphilic trigonal bipyramidal complexes, [Rh(Py3S3)(diene)]Cl. Sulfur bridges of the Py3S3 ligand in these complexes were selectively oxygenated by m-chloroperoxybenzoic acid in dichloromethane to give sulfinylcalix[3]pyridine complexes, [Rh(Py3(SO)3)(diene)]+, in which all three oxygen atoms of the SO groups occupy the equatorial positions. Structures of the complexes were analysed by X-ray crystallography and the oxidation reaction was investigated using 1H NMR spectroscopy and electrospray ionisation mass spectrometry showing that the oxygenation of the sulfur atoms in the ligand proceeded stepwise and further oxygenation of the SO moiety occurred only for the nbd complex having the smaller diene ligand resulting in [Rh(Py3(SO)2(SO2))(nbd)]+.