Luminescent rhenium(I)-gold(I) hetero organometallics linked by ethynylphenanthrolines

The first luminescent rhenium(I)-gold(I) hetero organometallics, Re{phenAu(PPh₃)}(CO)₃Cl (3) and Re{(PPh₃)AuphenAu(PPh₃)}(CO)₃Cl (4), have been prepared using the gold(I) complex AuCl(PPh₃) (PPh₃ = triphenylphosphine) and the novel rhenium(I) complexes Re(phenH)(CO)₃Cl (5) (phenH = 3-ethynyl-1,10-phenanthroline) or Re(HphenH)(CO)₃Cl (6) (HphenH = 3,8-bis(ethynyl)-1,10-phenanthroline). All the present rhenium(I) complexes 3-6 were revealed to possess a facial configuration (fac-isomer) with respect to the three carbonyl ligands. The main frameworks for these new gold(I) organometallics were constructed by the Au-C σ-bonding (with the η¹-type coordination) between the ethynylphenanthrolines and the Au(I) phosphine unit. Re(I)-Au(I) heterometallics 3 and 4 have shown single phosphorescence from the ³MLCT excited state and this observation can be interpreted in terms of the efficient intramolecular energy transfer from the Au(I) unit to the Re(I) unit.     

Synthesis and characterization of phenylacetylene-terminated poly(silyleneethynylene-4,4′-phenylethereneethynylene)s

Two kinds of phenylacetylene-terminated poly(silyleneethynylene-4,4′-phenylethereneethynylene)s, {C₆H₅CC[Si(R)₂CCC₆H₄OC₆H₄CC]_nC₆H₅} wherein R represents methyl or phenyl, were synthesized by condensation reaction between dichlorosilanes and 4,4′-diethynyldiphenyl ether using organomagnesium reagents. The polymers were characterized by NMR, IR, gel permeation chromatography, thermogravimetric analysis, and differential scattering calorimetry.     

Oxidatively induced reactions of a diimine platinum(IV) tetramethyl complex

The oxidation of the Pt(IV) tetramethyl complex [ArNCHCHNAr]PtMe₄ (Ar = 2,6-Me₂C₆H₃) has been investigated in acetonitrile and dichloromethane. Cyclic voltammetry demonstrates that the irreversible oxidation of [ArNCHCHNAr]PtMe₄ occurs at a slightly less positive oxidation potential than the irreversible oxidation of the analogous Pt(II) species [ArNCHCHNAr]PtMe₂. The product distribution arising from the oxidation depends strongly on the reaction conditions and includes cationic Pt(IV) species (acetonitrile, dichloromethane solvents) and Pt(II) species (dichloromethane only). Evidence is presented that suggests that homolytic cleavage of a weakened PtC bond in is involved in the oxidatively induced reactions.     

Preparation of soluble functional polymers by modification of nanosized polyacetylene

The reaction of electrophilic reagents such as halogens, nitric and sulfuric acids, and sulfur dioxide with nanosized stereoregular polyacetylene was studied. Polymers with chlorine content as much as 65% were obtained and the MW properties of the polymers were found to depend on the structure of pristine polyacetylene prepared under various conditions. The reaction between nitric acid and stereoregular polyacetylene occurred to give first [CH(NO₂)CHCHCH(OH)]_n while the totally nitrated product [CH(NO₂)CH(ONO₂)]_n was obtained with nitrogen content of 18.3% after complete nitration. GPC, NMR- and IR-spectroscopy were used for structural and MWD analysis of the original polyacetylene and obtained products. The mechanism of the reaction between electrophilic reagents and polyacetylene is discussed on the basis of the experimental and literature data.     

Synthesis and properties of conjugated bimetallic ruthenium complexes with σ,σ-bridging azobenzene chains

A versatile synthetic route to conjugated bimetallic ruthenium complexes with σ,σ-bridging azobenzene chains was developed, and new ruthenium complexes with various ligands were synthesized and characterized. These bimetallic complexes showed a remarkable absorption in the visible region (λ_max: 452-483 nm), and undergo trans-to-cis isomerization under UV light irradiation for short time. Electrochemical study showed that the metal centers in bimetallic complexes containing the CHCHC₆H₄NNC₆H₄CHCH bridge interact with each other.     

P-Modular bis(phosphines) based on the 1,2-trans-disubstituted cyclopentane framework in synthesis, coordination chemistry, and catalysis

The review describes a class of versatile bidentate phosphines having a homochiral 1,2-disubstituted cyclopentane backbone, the use of such ligands in coordination chemistry, and their application in transition metal-catalyzed synthesis, including CH activation, CC coupling, CC hydrogenation, and hydroformylation. In particular, the synthetic potential of the multi-purpose PH and PCl reagents (R,R)- and (S,S)-C₅H₈(PX₂)₂ (X = H, Cl) is highlighted, since these open up the possibility to incorporate virtually any other PO-, PN- or PC-bonded residue (“module”) into the homochiral bis(phosphine) framework. The resulting chelate ligands allow access to transition metal catalysts with stereodiscriminating properties determined by parameters such as (i) the presence of P-substituents that are equal or pairwise different in steric demand, (ii) the spatial orientation of such substituents with respect to the coordination plane of the catalyst complex, and (iii) the combination of C- and P-chirogenic stereoelements in matched (or mismatched) fashion. A comparative discussion of the crystal structures that are currently available for the free ligands and their transition metal complexes is also presented.     

Selective anodic fluorination of electrophilic alkenes

Anodic fluorination of some electrophilic alkenes (conjugated with electron-withdrawn groups), ethyl cinnamates, RC₆H₄CHCHCO₂Et (R = H, CH₃, CH₃O, F and CF₃), cinnamonitrile, C₆H₄CHCHCN, phenyl stryryl ketone, and t-butyl styryl ketone using ammonium fluorides as the fluorine source and supporting electrolyte, in CH₂Cl₂ as electrolytic solvent yields the expected vicinal difluoro compounds, as mixture of erythro and threo isomers. The anodic fluorination of phenyl 3,5-di-t-butyl-4-hydroxystyryl ketone yields two monofluoro compounds. A possible reaction mechanism is discussed.     

Crystal structure and FT-IR study of aqualithium 1-naphthylmethyl ester of monensin A perchlorate

The crystal [MON8LiClO₄H₂O] containing the neutral molecule of 1-naphthylmethyl ester of monensin A (MON8), lithium perchlorate and one water molecule was obtained and its structure was examined using X-ray diffraction and discussed in detail. The MON8LiClO₄H₂O supramolecular complex is crystallized in the non-centrosymmetric space group of the orthorhombic system (P2₁2₁2₁) with four molecules in the unit cell. Within MON8LiClO₄H₂O complex the Li⁺ cation is square-pyramidally coordinated by four oxygen atoms of the MON8 molecule and by the oxygen atom of the water molecule. The oxygen atoms (O9 and O14) of the two OH groups are involved in two intramolecular O(14)H?O(9) and O(9)H?O(14) hydrogen bonds of similar strength stabilizing a pseudo-cyclic structure of MON8. Additionally the coordinated water molecule acts as proton donor in the two hydrogen bonds. The FT-IR spectrum of the crystal provides spectroscopic evidence for the complex formation and it is discussed in detail.     

Reactivity of [CpRh(η-C6H3NH2-2,6-i-Pr2)](OTf)2 toward phosphines and alkynes

The cationic aniline complex [Cp^∗Rh(η⁶-2,6-(Me₂CH)₂C₆H₃NH₂)](OTf)₂ (1) was prepared from either [Cp^∗Rh(η²-NO₃)(η¹-OTf)] or [Cp^∗Rh(OH₂)₃](OTf)₂ and 2,6-diisopropylaniline. Complex 1 underwent substitution with phosphines or phosphites, indicating the labile character of the η⁶-aniline ligand. Complex 1 mediated cycloaddition reactions of several alkynes in refluxing ethanol: the [2 + 2] dimerization for PhCCPh and the [2 + 2 + 1] trimerization for PhCCH and CH₃C₆H₄CCH. The unexpected cyclobutadiene complex [Cp^∗Rh(η⁴-C₄(C(O)CH₃)₂H(SiMe₃))] was obtained from complex 1 and Me₃SiCCCCSiMe₃ and structurally characterized by X-ray diffraction.     

Solvent and phosphine dependency in the reaction of cis-RuCl2(P-P)2 (P-P = dppm or dppe) with terminal alkynes

Reaction of cis-[RuCl₂(dppm)₂] (dppm = 1,2-bis(diphenylphosphino)methane) with PhCCH and NaPF₆ utilising methanol as solvent results in the formation of the η³-butenynyl complex [Ru(η³-PhCCCCHPh)(dppm)₂][PF₆] in good yield. Similar reactions with Bu^tCCH and PrⁿCCH resulted in the corresponding alkyl-substituted complexes and all three of these compounds have been characterised by NMR spectroscopy and X-ray crystallography. The mechanism of this reaction has been probed by employing labelling experiments with both PhCCD and PhC¹³CH allowing the identity of possible intermediates in the reaction to be determined. Furthermore, [Ru(η³-PhCCCCHPh)(dppm)₂][PF₆] has been shown to be an effective regio- and stereo-selective catalyst for the dimerisation of PhCCH to Z-PhCCCHCHPh in the absence of solvent. In contrast, no evidence for the formation of alkyne coupling was obtained from the reaction of cis-[RuCl₂(dppe)₂] (dppe = 1,2-bis(diphenylphosphino)ethane) with PhCCH and NaPF₆.