Synthesis and structural characterization of novel bridged platinum(II) biscarbene complexes

Novel bridged platinum(II) biscarbene complexes are reported: 1,1′-dimethyl-3,3′-methylene-4-diimidazolin-2,2′-diylidene platinum(II) (3) and 1,1′-dimethyl-3,3′-ethylene-4-diimidazolin-2,2′-diylidene platinum(II) complexes 4 are directly accessible in high yields starting from platinum halides. The one-pot synthesis obviates the need for multi-step reactions via metal precursors or free carbenes. An X-ray crystal structure of 1,1′-dimethyl-3,3′-methylene-4-diimidazolin-2,2′-diylidene platinum(II) dibromide (3b) confirmed the structural similarity to the known corresponding palladium complexes. Since free 1,1′-di-R-3,3′-methylene-4-diimidazolin-2,2′-diylidenes are only available in low yields this synthetic route provides an easy access to the corresponding carbene complexes.     

Synthesis, characterization and photophysics of alkyne bridged bimetallic rhenium(I) and ruthenium(II) complexes

Six new homobimetallic and heterobimetallic complexes of rhenium(I) and ruthenium(II) bridged by ethynylene spacer [(CO)₃(bpy)Re(BL)Re(bpy)(CO)₃]²⁺ [Cl(bpy)₂Ru(BL)Ru(bpy)₂Cl]²⁺ and [(CO)₃(bpy)Re(BL)Ru(bpy)₂Cl]²⁺ (bpy = 2,2′-bipyridine, BL = 1,2-bis(4-pyridyl)acetylene (bpa) and 1,4-bis(4-pyridyl)butadiyne (bpb) are synthesized and characterized. The electrochemical and photophysical properties of all the complexes show a weak interaction between two metal centers in heterobimetallic complexes. The excited state lifetime of the complexes is increased upon introduction of ethynylene spacer and the transient spectra show that this is due to delocalization of electron in the bridging ligand. Also, intramolecular energy transfer from *Re(I) to Ru(II) in Re–Ru heterobimetallic complexes occurs with a rate constant 4 × 10⁷ s⁻¹.     

Synthesis and characterization of dinuclear pyrazolato bridged platinum(IV) complexes

Reactions of [PtMe₃(OCMe₂)₃](BF₄) and [(PtMe₃I)₄] with pyrazole (pzH) afforded mononuclear pyrazole platinum(IV) complexes [PtMe₃(pzH)₃](BF₄) (1) and [PtMe₃I(pzH)₂] (2), respectively. The formation of dinuclear pyrazolato bridged platinum(IV) complexes (PPN)[(PtMe₃)₂(μ-pz)₃] (3), (PPN)[(PtMe₃)₂(μ-I)(μ-pz)₂] · 1/2Et₂O (4) and [K(18C6)][(PtMe₃)₂(μ-I)(μ-pz)₂] (5) was achieved by the reaction of each 1 and 2 with [PtMe₃(OCMe₂)₃](BF₄) in the presence of KOAc followed by reaction with (PPN)Cl (PPN⁺ = bis(triphenylphosphine)iminium cation) and 18C6, respectively. The reaction of complex 4 with AgO₂CCF₃ followed by addition of RSR′ (R/R′ = Me/Me, Me/Ph) resulted in the formation of complexes [(PtMe₃)₂(μ-pz)₂(μ-RSR′)] (R/R′ = Me/Me, 6; Me/Ph, 7). All complexes were characterized unambiguously by microanalysis and NMR (¹H, ¹³C) spectroscopic investigations. Additionally, crystal structures of complexes 3 and 4 as well as DFT calculation are presented. Furthermore, in vitro studies on the anti-proliferative activity of complexes 2 and 5 were carried out.     

Synthesis and characterization of cationic heteronuclear complexes of platinum(II) and silver( I) bridged by alkynyl ligands

The dialkynyl complexes cis-[Pt(C CR)₂L₂] [R = Ph, L₂ = 2PPh₃, 2PEt₃, dppe (dppe = 1,2-bis(diphenylphosphino)ethane]; R ---^tBu, L₂ = 2PPh₃, dppe) react with silver perchlorate in a molar ratio 1:0.5 to give platinum-silver perchlorate salts of the type [Pt₂ Ag(C CR)₄L₄](ClO₄) in excellent yield. The X-ray crystal structure of [Pt₂Ag(C = CPh)₄(PPh₃)₄](ClO₄) 1 shows that the cation is formed by two nearly orthogonal cis-[Pt(C CPh)₂(PPh₃)₂] units connected through a silver cation which is unsymmetrically π-bonded to all four acetylene fragments. Similar reactions of cis-[Pt(C CR)₂L₂] with one equivalent of AgClO₄ afford cationic complexes of general formula [PtAg(C CR)₂L₂](ClO₄), which are believed to be salts, [Pt₂Ag₂(C CR)₄L₄](ClO₄)₂.     

Synthesis and characterization of poly(butylene succinate) and its copolyesters containing minor amounts of propylene succinate

High molecular weight poly(butylene succinate) (PBSu), poly(propylene succinate), and PBSu-rich copolyesters were synthesized using an effective catalyst, titanium tetraisopropoxide. The compositions of the copolyesters were determined in three ways from ¹H and ¹³C NMR spectra, and good agreement between the results was obtained. The analysis of the carbonyl carbon spectra indicates a random distribution of the comonomers. Thermal properties were studied using a differential scanning calorimeter and a thermogravimetric analyzer. No significant difference exists among the thermal stabilities of these polyesters. However, the window between the glass transition and the melting temperatures becomes narrower with the increase in the concentration of propylene succinate in the copolymers. Additionally, the cold crystallization ability reduces considerably. Wide-angle X-ray diffractograms of isothermally crystallized copolyesters also follow the same trend.     

Synthesis, characterization and electrochemistry of ferrocenylselenolate bridged palladium(II) and platinum(II) complexes

The dimeric ferrocenyl-selenolate complexes of Pd and Pt, [{μ-η¹-Fe(η⁵-C₅H₄Se)₂}M(PⁿBu₃)]₂ (M = Pd 2, Pt 3), and the monomeric ferrocenyl(bis-selenolate) complex of platinum, [{η²-Fe(C₅H₄Se)₂}Pt(PⁿBu₃)₂] (4), have been prepared from 1,1′-bis(trimethylsilylseleno)ferrocene 1 and trans-MCl₂(PⁿBu₃)₂ and cis-PtCl₂(PⁿBu₃)₂, respectively. Complexes 2 and 3 contain two edge-sharing, square-planar metal centres forming a planar M₂Se₂ four-membered ring and exhibit two one-electron redox waves indicating electronic communication between the two Fe centers.     

Synthesis, characterization and magnetism of binuclear cobalt (II) complexes bridged by tetracarboxylato groups

Three new binudear cobalt (II) complexes with extended te-tracarboxylato- bridge have been synthesized and characterized, namely [Co2 (PMTA) (bpy)4] (1), [Co2(PMTA)-(phen)4] (2) and [Co2(PMTA) (NO2phen)4] (3), where PMTA represents the tetraanion of pyroniellitic acid, and bpy, phen, NO2-phen denote 2,2'-bipyridine, 1,10-phenan-throline; 5-nirto-1, 10-plienanthroline, respectively. Based on elemental analyses, molar conductivity measurements, IR and electronic spectra studies, it is proposed that these complexes have PMTA-bridged structures and consist of two cobalt (II) ions, each in a distorted octahedral environment. These complexes were further characterized by variable temperature magnetic susceptibility measurements (4-300 K) and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, giving the exchange integral J = - 1.02 cm-1 for 1, J = -1.21 cm-1 for 2 and J = - 1.18 cm-1 for 3, respectively. These results revealed the operation of antiferromagneti     

Synthesis and reactivity of new chelate-N-heterocyclic biscarbene complexes of ruthenium

The carbene-ligand precursors methylenebis(N-alkylimidazolium) iodide (alkyl = methyl, neo-pentyl) and ethylenebis(N-methylimidazolium) chloride have been used in the preparation of several new Ru(II)-p-cymene complexes where the ligand behaves as mono- and bidentate. The molecular structures of the two biscarbene-complexes are reported. From the data reported, we can conclude that steric reasons (mainly the bisimidazolium linkers, methylene/ethylene) are the main factors determining both reactivity and synthetic difficulties of the products reported.     

Synthesis, structure and characterization of binuclear silver(I) complexes

Summary Two binuclear Ag^I complexes, [{Ag(dppp)}₂](NO₃)₂ (1) and [{Ag(dppb)}₂(NO₃)]₂ (2) (dppp = Ph₂P(CH₂)₃PPh₂, dppb = Ph₂P(CH₂)₄PPh₂], were synthesized and characterized by elemental analysis, t.g., i.r. and ³¹P-n.m.r. spectra. Single crystals of complex (2) were obtained from MeOH-CHCl₃. The X-ray crystal structure shows that the dppb ligand is bidentate, with two ligands bridging two metal ions to form a centrosymmetric dimer.     

Synthesis,structure and characterization of binuclear copper(I) complexes

Binuclear copper(I) complexes [Cu(dppm)(NO3)]2 (1), dppm=Ph2PCH2PPh2, [Cu(dppm)(2,9-Me2Phen)]2(NO3)2 (2), [Cu(dppm)(I)]2 (3) and [Cu(dppm)(py)]2(NO3)2 (4), (py=pyridine) have been synthesized by ligand reduction of cupric nitrate with dppm in EtOH and characterized by elemental analyses, molecular weight determination, t.g.a., 31P-n.m.r spectra; their electronic conductivities and c.v. waves have also been measured. The results show that dppm coordinates as a bridging bidentate ligand to the CuI atoms, and that NO3 behaves as a monodentate ligand or free ion in the newly prepared complexes.     

Hydrosilylation with biscarbene Rh(I) complexes: experimental evidence for a silylene-based mechanism

A detailed study investigating the mechanism of the hydrosilylation of 4-F-acetophenone by N-heterocyclic biscarbene rhodium(I) complexes was performed, delivering substantial experimental evidence for a recently proposed catalytic cycle and explaining the observed side-product formation. Labeling experiments, silylene trapping reactions, and specific catalytic reactions were employed to substantiate each step of the catalytic cycle and explain the differences observed for different types of chiral catalysts. It is further shown that hydrosilylation and dehydrocoupling reactions with dihydrosilanes are mechanistically related.     

Synthesis,characterization and X-ray crystal structures of polyether and ethylene bridged bis(azolyl) platinum(II) complexes

The preparation of platinum(II) complexes of the types [PtCl₂{Y(CH₂CH₂O) _x CH₂CH₂Y}] (Y: imidazol-1-yl, im; pyrazol-1-yl, pz or benzimidazol-1-yl, bim) and [PtI₂{im(CH₂CH₂O) _x CH₂CH₂im}] with varying ligand backbone length (x between 0 and 3) is described. A new bis(pyrazol-1-yl) polyether compound, pz(CH₂CH₂O)₂CH₂CH₂pz, is reported. Spectroscopic characterization of the complexes is discussed. Two crystal structures of the general formula [PtCl₂{im(CH₂CH₂O) _x CH₂CH₂im}] (x is 1 or 3) are also reported.     

Binuclear biscarbene complexes of furan

Carbene complexes of chromium and tungsten with a bridging furan substituent were synthesized from lithiated furan precursors and metal hexacarbonyls. The binuclear biscarbene complexes [(CO)5M{C(OEt)-C4H2O-C(OEt)}M'(CO)5](M = M'= Cr (3), W (4)) were obtained as well as the corresponding monocarbene complexes [M{C(OEt)-C(4)H3O}(CO)5](M = Cr (1), W (2)). A method of protecting the carbene moiety during the metal acylate stage was used to increase not only the yields of the binuclear Fischer biscarbene complexes 3 and 4 but to establish a method to synthesize analogous mixed heterobinuclear carbene complexes (M = W, M'= Cr (5)) in high yields. The binuclear biscarbene complexes 3 and 5 were reacted with 3-hexyne and yielded the corresponding benzannulated monocarbene complexes [M{C(OEt)-C14H17O3}(CO)5](M = Cr (6), W(7)). Complex 5 reacted regioselectively with the benzannulation reaction occurring at the chromium-carbene centre. The major products from refluxing 3 in the presence of [Pd(PPh3)4] were a monocarbene-ester complex [Cr{C(OEt)-C4H2O-C(O)OEt}(CO)5](8), the 2,5-diester of furan (9) and a carbene-carbene coupled olefin EtOC(O)-C4H2O-C(OEt)=C(OEt)-C4H2O-C(O)OEt (10). X-Ray structure analysis of 4 and 6 confirmed the molecular structures of the compounds in the solid state and aspects of electron conjugation between the transition metals and the furan substituents in the carbene ligands were investigated.     

Synthesis and electrochemistry of organometallic ethanethiolato bridged complexes of ruthenium(IV)

Reaction of the ruthenium(IV) chloro-bridged dimer [{Ru(η³ : η³-C₁₀H₁₆)Cl(μ-Cl)}₂], 1, with ethanethiol (EtSH) in CH₂Cl₂ gives the bridged-cleaved adduct [Ru(η³ : η³-C₁₀H₁₆)Cl₂(SHEt)], 2. Stirring of two molar equivalents of 2 in methanol with one equivalent of 1 gives the binuclear, mixed chloro/thiolato bridged compound [{Ru(η³ : η³-C₁₀H₁₆)Cl} ₂(μ-SEt)], 3. The related doubly thiolato bridged complex [{Ru(η³ : η³-C₁₀H₁₀)Cl(μ-SEt)}₂], 4, is formed by treatment of 1 with an excess of EtSH, or by prolonged stirring of 2 alone in methanol. Compounds 2–4 have been studied by cyclic voitammetry. Compound 2 undergoes only irreversible oxidation, whereas in the case of both 3 and 4 the observation of significant return waves is consistent with a greater stability of the primary redox products.     

Synthesis and characterisation of phenoxo bridged dinuclear complexes of copper(II)

A series of model complexes for the type III site, in oxidised hemocyanin, containing Cu₂(μ-0Ph)³⁺ core have been synthesised using a heptadentate ligand (H₃L) formed from the Schiff base condensation of triethylenetetramine and salicylaldehyde. The ligand provides one imine and one inbuilt imidazole nitrogen and two phenolic oxygen donors with both five- and six-membered chelate rings to each metal centre. In the pentacoordinated complexes [Cu₂(L)X]·nH₂O, a third exogenous bridging ligand is present. The TG curve indicates the loss of lattice water molecules between 70 and 125°C. The residue after decomposition is CuO above 550°C. Theg values of theX-band EPR spectrum of [Cu₂L(μ-OAc)]·2H₂O in methanol glass (77 K) are typical of a variety of bridged copper(II) dimers. The copper-copper magnetic interaction is dependent on the presence and nature of X in these complexes.     

Synthesis and characterization of Cu(I) and Cu(II) complexes containing ketiminate ligands

A series of Cu(I) and Cu(II) complexes containing substituted ketiminate ligands was synthesized. Reaction of CuCl₂ with 2 equiv. of Li[OC(Me)CHC(Me)N(Ar)] in toluene generated dark green solid of Cu[OC(Me)CHC(Me)N(Ar)]₂ (1). Similarly, Cu(I) complex, {Cu[OC(Me)CHC(Me)N(Ar)]Li[OC(Me)CHC(Me)N(Ar)]}₂ (2) was synthesized by reacting 2 equiv. of Li[OC(Me)CHC(Me)N(Ar)] with CuCl in toluene at room temperature for 12 h. While the reaction of CuCl with Li[OC(Me)CHC(Me)N(Ar)] in the presence of triphenylphosphine in THF solution at room temperature, a three-coordinated Cu[OC(Me)CHC(Me)N(Ar)](PPh₃) (3) can be isolated in high yield. Replacing the PPh₃ of 3 with N-heterocarbene (NHC) generates Cu[OC(Me)CHC(Me)N(Ar)](NHC) (4) in low yield. Complexes 2, 3, and 4 were characterized by ¹H and ¹³C NMR spectroscopies and all molecules were structurally characterized by X-ray diffractometry. Two coordination modes of ketiminate ligands were found in the molecular structure of 2, one of which is copper-coordinated terminal ketiminates and the other is lithium-copper-coordinated bridging ketiminates.     

Synthesis, characterization and photophysics of bimetallic manganese(I) and ruthenium(II) complexes

A series of new manganese(I) and ruthenium(II) monometallic and bimetallic complexes made of 2,2′-bipyridine and 1,10-phenanthroline ligands, [Mn(CO)₃(NN)(4,4′-bpy)]⁺, [{(CO)₃(NN)Mn}₂(4,4′-bpy)]²⁺ and [(CO)₃(NN)Mn(4,4′-bpy)Ru(NN)₂Cl]²⁺ (NN = 2,2′-bipyridine, 1,10-phenanthroline; 4,4′-bpy = 4,4′-bipyridine) are synthesized and characterized, in addition to already known ruthenium(II) complexes [Ru(NN)₂Cl(4,4′-bpy)]⁺ and [Cl(NN)₂Ru(4,4′-bpy)Ru(NN)₂Cl]²⁺. The electrochemical properties show that there is a weak interaction between two metal centers in Mn–Ru heterobimetallic complexes. The photophysical behavior of all the complexes is studied. The Mn(I) monometallic and homobimetallic complexes have no detectable emission. In Mn–Ru heterobimetallic complexes, the attachment of Mn(I) with Ru(II) provides interesting photophysical properties.     

Synthesis and structural characterization of luminescent trinuclear gold(I) complexes with dithiocarbamates

We have synthesized a series of trinuclear gold(I) complexes, namely, [Au3(mu-dpmp)(S2CNR2)nCl3-n] (n = 0-3; R = Me, CH2Ph), [Au3(mu-dpmp)(mu-S2CNR2)Cl](CF3SO3) (R = Me, CH2Ph), and [Au3(mu-dpmp)(mu-S2CNMe2)(C6F5)]X (X = Cl, CF3SO3), containing the triphosphine dpmp [bis(diphenylphosphinomethyl)phenylphosphine] and varying amounts of dithiocarbamate. NMR experiments show fluxional behavior in solution for most of these derivatives because several arrangements of the ligands are possible. The crystal structure of [(mu-dpmp)(AuCl)3] has been determined by X-ray diffraction studies; the molecule displays mirror symmetry and involves an angular arrangement of the gold atoms [Au-Au-Au 119.603(14) degrees, Au-Au 3.3709(4) A]. We have studied the optical properties of these derivatives in the solid state, finding a red shift as a function of the dithiocarbamate number and, for some derivatives, wavelength-dependent emission spectra at low temperature.     

Synthesis, characterization and dioxygen reactivity of copper(I) complexes with glycoligands

A new family of copper(I) complexes with "glycoligands" containing a central saccharide scaffold, with 2-picolyl ether groups or 2-picolylamine or N-imidazolylamine groups, has been prepared and characterized. For this purpose, the following tetradentate ligands have been synthesized: methyl 2,3-di-O-(2-picolyl)-alpha-D-lyxofuranoside (L1), 1,5-anhydro-2-deoxy-3,4-di-O-(2-picolyl)-d-galactitol (L2), 5-(amino-N-(2-salicyl))-5-deoxy-1,2-O-isopropylidene-3-O-(2-picolyl)-alpha-D-xylofuranose (L3), and 5-(amino-N-(2-salicyl))-5-deoxy-1,2-O-isopropylidene-3-O-(methylimidazol-2-yl)-alpha-D-xylofuranose (L4). The ligands and the complexes were characterized by elemental analysis, IR, 1H and 13C NMR spectroscopies, ESI mass spectrometry, and cyclic voltammetry. Collaterally with the experimental work, HF-DFT(B3LYP/6-31G*) computations were performed to obtain additional structural information. The Cu(I) complexes are found to be pentacoordinated. The redox properties and the O2-reactivity of the Cu(I)Ln complexes have been studied. Reactions of Cu(I) complexes with dioxygen in ethanol yield stable Cu(II) complexes as confirmed by UV-visible spectrophotometry and EPR spectroscopy.