Synthesis and properties of rhenium tricarbonyl complex bearing N-fused tetraphenylporphyrin ligand

An N-fused porphyrin rhenium complex was synthesized by the thermal reaction of an N-confused porphyrin with Re2(CO)10 and its structure was determined by X-ray crystallographic analysis.     

Olefin metathesis catalyst bearing a chelating phosphine ligand

An improved synthetic procedure for the complex (SPY-5-34)-dichloro-(κ²(C,P)-diphenyl-(2-benzylidene)-phosphine)-(1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydro-imidazol-2-ylidene)-ruthenium (2) was elaborated and the title compound was tested as latent initiator in Ring Opening Metathesis Polymerization (ROMP) and as catalyst for Ring-Closing Metathesis (RCM) at elevated temperatures. While not particularly suited as latent initiator for ROMP, exhibiting a switching temperature of only 42 °C in the polymerization of a typical norbornene derivative, 2 shows an appealing performance in RCM of α,ω-dienes at higher temperatures.     

Biphasic Suzuki coupling reactions of aryl or benzyl bromides employing cobalt-containing phosphine ligand coordinated palladium complex

Biphasic Suzuki-coupling reactions of aryl and benzyl bromides employing a cobalt-containing phosphine ligand chelated palladium complex 2 were carried out in various reaction conditions. Comparisons of the catalytic efficiencies in the presence/absence of a phase-transfer agent, TBAB, were presented. In addition, the effects of altering solvents, temperatures, catalysts, and substrates on the reactions were monitored and reported. Better yields were commonly observed while a phase-transfer agent TBAB was participated in the reactions. The factor of reaction time is more crucial than that of temperature in short reaction hour experiments. Obviously, an induction period for the reduction of Pd(II) to Pd(0) active species is needed for this type of reaction.     

Supramolecular complex composed of a covalently linked zinc porphyrin dimer and fulleropyrrolidine bearing two axially coordinating pyridine entities

A zinc porphyrin dimer-fullerene supramolecular complex with a large association constant is assembled; efficient intramolecular photoinduced electron transfer from the singlet excited state of zinc porphyrin to the fullerene is observed.     

Synthesis,characterization, and catalytic application of a zinc(II) complex bearing a pyrazole-based ligand

The reaction between ZnCl₂ and N,N-bis[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]-1-phenylethylamine (bdmppea) affords [(bdmppea)ZnCl₂], whose structure has been determined by X-ray crystallography. The [(bdmppea)ZnEt₂] complex in situ prepared by the reaction between [bdmppea] and ZnEt₂ exhibited high activity toward the polymerization reaction of rac-lactide at room temperature. However, its activity decreased sharply with decreasing temperature. Stereospecificity of this catalyst characterized by heterotacticity (P_r) was determined by homonuclear decoupled NMR spectroscopy, which value was ∼0.58.     

Distinct chiral units from an axially prochiral ligand in a photoluminescent zinc(II)–organic complex

The asymmetric unit of the title compound, poly[(dimethylamine‐κN)[μ₃‐(E)‐2,6‐dimethyl‐4‐styrylpyridine‐3,5‐dicarboxylato‐κ³O³:O^3′:O⁵]zinc(II)], [Zn(C₁₇H₁₃NO₄)(C₂H₇N)]_n, consists of one crystallographically independent distorted tetrahedral Zn^II cation, one (E)‐2,6‐dimethyl‐4‐styrylpyridine‐3,5‐dicarboxylate (mspda²⁻) ligand and one coordinated dimethylamine molecule. Two S‐ and R‐type chiral units are generated from the axially prochiral mspda²⁻ ligand through C—H...O hydrogen bonds. The R‐type chiral units assemble a left‐handed (M) Zn–mspda helical chain, while the right‐handed (P) Zn–mspda helical chain is constructed from neighbouring S‐type chiral units. The P‐ and M‐type helical chains are interlinked by carboxylate O atoms to form a one‐dimensional ladder. Interchain N—H...O hydrogen bonds extend these one‐dimensional ladders into a two‐dimensional supramolecular architecture. The title compound exhibits luminescence at λ_max = 432 nm upon excitation at 365 nm.     

Asymmetric allylic alkylation of cycloalkenediol diacetates using a chiral phosphine ligand bearing a carboxyl group

Asymmetric induction in the allylic alkylation of cycloalkenediol diacetates was performed using a chiral alkylphosphine ligand bearing a carboxyl group, 3-(diphenylphosphino)butanoic acid. An increase in enantiomeric excess of the monoalkylated products of cis-cycloalkenediol diacetates was observed through a sequential asymmetric allylic alkylation–kinetic resolution process.     

Ethylene polymerization of the new titanium complexes bearing a phosphine oxide‐bridged bisphenolato ligand

A series of novel titanium(IV) complexes combining a phosphine oxide‐bridged bisphenolato ligand TiCl₂{2,2′‐O?P‐R₃ (4‐R₂‐6‐R₁‐C₆H₂O)₂}(THF) ( 6a : R₁ = tBu, R₂ = H, R₃ = Ph; 6b : R₁ = Ph, R₂ = H, R₃ = Ph; 6c : R₁ = R₂ = tBu, R₃ = Ph; 6d : R₁ = R₂ = cumyl, R₃ = Ph; 6e : R₁ = tBu, R₂ = H, R₃ = PhF₅) were prepared by the reaction of corresponding bisphenolato ligands with TiCl₄ in THF. X‐ray analysis reveals that complex 6a adopts distorted octahedral geometry around the titanium center. These catalysts were performed for ethylene polymerization in the presence of modified methyaluminoxane (MMAO). The effects of reaction parameters on ethylene polymerization behaviors, such as cocatalyst concentration, polymerization temperature, and reaction time were studied in detail. In general, these new complexes exhibited high catalytic activity, good temperature tolerance, and long lifetime for ethylene polymerization. The resulting polymers possess high molecular weight, unimodal distribution, and linear structure. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7062–7073, 2008     

Dimerization of terminal alkynes catalyzed by a nickel complex having a bulky phosphine ligand

Ni(cod)(2)/P(t)Bu(3) system catalyzed the dimerization of terminal alkynes to give (E)-head-to-head dimerization products, in which the stannylacetylene dimer could be applied to a one-pot synthesis of a conjugated enyne, when combined with Migita-Stille coupling.     

Stereochemistry of the free‐radical polymerization of zinc methacrylates coordinated with a bidentate ligand

The polymerization of zinc methacrylates coordinated with a bidentate ligand ( 1 – 4 ) was carried out in chloroform at 60°C. The polymerization of these monomers gave chloroform‐insoluble polymers. Stereoregularity of the polymers was estimated from ¹H NMR spectra of poly(methyl methacrylate)s (PMMAs) derived from the original polymers. Monomers 1 and 2 gave slightly different polymers compared with conventional ones obtained by polymerization of methacrylic acid, while 3 afforded higher amounts of isotactic polymers than 1 and 2 . Conversely, 4 gave a polymer of high syndiotacticity. Furthermore, the relationship between triad tacticity and monomer concentration in the feed was studied. Consequently, it was demonstrated that the structure of bidentate ligands coordinated with zinc ion influences the stereoregularity of the resulting polymers.     

A zwitterionic triosmium cluster bearing a metallated azulene ligand coordinated perpendicularly as an alkylidene bridge

The cluster [Os₃(CO)₁₀(MeCN)₂] reacts readily with azulene in refluxing cyclohexane to give the oxidative addition product [Os₃(μ-H)(μ₂-η¹-C₁₀H₇)(CO)₁₀] 1 which was shown by its X-ray crystal structure to contain the C₅ ring of the azulenyl ligand bonded through a single carbon atom at the 1-position. We propose that the compound is zwitterionic, with the 7-membered ring a tropylium cation and the 5-membered ring coordinated as a μ-alkylidene to the metal cluster, which carries a formal negative charge. Thermal loss of one CO ligand leads by further oxidative addition to the known cluster [Os₃(μ-H)₂(μ₃-η¹:η¹:η¹-C₁₀H₆)(CO)₉] 2.     

Effects of phosphine ligand chelation on the reactivity of monomeric parent amido ruthenium complexes: synthesis and reactivity of such a complex bearing monodentate ligands

The parent amido complex cis-(PMe(3))(4)Ru(H)(NH(2)) (2) has been prepared via the deprotonation of [cis-(PMe(3))(4)Ru(H)(NH(3))(+)][BPh(4)(-)]. The amido complex is a somewhat weaker base than the DMPE analogue trans-(DMPE)(2)Ru(H)(NH(2)) but is still basic enough to quantitatively deprotonate fluorene and reversibly deprotonate 1,3-cyclohexadiene and toluene. Complex 2 exhibits very labile phosphine ligands, two of which can be replaced by DMPE to yield the mixed complex cis-(PMe(3))(2)(DMPE)Ru(H)(NH(2)). Because of the ligand lability, 2 also undergoes hydrogenolysis and rapid exchange with labeled NH(3). The amide complex reacts with alkyl halides to yield E2 and S(N)2 products, along with ruthenium hydrido halide complexes including the ruthenium fluoride cis-(PMe(3))(4)Ru(H)(F). Ruthenium hydrido ammonia halide ion pair intermediates [cis-(PMe(3))(4)Ru(H)(NH(3))(+)][X(-)] are observed in some deprotonation and E2 reactions, and measurement of the equilibrium constants for NH(3) displacement from these complexes suggests that they benefit from significant hydrogen bonding between X(-) and NH(3) groups. Cumulenes also react with complex 2 to afford the products of insertion into an NH bond. The rates of neither these NH insertion reactions nor the reversible deprotonation reactions show any dependence on the concentration of PMe(3) present, suggesting that these reactions take place directly at the NH(2) group and do not involve precoordination of substrate to the metal center.     

Dimeric zirconium complex bearing a dianionic ansa-bis(aminopyridinato) ligand

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Photocytotoxicity and photoinduced phosphine ligand exchange in a Ru(ii) polypyridyl complex

Two new tris-heteroleptic Ru(ii) complexes with triphenylphosphine (PPh₃) coordination, cis-[Ru(phen)₂(PPh₃)(CH₃CN)]²⁺ (1a, phen = 1,10-phenanthroline) and cis-[Ru(biq)(phen)(PPh₃)(CH₃CN)]²⁺ (2a, biq = 2,2′-biquinoline), were synthesized and characterized for photochemotherapeutic applications. Upon absorption of visible light, 1a exchanges a CH₃CN ligand for a solvent water molecule. Surprisingly, the steady-state irradiation of 2a followed by electronic absorption and NMR spectroscopies reveals the photosubstitution of the PPh₃ ligand. Phosphine photoinduced ligand exchange with visible light from a Ru(ii) polypyridyl complex has not previously been reported, and calculations reveal that it results from a trans-type influence in the excited state. Complexes 1a and 2a are not toxic against the triple negative breast cancer cell line MDA-MB-231 in the dark, but upon irradiation with blue light, the activity of both complexes increases by factors of >4.2 and 5.8, respectively. Experiments with PPh₃ alone show that the phototoxicity observed for 2a does not arise from the released phosphine ligand, indicating the role of the photochemically generated ruthenium aqua complex on the biological activity. These complexes represent a new design motif for the selective release of PPh₃ and CH₃CN for use in photochemotherapy.

New Ru(ii) complexes exhibit selective ligand dissociation driven by an excited state trans-type influence. The complexes are not toxic to triple-negative breast cancer cells in the dark, but induce cell death upon irradiation with visible light.     

Nucleophilicity of N-propargylanilines in the coordination to zinc tetraphenylporphyrin in chloroform

Thermodynamic parameters (ΔG ⁰ and ΔS ⁰) of the isoenthalpic (except for 4-halo derivatives) coordination of (tetraphenylporphyrinato)zinc(II) with anilines in chloroform at 273–313 K linearly correlate with the shift of their electronic absorption maxima in the reaction with anilines, as well as with the logarithms of the stability constants of the complexes, pK _a values of the ligands in water, and substituent constants σ⁺. The 2: 1 complex of (tetraphenylporphyrinato)zinc(II) with p-phenylenediamine was characterized by the X-ray diffraction data     

First helical zinc(II) complex with a salen ligand

The structure of a tetra-coordinated zinc(II) complex with a salen ligand was determined for the first time; unexpectedly, the complex was an interesting 2:2 metal-to-ligand complex.     

Atropo-enantioselective synthesis of an axially chiral C1-symmetric phosphine ligand and its application in the asymmetric hydrosilylation of styrenes

The axially chiral monodentate phosphine P-8 was synthesized in enantiomerically pure form, starting from the readily available, configurationally unstable lactone 1. Furthermore, its application as a ligand in the Pd-catalyzed stereoselective hydrosilylation of styrenes was investigated.     

Synthesis of a quinone-functionalized macrocyclic ligand and the intense fluorescence of its zinc complex

The redox-active quinone-functionalized macrocyclic ligand 1,4,14,17-tetrahydroxyhemiporphyrazine, H2hp(OH)4, has been synthesized and its zinc complex, [Zn(hp(OH)4)(py)], found to exhibit intense fluorescence.     

Organometallic fragments coordinated to a multiisocyanide ligand and their physical properties

Preparation of a triisocyanide ligand, 1,3,5-tris[(4-isocyano-3,5-diisoproyl-phenyl)ethynyl]benzene (5), is presented. Ligand 5 is obtained in three steps in 76% overall yield. Reaction of 5 with (eta5-Cp*)Rh(Cabs,s')(Cabs,s'= 1,2-S2C2B10H10-S,S') produced the rhodadithiolene adduct [[(eta5-Cp*)Rh(Cabs,s')(CNC6H2iPr2-2,6-CC-3)]3C6H3-1,3,5] (6). Ligand 5 reacts with Cr(CO)5(THF) to give the triisocyanide complex [[Cr(CO)5(CNC6H2iPr2-2,6-CC-3)]3C6H3-1,3,5] (8) and with [AuCl(SMe2)] to give the triisocyanide complex [[AuCl(CNC6H2iPr2-2,6-CC-3)]3C6H3-1,3,5] (9). As revealed by a single-crystal X-ray diffraction study, the C(9)-N(3)-C(61) angle of 5.9 degrees of trichromium complex 8 occurs in the plane of the bridge and the gold center has a slightly bent linear configuration with a Cl(1)-Au(1)-C(21) angle of 175.4(4) degrees . The rhenation and platination of 5 employing [Re(bpy)(CO)3(AN)]PF6 (AN= acetonitrile) and [(CwedgeNwedgeN)PtCl] ((HCwedgeNwedgeN)= 6-phenyl-2,2'-bipyridine) yielded the luminescent Re(I) and Pt(II) complexes. Full characterization includes structural study of complexes 2, 8, and 9.