Cobalt complexes based on 2-(1H-benzimidazol-2-yl)-phenol derivatives: preparation,spectral studies,DFT calculations and catalytic behavior toward ethylene oligomerization

In this study, five novel Co(II) complexes of 2-(1H-benzimidazol-2-yl)-phenol derivatives (HL_x: x = 1–5) have been synthesized and characterized. The general formula for complexes C1 and C2 is K₂[Co(HL_1,2)₂Cl₂]·H₂O, for complex C3 K₂[Co(HL₃)₂Cl₂], and for complexes C4 and C5 [Co(HL_4,5)₂]. In all complexes, the ligands are coordinated as bidentate, via one imine nitrogen and the phenolate oxygen atoms. The structures of the compounds were characterized by FT-IR, UV–vis, ¹H, ¹³C NMR spectroscopies, ICP and elemental analysis (C, H, and N). The purity of these compounds was ascertained by melting point (m.p.) and TLC. Geometry optimization of the studied complexes was done by Gaussian09 software at B3LYP/TZVP level of theory and satisfactory theoretical–experimental agreement was achieved for NMR and IR spectra of the compounds. Based on the combined experimental and theoretical studies, six-coordinate octahedral structures have been proposed for complexes C1–C3, while complexes C4 and C5 had distorted tetrahedral geometry. All complexes were activated with diethylaluminum chloride (Et₂AlCl), cobalt(II) complexes containing bulky methyl groups in the aryl moiety show high catalytic activities (1774 kg?mol^?1(Co)?h^?1) for ethylene oligomerization. The oligomers obtained from the cobalt complexes exhibit good selectivity for linear 1-butene and 1-hexene. Results revealed that both the steric and electronic effects of ligands strongly affect the catalytic activities and the properties of the catalytic products.     

Design,synthesis and theoretical analysis of functionalized dicarboxylate moieties based on organotin(IV) dinuclear complexes: crystal structure elucidation and biological studies

Dinuclear tin(IV) dicarboxylate complexes of the types [(n-Bu)₂Sn(oda)(4-pic)]₂·2H₂O (1) and [(n-Bu)₂Sn(pda)(H₂O)]₂ (2) [H₂oda = oxydiacetic acid; H₂pda = pyridine 2,6-dicarboxylic acid) were synthesized and characterized via physicochemical and spectroscopic studies. The spectroscopic results indicated that Sn is seven-coordinate having pentagonal bipyramidal (pbp) geometry in both complexes. The X-ray study of complex 2 further specified pentagonal bipyramidal geometry with dinuclear structural arrangement due to the involvement of carboxylate bridges formed by pda^2? moiety. The crystal structure is further stabilized by different weak interactions viz., C–C?H, C–C?O, C–H?O, C–C?O, and C–H?H. These interactions are further supported by Hirshfeld surface analysis along with 2-D fingerprint plots of complex 2. In vitro DNA-binding studies of both complexes were evaluated using spectroscopic techniques (absorbance and fluorescence) which ascertained optimum binding affinity of both complexes. However, cleavage activity of the complexes was assessed using supercoiled DNA (pBR322) via gel electrophoresis technique which demonstrated significant cleavage pattern of both complexes at different concentrations. Furthermore, chemotherapeutic potential of complexes 1 and 2 against MCF-7 and Hep carcinoma cell lines also suggested significant antiproliferative effect of complexes. These results revealed momentous exploration of drug–DNA interactions which may engender new insinuation for the advancement of metallo-pharmaceuticals.     

Four-membered chelate aminoalkenyl complexes of platinum(II). Synthesis,carbonylation and oxidation to aminoacidato complexes

Amination of Pt^II-allene complexes of the type cis[PtCl₂(Me₂CCCHR)(PPh₃)] gives the new four-membered C, N chelate aminoalkenyl complexes [$\text{PtC(CMe}{}_2\text{)CHRN}$Me₂(PPh₃)Cl]. These undergo ready insertion of carbon monoxide into the CPt σ-bond; the resulting acyl complexes are oxidized by hydrogen peroxide to aminoacidato complexes, and the free unsaturated β-aminoacids can be recovered in good yield by ligand displacement.     

C−N,C−S and S−S Bond Cleavage by Rhodium PCcarbeneP Pincer Complexes

Rhodium PC_carbeneP complexes 1‐L {L=PPh₃, PPh₂(C₆F₅)} react with isothiocyanate, carbodiimide and disulphide to enable C?S, C?N and S?S bond cleavage. The cleaved molecules are sequestered by the metal center and the pincer alkylidene linkage, forming η²‐coordinated sulfide or imide centered pincer complexes. When a C?S or S?S bond is cleaved, the resulting complexes can bridge two rhodium centers through sulphur forming dimeric complexes and eliminating a monodentate phosphine ligand.     

From Cluster to Polymer: Ligand Cone Angle Controlled Syntheses and Structures of Copper(I) Alkynyl Complexes

Copper(I) alkynyl complexes have attracted tremendous attention in structural studies, as luminescent materials, and in catalysis, and homoleptic complexes have been reported to form polymers or large clusters. Herein, six unprecedented structures of Cu^I alkynyl complexes and a procedure to measure the cone angles of alkynyl ligands based on the crystal structures of these complexes are reported. An increase of the alkynyl cone angle in the complexes leads to a modulation of the structures from polymeric [((PhC≡CC≡C)Cu)₂(NH₃)]_∞, to a large cluster [(TripC≡CC≡C)Cu]₂₀(MeCN)₄, to a relatively small cluster [(TripC≡C)Cu]₈ (Trip=2,4,6‐iPr₃‐C₆H₂). The complexes exhibit yellow‐to‐red phosphorescence at ambient temperature in the solid state and the luminescence behavior of the Cu₂₀ cluster is sensitive to acetonitrile.     

四个基于酰腙配体的双核苄基锡配合物的合成、晶体结构及体外抗癌活性

通过微波"一锅法"合成了4个双核苄基锡配合物:{[C_4H_3S(O)C=N-N=C(Me)COO](PhCH_2)_2Sn(MeOH)}_2(C1)、{[C_4H_3S(O)C=NN=C (Me)COO](p-Cl-C_6H_4CH_2)_2Sn (MeOH)}_2(C2)、{[C_4H_3S (O)C=N-N=C (PhCH_2)COO](PhCH_2)_2Sn (MeOH)}_2(C3)、{[C_4H_3S (O)C=N-N=C(PhCH_2)COO](p-Cl-C_6H_4CH_2)_2Sn(MeOH)}_2(C4),利用元素分析、IR、~1H NMR、~(13)C NMR、~(119)Sn NMR、HRMS以及X射线单晶衍射等表征了配合物结构。4个配合物分子均为双锡核分子,以Sn_2O_2四元环为中心对称,且中心锡原子与配位原子形成七配位畸变五角双锥构型。测试了配合物C1～C4的热稳定性以及配合物对癌细胞H460、HepG2、MCF7的体外抑制活性,结果表明:配合物C2是4个新合成的配合物中抑制癌细胞效果最好的化合物。     

THEORETICAL INVESTIGATION OF KETENE BONDING MODES IN BIS(PHOSPHINE) PALLADIUM KETENE COMPLEXES

Abstract

Theoretical studies were carried out on a series of bis(phosphine) palladium ketene complexes (PR₃)₂Pd(CH₂=C=O), and on the related CH₂=C=O and Pd(PR₃)₂ molecular fragments in order to investigate the electronic structure and the bonding of the ketene ligand to the metal fragment in these complexes. An analysis of the frontier MOs has been performed in order to understand the interactions between the ketene and the metal fragments. The calculated results have shown that the η²-(C,C) mode is preferred over the η²-(C,O) mode by 10–15 kcal/mol in bis(phosphine) palladium ketene complexes. The basicity and bulkiness of the phosphine ligands PR₃ have little effect on the bonding mode in (PR₃)₂Pd(CH₂=C=O) complexes. The most stable structure was calculated to be the η²-(C,C) square planar geometry with the CH₂ group of ketene out of the molecular plane. Comparison and discussion between the two bonding modes were also presented in this paper.     

Cyclohexylethynyl complexes of CoII and FeII

This paper deals with the synthesis of six σ-cyclohexylethynyl complexes of Co^II and Fe^II and their characterization by chemical analysis, infrared and ¹H NMR spectra, and magnetic measurements. Four of them are six-coordinate complexes, unsubstituted or substituted, namely K₄[M(C≡C—C₆H₁₁)₆] nNH₃(M = Co, n = 2; M = Fe, n = 0), K₂[Co(C≡C₆H₁₁)₄(NH₃)₂] and K₄[Fe(CN)₄-(C≡C—C₆H₁₁)₂]. Two are four-coordinate complexes of formula [(Ph₃P)₂M-(C≡C₆H₁₁)₂] (M = Co, Fe). All are low-spin complexes, the magnetic moment for the six-coordinate Co(II) complexes, measured at various temperatures, being intermediate between low- and high-spin values.     

Zur reaktion von metall-koordiniertem kohlenmonoxid mit yliden: XI. Einige neuartige η1-vinyl-komplexe des eisens durch deprotonierung kationischer carbenkomplexe mit trimethyl(methylen)phosphoran

Novel η¹-vinyl complexes of the type Cp(CO)(L)FeC(OMe)C(R)R′ (R = R′ = H, Me; R = H, R′ = Me; L = Me₃P, Ph₃P) are obtainied via methylation of the acyl complexes Cp(CO)(L)FeC(O)R (R = Me, Et, i-Pr) with MeOSO₂F and subsequent deprotonation of the resulting carbene complexes [Cp(CO)(L)FeC(OMe)R]SO₃F with the phosphorus ylide Me₃PCH₂. The same procedure can be applied for the synthesis of the pentamethylcyclopentadienyl derivative C₅Me₅(CO)(Me₃P)FeC(OMe)CH₂, while treatment of the hydroxy or siloxy carbene complexes [Cp(CO)(L)FeC(OR)Me]X (R = H, Me₃Si; X = SO₃CF₃) with Me₃CH₂ results in the transfer of the oxygen bound electrophile to the ylidic carbon. Some remarkable spectroscopic properties of the new complexes are reported.     

cis-Fashioned palladium (II) complexes of 2-phenylbenzimidazole ligands: Synthesis, characterization, and catalytic behavior towards Suzuki-Miyaura reaction

Reaction of 2-arylbenzimidazole with PdCl₂(CH₃CN)₂ in CH₂Cl₂ affords benzimidazole palladium (II) complexes in high yields. The structure of complexes C1, C2, and C3 has been confirmed by X-ray structure analysis. The configuration of complexes depends on the substituent on the 2-position of benzimidazole. Phenyl affords the complexes in cis-fashion due to π-π stacking of phenyl and benzimidazole. Tolyl affords the complex in trans-fashion. The catalytic studies show that cis-configured 2-phenylbenzimidazole palladium (II) complexes are highly efficient catalysts in the Suzuki-Miyaura reaction.     

β-Diketiminato Rare-Earth Metal Complexes: The Influence of Monoatomic Substituents in the N-aryl Moieties on Structures and Properties

Treatment of β-diketiminate ligands bearing different N-aryl monoatomic substituents [HL^H = (C₆H₅)N = C(Me)CH=C(Me)NH(C₆H₅), HL^F = (2,6-F₂C₆H₃)N=C(Me)CH=C(Me)NH(2,6-F₂C₆H₃), and HL^Cl = (2,6-Cl₂C₆H₃)N=C(Me)CH=C(Me)NH(2,6-Cl₂C₆H₃)] with Ln(CH₂SiMe₃)₃(THF)₂ (Ln = Y and Lu) afforded a variety of β-diketiminato rare-earth metal complexes depending on substituents, namely, phenyl ring C–H bond activated complexes (L')(L^H)Lu(THF) ( 1b , L' = (C₆H₄)N = C(Me)CH=C(Me)N(C₆H₅)), six-coordinate homoleptic complexes (L^H)₃Ln [Ln = Y ( 1aa ), Lu ( 1bb )], five-coordinate monoalkyl complexes (L^F)₂Ln(CH₂SiMe₃) [Ln = Y ( 2a ), Lu ( 2b )], and four-coordinate dialkyl complexes (L^Cl)Ln(CH₂SiMe₃)₂ [Ln = Y ( 3a ), Lu ( 3b )]. All these complexes were characterized with NMR spectroscopy, and lutetium complexes 1b , 1bb and 3b were structurally validated by single-crystal X-ray diffraction analysis. Moreover, dialkyl complexes 3 promoted the polymerization of 2-vinylpyridine (2-VP) to produce atactic poly(2-vinylpyridine) (P2VP) with quantitative yield. On activation with an equimolar amount of [Ph₃C][B(C₆F₅)₄], complexes 3 afforded highly isotactic P2VP with an mm value up to 94 %. Both ¹H NMR spectrum and MALDI-TOF mass analysis of an oligomer indicate that the polymerization was initiated by coordination insertion of 2-VP into the Y-CH₂SiMe₃ bond.     

New anticancer zinc(II) complexes comprising thiosemicarbazones of saturated ring: structure,DNA/protein binding,DNA cleavage,topoisomerase‐1 inhibition and anti‐proliferation studies

The reaction of the thiosemicarbazones (CH₂)₄C?NN(H)C(?S)NHR (R = H, Me) with zinc(II) acetate in methanolic solution proceeds readily under mild conditions to form stable mononuclear complexes Zn[(CH₂)₄C?NN?C(S)NHR]₂. DNA interaction studies show that the zinc(II) complexes bind to DNA via groove mode and exhibit efficient DNA cleavage activity in the presence of hydrogen peroxide. Also, the complexes display a binding affinity to bovine serum albumin protein with K_BSA values of ca 10⁵ M^?1. Topoisomerase catalytic inhibition studies suggest that both complexes are efficient topoisomerase‐I impeders. Furthermore, the anti‐proliferative effects of the two complexes on five human tumor cell lines (Caki‐2, MCF‐7, CaSki, NCI‐H322M and Co‐115) indicate that both complexes have the potential to act as effective anticancer drugs. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis, characterisation and biological activity of gold(III) catecholate and related complexes

The reactions of the cyclometallated gold(III) complexes [LAuCl₂] [L=2-(dimethylaminomethyl)phenyl, 2-benzylpyridyl or 2-anilinopyridyl] with catechol, tetrachlorocatechol, or the cyclic α,β-diketone SCH(CO2Et)C(O)C(O)CH(CO2Et) give stable complexes containing five-membered Au-O-C-C-O rings. These represent the first examples of well-characterised gold(III) catecholate complexes. Similarly, reactions with 2-acetamidophenol [HOC₆H₄NHC(O)CH₃] give complexes with the related AuNCCO ring. The complexes were characterised by NMR spectroscopy, electrospray ionisation mass spectrometry, elemental microanalysis, and in the case of the complex [(2-benzylpyridyl)Au{OC₆H₄NC(O)CH₃}] by an X-ray crystal structure determination. Several complexes show high activity towards P388 murine leukemia cells.     

CH Bond Activation by f‐Block Complexes

Most homogeneous catalysis relies on the design of metal complexes to trap and convert substrates or small molecules to value‐added products. Organometallic lanthanide compounds first gave a tantalizing glimpse of their potential for catalytic C? H bond transformations with the selective cleavage of one C? H bond in methane by bis(permethylcyclopentadienyl)lanthanide methyl [(η⁵‐C₅Me₅)₂Ln(CH₃)] complexes some 25 years ago. Since then, numerous metal complexes from across the periodic table have been shown to selectively activate hydrocarbon C? H bonds, but the challenges of closing catalytic cycles still remain; many f‐block complexes show great potential in this important area of chemistry.     

Synthesis,characterization and biological activities of two novel orthopalladated complexes: Interactions with DNA and bovine serum albumin,antitumour activity and molecular docking studies

[Pd(L₁)(C,N)]CF₃SO₃ and [Pd(L₂)(C,N)]CF₃SO₃ (L₁ = 2,2′ ‐bipyridine, L₂ = 1,10‐phenanthroline and C,N = benzylamine) novel orthopalladated complexes have been synthesized and characterized using various techniques. The binding of the complexes with native calf thymus DNA (CT‐DNA) was monitored using UV–visible absorption spectrophotometry, fluorescence spectroscopy and thermal denaturation studies. Our results indicate that these complexes can strongly bind to CT‐DNA via partial intercalative mode. In addition, fluorescence spectrometry of bovine serum albumin (BSA) with the complexes shows that the fluorescence quenching mechanism of BSA is a static process. The results of site‐competitive replacement experiments with specific site markers clearly indicate that the complexes bind to site I of BSA. Notably, the complexes exhibit significant in vitro cytotoxicity against two human cancer cell lines (Jurkat and MCF‐7) with IC₅₀ values varying from 37 to 53 μM. Finally, a molecular docking experiment effectively proves the binding of the Pd(II) complexes to DNA and BSA.     

Efficient Deep Blue Platinum Acetylide Phosphors with Acyclic Diaminocarbene Ligands

Here we report five blue-phosphorescent platinum bis-phenylacetylide complexes with an investigation of their photophysical and electrochemical attributes. Three of the complexes ( 1 – 3 ) are of the general formula cis-Pt(CNR)₂(C≡CPh)₂, in which CNR is a variably substituted isocyanide and C≡CPh is phenylacetylide. These isocyanide complexes serve as precursors for complexes of the general formula cis-Pt(CNR)(ADC)(C≡CPh)₂ ( 4 and 5 ), in which ADC is an acyclic diaminocarbene installed by amine nucleophilic addition to one of the isocyanides. All of the complexes exhibit deep blue phosphorescence with λ_max ∼430 nm in poly(methyl methacrylate) (PMMA) thin films. Whereas isocyanide complexes 1 – 3 exhibit modest photoluminescence quantum yields (Φ_PL), incorporation of one acyclic diaminocarbene ligand results in a three-fold to 16-fold increase in Φ_PL while still maintaining an identical deep blue color profile.     

Übergangsmetall-heteroallen-komplexe XV. Reaktionen von keteniminen mit eisencarbonylen

Photolysis of triaryl ketenimines (Ph₂CCNAr; Ar = Ph, p-tolyl) with Fe(CO)₅ leads to organic imidazolidinone derivatives in good yields (50–60%). By-products of this reaction are dinuclear aza-allyl complexes (yield 25%). In addition reaction of the ketenimines Ph₂CCNAr with Fe₂(CO)₉ gives ferra-indene complexes. The dialkylketenimine Me₂CCNPh reacts with Fe₂(CO)₉ to give an aza-ferrole complex in low yield (8%). The structures of all compounds were determined from X-ray analyses.     

Direct infrared spectroscopic evidence for the ejection of vinyl chloride on photolysis of rhodium- (acetylacetonate)bis(vinyl chloride) in frozen gas matrices at 12 K

Infrared spectroscopic studies using Rh(acac)L₂ (acac= acetylacetonate; L = CH₂ CHCl, CH₂ CHMe) complexes have demonstrated for the first time that ν (CC) can be used to characterise unstable species in matrix isolation experiments on metal-olefin complexes at ca. 12 K provided that the olefin is asymmetric such that ν (CC) is a relatively high intensity mode in both the metal complexes and the “free” ligand.     

Selected properties of bi- and trinuclear complexes prepared by the reactions of Ru3(CO)12 with β-substituted oxadienes

The reactions of Ru₃(CO)₁₂with 4-phenylbut-3-an-2-ine (1a), 3-phenyl-1-p-tolylprop-2-an-1-ine (1b), and 1,3-diferrocenylprop-2-an-1-ine (1c) afforded the Ru₂(CO)₆(-H)(O=C(R¹)C(H)=C(R²)) (2) and Ru₃(CO)₈(O=C(R¹)C(H)=C(R²))₂(3) complexes. Dissolution of these complexes in CHCl₃or CH₂Cl₂gave rise to the Ru₂(CO)₄(-Cl)₂(O=C(R¹)C(H)=C(R²)) complexes (4). The thermal transformations of complexes 2and 3in the presence of an excess of the ligand yielded the Ru₂O₂(CO)₄(³-OC(R¹)C(H)(CH₂R²)C(R²)C(H)C(R¹))₂(5) and Ru(CO)₂(O=C(R¹)C(H)=C(R²))₂(6) complexes. Analogous complexes were obtained upon more prolonged heating of the starting reaction mixtures. The structures of complexes 4a, 5a, and 6cwere established by X-ray diffraction analysis and confirmed by spectroscopic data.     

The B–C and C–C bonds as preferred electron source for H-bond and Li-bond interactions in complex pairing of C<Subscript>4</Subscript>B<Subscript>2</Subscript>H<Subscript>6</Subscript> with HF and LiH molecules

Ab initio calculations were used to analyze the interaction of C₄B₂H₆ with HF and LiH molecules at the mp2/6-311++g(2d,2p) computational level. Interaction of C₄B₂H₆ with HF results to H–F···H–C and C–B···H–F, C–C···H–F hydrogen bond as well as B–H···H–F dihydrogen bond complexes. Also interaction of C₄B₂H₆ with LiH results to B–C···LiH, C–C···LiH and B–H···LiH lithium bond as well as C–H···H–Li dihydrogen complexes. In the both cases, complexes involving interaction of HF or LiH with peripheral B–C and C–C bonds of the C₄B₂H₆ backbone have greater stabilities. The structures of complexes have been analyzed using AIM and NBO methodologies.