Synthesis, structures and comparative electrochemical study of 2,5-bis(trimethylsilylethynyl)thiophene coordinated cobalt carbonyl units

The reaction between 2,5-bis(trimethylsilylethynyl)thiophene and Co₂(CO)₈ or Co₂(CO)₆(X), (X = dppa, dppm), gave rise to the formation of substituted ethynylcobalt complexes containing one or two Co₂(CO)₆ or Co₂(CO)₄(X) units, 2-[Co₂(CO)₄(X){μ₂-η²-(SiMe₃)C₂}]-5-(Me₃SiCC)C₄H₂S (X = 2CO (1), dppa (3) or dppm (4)) and 2,5-[Co₂(CO)₄(X){μ₂-η²-SiMe₃C₂}]₂C₄H₂S (X = 2CO (2), dppa (5) or dppm (6)). Desilylation of the non-metallated and metallated alkynes in 3, 4 and 6 occurred on treatment with KOH and tetrabutylammonium fluoride to give 2-[Co₂(CO)₄(μ-X){μ₂-η²-SiMe₃C₂}]-5-(CCH)C₄H₂S (X = dppa (7), dppm (8)) and 2,5-[Co₂(CO)₄(μ-dppm){μ₂-η²-HC₂}]₂C₄H₂S (9), respectively. Crystals of 6 suitable for single-crystal X-ray diffraction were grown and the molecular structure of this compound is discussed. A comparative electrochemical study of all these complexes is presented by means of the cyclic and square-wave voltammetry techniques.     

Nanoscale octadecacobalta- and hexacosacobaltaclusters: Synthesis and spectroscopic fingerprinting

Strategies for the construction of TMS-protected first generation star and dendritic polyynes, which are subsequently metallated to give multiple Co₂C₂(CO)₆ clusters, are reported. In the absence of crystallographic data, well-resolved ¹³C NMR spectroscopy is a powerful technique for confirming the presence of core, inner and peripheral cluster domains.     

A simple and efficient synthesis of bisphosphine platinum(0) complexes with various P-Pt-P angles

Improved syntheses of a series of [(L)₂Pt(η²-nb)] (4)-(8) (L = PPh₃, 1/2 dpp(o-xyl), 1/2 dppb, 1/2 dppbe, 1/2 dppn) complexes are described. Complexes 4-8 have been characterized by ¹H, ³¹P NMR, IR spectroscopy as well as mass spectrometry and elemental analysis. The reaction of [(dppbe)Pt(Cl₂)] with sodium borohydride and tolan was investigated by ³¹P NMR spectroscopy. The complex [(dppbe)Pt(η²-tolan)] (11) has been isolated and characterized. The reactivity of [(dppn)Pt(η²-nb)] with the spirocyclohexyl-1,2,4-trithiolane 12 and the sterically hindered 2,2,4,4-tetramethyl-3-thioxocyclobutanone 13 was tested. The complex [(dppn)Pt(η²-13)] (14) has been isolated and characterized by ¹H, ³¹P NMR, IR spectroscopy as well as mass spectrometry and elemental analysis. X-ray crystal analyses have been performed on complex 8, 11 and 14.     

Syntheses and molecular structures of some phosphine-gold(I) derivatives of 1,3-diynes

The syntheses of several diynylgold(I) phosphine complexes, including Au(CCCCH){P(tol)₃} (1), Au(CCCCSiMe₃)(PR₃) (R = Ph 2-Ph, tol 2-tol), Au(CCCCFc)(PPh₃) (3), {(tol)₃P}Au(CC)_nAu{P(tol)₃} [n = 2 (4), 3 (6), 4 (7)], {(Ph₃P)Au}CCCC{Au[P(tol)₃]} (5), [ppn][Au{CCCCAu[P(tol)₃]}₂] (8), [Au₂(μ-I)(μ-dppm)₂][Au(CCCCSiMe₃)₂] (9), Hg{CCCCAu(PR₃)}₂ (R = Ph 10-Ph, tol 10-tol) and {(triphos)Cu}CCCC{Au[P(tol)₃]} (11) are described. Of these, the X-ray molecular structures of 1, 2-tol, 3, 4 and 9 have been determined.     

Syntheses and molecular structures of new ferrocenylacetylide-bridged binuclear cobalt carbonyl cluster compounds

The reaction of ferrocenylacetylide compounds with Co₂(CO)₈ at room temperature affords four complexes bearing ferrocenyl units with approximately tetrahedral (μ-alkyne)dicobalt moieties [R–(C≡C) _n –R′] [Co₂(CO)₆] _{n ′} [R?=?C₅H₅FeC₅H₄-C(CH₃)₂-C₅H₄FeC₅H₄, R′?=?H, n?=?1, n′?=?1 (1); R?=?C₅H₅FeC₅H₄ [ferrocenyl (Fc)], R′?=?–CH=CHCl, n?=?1, n′?=?1 (2); R?=?Fc, R′?=?Fc, n?=?2, n′?=?1 (3), n′?=?2 (4)]. The compounds were characterized by elemental analysis, IR, ¹H(¹³C) NMR, MS and single-crystal X-ray diffraction analysis. The X-ray analyses show that coordination of the carbon–carbon triple bond and the dicobalt unit result in the formation of a Co₂C₂ tetrahedral core, and the substituents on the acetylenic units show a distortion from linearity that reflects this coordination mode.     

Synthesis,molecular structure and reactivity of new biferrocenylpropane derivatives

New biferrocenylpropane derivatives FcC(CH₃)₂Fc′-C≡C–R [Fc?=?C₅H₅FeC₅H₄; Fc′?=?C₅H₅FeC₅H₃, R?=?C₆H₅ (L ₁ ), Fc (L ₂ )] and their complexes [FcC(CH₃)₂Fc′-C≡C–R][Co₂(CO)₆] [R?=?C₆H₅ (1); R?=?Fc (2)] have been synthesized by the Castro-Stephens coupling reaction and the reactions of ligands L ₁ , L ₂ with Co₂(CO)₈. Compounds L ₁ , L ₂ , 1 and 2 were characterized by elemental analysis, IR, ¹H (¹³C) NMR and MS, and the molecular structures of ligands L ₁ , L ₂ were determined by X-ray single crystal analysis. The electrochemical properties of L ₁ , L ₂ , 1 and 2 demonstrate two or three resolved one-electron redox processes.     

The crystal and molecular structures of some germatrane derivatives

The crystal and molecular structures of seven germatrane derivatives have been determined from three-dimensional X-ray data in order to investigate the main geometrical regularities of the germatrane molecules.     

Convenient synthesis,antimicrobial evaluation and molecular modeling of some novel quinoline derivatives

α, β-Unsaturated carbonyl compounds 2a, 2b, 3, and 4 were synthesized by the Knoevenagel condensation between 2-substituted quionoline-3-carboxaldehyde 1a and/or 1b with active methylene compounds. In addition, the synthesis of azlactone is achieved starting from 1a and N-acetylglycine. Synthesis of pyridine, pyrene, and pyrimidine derivatives 6–8 were accomplished via one-pot multicomponent reaction of 1b with acetyl acetone, malononitrile, and ammonium acetate; acetophenone, malononitrile, and NaOH; or acetyl acetone and urea in acidic medium. The new synthesized compounds showed good antimicrobial activities. The DFT calculations have been used to predict the electronic properties of the studied compounds.     

Five new cobalt(II) complexes based on indazole derivatives: synthesis,DNA binding and molecular docking study

Five cobalt(II) complexes based on 1H-indazole-3-carboxylic acid (H₂L), [Co(phen)(HL)₂]·2H₂O (1), [Co(5,5′-dimethyl-2,2′-bipy)(HL)₂] (2), [Co(2,2′-bipy)₂(HL)₂]·5H₂O (3), [Co₂(2,9-dimethyl-1,10-phen)₂(L)₂] (4) and [Co₂(6,6′-dimethyl-2,2′-bipy)₂(L)₂]·H₂O (5) (2,2'-bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline), have been synthesized and structurally characterized by elemental analyses, IR and UV-vis spectroscopies and single-crystal X-ray crystallography. The results indicate that 1–3 possess mononuclear Co(II) structures, while 4 and 5 exhibit binuclear structure. 1D water tape which is linked by the multiple hydrogen bonds was embedded in the 3D motif of complex 3. Complexes 4 and 5 show two orthogonal planes of motif that was constituted by phen/2,2′-bipy and indazole acid, respectively. The intermolecular interactions including hydrogen bonding and π-π stacking interactions are stabilizing these complexes. The interactions of the synthesized complexes with calf-thymus DNA (CT-DNA) have been investigated by UV-vis absorption titration, ethidium bromide displacement assay and viscosity measurements. The results reveal that the complexes could interact with CT-DNA via a groove binding mode. Their behavior rationalization was further theoretically studied by molecular docking.     

A simple synthesis of trans-RuCl(CCR)(dppe)2 complexes and representative molecular structures

The five-coordinate complex [RuCl(dppe)₂]OTf ([2]OTf) is obtained in high yield by the sequential reduction of RuCl₃ · nH₂O to RuCl₂(PPh₃)₃, subsequent phosphine substitution to give trans-RuCl₂(dppe)₂ (trans-1) and finally chloride abstraction (AgOTf, CH₂Cl₂). The use of [2]OTf as an entry point to mono-acetylide complexes trans-RuCl(CCC₆H₄R-4)(dppe)₂ (3) is described, and represents an alternative route to the long-standing methods based on cis-RuCl₂(dppe)₂ (cis-1), which is always prepared as a mixture with the more thermodynamically stable trans isomer when prepared by phosphine substitution reactions of RuCl₂(dmso)₄. The molecular structures of [2]OTf, trans-RuCl(CCC₆H₄OMe-4)(dppe)₂ (3b), trans-RuCl(CCC₆H₄Me-4)(dppe)₂ (3c) and trans-RuCl(CCC₆H₄CO₂Me-4)(dppe)₂ (3e) are described. A facile and reproducible synthesis of cis-1 is also reported.     

Synthesis,structures and polyphenol oxidase activities of dicopper and dicobalt complexes

Two dinuclear complexes [M₂(EGTB)(NO₃)₂(DMF)₂](NO₃)₂ · 2DMF (M = Cu, 1; Co, 2) were synthesized and structurally characterized, EGTB is N,N,N′,N′-tetrakis (2-benzimidazolylmethyl)-1,4-diethylene amino glycol ether, and DMF is dimethylformamide. The polyphenol oxidase (PPO) activities of 1 and 2 on pyrogallol oxidation have been investigated, showing that the rate constants k _cat increase with increases of reaction temperatures and pH.     

Synthesis and crystal structures of some cobalt halide derivatives containing alkyl or silanolato groups

The alkylcobalt halide (2) and the lithium silanolatocobaltates Li(THF)₂(μ-Br)₂Co(μ-OSiMe₃)₂Co(μ-Br)₂Li(THF)₂ (4) and [LiBr{Li(THF)}₂{CoBr(OSiMe₃)₃}]₂ (5) form centrosymmetrical halogen-bridged dimers in the crystalline state. Compound 4 shows bromide bridges between lithium and cobalt, and silanolato bridges between the cobalt atoms. Below 200 K there are significant antiferromagnetic interactions between the cobalt centres. Compound 5 crystallises in a novel structure in which two cubane-like fragments containing silanolato bridges are linked together through a Li₂Br₂ ring.     

Cobalt(II) complexes with thiosemicarbazone as potential antitumor agents: synthesis,crystal structures,DNA interactions,and cytotoxicity

Two cobalt(II) complexes [Co(QCT)₂]·Cl·1.5H₂O (1) (QCT = quinoline-2-carboxaldehyde thiosemicarbazone) and [Co(QCMT)(CH₃OH)Cl₂] (2) (QCMT = quinoline-2-carboxaldehyde N⁴-methyl-thiosemicarbazone) have been synthesized and structurally characterized. Complex 1 crystallizes in a triclinic system with space group P–1 and complex 2 crystallizes in a monoclinic system with space group P2(1)/n. In both complexes the cobalt(II) center is six coordinated with distorted octahedral geometry. The interactions of two complexes with CT-DNA were investigated by electronic absorption spectra, circular dichroism (CD) spectra and fluorescence spectra. Results suggest that the complexes bind to DNA via groove binding mode, and complex 2 has stronger binding ability than complex 1. The in vitro cytotoxicity has been tested against the human lung adenocarcinoma cell line A-549, cisplatin-resistant cell line A-549/CDDP, and human breast adenocarcinoma cell line MCF-7. Complex 2 is more cytotoxic than complex 1, and both of them show higher cytotoxicity than the parent ligands alone. Compared with cisplatin, the two cobalt(II) complexes are more active against A-549/CDDP and MCF-7 cell lines at most experimental concentrations. Notably, although complex 2 is found to be less effective than cisplatin against the parent cell line A-549, it is much more effective than cisplatin against the resistant cell A-549/CDDP.     

On the electronic and molecular structures of some fluoro-substituted cyclopropane derivatives

Ab initio calculations of double zeta quality have been carried out on cyclopropyl fluoride and 1,1-difluorocyclopropane. A partial geometry optimization has been carried out, and results have been compared to cyclopropane. An attempt is made to explain the differences in structure between cyclopropane and the fluorine derivatives.     

New binuclear half-titanocene derivatives with aryl-substituted cyclopentadienyl ligands: synthesis,structures, and catalytic properties

Two binuclear oxo-bridged half-titanocene complexes, µ-oxo-bis[(1-aryl-2,3,4,5-tetramethylcyclopentadienyl)dichlorotitanium] [(ArMe₄CpTiCl₂)₂O, Ar?=?4- ⁱ PrC₆H₄ (3), 4- ^t BuC₆H₄ (4)], have been prepared by the treatment of 1-aryl-2,3,4,5-tetramethylcyclopentadienyltitanium trichloride [ArMe₄CpTiCl₃, Ar?=?4- ⁱ PrC₆H₄ (1), 4- ^t BuC₆H₄ (2)] with 0.5?equiv of H₂O. Complexes 3 and 4 have been characterized by elemental analysis and ¹H- and ¹³C-NMR (nuclear magnetic resonance; NMR) spectroscopies, and their molecular structures have been determined by X-ray crystallography. When activated with ⁱ Bu₃Al and Ph₃CB(C₆F₅)₄, complexes 3 and 4 both exhibit reasonable catalytic activity for ethylene polymerization (90?×?10³ to 280?×?10³?kg PE (mol?Ti)^?1?bar^?1?h^?1), producing polyethylenes with moderate molecular weight.     

Super fast cobalt carbonyl-mediated synthesis of ureas

Fast cobalt carbonyl-mediated generation of ureas from primary amines was performed using high-density microwave irradiation. This enhanced method permitted the preparation of symmetrical ureas in good yields and unsymmetrical ureas in moderate yields. The reaction times varied between 10 s and 40 min. The proposed mechanism for the reaction includes in situ generation of an intermediate isocyanate that subsequently traps the free amine, producing the urea product.     

Syntheses and molecular structures of some compounds containing many-atom chains end-capped by tricobalt carbonyl clusters

Several complexes containing Co₃ carbonyl clusters end-capping carbon chains of various lengths are described. Pd(0)/Cu(I)-catalysed reactions between {Co₃{μ₃-C(CC)₂Au(PPh₃)}(μ-dppm)(CO)₇ and I(CC)₂SiMe₃ or FcCCI gave {Co₃{μ₃-C(CC)_xR}(μ-dppm)(CO)₇ [x = 4, R = SiMe₃3; x = 3, R = Fc 8]; treatment of 3 with NaOMe and AuCl(PPh₃) gave 4 [x = 4, R = Au(PPh₃)]. Related preparations of Co₃{μ₃-C(CC)₂[Ru(PP)Cp′]}(μ-dppm)_n(CO)_9−2n [PP = (PPh₃)₂, Cp’ = Cp, n = 1, 5; PP = dppe, Cp′ = Cp^∗, n = 1, 6; 0, 7] are also described. Syntheses of bis-cluster complexes {Co₃(μ-dppm)(CO)₇}₂(μ-C_x) (x = 14, 12; 16, 9; 18, 11; 26, 10) - the latter being the longest cluster-capped C_x chains so far described - and the mercury-bridged compounds Hg{(CC)_xC[Co₃(μ-dppm)(CO)₇]}₂ (x = 1, 13; 2, 14) are reported. The molecular structures of 7, 12, 13 and 14, as well as of Co₃(μ₃-CCCSiMe₃)(μ-dppm)(CO)₆(PPh₃) (15) and Co₃{μ₃-CC(O)OEt}(μ-dppm)(CO)₇ (16), are reported.     

One-pot synthesis of new iso-DPP derivatives from terminal alkynes and isocyanates

The reaction of phenyl acetylide anion with aryl isocyanates followed by quenching with water is shown to produce pyrrolopyrrole (iso-DPP) derivatives in addition to the isomeric cyclopentadienone imines previously reported. If the reaction is quenched with dilute HCl, 5-ylidenepyrrol-2(5H)-ones, formed by a Meyer-Schuster rearrangement, can be isolated instead. A possible mechanism for this reaction is suggested.