Search results for "COORDINATION CHEMISTRY"
showing 10 items of 231 documents
Understanding the reactivity of transition metal complexes involving multiple spin states
2003
International audience; In coordination chemistry, many reactions involve several electronic states, in particular states of different spin. This phenomenon of ‘Multiple-State Reactivity’ has been recognized for some time, both for gas-phase reactions of ‘bare’ metal ions, and for transition metal complexes in solution. Until recently, however, much of the discussion of these systems has remained qualitative, because standard computational methods do not allow the location of the critical points for these processes, the Minimum Energy Crossing Points (MECPs) between states of different spin. Increased computational resources and new algorithms now enable MECPs to be located for large, reali…
Synthesis of new half sandwich tetrachloro derivatives of molybdenum(V) and tungsten(V). X-ray structures of (C5HPri4)W(CO)3(CH3) and (C5Et5)WCl4
2002
International audience; The new synthetic intermediates (Ring)MCl4 [Ring=C5HPri4 or 4Cp, M=Mo, 2; Ring=C5Et5 or VCp, M=W, 4, Ring=4Cp, M=W, 6] containing sterically protecting cyclopentadienyl ligands have been synthesized. Along the synthetic pathway to 2, it was found that the treatment of [4CpMo(CO)3]− with an aqueous ferric solution according to the well established Manning procedure affords the hydride compound 4CpMo(CO)3H (1) by hydrolysis rather than the expected neutral dimer by oxidation. Compound 1 could be converted, however, to 2 upon oxidation with PhICl2 in good yields. Compound 4 is shown by a single crystal X-ray analysis to adopt a monomeric four-legged piano stool structur…
Electrochemical and DFT studies of the oxidative decomposition of the trihydride complexes Cp*M(dppe)H3 (M = Mo, W) in acetonitrile
2006
International audience; A detailed electrochemical study of the oxidative decomposition of the trihydride complexes Cp*M(dppe)H3 (M = Mo, W) in acetonitrile is presented. For the Mo complex, the decomposition occurs by four different pathways involving classical and non-classical tautomers, whereas only the classical form is accessible for the W derivative. Each of the decomposition pathways has been quantitatively assessed by analyses of the linear sweep voltammograms. In addition to the previously established (B. Pleune, D. Morales, R. Meunier-Prest, P. Richard, E. Collange, J. C. Fettinger and R. Poli, J. Am. Chem. Soc., 1999, 121, 2209–2225) deprotonation, disproportionation, and H2 red…
Single chain magnet behaviour in an enantiopure chiral cobalt(II)–copper(II) one-dimensional compound
2010
The self-assembly of an enantiomerically pure, chiral dianionic oxamatocopper(II) complex with cobalt(II) ions leads to neutral oxamato-bridged heterobimetallic chains that combine chirality and slow magnetic relaxation, providing thus the first example of ‘‘chiral single chain magnets (CSCMs). Ruiz Garcia, Rafael, Rafael.Ruiz@uv.es ; Lloret Pastor, Francisco, Francisco.Lloret@uv.es
Synthesis of Polyfused Heterocycle Derivatives Containing the Dipyridoimidazole Core by Friedländer’s Reaction: Access to Analogs of Ellipticine
2005
Reaction of 3-amino-2-formylimidazo[l,2-a]pyridine with various aldehydes and ketones by Friedlander's methodology afforded an entry to dipyridoimidazole, tri(tetra)azacyclopenta[b]fluorene, tri(tetra)azabenzo[b]-fluorene and triazaindeno[2,1-b]phenanthrene derivatives. Intercalation with a synthetic oligodeoxynucleotide was examined.
[Fe(TPT)(2/3){M(I)(CN)2}2]⋅nSolv (M(I) = Ag, Au): new bimetallic porous coordination polymers with spin-crossover properties.
2013
Two new heterobimetallic porous coordination polymers with the formula [Fe(TPT)2/3{MI(CN)2}2]¿nSolv (TPT=[(2,4,6-tris(4-pyridyl)-1,3,5-triazine]; MI=Ag (nSolv=0, 1¿MeOH, 2¿CH2Cl2), Au (nSolv=0, 2¿CH2Cl2)) have been synthesized and their crystal structures were determined at 120¿K and 293¿K by single-crystal X-ray analysis. These structures crystallized in the trigonal R-3m space group. The FeII ion resides at an inversion centre that defines a [FeN6] coordination core. Four dicyanometallate groups coordinate at the equatorial positions, whilst the axial positions are occupied by the TPT ligand. Each TPT ligand is centred in a ternary axis and bridges three crystallographically equivalent Fe…
A novel polynitrile ligand with different coordination modes: Synthesis, structure and magnetic properties of the series [M(tcnoprOH)2(H2O)2] (M=Mn, …
2008
International audience; A novel polynitrile ligand (tcnoprOH− = [(NC)2CC(OCH2CH2CH2OH)C(CN)2]−) with up to five potentially coordinating groups has been synthesized in a one-pot reaction from a cyclic acetal and malononitrile. The combination of this novel ligand with different transition metal ions has led to the synthesis of two different structural types with the same formula but with different coordination modes in the ligand. Mn(II) and Cu(II) lead to a μ2-N,O-coordinating mode in the series of compounds formulated as [M(N,O-tcnoprOH)2(H2O)2] (M = MnII (1) and CuII (2)), whereas Co(II) and, most probably Ni(II), lead to a μ2-N,N′-coordinating mode in [Co(N,N′-tcnoprOH)2(H2O)2] (3). Bot…
Synthesis and Characterization of Copper Complexes Containing the Tripodal N7 Ligand Tris{2-[(pyridin-2-ylmethyl)amino]ethyl}amine (=N′-(Pyridin-2-yl…
2005
The stability constants of the CuII chelates with the tripodal heptadentate ligand tris{2-[(2-pyridylmethyl)amino]ethyl}amine (=N′-(pyridin-2-ylmethyl)-N,N-bis{2-[(pyridin-2-ylmethyl)amino]ethyl}ethane-1,2-diamine; tpaa), determined by potentiometry and UV spectrometry, show the formation of [Cu(tpaaH)]3+ and [Cu(tpaa)]2+ species. In the solid state, two mononuclear CuII compounds, [Cu(tpaa)](PF6)2 (1) and [Cu(tpaaH)](ClO4)3⋅H2O (2), and one trinuclear [Cu3(tpaa)2(ClO4)2](ClO4)4⋅2 H2O (3) complex were isolated and characterized by IR, UV/VIS, and EPR spectroscopy. An X-ray structure of the mononuclear protonated complex 2 shows that the Cu2+ ion has a distorted square-pyramidal geometry (τ=…
Bimetallic ruthenium-tin chemistry: synthesis and molecular structure of arene ruthenium complexes containing trichlorostannyl ligands
2010
A series of neutral, anionic and cationic arene ruthenium complexes containing the trichlorostannyl ligand have been synthesised from SnCl2 and the corresponding arene ruthenium dichloride dimers [(η6-arene)Ru(μ2-Cl)Cl]2 (arene = C6H6, PriC6H4Me). While the reaction with triphenylphosphine and stannous chloride only gives the neutral mono(trichlorostannyl) complexes [(η6-C6H6)Ru(PPh3)(SnCl3)Cl] (1) and [(η6-PriC6H4Me)Ru(PPh3)(SnCl3)Cl] (2), the neutral di(trichlorostannyl) complex [(η6-PriC6H4Me)Ru(NCPh)(SnCl3)2] (3) could be obtained for the para-cymene derivative with benzonitrile as additional ligand. By contrast, the analogous reaction with the benzene derivative leads to a salt compose…
Preparation of trichloro- and tribromocyclopentadienyltungsten(IV)
2000
International audience; The thermal decarbonylation of (Ring)WX3(CO)2 in refluxing toluene has led to the preparation of the CO-free compounds [(Ring)WX3]2 [Ring=η5-C5H5 (Cp) and X=Cl (1a) or Br (1b); Ring=η5-C5H4Me (Cp′), X=Cl (2a) or Br (2b); Ring=η5-C5Me5 (Cp*), X=Cl (3)]. The NMR properties of these molecules are consistent with diamagnetism and thereby indicate a different structure from that of the paramagnetic molybdenum analogues. Compounds 1a and 2a react with dppe to afford mononuclear 18-electron adducts, (Ring)WCl3(dppe) (Ring=Cp (4) or Cp′ (5)). The X-ray structure of 5 shows a pseudo-fac-octahedral geometry with the dppe ligand occupying two equatorial (e.g. cis relative to Cp…