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1.
Chemistry ; 19(5): 1629-36, 2013 Jan 28.
Artículo en Inglés | MEDLINE | ID: mdl-23292919

RESUMEN

After the lithiation of PYR-H(2) (PYR(2-) =[{NC(Me)C(H)C(Me)NC(6)H(3)(iPr)(2)}(2)(C(5)H(3)N)](2-)), which is the precursor of an expanded ß-diketiminato ligand system with two binding pockets, its reaction with [NiBr(2) (dme)] led to a dinuclear nickel(II)-bromide complex, [(PYR)Ni(µ-Br)NiBr] (1). The bridging bromide ligand could be selectively exchanged for a thiolate ligand to yield [(PYR)Ni(µ-SEt)NiBr] (3). In an attempt to introduce hydride ligands, both compounds were treated with KHBEt(3). This treatment afforded [(PYR)Ni(µ-H)Ni] (2), which is a mixed valent Ni(I)-µ-H-Ni(II) complex, and [(PYR-H)Ni(µ-SEt)Ni] (4), in which two tricoordinated Ni(I) moieties are strongly antiferromagnetically coupled. Compound 4 is the product of an initial salt metathesis, followed by an intramolecular redox process that separates the original hydride ligand into two electrons, which reduce the metal centres, and a proton, which is trapped by one of the binding pockets, thereby converting it into an olefin ligand on one of the Ni(I) centres. The addition of a mild acid to complex 4 leads to the elimination of H(2) and the formation of a Ni(II)Ni(II) compound, [(PYR)Ni(µ-SEt)NiOTf] (5), so that the original Ni(II) (µ-SEt)Ni(II) X core of compound 3 is restored. All of these compounds were fully characterized, including by X-ray diffraction, and their molecular structures, as well as their formation processes, are discussed.

2.
Inorg Chem ; 48(21): 10049-59, 2009 Nov 02.
Artículo en Inglés | MEDLINE | ID: mdl-19803532

RESUMEN

The synthesis of three pyrazole-based, potentially binucleating ligands 3,5-bis(R(1)N(CH(3))CH(2))-4-R(2)pyrazole (L(1)H: R(1) = pyridyl-2-methyl-, R(2) = Ph; L(2)H: R(1) = 8-quinolyl-, R(2) = H; L(3)H: R(1) = 8-quinolyl-, R(2) = Ph) is described. Reaction of L(1-3)H with 1 equiv. of mesitylcopper affords oligonuclear homoleptic complexes of the type [CuL](n) (1-3). The single crystal X-ray structure of 2 shows a tetranuclear assembly of linear coordinated copper(I)-centers bridged by pyrazolato ligands that alternate above and below the Cu(4) plane, with additional weak interactions from some of the ligand side arms. As the single crystal X-ray structure of 3 reveals, phenyl substitution at the 4-position of the pyrazolato framework leads to significant structural modification of the Cu(4) array, giving a rhombical tetranuclear complex with two linear coordinated copper(I) centers that exhibit a short intramolecular Cu...Cu contact (2.8212(10) A) and two peripheral copper(I) centers in a distorted tetrahedral coordination mode. Thus, 3 represents a very rare example of an inorganic pyrazolato cuprate which can also be viewed as a partly rearranged structural isomer of 2. Furthermore, the crystal lattice of 3 shows an extended network of intra- and intermolecular pi-pi stacking interactions between the aromatic rings. In solution, 1-3 each form two types of oligomers a and b that slowly (<1 s(-1)) equilibrate at room temperature. Using Diffusion Ordered Spectroscopy (DOSY) and variable temperature (1)H NMR spectroscopy it can be shown that a and b correspond to a tetrameric and a (planar) trimeric species. Coordination of the pyridyl/quinolyl side arms that is observed in the solid state seems to be only transient in solution.

3.
Dalton Trans ; 45(7): 2989-96, 2016 Feb 21.
Artículo en Inglés | MEDLINE | ID: mdl-26757878

RESUMEN

After lithiation of PYR-H2 (PYR = [(NC(Me)C(H)C(Me)NC6H3(iPr)2)2(C5H3N)](2-)) - the precursor of an expanded ß-diketiminato ligand system with two binding pockets - with KN(TMS)2 the reaction of the resulting potassium salt with FeBr2 led to a dinuclear iron(ii) bromide complex [(PYR)Fe(µ-Br)2Fe] (1). Through treatment with KHBEt3 the bromide ligands could be replaced by hydrides to yield [PYR)Fe2(µ-H)2] (2), a distorted analogue of known ß-diketiminato iron hydride complexes, as evidenced by NMR, Mößbauer and X-ray absorption spectroscopy, as well as by its reactivity: for instance, 2 reacts with the proton source lutidinium triflate via protonation of the hydride ligands to form an iron(ii) product [(PYR)Fe2(OTf)2] (4), while CO2 inserts into the Fe-H bonds generating the formate complex [(PYR)Fe2(µ-HCOO)2] (5); in the presence of traces of water partial hydrolysis occurs so that [(PYR)Fe2(µ-OH)(µ-HCOO)] (6) is isolated. Altogether, the iron(ii) chemistry supported by the PYR(2-) ligand is distinctly different from the one of nickel(ii), where both, the arrangement of the two binding pockets and the additional pyridyl donor led to diverging features as compared with the corresponding system based on the parent ß-diketiminato ligand.


Asunto(s)
Complejos de Coordinación/química , Complejos de Coordinación/síntesis química , Compuestos Ferrosos/química , Hierro/química , Cristalografía por Rayos X , Ligandos , Estructura Molecular , Espectroscopía de Mossbauer
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