Search results for "Hexacoordinate"
showing 6 items of 16 documents
Adducts of Tellurium Tetrachloride with Allyl Alcohol and Allyl Acetate: 1,2- vs 1,3-Addition and Structure and Dynamics of Te···O Interactions in D…
2002
The compounds Cl 3 Te[CH 2 CH(Cl)CH 2 O(H)...].Cl 2 Te[-CH 2 CH(Cl)CH 2 O-] (1) and Cl 3 Te-[CH 2 CH(CH 2 Cl)OC(CH 3 )=O...] (2) were prepared by the reaction of TeCl 4 with allyl alcohol and allyl acetate, respectively. Their molecular and crystal structures were investigated by single-crystal X-ray analysis, 1 H- 1 H-NOESY experiments, IR spectroscopy, and ab initio geometry optimization. 1 is a composite compound, whose subunits Cl 2 Te[-CH 2 CH(Cl)-CH 2 O-] (1A) and Cl 3 Te[CH 2 CH(Cl)CH 2 O(H))...] (1B) are linked in the solid state via Te...Cl-Te and O...H-O bridges. Both Te atoms are involved in similar five-membered rings, having a covalent Te-O bond in one case (1A) and a dative Te…
Investigations on organoantimony compounds
1977
Abstract Trichlorodiorganoantimony(V) compounds, R2SbCl3, in which the antimony atom is part of a heterocyclic ring have been synthesized. They have been converted into the corresponding tetramethylammonium tetrachlorodiorganoantimonates, [R2SbCl4]− [Me4N]+, which are hexacoordinate diorganoantimony(V) species in which the antimony-carbon bonds are forced into a cis-position. 5,5,5-Trichlorodibenzostibole, 10,10,10-trichlorophenoxantimonin, 5,5,5-trichloro-5,10-dihydrodibenz[b, e]antimonin and 5,5,5-trichloro-10,11-dihydro-5H-dibenzo[b, f]stibepin have been prepared by chlorination of the corresponding heterocyclic chlorodiarylstibines. Heterocyclic trichlorodialkylantimony(V) compounds hav…
The nerve hemoglobin of the bivalve mollusc Spisula solidissima
2006
Abstract Members of the hemoglobin (Hb) superfamily are present in nerve tissue of several vertebrate and invertebrate species. In vertebrates they display hexacoordinate heme iron atoms and are typically expressed at low levels (μm). Their function is still a matter of debate. In invertebrates they have a hexa- or pentacoordinate heme iron, are mostly expressed at high levels (mm), and have been suggested to have a myoglobin-like function. The native Hb of the surf clam, Spisula solidissima, composed of 162 amino acids, does not show specific deviations from the globin templates. UV-visible and resonance Raman spectroscopy demonstrate a hexacoordinate heme iron. Based on the sequence analo…
Human neuroglobin: crystals and preliminary X-ray diffraction analysis
2002
Neuroglobin, a recently discovered member of the haemoglobin superfamily, is primarily expressed in the brain of humans and other vertebrates, where it has been proposed to enhance O(2) supply in response to hypoxia or ischaemia, protecting the neuron from hypoxic injury. Neuroglobin is the first example of a vertebrate haemoglobin in which a hexacoordinate haem geometry has been detected. A triple mutant (replacing three Cys residues) of human neuroglobin (151 amino acids) has been expressed in Escherichia coli, purified and crystallized in two crystal forms, the best of which diffracts to 1.95 A resolution using synchrotron radiation. The crystals belong to space group P2(1), with unit-ce…
Expanding the 3d-4f heterometallic chemistry of the (py)2CO and pyCOpyCOpy ligands: structural, magnetic and Mössbauer spectroscopic studies of two F…
2011
Complex [Fe(II)Gd(III){pyCO(OEt)pyCOH(OEt)py}(3)](ClO(4))(2) (1) crystallizes in the Cc space group and contains one hexacoordinate ferrous ion and one enneacoordinate Gd(III) ion. Complex [Fe(2)(II)Gd(III){pyCO(OEt)py}(4)(NO(3))(H(2)O)][Gd(NO(3))(5)](0.5)(ClO(4)) (2) crystallizes in the C2/c space group and contains two hexacoordinate ferrous ions and one octacoordinate Gd(III) ion. Both complexes have been prepared by the metal-assisted ethanolysis of ligands di-2,6-(2-pyridylcarbonyl)pyridine (pyCOpyCOpy, dpcp) and di-2-pyridyl ketone ((py)(2)CO, dpk), which exhibit similar structures. Mössbauer spectroscopic studies of 2 revealed the presence of two quadrupole-split doublets of equal in…
Spin crossover in mononuclear and binuclear iron(III) complexes with pentadentate Schiff-base ligands
2000
Abstract A series of mononuclear hexacoordinate iron(III) complexes, [Fe( 5 L )(py)]BPh 4 , and binuclear hexacoordinate iron(III) complexes, [( 5 L )Fe(μ 2 -bpy)Fe( 5 L )](BPh 4 ) 2 , has been prepared and their magnetic properties were investigated; the pentadentate ligands were derivatives of 5 L =saldptn=N,N′-bis(2-hydroxybenzyliden)-1,7-diamino-4-azaheptane. Temperature variation of the effective magnetic moment for them shows that a spin transition from the low-spin to the high-spin state occurs. The magnetic data were fitted to an Ising-like model appropriate for the mono- and binuclear systems.