1,721,066 research outputs found
TETRAHYDROFURAN AND 1,2-DIMETHOXYETHANE DERIVATIVES OF VANADIUM(II) AND VANADIUM(III)
No full textThe vanadium(II) derivatives [V-2(mu-Cl)(3)(THF)(6)](2)[M(2)Cl(6)] (M = Mn, Fe) have been prepared by reduction of VCl3(THF)(3) with manganese or iron metal powders in THF and structurally characterized for M = Mn. [V-2(mu-Cl)(3)(THF)(6)](2)[Mn2Cl6] crystallizes in the triclinic space group P (1) over bar (No. 2) with a = 10.867(6), b = 11.626(8), c = 15.486(6) Angstrom, alpha = 75.70(4), beta = 71.25(4), gamma = 80.29(5)degrees, V = 1787(2) Angstrom(3), Z = 1. The structure contains discrete [V-2(mu-Cl)(3)(THF)(6)](+) cations and [Mn2Cl6](2-) anions, the anion consisting of two MnCl4 tetrahedra sharing an edge. By treatment of VCl3(THF)(3) with DME the new vanadium(III) coordination compound VCl3(DME)(THF) has been obtained which crystallizes in the space group Pnma (No. 62) with unit cell dimensions a = 14.193(8), b = 11.99(1), c = 7.92(1) Angstrom, V = 1347(2) Angstrom(3), Z = 4. VCl3(DME)(THF) shows a fac-stereochemistry of the ligands in a distorted octahedral coordination around the vanadium atom. The same compound has been obtained by reaction of VCl3(DME)(1.5) with a stoicheiometric amount of THF in toluene
Topotactic reversible phase transition between room temperature and a low-temperature modification in the MCl3(THF)3 system
No full textBoth single crystals of VCI3(THF) 3 as well as isotypic cocrystals of the composition MC13(THF)3,
M = Ti/V ~ 1/3, undergo a topotactic reversible phase transition to a hitherto unknown lowtemperature
modification. The close relationship between this new structure and the room-temperature
phase determined by Cotton et al. is discussed from the molecular and the intermolecular
point of view: Both modifications are built up by conformationally very similar molecules which
change their arrangement during the phase transition. Lattice energy calculations confirm that
these two alternative arrangements correspond to minima of almost the same packing energy
Synthesis, reactivity and structures of mono- and dihaloacetato complexes of copper(I) and copper(II)
No full textThe reactions of copper(I) oxide with the carboxylic acids CH3nXnCOOH (X/Cl, Br, n/1, 2; X/I, n/1) and dioxygen give
the corresponding haloacetates of copper(II) Cu(CH3nXnCOO)2 or Cu(CH3nXnCOO)2L, L/RCOOH, H2O. Lewis base
adducts of general formula Cu2(CH3nXnCOO)4L2 (X/Cl, n/1, L/THF; X/Cl, n/2, L/CH3CN; X/Br, n/1, L/py)
have been obtained and structurally characterized. They are dinuclear compounds showing the typical paddle-wheel dinuclear
structure, i.e., with four bridging haloacetato groups and two axial ligands. Monohaloacetato complexes of copper(I) have been
prepared by reacting Cu2O with CH2ClCOOH or by haloacetato exchange from Cu(CF3COO) in excellent (X/Cl, Br) or low (X/
I) yields. The copper(I) derivatives Cu(CH2XCOO) reversibly bind carbon monoxide both in the solid state and in toluene, the
carbonyl derivative Cu(CH2ClCOO)(CO) being quantitatively obtained by carbonylation of Cu(CH2ClCOO) in the solid state
Redox reactions with bis(h6-arene) derivatives of early transition metals
No full textThe reactivity of M(h6{arene)2 derivatives of early transition metals (M = Ti, Cr, Mo, arene = MeC6H5; M = V, Nb, arene = 1,3,5-h6{Me3C6H3) has been investigated and the syntheses of new and known compounds are described. The derivatives M(CH3COO)3, M = Ti, V, Nb, Cr; M(CF3COO)3, M = Ti, Nb, Cr; M(acac)3, M = Ti, V, Mo, acac = acetylacetonato, and M(F6acac)3, F6acac = hexafluoroacetylacetonato, M = V, Nb have been prepared by reaction of the metal bis(arene) derivatives with the appropriate Lewis acid. The crystal and molecular structure of V(F6acac)3 has been determined. Hydrogen halides or halogens react with M(h6{arene)2 with formation of metal halides, a highly reactive form of VCl3 being obtained from V(h6{1,3,5-{Me3C6H3)2 and hydrogen chloride in heptane. TiCl4 oxidizes Ti(h6{arene)2 with complete loss of the arene ligands. An electron transfer process affording ionic derivatives of formula [M(h6{MeC6H5)2][TiCl4(THF)2], M = Cr (structurally characterized), Mo, has been observed between the THF-adduct of TiCl4 and the appropriate metal-arene derivative of Group 6
STUDIES ON CARBONYL DERIVATIVES OF EARLY TRANSITION-ELEMENTS - A CONVENIENT METHOD FOR THE PREPARATION OF THE [NB(CO)6]- ANION AT ATMOSPHERIC-PRESSURE AND ROOM-TEMPERATURE - CRYSTAL AND MOLECULAR-STRUCTURE OF [NB(CO)6]-,[TA(CO)6]- AS THEIR "BIS(TRIPHENYLPHOSPHINE)NITROGEN(1+) DERIVATIVES
No full textA new method is reported for the preparation of [Nb(cO),]- and [Ta(CO)6]- by reductive carbonylation of M2ClIo (M
= Nb, Ta) with the magnesium-zinc-pyridine-CO system. In the case of niobium, the reductive carbonylation occurs
at atmospheric pressure and room temperature with yields as high as 48%. The tetrahydrofuran-stabiliied sodium derivatives
[Na(THF)] [M(CO),] and the bis(triphenylphosphie)nitrogen( 1+) derivatives, PPN[M(CO),] (M = Nb, Ta), are reported.
The crystal and molecular structures of both niobium and tantalum ppN[M(CO),] complexes are described. Both compounds
are isostructural with the corresponding vanadium derivative: rhombohedral, space group Rg, one molecule per cell; M
= Nb, a = 9.832 (4) A, a = 91.98 ( S ) ' , V = 948.7 (7) A3, paid = 1.399 g ~ m -R~ =, 0.0391; M = Ta, a = 9.814 (4)
A, a = 92.02 (8)', V = 943.4 (7) A', pal& = 1.562 g ~ m -R~ =, 0.0294 (Mo Ka,X = 0.71069 A). The geometry of the
two hexacarbonylmetalates is that of an almost perfect octahedron. Chemical and spectroscopic comparisons of the three
[M(CO),]- (M = V, Nb, Ta) anions are made
Role of the Pt-O fragment in the reactivity of a phosphinito bridged diplatinum(I) complex
No full text
[NB(B(ETA-6-C6H5)2(C6H5)2)(ETA-2-H3CC2CH3)] - THE 1ST COMPOUND WITH BENT TETRAPHENYLBORATE AS 12-ELECTRON DONOR LIGAND
No full textThe "counterion" BPh4- functions a sandwich ligand in the niobium(I) complex 1. This is confirmed by the X-ray structure analysis of 1a. The BPh4- complexes 1 are the first in which two of the four phenyl rings of the tetraphenylborate bind to one metal center. Such complexes could be important as model compounds for catalytic processes
Oxidation products of vanadocene and of its permethylated analogue, including the isolation and the reactivity of the unsolvated VCp2+ cation
No full textThe one-electron oxidation of vanadocene, VCp2, by [FeCp2]+ in toluene affords the 14-
electron [VCp2]+ cation, which has been isolated as an unsolvated species for the first time.
Vanadium hexacarbonyl reacts with VCp2 to give the í-isocarbonyl derivative Cp2V(í-OC)V-
(CO)5 as a transient species, which has been characterized in solution by IR analysis. By
reaction of VCp2 with V(13CO)6 followed by treatment with 12CO, the ionic dicarbonyl
derivative [VCp2(12CO)2][V(13CO)6] is formed, thus showing that during the formation of the
ionic compound no redistribution of the carbonyl ligands between the two metal centers
occurs. Bis(cyclopentadienyl)vanadium(II) and Co2(CO)8 give Cp2VCo(CO)4, which slowly
decomposes in solution even at low temperature to give [VCp2(CO)2][Co(CO)4], which was
identified by conventional methods, including single-crystal X-ray diffraction. The reactivity
of the unsolvated [VCp2]+ cation as well as that of the heterobimetallic compound containing
vanadium and cobalt with several Lewis bases is reported
Synthesis of Heterodimetallic Complexes by Reaction of a Terminal Phosphido Pt Complex with Metal Based Nucleophiles and Electrophiles
No full textThe complex trans-[PtCl(PCy2)(PHCy2)2] (1) possesses a terminal
phosphanido group (PCy2) and a chloride ligand,
which render it a good candidate for the synthesis of phosphanido-
bridged heterodimetallic species (PHCy2)2Pt(μ-
PCy2)M–L by reaction either with carbonyl metalates, as
metal-based nucleophiles, or with metal-based electrophiles.
The heterodinuclear complexes [(PHCy2)2Pt(μ-PCy2)Co-
(CO)3](Pt–Co) (2), [(PHCy2)2Pt(μ-PCy2)Mo(CO)2Cp](Pt–Mo)
(3), and [(PHCy2)2Pt(μ-PCy2)W(CO)2Cp](Pt–W) (4) are obtained
by reaction of 1 with the carbonyl metalates Na[Co-
(CO)4], Na[Mo(CO)3Cp] and Na[W(CO)3Cp], respectively.
Although 2 is reluctant to react with carbon monoxide, 3 and
4 are promptly carbonylated under ambient conditions to afford
mixtures of the cis and trans isomers of [(PHCy2)(CO)-
Pt(μ-PCy2)M(CO)2Cp] (M = Mo or W), which interconvert
through dissociation/reassociation of the CO ligand coordinated
to the Pt centre. The reaction of 1 with AuCl(PPh3)
leads to the formation of the trinuclear Pt2Au complexes cisand
trans-[{Cl(PHCy2)2Pt(μ-PCy2)}2Au]Cl (cis- and trans-
[8]Cl), in which a Au atom bridges two molecules of 1
through the originally terminal phosphanide ligands
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