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Aromatic Hydrocarbons as Ligands. Recent Advances in the Synthesis, the Reactivity and the Applications of bis(eta6-Arene) Complexes
No full textSynthetic procedures for bis(6-arene) metal derivatives and aspects of their reactivity are reviewed.
Attention is focused on early transition metals (Groups 4–6) but, when necessary, reference will be made
to arene derivatives of Groups 7–10, lanthanides and actinides.
After a short historical presentation of bis(6-arene) derivatives, aimed at illustrating the relevance
of this class of compounds to the origin and the evolution of organometallic chemistry, the synthetic
procedures to bis(6-arenes) will be discussed in the light of the most recent results. As far as the reactivity
of bis(6-arene) compounds is concerned, particular attention is given to the electron transfer reactions
occurring with or without arene displacement; data are reported for the use of low-valent bis(6-arene)
compounds as a useful entry into the inorganic and coordination chemistry of the corresponding metal
in non aqueous systems.
The use of bis(6-arene) derivatives of transition metals in low oxidation states (0, +1) as precursors to
catalytic systems for the oligomerisation and polymerization of unsaturated monomers and as starting
compounds for the preparation of molecule-based magnets, ordered crystals and new materials and
supports is described
Inorganic Synthesis
No full textAfter a short introduction to the Periodic Table and to the transition metals, some general features of the coordination compounds are discussed aimed to introduce the reader to the most important features of this class of compounds. For sake of clarity, distinction is made between classical Werner complexes and transition metal organometallic compounds, i.e., complexes containing at least one metal-carbon bond. A Section is devoted to the reactivity of coordination compounds and some of the most important reaction modes involving the central metal atom have been considered
REDOX REACTIONS OF METAL-CARBONYLS OF GROUP-5A
No full textRedox reactions of V(CO)6w ith [Co(CO)4]-, [Mn(CO)5]-, [M2(C0),012-,o r [M(T~-C~H~) (C(OM) =~ ]C-r , Mo, W), or
C O ( ~ ~ - Co~ccHur~ ra)p~id ly at 25 "C and lower in hydrocarbons; on the other hand, V(C0)s is oxidized to
V(T-~-C~H~)(CbOy )M, n(q5-C5H5)o* r N i ( ~ f - c ~ Han~d )th~e two-electron oxidation of [Nb(CO)6]- to the
[Nb2X3(C0)8]a- nion (X = CI, Br, I, acetylacetonato), can be carried out using a number of oxidizing agents
(Hgll, Cull, Cul, Agl, or Fell')
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
REACTIONS OF HEXACARBONYL DERIVATIVES OF GROUP-5 METALS (V, NB, TA) WITH 9,10-PHENANTHRENEQUINONE
No full textCharacterization and Thermal Activation of Adducts of Group 4 Tetrahalides with 1,2-Dialkoxyalkanes
Full text linkCoordination compounds of general formula MX4[κ2-O(R)CH2CH(R′)OR′′], 2a–i, have been prepared in high yield upon addition of a variety of 1,2-dialkoxyalkanes, ROCH2CH(R′)OR′′, to MX4 (M = Ti, X = F, 1a, I, 1b; M = Zr, X = Br, 1c, I, 1d). The new complexes have been characterized by elemental analysis and NMR spectroscopy. The thermal stability of 2 has been studied. Fragmentation of the TiI4 adducts takes place in chloroform solution at 90 °C: after hydrolysis of the reaction mixtures, MeI and CH2ICH2I have been detected from TiI4[dme] [dme = MeO(CH2)2OMe], MeI and Me2O from TiI4[MeOCH2CH(Me)OMe], and MeI, CH2ICH2I, Me2O, CH2ClI from TiI4[MeO(CH2)2OCH2Cl]. The diether MeO(CH2)2OCH2Cl is thermally activated also when coordinated to ZrX4 (X = Br, I): after hydrolysis, MeBr, CH2BrCH2Br, O(CH2CH2Cl)2 and Me2O (X = Br) and MeI, CH2ClI and CH2ICH2I (X = I) have been found, respectively
Aromatic hydrocarbons, carbocyclic ligands spanning several oxidation states in both main Group and transition elements. Recent advances with early transition d elements
No full textIn this paper some synthetic procedures to obtain (eta(6)-arene)metal derivatives are reviewed. The metal-atom-arene-vapour co-condensation technique is the most appropriate to generate complexes of polycyclic aromatic hydrocarbons or heterocycles. As far as the aluminium halide-mediated synthesis is concerned, two classes of reaction are observed. When AlX(3) is used with a metal halide in the presence of an aromatic hydrocarbon in the absence of any reducing agent, AlX(3) can function as a dehalogenating agent, to give ionic compounds of general formula [M(eta(6)-arene)n](AlX(4))(m), or it can add across the M-X bond with formation of M(mu-X)(n)AlX(4-n), systems. In both cases the metal displays its typical oxidation state. However, the use of AlX(3) in combination with aluminium (the Fischer-Hafner reducing system) affords ionic or covalent low-oxidation-state metal(eta(6)-arene) complexes. Attention is focused on our most recent results concerning the synthesis, properties and reactivity of eta(6)-arene derivatives of Group 4 and 5 elements, showing, inter alia, the first example of a tetraarylborate anion behaving as a 12-electron donor to one metal atom and low-valent eta(6)-arene compounds as useful reagents in the inorganic and coordination chemistry of the corresponding metal in nonaqueous systems
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