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Oxidation state VI d

The first preparations of the tetrathiometallates [WS4j and [MoS4] were reported by Berzelius and their true composition established by Krtiss and CorleisJ In 1883 crystals were obtained but their complete structures were not solved until 19633 ° In those [MS4j anions, the metal ion has a high formal oxidation state (VI), is located at the center of a tetrahedron of sulfides, with M-S distances of about 2.17 A, and has low-lying d-orbitals, as represented in Scheme 2. [Pg.220]

As mentioned above, the classical polyoxoanion forming metals are molybdenum and tungsten in the oxidation state VI. It is assiuned that for these metal cations the combination of ion-radius and -charge and the availability of empty d-orbitals for the formation of metal-oxygen-rx-bonds is especially favorable. However, other metals can act as polyoxoanion-builders as well. Vanadimn-, niobiiun- and tantalum-V, technetium-, rhenium-, ruthenium- and osmium-Vl, chromium-, molybdenum-, timgsten-, technetium- and rhenium-V and tita-niiun-, vanadium-, chromium-, molybdenum- and tungsten-IV can build poly-oxometallate-clusters. [Pg.236]

It is often useful to refer to the oxidation state and d" configuration, but they are a formal classification only and do not allow us to deduce the real partial charge present on the metal. It is therefore important not to read too much into oxidation states and d" configurations. Organometallic complexes are not ionic, and so an Fe(II) complex, such as ferrocene, does not contain an Fe " " ion. Similarly, WHeLs, in. spite of being W(VI), is certainly closer to W(CO)5 in terms of the real charge on the metal than to WO3. In real terms, the hexahydride may even be more reduced and more electron rich than the W(0) carbonyl. CO groups are excellent n acceptors, so the metal in W(CO)g has a much lower electron density than a free W(0) atom on the other hand, the W-H bond in... [Pg.39]

Chromium is able to use all of its >d and As electrons to form chemical bonds. It can also display formal oxidation states ranging from Cr(—II) to Cr(VI). The most common and thus most important oxidation states are Cr(II), Cr(III), and Cr(VI). Although most commercial applications have centered around Cr(VI) compounds, environmental concerns and regulations ia the early 1990s suggest that Cr(III) may become increasingly important, especially where the use of Cr(VI) demands reduction and incorporation as Cr(III) ia the product. [Pg.133]

As in the preceding transition-metal groups, the refractory behaviour and the relative stabilities of the different oxidation states can be explained by the role of the (n — l)d electrons. Compared to vanadium, chromium has a lower mp, bp and enthalpy of atomization which implies that the 3d electrons are now just beginning to enter the inert electron core of the atom, and so are less readily delocalized by the formation of metal bonds. This is reflected too in the fact that the most stable oxidation state has dropped to +3, while chromium(VI) is strongly oxidizing ... [Pg.1005]

Although the 0<(>D[IB]CMP0 is a particularly strong extractant for actinides in the III, IV, and VI oxidation states and has good... [Pg.443]

The M(VI) oxidation state is represented in the 4d series by the hexafluorides, MFg, of the elements Mo, Tc, Ru, and Rh. All are obtained by direct fluorination of the metal and are unstable powerfully oxidising species — once again the instability seems most marked at the end of the series. Unfortunately hardly any electronic spectral data exist. The first charge-transfer band of the d°MoF(s has been located at 54 kK. (42), and a study of the vibrational spectrum of RuF6 (43) revealed electronic bands at 1.95 and 1.4 kK., which are probably the F2, r5 Ti, and /13,... [Pg.127]

Fully conjugated 1,2-thiazines have been prepared with both S(ll) and S(vi) oxidation states. While the zwitterionic compound 11 has been known for some time <1984CHECI(3)995, 1996CHEC-II(6)349>, thiazinylium salts 12 have only recently been prepared. Both fully unsaturated 1,2-thiazine derivatives are considered to be nonaromatic due to poor p-d Jt-bonding. Eurthermore, the six-membered ring of l-alkyl-l,2-thiazine 1-oxide 11 is not planar, but instead exists in a puckered, half-boat conformation thereby precluding aromaticity <1978CC197>. [Pg.515]

The second class of fully conjugated ring systems include the S(vi) oxidation state compounds, such as 85a-d, which react only under forcing conditions. For instance, the 2-alkenylanilines 86a-d have been prepared via the reduction of sulfoximines 85a-d with sodium amalgam (Equation 1) <1995S713>. In the case of disubstituted sulfoximines 85c and 85d, the major products 86c and 86d of this reaction contain a (Z)-double bond. The corresponding ( )-by-products are usually isolated in <10% yield. [Pg.529]

The series of 3d elements from scandium to iron as well as nickel preferably form octahedral complexes in the oxidation states I, II, III, and IV. Octahedra and tetrahe-dra are known for cobalt, and tetrahedra for zinc and copper(I). Copper(II) (d ) forms Jahn-Teller distorted octahedra and tetrahedra. With higher oxidation states (= smaller ionic radii) and larger ligands the tendency to form tetrahedra increases. For vanadium(V), chromium(VI) and manganese(VII) almost only tetrahedral coordination is known ( VI j is an exception). Nickel(II) low-spin complexes (d ) can be either octahedral or square. [Pg.80]


See other pages where Oxidation state VI d is mentioned: [Pg.1023]    [Pg.1055]    [Pg.1085]    [Pg.1023]    [Pg.1055]    [Pg.1085]    [Pg.1023]    [Pg.1055]    [Pg.1085]    [Pg.1023]    [Pg.1055]    [Pg.1085]    [Pg.27]    [Pg.103]    [Pg.267]    [Pg.267]    [Pg.1128]    [Pg.5]    [Pg.259]    [Pg.23]    [Pg.83]    [Pg.44]    [Pg.152]    [Pg.93]    [Pg.371]    [Pg.45]    [Pg.200]    [Pg.395]    [Pg.299]    [Pg.259]    [Pg.184]    [Pg.81]    [Pg.254]    [Pg.260]    [Pg.3]    [Pg.391]    [Pg.188]    [Pg.99]    [Pg.110]    [Pg.391]    [Pg.940]   


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