Tetravalent oxidation state

Tin amidinates display a rich coordination chemistry with the metal in both the di- and tetravalent oxidation states. The first results in this area were mainly obtained with N-silylated benzamidinate ligands. Typical reactions are summarized in Scheme 48. A stannylene containing unsymmetrically substituted amidinate ligands, [o-MeC6H4C(NSiMe3)(NPh)]2Sn, has been prepared accordingly and isolated in the form of colorless crystals in 75% yield. ... 

The positive charge on the transition metal in XXVII is a consequence of the tetravalent oxidation state of the transition metal in Cp2TiCl2. The active sites in traditional Ziegler-Natta polymerizations may be neutral because the transition metal is trivalent in those initiators (Secs. 8-4e, 8-4h-l). The group 3 metallocene initiators have neutral metal centers because those metals are trivalent. 

All the stable Si species in solutions are under the tetravalent oxidation state. No studies of electron transfer between soluble Si compounds can be found in the literature. Several investigations were devoted to the electrochemical deposition of elemental silicon from solute species. 

Cyclopentadienyl complexes of platinum are known for both the divalent and tetravalent oxidation states. Examples of both rfs and rj1 complexes are shown in equations (290) and... 

Platinum porphyrin complexes can be prepared by reaction with PtCl2(PhCN)2. Purification of the final complex is by medium pressure liquid chromatography on alumina. The strongly phosphorescent platinum(II) porphyrin complexes are efficient sensitizers for stilbene isomerization. The quantum yields for the cis to trans process are greater than unity because of a quantum chain process in which the metalloporphyrin serves both as an energy donor and an acceptor.1110 Picosecond laser spectroscopy has been used to obtain time-resolved excited-state spectra of platinum octaethylporphyrin complexes, and to probe the excited-state energy levels.1111 Tetrabenzoporphyrin complexes have been prepared for platinum in both the divalent and tetravalent oxidation states. The divalent complex shows strong phosphorescence at 745 nm.1112... 

Scheme 10). In this compound one pyrrole ring was isomerized by shifting the attachment of the chain from the a- to the (3-position GV-confused) while the formal tetravalent oxidation state is provided by the presence of the ethoxide group. The origin of the LiOEt unit is the result of a one-electron attack on thf followed by H abstraction, which accounts for the tetravalent state of uranium in the product. 

Some of the rare earths exhibit two different oxidation states in the same compound. A familiar example is Tb/jOy which contains the +3 and +4 oxidation states. XPS bands due to trivalent and tetravalent oxidation states are seen in 4f, 4d and 5d bands [30]. The... 

Organoactinide chemistry initially developed around the use of the ubiquitous cyclopentadienyl ligand (see Cyclopentadienyl), Cp = C5H5, and subsequently its alkyl- and silyl-substituted derivatives. The tetravalent oxidation state... 

Cerium is the only lanthanide metal with areadily accessible tetravalent oxidation state. Synthesis and molecular structure determination of organometallic Ce(IV) complexes are of interest and a challenge, because the Ce(IV) ion is strongly oxidizing and the anionic ligands typically... 

A second reason for the wealth of chemical investigations of the early actinide elements is the relative diversity of their chemistry. While the chemistry of the later actinides is most often restricted to that of the tri- and tetravalent oxidation states, compounds of the early actinides can be isolated in all oxidation states from +3 to +7. The accessibility of a range of oxidation states is the impetus for signficant chemical interest in the early actinides, but also vastly complicates investigation of these elements under some circumstances, such as aqueous redox behavior. In the case of plutonium, ions in four different oxidation states (+3, +4, +5, and - -6) can exist simultaneously in comparable concentrations in the same solution. 

The chemistry of actinide ions is generally determined by their oxidation states. The trivalent, tetravalent and hexavalent oxidation states are strongly complexed by numerous naturally occurring ligands (carbonates, humates, hydroxide) and man-made complexants (like EDTA), moderately complexed by sulfate and fluoride, and weakly complexed by chloride (7). Under environmental conditions, most uncomplexed metal ions are sorbed on surfaces (2), but the formation of soluble complexes can impede this process. With the exception of thorium, which exists exclusively in the tetravalent oxidation state under relevant conditions, the dominant solution phase species for the early actinides are the pentavalent and hexavalent oxidation states. The transplutonium actinides exist only in the trivalent state under environmentally relevant conditions. 

The HSiF3 molecule is finally oxidized by water to the tetravalent oxidation state, i.e. we have... 

The first metallasilsesquioxanes incorporating lanthanides were described in 1994 by Herrmann et alJ More recently, several Ln silsesquioxanes resulting from reactions of 1 with lanthanide silylamides and aryloxides have been reportedJ Our own efforts in this field resulted in the isolation of a novel Ce(lV) silsesquioxane complex as well as the structural characterization of a bimetallic Yb/Li derivative.Treatment of [Ce N(SiMe3)2 3] or anhydrous CeCls with two equivalents of Cy8Si80n(0H)2 (42) in diethyl ether in the presence of an excess of pyridine exclusively afforded the diamagnetic complex (Cy8Si80]3)2Ce(py)3 (43, Scheme 29.11). Quite surprisingly, in both cases cerium was oxidized to the tetravalent oxidation state. 

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