Trivalent complexes

Phosphoms haUdes and metals or metal salts form addition complexes. Some typical compounds are PCl iSbCl and PCl iAlCl. The trivalent complexes contain metal—phosphoms bonds. The pentavalent complexes involve rearrangements to produce assembles of tetrahedral PX cations and various anions. 

Trivalent complexes of biguanide and periodate are also prepared commercially for water sanitation. The trivalent silver periodate, for example, is prepared by the action of potassium periodate and potassium hydroxide on Ag O ... 

In contrast to the situation observed in the trivalent lanthanide and actinide sulfates, the enthalpies and entropies of complexation for the 1 1 complexes are not constant across this series of tetravalent actinide sulfates. In order to compare these results, the thermodynamic parameters for the reaction between the tetravalent actinide ions and HSOIJ were corrected for the ionization of HSOi as was done above in the discussion of the trivalent complexes. The corrected results are tabulated in Table V. The enthalpies are found to vary from +9.8 to+41.7 kj/m and the entropies from +101 to +213 J/m°K. Both the enthalpy and entropy increase from ll1 "1" to Pu1 with the ThSOfj parameters being similar to those of NpS0 +. Complex stability is derived from a very favorable entropy contribution implying (not surprisingly) that these complexes are inner sphere in nature. 

The 14-membered macrocycle 1,4,8,11-tetraazacyclotetradecane (cyclam or [14]aneN4), unlike cyclen, is capable of encircling most transition metal ions and in the case of Co111 the trans configuration is much preferred by comparison with the folded cis isomer. Electrochemical reduction of A,v-[Co(cyclam)(OI I)2]+ in 3M NaOH leads to rapid isomerization to the trans form, and the relative stabilities of the trans and cis isomers of the di- and trivalent complexes were determined from a thermodynamic cycle.702 This preference for trans orientation of the non-macrocyclic donors has enabled the isolation and investigation of many Co complexes without the complications of isomerization. Some novel examples include /r[Pg.61]

Table 10 shows the results of polymerization of oc-olefins catalyzed with trivalent complexes. When a bulkiler tBuMe2Si group instead of the Me3Si group was introduced into the yttrium complex, the racemic complex was formed exclusively [74c]. However, this alkyl complex did not react with olefins, and hence it was converted to a hydride complex by reaction with H2. The complex obtained was reactive to various olefins and produced polymers at... 

Table 2 E-M bond distances for new crystallographically characterized trivalent complexes of the form EX3 x(MLn)x and ER3 x(MLn)...

Table 4 E-M bond distances in new crystallographically characterized ligand-stabilized trivalent complexes...

Several lanthanide cyclooctatetraene complexes have been synthesized, including both the divalent metal complexes Eu(CgHg) and Yb(CgH8) 44), and the trivalent complexes [M(CgH8)2] (M =Ce, Pr, Nd, SmorTb) 35). The former were preprired by direct reaction of the metal with cyclooctatetraene in liquid ammonia. No structural data exist for these divalent compounds, but they probably involve some kind of bridging interaction since, even with coordinated solvent, one COT... 

The trivalent complexes were prepared from the anhydrous metal trichlorides as follows ... 

Chromatography cyclophosphazenes, 21 46, 59 technetium, 11 48-49 Chromites, as spinel structures, 2 30 Chromium, see Tetranuclear d-block metal complexes, chromium acetylene complexes of, 4 104 alkoxides, 26 276-283 bimetallics, 26 328 dimeric cyclopentdienyl, 26 282-283 divalent complexes, 26 282 nitrosyls, 26 280-281 trivalent complexes, 26 276-280 adamantoxides, 26 320 di(/ >rt-butyl)methoxides, 26 321-325 electronic spectra, 26 277-279 isocyanate insertion, 26 280 substitution reactions, 26 278-279 [9]aneS, complexes, 35 11 atom... 

Axial substitution has both a thermodynamic and a kinetic effect in stabilizing the trivalent complex. In the presence of an excess of the oligopeptide ligands, long-lived bis complexes form (118). Reaction of... 

The heteroscorpionate pyrazolylborate derivative K[H2B(pzf Bu,Me)(pzMe2)] upon reaction with UI3(thf)4, afforded a series of seven-coordinated trivalent complexes of formula U /t, -BpzM " Me (Hpzf"Bu Me)I(p-I)]2 (55). The absence of empty coordination sites provide these complexes with a remarkable stability. Along the same line, the reaction of bis(2-mercapto-2-methylimidazolyl)borates [H(R)B(tim)2 R = H, Ph] with UI3(thf)4 in the presence of Tl(BPh4) in THF gave another rare case of a cationic trivalent uranium complex U[H(R)B-(tim)2]2 (thf)3 (BPh4) (56). 

These trivalent complexes are useful starting materials for other osmium phospine complexes, and some of the reactions are indicated in Schemes 13 and 14. In not all of the cases is it clear whether the mer or fac isomer was used and so we have omitted these prefixes, although it is likely in most cases that the mer was in fact the starting isomer. In order to simplify the schemes, general reactions only are indicated. 

The reaction of C0X2, where X = Cl, Br, 1, with 1 equiv LiCp yields the [Co(Cp )X]2 dimers . A mixture of Co3(C5Me4Et- )2Cl6 and the trivalent dimer, [Co(C5Me4Et-j )Cl2]2, is obtained from CoClj and (CjMe4Et)SnMej, followed by treatment with Clj gas. Analogous trivalent complexes are prepared in good yields from RhClj 3 HjO and cyclopentadiene, hexamethyl Dewar benzene or... 

Evans, W.J. (2002) The expansion of divalent organolanthanide reduction chemistry via new molecular divalent complexes and sterically induced reduction reactivity of trivalent complexes. Journal of Organometallic Chemistry, 647, 2. 

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