INSERTION OF CATION

Few examples of C-H insertions have been reported for carbene complexes without electron-withdrawing groups attached to the carbene carbon atom [696]. Most of these are C-H insertions of cationic iron(IV) carbene complexes. 

Quartz crystal microbalance studies have shown that the movement of the solvent molecules associated with ions can be considerable. Using PPy prepared in sodium dodecyl sulfate, a mix of both cation- and anion-driven processes was seen when cycled in NaCl, and the mass changes involved indicated that four water molecules moved per Cl and 15 water molecules per Na" " [11]. The role of solvent water molecules has also been examined for PPy in dodecyl benzene sulfonate (DBS), a very widely studied system, where the insertion of cations accounted for only 20% of the mass change upon polymer reduction, indicating that four water molecules were brought into the film with each Na+ [12]. As the electrolyte concentration was changed from 0.1 M to 6 M, the total inserted mass became smaller and the mechanism moved from pure cation transport to an equal amount of anion transport [13]. These results were said to support an osmotic expansion model, whereby the difference in osmotic pressure between the electrolyte and polymer bulk (greater with more dilute electrolyte solutions) drives solvent movement. 

Moser. A. Yap, G.A.P. Detellier. C. Concurrent insertion of cationic guest and solvent molecules in molecular receptors. Co-complexation of the sodium cation and acetonitrile by a calix[4]arene tetraacetamide. J. Chem. Soc. Dalton Trans. 20102. 428-434. 

Zeolites may be modified by post-synthesis introduction of cations into their framework or onto cation sites of their lattice. Insertion of cations into the anionic framework of a zeolite after its synthesis is a relatively new field of research activity. In particular, the insertion of Al into the framework of zeolites was dealt with [1-3] but also the possibility of insertion of cations such as Fe , Ti , Cr orSn was investigated [4-5]. 

The presence of a multicolour electrochromic effect in rare-earth diphthalo-cyanines was first reported in 1970 by Moskalev et al. . Lutetium diphthalocyanine, LuH(Pc)2, has been studied extensively at Rockwell International Corporation by Nicholson and co-workers . This material may display different colours when polarized either anodically (red, orange) or cathodically (blue, violet) from its initial rest potential. The initially green complex film is obtained by vacuum evaporation. The anodic reaction occurs by the insertion of anions into the film and extraction of electrons rather than by loss of protons. The cathodic reaction, leading to blue and violet products, occurs by the insertion of cations. When protons are present in the electrolyte, the reaction is the following . 

Keto esters are obtained by the carbonylation of alkadienes via insertion of the aikene into an acylpalladium intermediate. The five-membered ring keto ester 22 is formed from l,5-hexadiene[24]. Carbonylation of 1,5-COD in alcohols affords the mono- and diesters 23 and 24[25], On the other hand, bicy-clo[3.3.1]-2-nonen-9-one (25) is formed in 40% yield in THF[26], 1,5-Diphenyl-3-oxopentane (26) and 1,5-diphenylpent-l-en-3-one (27) are obtained by the carbonylation of styrene. A cationic Pd-diphosphine complex is used as the catalyst[27]. 

The considerable reduction in the extent of hydration of the quin-azoline cation which results from the insertion of a 4-methyl group has been used in deriving estimates from spectral data of the extent of hydration of other quinazoline species. ... 

A positive value of ME means that the insertion of a hetero atom or group makes the molecule more lipophilic. If ME is negative, the hetero surfactant is more hydrophilic. In general, hetero atom insertion hydrophilizes the surfactant molecule as does the shift of the hetero group to the middle of the carbon chain [71]. ME values are temperature-dependent. / and ME values can also be useful to take into account the influence of various cations on the critical micelle concentration. 

The synthesis, structures, and reactivity of neutral and cationic mono- and bis(guanidinato)zirconium(rV) complexes have been studied in detail. Either salt-metathesis using preformed lithium guanidinates or carbodiimide insertion of zirconium amides can be employed. Typical examples for these two main synthetic routes are illustrated in Schemes 73 and 74. Various cr-alkyl complexes and cationic species derived from these precursors have been prepared and structurally characterized. 

The diamagnetic ylide complexes 34 have been obtained from the reaction of electron-deficient complexes [MoH(SR)3(PMePh2)] and alkynes (HC=CTol for the scheme), via the formal insertion of the latter into the Mo-P bond. The structural data show that 34 corresponds to two different resonance-stabilized ylides forms 34a (a-vinyl form) and 34b (carbene ylide form) (Scheme 17) [73]. Concerning the group 7 recent examples of cis ylide rhenium complexes 36 cis-Me-Re-Me) have been reported from the reaction of the corresponding trans cationic alkyne derivatives 35 with PR" via a nucleophilic attack of this phosphine at the alkyne carbon. 

Extrinsic Defects Extrinsic defects occur when an impurity atom or ion is incorporated into the lattice either by substitution onto the normal lattice site or by insertion into interstitial positions. Where the impurity is aliovalent with the host sublattice, a compensating charge must be found within the lattice to pre-serve elec-troneutality. For example, inclusion of Ca in the NaCl crystal lattice results in the creation of an equal number of cation vacancies. These defects therefore alter the composition of the solid. In many systems the concentration of the dopant ion can vary enormously and can be used to tailor specific properties. These systems are termed solid solutions and are discussed in more detail in Section 25.1.2. 

The reactions of a neutral 10 as well as a cationic dihydrido(acetato)osmium complex 12 with acetylenic compounds were examined (Scheme 6-17) [11-13]. A vinyU-dene 99, an osmacyclopropene 100, or a carbyne complex 101 were obtained, depending on the starting hydrido(acetato) complexes or the kind of acetylene used. In any case, the reaction proceeded by insertion of a C C triple bond into one of the two Os-H bonds, but the acetato ligands do not take part in the reaction and act as stabilizing ligands. 

The authors propose that this reaction proceeds by initial insertion of the 7t-bond into a Pd - H bond, in contrast to the Pd - Si insertion seen in the reaction between El3SiH and dienes catalyzed by 100 (Scheme 24) [71]. A weak bond between the cationic palladium and the electron-poor C Si group favoring Pd - H formation accounts for the change in mechanism. 

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