Complex displacement

These reactivity sequences have been explained by considering initiation to involve four steps, e.g. complexation, displacement, ionization and initiation and subsequently proposing that displacement or ionization is rate controlling. The initiator reactivity order is shown to change depending on whether displacement or ionization becomes rate governing. 

The hexanuclear cyclometallated complex 61 (Scheme 1 and Table 1) shows a single reversible oxidation process at +1.31 V (Table 2), which involves four electrons. This process can be attributed to the oxidation of the four, almost noninteracting, peripheral Ru(ll) metals. The lack of other oxidation processes is an expected result since the increase (+4) in the charge of the complex displaces the oxidation of the core outside the accessible potential window. 

The syntheses of iron isonitrile complexes and the reactions of these complexes are reviewed. Nucleophilic reagents polymerize iron isonitrile complexes, displace the isonitrile ligand from the complex, or are alkylated by the complexes. Nitration, sulfonation, alkylation, and bromina-tion of the aromatic rings in a benzyl isonitrile complex are very rapid and the substituent is introduced mainly in the para position. The cyano group in cyanopentakis(benzyl isonitrile)-iron(ll) bromide exhibits a weak "trans" effect-With formaldehyde in sulfuric acid, benzyl isonitrile complexes yield polymeric compositions. One such composition contains an ethane linkage, suggesting dimerization of the transitory benzyl radicals. Measurements of the conductivities of benzyl isonitrile iron complexes indicate a wide range of A f (1.26 e.v.) and o-o (1023 ohm-1 cm.—1) but no definite relationship between the reactivities of these complexes and their conductivities. 

The proton magnetic resonance spectrum has a doublet centered at t 27.1 (stretching frequency, in the infrared spectrum (Nujol mull), is at 2079(s) cm.-1. The interaction of the complex with alkenes produces5 stable alkyl complexes of the type [Rh(NH3)5R]S04. In solution the complex reacts with molecular oxygen to give a blue peroxo complex displacement of ammonia by ethylenediamine can also be achieved.6... 

A cyclopentadienylcopper-fcr/-butyl isocyanide complex catalyzes the Michael addition of dimethyl methylmalonate to acrylonitrile at room temperature to give an S6% yield of the adduct 249). As the CU2O—BNC complex can also catalyze the addition of indene to methyl acrylate, the intermediate is most likely an organocopper complex. The reactions and kinetic data support the mechanism given by Eq. (118) to (120), involving metalation and nucleophilic attack by the carbanion on the olefin within the complex. Displacement of a solvent ligand by the olefin and coordination of the latter to the copper species are essential features of the mechanism. The rate of reaction is decreased if the compound with the... 

Admittance-vs-frequency measurements made at several temperatures on a polyisobutylene-coated TSM resonator were fit to the equivalent-circuit model of Sections 3.1.3 and 3.1.9 to determine values of G and G for the film [66]. These extracted values are shown in Figure 4.4, along with 5-MHz values obtained from the literature for polyisobutylene having an average molecular weight of 1.56 X 10 [44]. We note excellent agreement between the extracted and literature values of G from —20°C to 60°C, and in G" from —20°C to 10°C. Above 10°C, the extracted G" values are approximately 30% higher than the literature values. These results illustrate how AW devices can be used to quantitatively evaluate the viscoelastic properties of polymer films. Similar models for other AW devices, such as the model for SAW devices coated with viscoelastic layers (Section 3.2.7 and [61]), can enable these other devices also to be used to determine modulus values. However, the pure shear motion of the TSM does simplify the model, and the evaluation of the modulus values as compared with the more complex displacements of other AW devices such as the SAW device (a comparison of the models of Section 3.1.9 for the TSM and Section 3.2.7 for the SAW demonstrates this point). 

Stereochemistry A Pd(0) complex displaces allylic leaving groups (with inversion of configuration) to generate cationic Tr-allyl palladium species A. This complex is electronically deficient and undergoes attack of a suitable soft nucleophile (with inversion) to give a product with overall retention (Scheme 5.8). 

Addition to either the CO or arene ligands of [Mn(CO)3(arene- f )] complexes, displacement of the arene, or displacement of CO by nucleophilic reagents may be observed, depending on the complex and on the nucleophile. ... 

Fig. 1 Removal and separation of cobalt and nickel ions by CCC. Stationary phase heptane + diethyl hexyl phosphoric acid (HA 0.5M) mobile phase aqueous solution of cobalt and nickel acetate (O.OIM each). Step 1 The CCC machine is equilibrated with water. Step 2 The ionic solution is introduced in the machine, the ions are extracted into the stationary phase, and the cobalt complex displaces the nickel one less stable.

Whenever you see retention of stereochemistry, you should think double inversion, and in fact double inversion occurs in this reaction. The Pd(0) complex acts as a nucleophile toward the allylic carbonate or acetate, displacing MeOCC>2 or AcO by backside attack and giving an allylpalladium(II) complex. The nucleophile then attacks the allylpalladium(II) complex, displacing Pd by backside attack to give the product and regenerate Pd(0). The regio-chemistry of attack (Sn2 or Sn2 ) is dependent on the structure of the substrate. 

Heterobimetallic complexes of zirconium and molybdenum have also been prepared from zirconocene olefin complexes. Displacement of 1-butene from the phosphine-substituted zirconocene 1-butene complex, (775-C5H4PPh2)2Zr( 72-CH2=CHCH2CH3) 107, by addition of /< //-butyl isonitrile in the presence of Mo(CO)4(norbornadiene) furnishes the formal zirconium(n)-molybdenum(0) compound, 108 (Equation (4)).47... 

Metal ions dissolved in water are effectively complexed to water molecules. Displacing the set of water ligands, partially or entirely by another set in such aqua metal ions, results in forming what is more conventionally known as complexes. Displacement of water molecules by multidentate ligands results in more stable complexes than similar systems with none or fewer chelates. 

Ohta has also studied triphenylene-based porphyrazinato metal(II) complexes (Figure 70), which have an extended core compared to phthalocyanines [133]. It was found that both the nickel(II) and coppeifll) complexes displaced a Coltet.o between — 100°C and the onset of decomposition at 300°C, so that extension of the core size appears to have a beneficial effect with regard to the mesophase range. 

Surprisingly, certain complexes with pKa much higher than that of H30+ (-1.74) such as [TpRu(H2XMeCN)(PPh3)]+ (8.9) are found to be deprotonated by water.54 A base as weak as H20 would not have been expected to deprotonate such complexes displacement of H2 to form [TpRu(H2OXMeCN)(PPhj)]+ would seem more likely. Solvation effects could play a role here since H20 strongly solvates H+. Also the difference in the pKe of the H2 complexes in aqueous solution may not actually be as large as the experimental pseudoaqueous values imply. 

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