Coordination compounds ionization

Thus, [PtMe(RCN)L2] , on addition of NaBPh4, forms a precipitate of [PtMe(RCN)L2)[BPh4] in methanol. These [PtMe(RCN)L2][BPh4l salts are freely soluble in dichloromethane. Clearly, the precipitation of the complexes from aqueous solution by lipophilic counterions and the simultaneous increase in solubility of the complexes in organic solvents are closely related to one another. Accordingly, it is helpful to consider existing ideas about the solubilities of coordination compounds ionized in water. 

Figure 16.18 summarizes the types of isomerism found in coordination complexes. The two major classes of isomers are structural isomers, in which the atoms are connected to different partners, and stereoisomers, in which the atoms have the same partners but are arranged differently in space. Structural isomers of coordination compounds are subdivided into ionization, hydrate, linkage, and coordination isomers. 

Yang et al. [12] determined the ionization constants of primaquine by a titrimetric method and studied its coordination ratio with vitamin C. The ionization constants of primaquine in 50% (v/v) ethanol in water determined at 25 °C in the ionic strength range of 5 x 10 to 5 x 10-2 mol/L are given. The coordination ratio of primaquine to vitamin C is determined by continuous variation and mole ratio methods based on pH and conductance measurements to be 1 1, indicating that the coordination compound formed in the solution is mainly a 1 1 compound. 

Ionizations are evident before ligand ionizations with early transition metals Ti(m), V(III), or Cr(III), not evident at all or masked under ligand ionization bands with late transition metals such as Cu(ll) or Zn(II), and highly intermixed with the first ligand ionizations for intermediate transition metal configurations such as d6 of Co(III) or d6 of Ni(H). (Fig. 11). This type of behavior is probably of general occurrence and is in fact found also in other classes of coordination compounds, especially with sulfur ligands. 

The point of the identification of d-ionization bands in complex P.E. spectral patterns of coordination compounds lends itself to several empirical considerations. 

There are further possible advantages from the use of P.E. spectroscopy in the elucidation of the electronic structure of coordination compounds, and information not otherwise available or only indirectly available may thus come to light. The energy position of ionization bands of nonbonding orbitals, such as 6 s2 in (T1(I),... 

Continuous-flow FAB was reported earlier but is of no practical importance nowadays. Only few reports have been published dealing with (offline) coupling of CE to MALDI-MS. Recently, a new ionization approach, coordination ion spray (CIS) MS, has been presented (11) in it, charged coordination compounds are formed on-line. 

According to these principles, carbon ionization requires the loss of four electrons. In ionization, a coordination complex called a ligand may be formed in which a molecule or an ion donates a pair of electrons to a metal atom and ligands attach to the central ion electrostatically. For example, in (PtCU) " with four Cl ions are coordinated with the central Pt + ion. Such coordination compounds (and the lone pair the electron ligands donate) play a key role in defining the structural properties of metal complexes and ligand field theory has evolved to study their properties. 

A large number metal-bridged phosphonium salts have been synthesized and characterized by cyclic voltammetry49 58. With these coordinated compounds, the electrochemical features generally arise from the ionized species. For example, in the phosphonium salts shown in Table 10, the cyclic voltammetric reduction occurs from the anions. 

Coordination compounds containing halogen ligands (of which the great majority are fluorides) form the largest group of compounds for these elements. They are best considered as based on the neutral species, with cations and anions, which can be theoretically derived (and usually practically prepared) from the formal self-ionization of the neutral compound. 

Coordination compounds have the potential to be used in both diagnostic and therapeutic applications, but only the former have been extensively developed so far. This reflects the differing nature of the two types of application. In diagnosis it is only necessary to detect the location of the radionuclide in the body. Since extremely sensitive devices are available for the detection of ionizing radiation, useful diagnostic information may be obtained with relatively low patient... 

The thus prepared ligands la-le-H4 are introduced into coordination studies with titanium(IV) ions in the presence of base (M2C03 M = Li, Na, K) with methanol as solvent. Negative ESI-MS (electron spray ionization mass spectrometry) of the obtained orange-red solids in methanol reveals that coordination compounds of general formula M2[l2(OCH3)2Ti2] are formed (Scheme 1.3.2) [20, 21]. 

For transition metal coordination compounds AG° involves terms related to the ionization potential / of the free metal ion, the difference in complexation free energy A(AGc), involving the oxidized and the reduced free metal ion, and the difference in solvation free energy A(AGaq), involving the complexes in the two oxidation states ... 

Keywords. Electrospray ionization, Ion-molecule chemistry, Transition-metal coordination compounds, Organometallic catalysis... 

The phosphine combines with cobalt(II) dihalides to give the 5-coordinate derivatives, LXXVIII, but these do not undergo ionization in organic solvents. Rhodium (III) trihalides give normal 6-coordinate compounds, LXXIX, whereas sodium hexachloroiridate(IV), Na2lrCl6,... 

Our purpose is not to focus on the methods of mass spectrometry but rather to provide illustrations of some of the types of situations that may occur when this technique is used to characterize organometallic compounds. A brief but useful description of some of the techniques used in the mass spectrometry of coordination compounds, including organometallic compounds, is available.54 Because mass spectrometry relies on the interaction of ions rather than neutral molecules with magnetic fields, the selection of ionizing techniques is an important consideration. Some of the most common ionizing techniques are listed in Table 6-8. 

Structural (constitutional) isomers (Applied to coordination compounds.) Isomers whose differences involve more than a single coordination sphere or else different donor atoms they include ionization isomers, hydrate isomers, coordination isomers, and linkage isomers. 

On this basis the strong poisoning effect of certain substances (e.g., of KCN, Na,S, CO in the case of platinum or palladium) can be easily understood it is likely that the metal ions on the surface can form (surface) coordination compounds with these inhibitors, and it is well known that in many of these coordination compounds closed electron shells are present, which, on account of their high ionization potentials would greatly reduce the occurrence of electron transfer processes on the surface which appear to be essential for the catalytic activity of the metal. 

The R3SnX (and also R3PbX) compounds also form 1 1 and 1 2 adducts with Lewis bases and these also generally appear to contain 5-coordinate Sn, with the alkyl groups in axial positions. In water the perchlorate and some other compounds ionize to give cationic species, e.g., [Me3Sn(H20)2]+. 

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