Doubly Charged Cations

Ab initio calculations using the fourth-order Moller-Plesset perturbation theory (MP4(SDTQ)) were performed on HeN in its ground (X IT) and excited states ( X ) which both were found to be covalently bound. HeN is metastable and dissociates via the exothermic charge-separation reactions HeN (X Il) He ( S) + N ( P) and HeN ( 2 ) He ( S) + N ( D). There is a barrier to dissociation of 201.7 kJ/mol for ground-state HeN. Other calculated data are [1]  

Ab initio SCF calculations of (HeNN) gave a dissociation energy of 359 kJ/mol relative to He and N. The molecule is nonlinear with a bond angle NNHe of 92.3° and bond distances re(NN) = 1.44 and re(NHe) = 1.50 A [2]. 

The potential energy curve for ground-state NeN has its quasi-bound maximum 6.1 eV above the dissociation limit. The translational energy release associated with the NeN - Ne + N process was determined by ion kinetic energy spectroscopy to be 6.5 0.5 eV [8] and calculated to be 5.51 eV [7]. 

A bond distance r(NeN) = 1.602 A and a bond angle NeNNe of 98° were calculated with ab initio methods at the MP2 level for (NeNNe) in its state (C2V symmetry). An exothermic dissociation energy of -234kJ/mol was calculated at the MP4(SDTQ) level for the charge-separation process Ne2N ( Bi)- N ( P) Ne ( P) Ne( S). An endothermic energy of 558 kJ/mol was calculated for the process Ne2N ( Bi) - N ( P) 2 Ne( S) [5]. 

ArN was formed by charge-stripping of the precursor ArN [8]. Ab initio calculations were performed on ArN in its ground state at the complete active space (CAS) SCF, MP3 and MP4 levels of theory. ArN was found to be metastable with an exothermic dissociation energy of -449 kJ/molforthe process ArN - Ar + N. The barrier to dissociation was determined to be 24 kJ/mol. The equilibrium distance, re(ArN) = 1.657 A, was calculated at the MP3 level. The spectroscopic constants (in cm ), C0e = 562, 0eXe = 14.3, = 0.54, 

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An electron carries one unit of negative electrical charge (Figure 46.2). Its mass is about 1/2000 that of a proton or neutron. Therefore, very little of the mass of an atom is made from the masses of the electrons it contains, and generally the total mass of the electrons is ignored. For example, an atom of iron has a mass of 56 atomic units (au also called Daltons), of which only about 0.02% is due to the 26 electrons. Thus an iron atom (Fe ) is considered to have the same mass as a doubly charged cation of iron (Fe " ), even though there is a small mass difference. 

Experimental and empirical studies have demonstrated that certain doubly charged cations of ionic radius less than calcium (e.g., Mn2 +, Zn2+, Fe2+, Cd2 +, and Co 2+) can be extensively incorporated into calcite precipitated from aqueous solution at... 

The disappearance of all but the non-specific absorption from the spectrum with increasing acidity reflects a loss of conjugation as the doubly charged cation is formed (equation ii) this transformation is represented by the formation of (LXVII) (BH ) which permits the widest charge separation. 

Water is the most abundant compound on earth. Seawater, which accounts for 97.3% of the world s water supply, contains 3.5 mass % of dissolved salts. Purification of drinking water involves preliminary filtration, sedimentation, sand filtration, aeration, and sterilization. Hard water, which contains appreciable concentrations of doubly charged cations such as Ca2+, Mg2+, and Fe2+, can be softened by ion exchange. Water is reduced to H2 by the alkali metals and heavier alkaline earth metals, and is oxidized to O2 by fluorine. Solid compounds that contain water are known as hydrates. 

N diffuses into the structural pores of clinoptilolite 10 to 10 times faster than does CH4. Thus internal surfaces are kinetically selective for adsorption. Some clino samples are more effective at N2/CH4 separation than others and this property was correlated with the zeolite surface cation population. An incompletely exchanged clino containing doubly charged cations appears to be the most selective for N2. Using a computer-controlled pressure swing adsorption apparatus, several process variables were studied in multiple cycle experiments. These included feed composition and rates, and adsorber temperature, pressure and regeneration conditions. N2 diffusive flux reverses after about 60 seconds, but CH4 adsorption continues. This causes a decay in the observed N2/CH4 separation. Therefore, optimum process conditions include rapid adsorber pressurization and short adsorption/desorp-tion/regeneration cycles. 

Ethylenediamine, NH2C2H4NH2, is a base that can add one or two protons. The successive pKy values for the reaction of the neutral base and that of the monovalent (+1) cation with water are 3.288 and 6.436, respectively. In a 0.0100 M solution of ethylenediamine, what are the concentrations of the singly charged cation and of the doubly charged cation ... 

Suppose 0.0100 mol NaOH were added to a liter of the solution in the preceding problem. What would the concentrations of singly charged and doubly charged cations be after the addition ... 

Suppose that, instead of 0.0100 mol NaOH, 0.0100 mol HC1 had been added to the solution in the previous problem. Calculate the molar concentrations of the singly charged cation, doubly charged cation, and neutral ethylenediamine. 

Pseudo-halogens may be used in a similar manner. The pseudo-interhalogens C1N3 or BrN3 react with iron pentacarbonyl to produce a remarkable bridged, binuclear, doubly charged cation, which is paramagnetic. 

The substituted tricarbonyl complexes react in a similar fashion to the tetracarbonyl complexes with halogens, whereas electrochemical oxidation appears to cause the formation of a doubly charged cation, [M(CO)3 (triars)]2+, where M = Cr, Mo, W (67). Allyl halides react with the tripyridine-substituted carbonyls of the type Mo(CO)3(bipy)py [or Mo(CO)3 (phen)py phen = phenanthroline] to form a 77-allylic carbonyl cation, such as [Mo(CO),(bipy)py(7r-allyl)]+ (146). The cation reacts with sulfur dioxide to form Mo(CO)2(bipy)(S02)2 (147). 

The [Mn(CO)2(diphos)2]+ cation forms a paramagnetic doubly charged cation [Mn(CO)2(diphos)2]2+ on oxidation (227). The reaction of aromatic ligands with the pentacarbonyl halides generally results in the formation of a substituted metal tricarbonyl cation. 

In contrast, studies on aqueous solutions of titanium(IV) in 2M HCIO4 are consistent with the presence of doubly charged cationic species. However, it is not clear whether the predominant species is [TiO] + or [Ti(OH)2] +. ... 

A cation I + might suffer another collision which would cause it to lose a second electron, converting it into a doubly charged cation ... 

Although arene-cyclopentadienyl iron cations are isoelectronic with ferrocene and contain a formally bivalent iron, they are extremely stable towards oxidation. Even such reagents as HjOj/NaOH, Cr03/H2S04, and KMn04 failed to oxidize them to the desired doubly-charged cation [351). 

G. Corongiu and E. Clementi, Study of the structure of molecular complexes. XVI. Doubly charged cations interacting with water., J. Chem. Phys. 69,4885-4887 (1978). 

Under the conditions applied by Marr and King [55], the doubly-charged cation was the most abundant ion for paraquat. Furthermore, peaks were observed at m/z 185 and 171 due to [Cation-H]" and [Cation-CHj], respectively. For diquat, the ion at m/z 183 due to [Cation-H]" was the base peak, while the doubly-charged cation was observed as well. In MS-MS of [Cation-H], the loss of CjHj was observed for diquat, and the losses of either CHj or HCN for paraquat [55]. 

On the basis of the donor-acceptor model the first calculational search for bonded systems between He and doubly charged cations was performed [7,11,... 

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