X alkali metals

The large lead atom might also be hepta- or octa-coordinated, but computations indicate that PbNa7 and PbNas clusters are only weakly bound, with dissociation energies to MX i + X of only 7.9 and 6.7 kcalmol-1, respectively (26.3 kcalmol-1 in PbNag)165. 

---

Miriam Kami, Yitzhak Apeloig, Jiirgen Kapp and Paul von R. Schleyer 3. MXq, MX7 and MXa, X = alkali metals... 

TABLE 15. Calculated properties of octahedral group 14 MX (X = alkali metal) clusters... 

Nearly all of these cluster phases fall in the family A x[M0Xi2(Z)IX3. Zirconium clusters occur in structures for all n between 0 and 6, as well as with x alkali-metal cations (A ) per cluster over the same range. (A few phases are also known with Ba2 +. ) Accepting for the moment the condition that 14 cluster-based electrons are optimal when Z has s and p valence orbitals, we can devise diverse ways in which 14-e counts can be achieved via the three variables x, n and the number of electrons brought by Z. Some sample categories are given in Table 1 for a few of the many dozen compositions known with Zr0Cli2Z-type clusters. 

Rodriquez CF, Fournier R, Chu IK, Hopkinson AC, Siu KWM. A possible origin of [M-nH + mX] "" " ions (X=alkali metal ion) in electrospray ionization mass spectrometry of peptides. Int J Mass Spectrom. 1999 192 303-17. 

H3 (and its isotopomers) and the alkali metal triiners (denoted generally for the homonuclears by X3, where X is an atom) are typical Jahn-Teller systems where the two lowest adiabatic potential energy surfaces conically intersect. Since such manifolds of electronic states have recently been discussed [60] in some detail, we review in this section only the diabatic representation of such surfaces and their major topographical details. The relevant 2x2 diabatic potential matrix W assumes the fomi... 

In this section, we extend the above discussion to the isotopomers of X3 systems, where X stands for an alkali metal atom. For the lowest two electronic states, the permutational properties of the electronic wave functions are similar to those of Lij. Their potential energy surfaces show that the baniers for pseudorotation are very low [80], and we must regard the concerned particles as identical. The Na atom has a nuclear spin " K, and K have nuclear... 

In the sodium atom pairs of 3/2 states result from the promotion of the 3s valence electron to any np orbital with n > 2. It is convenient to label the states with this value of n, as n P 1/2 and n f 3/2, the n label being helpful for states that arise when only one electron is promoted and the unpromoted electrons are either in filled orbitals or in an x orbital. The n label can be used, therefore, for hydrogen, the alkali metals, helium and the alkaline earths. In other atoms it is usual to precede the state symbols by the configuration of the electrons in unfilled orbitals, as in the 2p3p state of carbon. 

Alkali Metal Perchlorates. The anhydrous salts of the Group 1 (lA) or alkah metal perchlorates are isomorphous with one another as well as with ammonium perchlorate. Crystal stmctures have been determined by optical and x-ray methods (38). With the exception of lithium perchlorate, the compounds all exhibit dimorphism when undergoing transitions from rhombic to cubic forms at characteristic temperatures (33,34). Potassium perchlorate [7778-74-7] KCIO, the first such compound discovered, is used in pyrotechnics (qv) and has the highest percentage of oxygen (60.1%). 

Derivatives of Antimony Pentabromide and Pentaiodide. The existence of SbBr and Sbl is in doubt, although from time to time they are reported in the Hterature (35). The existence of a 1 1 adduct, SbBr 0(0244 )2, however, is generally accepted. In addition, the SbBr ion is known, and from x-ray studies has been found to have a slightly distorted octahedral stmcture (36). Indeed, there are quite a number of complex bromoantimony compounds with alkali metals and organic bases, some of wliich contain Sb(V). Thus the quinuclidinium salt (C24423N44)4Sb2Br2g is actually made up of... 

In the polyetherification route the condensation reaction proceeds by reactions of types (1) and (2) where M is an alkali metal and X a halide. 

The doping of Ceo with alkali metals creates carriers at the Fermi level in the tiu-derived band and decreases the electrical resistivity p of pristine solid Ceo by several orders of magnitude. As x in Ma C6o increases, the resistivity p(.-r) approaches a minimum at x = 3.0 0.05 [9, 112], corresponding to a half-filled flu-derived conduction band. Then, upon further increase in x from 3 to 6, p x) again increases, as is shown in Fig. 11 for various alkali metal dopants... 

Fig. 11. Composition dependence of the resistivity p x) for thick films of Cbo doped with Na, K, Rb, and Cs. Points indicate where exposure to the alkali-metal source was stopped and x-ray and ultraviolet photoemission spectra were acquired to determine the concentration x. The labels indicate the known fulleride phases at 300 K. The minima in p x) occur for stoichiometries corresponding to NaQCeo, K.iCeo and Cs,.,.Cfio[ll3].

When eoating fullerenes with larger alkali metal atoms, the even-odd alternation is interrupted before reaeliing x = 21, so the structural sequence must be different for these. Nevertheless, we do suggest that the first 6 alkali metal atoms, having transferred their valence electron to the fullerene moleeule, will remain distributed over the surfaee of the fullerene, gather-... 

Doping of alkali-metals into CNTs has been examined [11]. The X-ray powder diffraction (XRD) patterns of the K- or Rb-doped CNTs show that alkali-metals are intercalated between the CNT layers. The hexagonal unit cell is essentially the same as that of the stage-1 alkali-metal intercalated graphite ACg (A=K, Rb). For a sample doped with Rb, the observed lattice parameter of the perpendicular... 

The hydrogen atom has a high ionization energy (1312kJmol ) and in this it resembles the halogens rather than the alkali metals. Removal of the Is electron leaves a bare proton which, having a radius of only about 1.5 x 10 pm, is not a stable chemical entity in the condensed phase. However, when bonded to other species it is well known in solution and in... 

All the alkali metals have characteristic flame colorations due to the ready excitation of the outermost electron, and this is the basis of their analytical determination by flame photometry or atomic absorption spectroscopy. The colours and principal emission (or absorption) wavelengths, X, are given below but it should be noted that these lines do not all refer to the same transition for example, the Na D-line doublet at 589.0, 589.6 nm arises from the 3s — 3p transition in Na atoms formed by reduction of Na+ in the flame, whereas the red line for lithium is associated with the short-lived species LiOH. 

In addition to the above oxides M2O, M2O2, M4O6, MO2 and MO3 in which the alkali metal has the constant oxidation state 4-1, rubidium and caesium also form suboxides in which the formal oxidation state of the metal is considerably lower. Some of these intriguing compounds have been known since the turn of the century but only recently have their structures been elucidated by single crystal X-ray analysis. Partial oxidation of Rb at low temperatures gives RbeO which decomposes above —7.3°C to give copper-coloured metallic crystals of Rb902 ... 

The C102 ion is nonlinear, as expected, and X-ray studies of NH4CIO2 (at —35°) and of AgC102 lead to the dimensions Cl-O 156 pm, angle O-Cl-O 11 r. The chlorites of the alkali metals and alkaline earth metals are colourless or pale yellow. Heavy metal chlorites tend to explode or detonate when heated or struck (e.g. those of Ag+, Hg+, T1+, Pb + and also those of Cu + and NH4+). Sodium chlorite is the only one to... 

By incorporation of alkali metal halides in the reaction mix, materials of composition M4-[MfiXig] can be produced in which each MgXn unit has a further six X atoms attached to its apices, so forming discrete clusters. 

---