Alkali metal salt clusters

Calibrants are required to calibrate the mass scale of any mass spectrometer, and it is important to find reference compounds that are compatible with a particular ion source. Calibrants commonly used in electron ionization (El) and chemical ionization (Cl), such as perfluorocarbons, are not applicable in the ESI mode. The right calibrants for LC-ESI-MS should (1) not give memory effects (2) not cause source contamination through the introduction of nonvolatile material (3) be applicable in both positive- and negative-ion mode. The main calibrants used or still in use to calibrate ESI-MS can be divided into the following categories polymers, perfluoroalkyl triazines, proteins, alkali metal salt clusters, polyethers, water clusters, and acetate salts. 

In order to characterize the alkali metal salts of the 11-vertex nido-dicarbaborates [C2B9H11]2- in solution, a series of salts were synthesized and studied by NMR spectroscopy and quantum mechanical calculations. Comparison of the theoretical nB, 13C, and H NMR chemical shifts of the isomeric dianions 7,8-, 7,9-, and [2,9-C2B9Hn]Z, and the ion pairs [ap-M-CzBgHn]- and MHP-MC2B9HH] with the observed data indicate that the alkali metal salts M2[C2B9Hn] exist in solution as anionic ion pairs [ap-M-C2B9Hn]- with the metal in apical position (ap) coordinated at the five-membered open face of the cluster.14... 

Hetero-atomic clusters, moreover, may be derived from the binary structures mainly through the introduction of late transition or earlier post-transition elements. Examples of ternary alloys containing such structures are the alkali metal salts of centred clusters In10Me10 (Me = Ni, Pd, Pt), Tl12 Me12- (Me = Mg, Zn, Cd, Hg), etc. The crystal structure of the phase Na T Cdi x)27 (0.24 < x < 0.33)... 

Example ED from untreated wire emitters in the presence of intentionally added alkali metal salts was used to obtain mass spectra of tartaric acid, arginine, pentobarbital and other compounds. [78,80] Besides [Mh-H]" quasimolecular ions, m/z 175, the FD mass spectrum of arginine exhibits [M+Na], m/z 197, and [Mh-K]", m/z 213, ions due to alkali metal cationization as well as [2M-i-H], m/z 349, cluster ions (Fig. 8.14). [37]... 

A particularly interesting development concerns the solution chemistry of [Zr6Gi2Z] clusters. [100, 101] Alkali metal salts of the kind A Zr Q,2+ Z can be dissolved (e.g. in CH3CN in the presence of a cryptand) and the clusters are then isolated as R4N or (C H5)4P salts. This solution chemistry of interstitially stabilized clusters entered via solid state preparations promises great versatility and adds new facets to the traditional cluster chemistry of the neighboring elements Nb and Ih. 

The synthetically useful dianions [M3(CO)u]2- were first isolated by Shore and co-workers as the Ca2+ (M=Ru) and the K+ (M=Os) salts by the reduction of M3(CO)12 using alkali metal benzophenone solutions in THF.1 [Ru3(CO) J2 reacts with Ru3(CO) 2 to form the higher nuclearity clusters [Ru4(CO)13]2- and [Ru6(CO)i8]2- but the triruthenium anion can be obtained in high purity by slowly adding triruthenium dodecacarbonyl to an excess of reducing solution using vacuum-line techniques.2 Vacuum-line syntheses of both dianions have been described in detail.1... 

In a similar manner the so-called Zintl salts composed of alkali metal cations and clusters of metals as anions (see Chapter 16) were known in liquid ammonia solution but proved to be impossible to isolate Upon removal of the solvent they reverted to alloys. Stabilization of the cations by complexation with macrocyclic ligands allowed the isolation and determination of the structures of these compounds. 

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