Chemical ionization mass spectrometry of selected boron hydrides

Abstract

Chemical ionization mass spectra for diborane, tetraborane, pentaborane(9), pentaborane(1 l), and hexaborane(l0) in methane have been obtained. The boron hydrides B4HI0, and BjHll are ionized by

Unusual cationic rhodathiaboranes: synthesis and characterization of [8,8,8-(H)(PR3)2-9-(Py)-nido-8,7-RhSB9H10]+and [1,3-μ-(H)-1,1-(PR3)2-3-(Py)-isonido-1,2-RhSB9H8]+

“…Since the yields of these neutral 11-vertex rhodathiaboranes are generally good, this is a convenient entry into the area of polyhedral boron-containing cations which is scarcely explored with only a small number of reported cationic boranes and metallaheteroboranes. [39][40][41][42][43][44][45][46][57][58][59][60][61][62][63] It is important to recall that the majority of reported cationic metallaheteroboranes generally contain charge-compensating ligands; [41][42][43][44][45][46] and the number of cationic polyhedral boron clusters formed by simple protonation is very small indeed. 39,40 The herein reported reactions with TfOH together with previous results with HCl 36,64 give an overall view of the reactivity of this family of rhodathiaboranes with Brønsted acid (Scheme 4).…”

Thenido–osmaboranes [2,2,2-(CO)(PPh3)2-nido-2-OsB5H9] and [6,6,6-(CO)(PPh3)2-nido-6-OsB9H13]

“…The short B4ÐB5 distance in (I) implies that the metallaborane species may have some Lewis base character, as has been noted in hexaborane(10) (Solomon & Porter, 1972;Brennan et al, 1973). Some evidence for this has, for example, been adduced in the reaction of (II) with Fe 2 (CO) 9 to yield closo-[B 5 H 4 PPh 3 {Fe(CO) 3 }{Ir(CO)PPh 3 }] via an initial [(PPh 3 ) 2 -(CO)IrB 5 H 8 {"(Fe(CO) 4 )}] intermediate (Bould, Rath, Fang & Barton, 1996).…”

Comparison of the orders of gas-phase basicities and ammonium ion affinities of polyethers by the kinetic method and ligand exchange technique

“…Often the popular equilibrium methods are not viable for measurement of ion binding affinities owing to the inability to precisely control or monitor the gasphase concentrations of analytes, as in laser-desorbed species. Thus, two alternative techniques have been commonly applied for such measurements: the kinetic method [9] and the ligand exchange and/or bracketing technique [10][11][12][13]. The kinetic method was first described for the determination of relative gas-phase basicities of simple organic molecules [9].…”

“…In contrast, the ligand exchange or bracketing technique is a method in which a cation (i.e., proton, metal ion) is allowed to transfer between two bases in the gas phase [12][13][14]. For example, one cationized base is permitted to interact with a second neutral base, and observation of the transfer of the cation to the second base indicates that the second base has a higher intrinsic cation affinity.…”

“…Typically, the cation transfer reaction is observed in both directions to confirm the order of affinities. Originally, this method was typically performed in a relatively high-pressure ion source, and the total pressure of reactants admitted was varied systematically to observe the change in product ion distribution and thus determine the favored direction of the cation transfer reaction [12,13]. In recent years, ion trapping techniques have often been used to undertake this type of experiment [14], with the added advantages that the cation transfer reactions can be monitored as a function of time, and one reactant ion may be isolated and allowed to selectively react with the second reactant neutral, This latter feature allows determination of affinities without requiring the ability to uniformly vary the total reactant pressure; however, the neutral gas-phase concentrations of each base must be controlled in some way to ensure nearly equivalent or at least well-characterized collision probabilities between the two bases, allowing accurate extraction of thermodynamic data.…”