Equilibrium studies have been performed to determine the Brønsted acidity of [(C 6 F 5 ) 3 B(OH 2 )]‚ H 2 O, the aqua species that exists in acetonitrile solutions of B(C 6 F 5 ) 3 in the presence of water. NMR spectroscopic analysis of the deprotonation of [(C 6 F 5 ) 3 B(OH 2 )]‚H 2 O with 2,6-Bu t 2 C 5 H 3 N in acetonitrile allows a pK value of 8.6 to be determined for the equilibrium [(C 6 F 5 ) 3 B(OH 2 )]‚H 2 O a [(C 6 F 5 ) 3 B(OH)] -+ [H 3 O] + . On the basis of a calculated value for the hydrogen bond interaction in [(C 6 F 5 ) 3 B(OH 2 )]‚H 2 O, the pK a for (C 6 F 5 ) 3 B(OH 2 ) is estimated to be 8.4 in acetonitrile. Such a value indicates that (C 6 F 5 ) 3 B(OH 2 ) must be regarded as a strong acid, with a strength comparable to that of HCl in acetonitrile. Dynamic NMR spectroscopic studies indicate that the aqua and acetonitrile ligands in (C 6 F 5 ) 3 B(OH 2 ) and (C 6 F 5 ) 3 B(NCMe) are labile, with dissociation of H 2 O being substantially more facile than that of MeCN, by a factor of ca. 200 in rate constant at 300 K. Ab initio calculations were performed in the gas phase and with a dielectric solvent model to determine the strength of B-L bonds (L ) H 2 O, ROH, MeCN) and hydrogen bonds involving B-OH 2 and B-O(H)R derivatives.

No abstract

i 11. SUPPLEMENTARY NOTES repared for publication in Organometallics 12a. OISTRIBUTIONi AVAILABIUTY STATEMENT 12b. DISTRIBUTION CODE Reproduction in whole or in part is permitted for any-Purpose of the United States Government. This document has been approved for public release and sale; its distri-•ution is unlimited. _ ".. ABSTRACT (Maximum 2C0 worosJ 14. SUBJECT TERMS 1s. NU•R OF PAGES 16. PRICE CODE 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRAC-',rOF REPORT

MesB(C6F5)2 (1) has been prepared from MesMgBr and FB(C6F5)2·OEt2, while Mes2B(C6F5) (2) is readily available from CuC6F5 and Mes2BBr. The reduction potential E° of 1 vs Cp2Fe0/+ in THF is −1.72 V, while that of 2 is −2.10 V, and that of Mes3B (3) is −2.73 V. 11B and 1H NMR show that neither 1 nor 2 binds THF significantly. These results have been used to estimate the reduction potential of B(C6F5)3 in THF as −1.17 V vs Cp2Fe0/+ or as −0.64 V vs SCE.

No abstract

No abstract

I z (rC3-o),(cC-o),(cC-oH)41In contrast to the extensive oxide and oxide-hydroxide chemistry observed for aluminum and indium,"] there are relatively few studies of the analogous chemistry of gallium. A recent 'IGa NMR spectral study has indicated the formation of the unstable cationic cluster, [Ga,,04(OH),4(H,0),,]7+, whose structure is proposed to be identical to that of the aluminum Similarly, the first organogallium-oxo compound reported, [tBuGa(p3-O)19, was determined by mass spectrometry and NMR spectroscopy to also be isostructural to its aluminum analog.[31 The first reported examples of apparent diversification between the chemistry of aluminum and gallium oxide and oxide-hydroxide clusters was for the hexagallium compounds [Ga,Mes,O,X,], Mes = mesityl, X = F,I4] OH'51 for which the equivalent aluminum compounds did not exist. We now report the structural characterization of the largest galloxane hydroxide isolated thus far, as well as the aluminum analog of Oxidation of [tBu,Ga(Spy)] (H-Spy = 2-mercaptopyridine),@] followed by atmospheric hydrolysis yields colorless crystals with a composition corresponding to [Ga,,tBu,,O,,(OH),] (1). Single crystals of 1 suitable for X-ray structure analysis['] were obtained from Et,O and four molecules of solvent are present in [GatjR,O4(OH)4].the formula unit. While the Et,O molecules of solvation are disordered, the 0 . . 0 distances are within the range expected for weak hydrogen bonding interaction. The molecular structure of 1 is shown in Figure 1. Each of the gallium atoms and bridging 0 atoms (Ga-0-Ga) lie on a mirror plane. The cage structure consists of twelve fused six-membered rings. Each gallium atom is coordinated to one carbon and three oxygens, while there are two types of oxygen atom sites; six oxygens bridging two galliums [O(l)], and eight oxygens capping three galliums [0(2)]. However, the structure may also be considered to consist of an 0x0-cube [0(2)], with each face capped by a [tBuGa(p-X)GatBu] unit, X = 0 or OH. Fig. 1. Molecular structure of 1. The methyl groups have been omitted for clarity. The bridging oxygen atom, O(1), exists as a 40: 60 disorder of an 0x0 and a hydroxo ligand. Selected bond lengths [A] and angles ["I: Ga

No abstract