Attempted protonation of the [closo-B9H9]2− under the moisture-free conditions did not afford the expected monoanion [closo-B9H10]−, while its reaction with HCl in dichloromethane afforded the first chlorine-containing monoanion [arachno-B9H12-4,8-Cl2]− in a high yield.
Eleven-vertex closo and nido boron clusters with one or two exo-cyano groups were obtained by a series of consecutive cage-opening and cage-closure reactions starting from K2 [closo-B11 H11 ] (K2 1). In the first step, K2 1 reacts with KCN in water at elevated temperatures to yield [7-NC-nido-B11 H12 ]2- (5 a). Oxidation of 5 a with PbO2 gives [NC-closo-B11 H10 ]2- (2). In analogous subsequent reactions, dianion 2 was converted with KCN regioselectively to [7,9-(NC)2 -nido-B11 H11 ]2- (6 a), which was further oxidized to [(NC)2 -closo-B11 H9 ]2- (3). The {nido-B11 } dianions 5 a and 6 a were protonated to yield [7-NC-nido-B11 H13 ]- (5 b) and [7,9-(NC)2 -nido-B11 H12 ]- (6 b). All anions were studied by NMR spectroscopy and, except for 6 b, salts of all anions were characterized by IR and Raman spectroscopy and by elemental analysis. The position of the cyano group(s) in 5 a and 6 a were confirmed by NMR data and single-crystal X-ray diffraction studies on [Ph4 P]2 5 a⋅CH2 Cl2 and [Et4 N]2 6 a. The {closo-B11 } clusters are fluxional in solution. In the crystal of [EMIm]2 2 the BCN vertex is in the 2-position. Two isomers of dianion 3, [2,3-(NC)2 -closo-B11 H9 ]2- and [2,6-(NC)2 -closo-B11 H9 ]2- , were identified in the crystal of its [Et4 N]+ salt. The peak oxidation potentials Epa of anions 1-3, 5 a, 6 a, 5 b, and [nido-B11 H14 ]- (4 b), determined by cyclic voltammetry, increase with increasing number of cyano groups. Increasing Epa in the order 1<2<3 parallels the increasing reactivity toward cyanide anions.
Deprotonation of 8bH-tetrabenzo[a,c,g,i]fluorene (8bH-Tbf), an extremely large benzannulated cyclopentadienyl derivative, by [NR3R'][OH] (R = (n)Bu, Et; R' = (n)Bu, Et, Bn) leads to a series of Tbf ammonium salts of the type [NR3R'][Tbf]. These cyclopentadienide analogs were smoothly isolated from a hydrous medium and structurally characterized by single X-ray diffraction. Subsequent reactions demonstrate the high potential of derivatization by converting the presented [Tbf] anions into functionalized Tbf compounds.
AbstractThe [B8H8]2‐ and [B8H9]‐ ions are characterized by NMR spectroscopy, single crystal XRD, and DFT calculations.
[B21H18] reacts with anhydrous HF at 100 degrees C, depending on the reaction time, to various compounds with the form[7-F-B21H17], [7, 8'-F2-B21H16], [7, 8-F2-B21H16], [7, 8, 9'-F3-B21H15]and [7, 8, 9-F3-B21H15]. [B21F18] is available by the reaction of [B21H18] with F2 in aHF. The mentioned borates were characterized by NMR spectroscopy. Crystal structures of salts with [B21H18xFx](x = 13) were determined.
Protonation of M(2)[B(8)H(8)] with HCl or NEt(3)·HCl resulted in M[B(8)H(9)] (M = [PPh(4)](+) or [N(n-Bu(4))](+)). The monoanion was isolated and characterized by (1)H, (1)H{(11)B}, (11)B, and (11)B{(1)H} NMR spectroscopy. The "protonated" form [B(8)H(9)](-) showed a dynamic behavior in solution, which was analyzed by NMR spectroscopy and compared with theoretical calculations. The structures of [B(8)H(9)](-) as well as [B(8)H(8)](2-) were determined by single-crystal X-ray diffraction.
