9790 Inorganic Chemistry, Vol. 48, No. 20, 2009
Zhang et al.
Scheme 5. Possible Reaction Pathways for the Formation of nido-
C2B11 and closo-CB11 Anions
(d, JBH = 136 Hz, 1B). IR (KBr, cm-1): νΒH 2522 (vs). Anal.
Calcd for C9H30B11NO: C, 37.63; H, 10.53; N, 4.88. Found: C,
38.10; H, 10.77; N, 4.68.
Concentration of the mother liquor yielded few colorless
X-ray-quality-crystals identified as [Me3NH][2c].
Preparation of [Me3NH][8,9-(CH2)3-μ-11,12-(MeO)BH-8,9-
C2B11H11] ([Me3NH][3a]). To a MeOH solution (5 mL) of 1
(54 mg, 0.26 mmol) was added an aqueous solution of Me3N
(45%, 0.5 mL, 7.00 mmol), and the reaction mixture was stirred
at room temperature for 1 min. After removal of solvents under
vacuum, the solid residue was thoroughly washed with hexane
and Et2O to give [Me3NH][3a] as a white solid (75 mg, 96%).
Recrystallization from a CH2Cl2 solution afforded colorless
crystals. 1H NMR (CD2Cl2): δ 9.04 (brs, 1H, NH), 3.35
(s, 3H, OCH3), 2.97 (s, 9H, NCH3), 2.58 (m, 2H, CH2), 1.95
(m, 2H, CH2), 1.88 (m, 1H, CH2), 1.60 (m, 1H, CH2). 13C{1H}
NMR (CD2Cl2): δ 86.1 (br, cage C), 60.3 (OCH3), 46.8 (NCH3),
41.1 (CH2), 25.1 (CH2). 11B NMR (CD2Cl2): δ 22.3 (d, JBH
=
138 Hz, 1B), 9.8 (d, JBH = 149 Hz, 2B), 4.5 (d, JBH = 133 Hz,
1B), -1.2 (d, JBH = 136 Hz, 2B), -4.1 (d, JBH = 148 Hz, 2B),
-8.5 (d, JBH = 120 Hz, 3B), -28.3 (d, JBH = 138 Hz, 1B). IR
(KBr, cm-1): νΒH 2517 (vs). Anal. Calcd for C9H31B12NO: C,
36.14; H, 10.45; N, 4.68. Found: C, 36.41; H, 10.53; N, 4.77.
Preparation of {K(THF)}{8,9-(CH2)3-μ-11,12-(tBuO)BH-
8,9-C2B11H11} ({K(THF)}{3b}). To a THF solution (10 mL)
of 1 (104 mg, 0.50 mmol) was added tBuOK (84 mg, 0.75 mmol)
under stirring at room temperature The reaction was complete
in 1 min. Removal of THF gave a yellow solid, which was
extracted with Et2O (3 ꢀ 10 mL). Slow evaporation at room
temperature afforded {K(THF)}{3b} as colorless needle crystals
(88 mg, 55%). Single-crystals suitable for X-ray analyses were
formation of nido-C2B12, nido-C2B11, and closo-CB11 carbor-
ane anions dependent upon the nature of the nucleophiles. It
is more reactive than 12-vertex carboranes but is less reactive
than 13-vertex ones.
Experimental Section
General Procedures. Unless otherwise noted, all experiments
were performed under an atmosphere of dry dinitrogen with the
rigid exclusion of air and moisture using standard Schlenk or
cannula techniques, or in a glovebox. 2,3-(CH2)3-2,3-C2B12H12
was prepared according to literature method.11 THF was re-
fluxed over sodium benzophenone ketyl for several days and
freshly distilled prior to use. All other chemicals were purchased
from either Aldrich or Acros Chemical Co. and used as received
unless otherwise noted. Infrared spectra were obtained from
KBr pellets on a Perkin-Elmer 1600 Fourier transform spectro-
1
grown from a THF/hexane solution at room temperature. H
NMR (acetone-d6): δ 3.62 (m, OC4H8), 2.48 (m, 2H, CH2), 1.98
(m, 2H, CH2), 1.78 (m, 5H, CH2 þ OC4H8), 1.56 (m, 1H, CH2),
0.99 (s, 9H, OC(CH3)3). 13C{1H}NMR (acetone-d6): δ 83.6 (br,
cage C), 74.0 (OC(CH3)3), 67.8 (OC4H8), 41.2 (CH2), 30.4
(OC(CH3)3), 25.8 (OC4H8), 25.0 (CH2). 11B NMR (acetone-
d6): δ 24.3 (d, JBH = 132 Hz, 1B), 7.5 (d, JBH = 145 Hz, 2B),
3.5 (d, JBH = 142 Hz, 1B), 0.8 (d, JBH = 139 Hz, 2B), -1.5 (d,
1
JBH = 145 Hz, 2B), -4.8 (d, JBH = 132 Hz, 2B), -7.4 (d, JBH
=
meter. H NMR spectra were recorded on a Bruker DPX 400
169 Hz, 1B), -28.0 (d, JBH = 132 Hz, 1B). IR (KBr, cm-1): νΒH
2519 (vs). Anal. Calcd for C11H31B12KO1.5 (M - 0.5THF):
C, 37.09; H, 8.77. Found: C, 37.64; H, 8.43.
spectrometer at 400.0 MHz. 13C NMR spectra were recorded on
a Bruker DPX 300 spectrometer at 75.5 MHz or a Bruker DPX
400 spectrometer at 100.6 MHz. 11B NMR spectra were re-
corded on a Bruker DPX 300 spectrometer at 96.3 MHz. 31P
NMR spectra were recorded on a Bruker DPX 300 spectrometer
at 121.5 MHz. All chemical shifts were reported in δ units with
reference to the residual solvent resonances of the deuterated
solvents for proton and carbon chemical shifts, to external
Preparation of [PPN][8,9-(CH2)3-μ-11,12-(Me2N)BH-8,9-
C2B11H11] ([PPN][3c]). To a THF solution of 1 (52 mg, 0.25
mmol) was added LiNMe2 (26 mg, 0.50 mmol) under stirring at
room temperature. The reaction was finished in 1 min.
A saturated MeOH solution of [PPN]Cl was then added until
the precipitation was complete. An orange-yellow solid was
collected and washed with MeOH (3 ꢀ 2 mL). Recrystallization
from acetone gave [PPN][3c] as orange-yellow crystals (158 mg,
80%). 1H NMR (acetone-d6): δ 7.71 (m, 18H, C6H5), 7.58
(m, 12H, C6H5), 2.59 (s, 6H, NCH3), 2.37 (m, 2H, CH2), 1.89
(m, 2H, CH2), 1.75 (m, 1H, CH2), 1.47 (m, 1H, CH2). 13C-
{1H}NMR (acetone-d6): δ 134.6, 133.3, 130.5, 129.0, 127.5
(C6H5), 41.2 (CH2), 25.3 (CH2). 11B NMR (acetone-d6): δ 25.7
BF3 OEt2 (0.00 ppm) for boron chemical shifts, and to external
3
85% H3PO4 (0.00 ppm) for phosphorus chemical shifts. Ele-
mental analyses were performed by the Shanghai Institute of
Organic Chemistry, the Chinese Academy of Sciences, China.
Reaction of 1 with MeOH. A MeOH solution (5 mL) of 1
(78 mg, 0.38 mmol) in a closed Schlenk flask was heated to re-
flux at 70 °C for 48 h. After addition of [Me3NH]Cl (72 mg,
0.75 mmol), the mixture was stirred for another 1 h at room
temperature. Removal of the volatile materials gave a white
solid that was washed with water to remove the excess amount of
(d, JBH = 140 Hz, 1B), 4.5 (d, JBH = 154 Hz, 2B), 1.6 (d, JBH
=
140 Hz, 2B), -0.2 (d, JBH = 138 Hz, 3B), -6.9 (d, JBH = 103
Hz, 3B), -28.5 (d, JBH = 137 Hz, 1B). 31P NMR (acetone-d6):
δ 38.5. IR (KBr, cm-1): νΒH 2504 (vs). Anal. Calcd for
C43H54B12N2P2: C, 65.33; H, 6.88. Found: C, 65.52; H, 6.46.
Preparation of [PPN][8,9-(CH2)3-8,9-C2B11H12] ([PPN][4]).
A piperidine solution (2 mL) of 1 (52 mg, 0.25 mmol) was stirred
at room temperature for 8 h. After removal of piperidine under
vacuum, the residue was dissolved in MeOH (2 mL). A saturated
MeOH solution of [PPN]Cl was added to the above solu-
tion until the precipitation was complete. The white solid was
collected by filtration and washed with MeOH (3 ꢀ 2 mL).
Recrystallization from acetone gave [PPN][4] as colorless
1
[Me3NH]Cl. The H NMR of the crude product showed the
molar ratio of [2a]-/[2b]- was about 1:1.1. Fractional recrys-
tallization from acetone afforded [Me3NH][2b] as colorless
crystals (38 mg, 35%). 1H NMR (acetone-d6): δ 6.70 (brs, 1H,
NH), 3.21 (m, 1H, OCH), 3.18 (s, 12H, NCH3 þ OCH3), 2.01
(m, 1H, CH2), 1.92 (m, 1H, CH2), 1.55 (m, 1H, CH2), 1.48 (m,
1H, CH2), 1.28 (m, 1H, CH2), 0.74 (m, 1H, CH2). 13C{1H} NMR
(acetone-d6): δ 79.9 (OCH), 67.7 (cage C), 54.7 (OCH3), 46.0
(NCH3), 36.1 (CH2), 31.9 (CH2), 21.4 (br, BCH2). 11B NMR
(acetone-d6): δ -7.0 (s, 1B), -9.9 (d, JBH = 130 Hz, 1B), -12.1
(d, JBH = 122 Hz, 7B), -13.5 (d, JBH = 171 Hz, 1B), -15.6