Goedde et al.
extracts are filtered and combined with the original supernatant.
The resulting solution is concentrated to ca. 250 mL by distillation
under nitrogen, and then, the concentrate is transferred by cannula
to a 500 mL flask. Vacuum removal of the diethyl ether at room
temperature over 4 h produces a white solid that coats the flask
walls. The white solid is maintained under dynamic vacuum
overnight and then scraped down off the walls under nitrogen,
washed with degassed pentane (2 × 100 mL), and dried under
were allowed to warm to room temperature with agitation. The
solution was transferred to a 100 mL volumetric Teflon flask with
washings of 6 M HCl in deionized water. Additional HCl solution
was added to the volumetric flask to bring the total volume to 100
mL. The hydrolyzed sample of 1 was analyzed by ICP elemental
analysis to contain 317.2 µg of boron and 246.7 µg of Cr; the
+
relative B/Cr atomic ratio was 6.18:1.00. Addition of Ag to another
hydrolyzed sample of 1 gave a negative test for chloride.
Bis(octahydrotriborato)chromium(II), Cr(B H ) . A sample
vacuum (1 h) to give NaB
Et O). Anal. Calcd for NaB
Found: Na, 34.0; B, 53.6; H, 12.8. H NMR (tetrahydrofuran-d
3
H
8
(25.5 g, 55% yield based on BF
3
‚
3
8 2
2
3
H
8
: Na, 36.2; B, 51.1; H, 12.7.
3 3 8
of 1, prepared from CrCl (1.49 g, 9.41 mmol) and NaB H (1.89
1
8
):
δ 0.05 (decet, 8H, J11B-H ) 33 Hz). IR (cm ): 2472 (s), 2424
s), 2400 (sh), 2361 (s), 2334 (s), 2131 (m), 2098 (m), 1173 (s),
g, 29.8 mmol) by method B described previously, was freed of
excess pentane under vacuum at 0 °C and then stored under argon
at room temperature until conversion to blue crystals was complete
(ca. 3 h). Blue crystals of Cr(B H ) at 0 °C were washed with
-
1
(
1007 (s), 791 (w), 738 (w), 443 (m).
3
8 2
Regeneration of Materials. After the generation of diborane in
pentane (2 × 10 mL) and purified by sublimation (35 °C, 20
flask #1 has been completed, NaBF
4
is essentially the only solute
mTorr). Yield: 0.296 g (24% based on Cr). Mp: 64 °C (dec). Anal.
dissolved in the tetraglyme. NaBF is soluble in tetraglyme at room
4
Calcd for B
46.6; Cr, 38.9. H NMR (C
Hz, see text for assignment). Magnetic moment (benzene, 20 °C):
B
4.8 µ . IR (Nujol, cm ): 2557 (m), 2541 (s), 2515 (m), 2504 (m),
6
H
16Cr: H, 12.1; B, 48.8; Cr, 39.1. Found: H, 11.3; B,
temperature but is much less soluble above 100 °C.65 The solution
is stirred and slowly heated to 150 °C under a purge of nitrogen,
which sweeps the small amounts of liberated diborane out of the
flask and into the hood. This temperature is maintained overnight
1
6 6
D , 20 °C): δ 108.5 (s, fwhm ) 1800
-
1
2489 (sh), 2482 (s), 2432 (sh), 2406 (s), 2269 (w), 2155 (sh), 2131
(s), 2081 (s br), 2017 (sh), 1307 (w), 1266 (w), 1207 (w), 1168
(m), 1140 (m), 1054 (w), 1020 (sh), 1009 (s), 973 (s), 918 (sh),
889 (w), 869 (m), 769 (m), 731 (s), 666 (m), 632 (s br), 510 (m).
Bis(octahydrotriborato)bis(diethylether)chromium(II), Cr-
(B H ) (Et O) . To a suspension of CrCl (0.86 g, 5.4 mmol) in
while colorless crystals of NaBF
While hot, the tetraglyme is decanted from the NaBF
and readied for reuse by vacuum distillation from molten sodium.
After the NaB has been removed, flask #2 contains NaBH
and spent amalgam. Cold water is slowly added to flask #2 against
a stream of nitrogen. The aqueous solution of NaBH is slowly
4
accumulate on the flask wall.
4
by cannula
3
H
8
4
3
8 2
2
2
3
4
3 8
diethyl ether (20 mL) at 0 °C was added a solution of NaB H
acidified with dilute HCl until gas evolution subsides. The aqueous
layer is discarded, and traces of HCl are removed from the mercury
by washing with water. The mercury is then readied for reuse by
drying under vacuum at room temperature.
(1.30 g, 20.5 mmol) in diethyl ether (20 mL). The slurry was stirred
at 0 °C for 3 h; over this period, gas slowly evolved and the
originally purple solution became dull green. The solvent was
removed at 0 °C, and the residue was extracted with pentane (70
mL). The extract was filtered into a flask cooled to 0 °C, and the
solvent was removed under vacuum. The residue was extracted with
diethyl ether (10 mL), and the green extract was filtered and cooled
(
Hydrido)bis(octahydrotriborato)chromium(III), CrH(B
3 8 2
H ) .
Method A. A mixture of CrCl (0.45 g, 2.8 mmol) and NaB
3
H
3 8
(0.82 g, 13 mmol) was placed in a 250 mL round-bottomed flask,
and 100 steel balls (4.5 mm diameter) were added. The flask was
gently agitated by hand for 15 min; and over this period, gas evolved
and the reactant powders became damp and changed color to dark
purple. The purple product was transferred under vacuum into a
flask cooled to -196 °C. Yield: approximately 0.5 mL of purple
liquid. Mp: below -20 °C. EPR (toluene, -196 °C): three features
to -78 °C to afford blue crystals, which were dried under vacuum
1
at -20 °C. Yield: 0.98 g (64%). Mp: 39 °C. H NMR (C
6 6
D ,
20 °C): δ 28.4 (s, fwhm ) 1200 Hz, CH
2
), 12.2 (s, fwhm ) 530
. IR (Nujol,
Hz, CH ). Magnetic moment (benzene, 20 °C): 4.4 µ
3
B
-
1
cm ): 2515 (s), 2459 (s), 2372 (w), 2343 (w), 2153 (s br), 2105
(s br), 1303 (w), 1262 (w), 1183 (w), 1148 (m), 1089 (m), 1028
(s), 1011 (sh), 976 (w), 899 (m), 865 (w), 830 (m), 777 (m), 616
(m br), 513 (w).
-
1
at 125, 170, and 330 mT. IR (pentane, cm ): 2588 (sh), 2568
(
(
sh), 2554 (vs), 2541 (sh), 2485 (vs), 2261 (w), 2131 (m), 2068
w), 2005 (vs br), 1160 (w), 1135 (m), 1040 (w), 996 (m), 972 (m
Bis(octahydrotriborato)bis(tetrahydrofuran)chromium(II), Cr-
(B H ) (THF) . A sample of Cr(B H ) (Et O) (0.70 g, 2.5 mmol)
br), 872 (m br), 819 (s br), 620 (m br).
Method B. A mixture of CrCl (1.49 g, 9.41 mmol) and NaB
1.89 g, 29.8 mmol) was treated as described in Method A.
3
8 2
2
3
8 2
2
2
3
H
3 8
was dissolved in tetrahydrofuran (10 mL) at -78 °C, and the
solution was warmed to room temperature over 10 min to give a
pastel-blue slurry. The solvent was removed under vacuum, and
the residue was extracted with diethyl ether (4 × 15 mL). The
extracts were filtered, combined, and cooled to -20 °C to afford
blue crystals. Yield: 0.55 g (80%). Mp: 92 °C (dec). Anal. Calcd
(
However, instead of carrying out a vacuum transfer, the purple
liquid was extracted from the reaction flask with pentane (2 × 80
mL). The extracts were filtered, combined, and the pentane was
removed under vacuum at 0 °C to afford a purple liquid.
Method C. To a mixture of CrCl
NaB (0.80 g, 13 mmol) at room temperature were added a Teflon
magnetic stir bar, 40 Pyrex spheres (3 mm diameter), and pentane
30 mL). As the slurry was stirred rapidly, gas evolved, and the
3
(0.46 g, 2.9 mmol) and
for C
34.8; H, 11.5; B, 21.9; Cr, 19.1. H NMR (C
fwhm ) 3200 Hz, â-CH ). Magnetic moment (benzene, 20 °C):
. IR (Nujol, cm ): 2515 (sh), 2496 (s), 2483 (s), 2445 (s),
8 32 6 2
H B O Cr: C, 34.7; H, 11.6; B, 23.4; Cr, 18.8. Found: C,
1
H
3 8
7 8
D , 20 °C): δ 66 (s,
2
-
1
(
4.6 µ
B
solution color became purple. After 3 h, the solution was filtered,
and the residue was washed with pentane (5 × 30 mL). The
washings were filtered and combined with the original solution,
and the solvent was removed under vacuum at 0 °C to afford a
purple liquid. The B/Cr ratio was determined in the following
manner. Deionized water (20 mL) was added to a 100 mL argon-
filled flask by syringe and then frozen by cooling to -78 °C. A
small amount of 1 in pentane (ca. 0.5 mL) was layered above the
ice, and a ground-glass stopper sealed the flask. The flask contents
2352 (w), 2279 (w), 2205 (s br), 2114 (m br), 1889 (w), 1246 (w),
1170 (m), 1147 (m), 1102 (w), 1039 (m), 1015 (s), 974 (m), 922
(m), 864 (s br), 816 (m br), 724 (s), 696 (w), 619 (s br), 501 (w),
422 (s).
Bis(octahydrotriborato)bis(trimethylphosphine)chromium-
(II), Cr(B
3 8 2 3 2 3
H ) (PMe ) . To CrCl (0.66 g, 4.15 mmol) suspended
in diethyl ether (20 mL) at 0 °C was added a solution of NaB
3
H
8
(0.848 g, 13.4 mmol) in diethyl ether (20 mL). The mixture was
stirred at 0 °C for 3 h. The resulting blue solution was cooled to
2822 Inorganic Chemistry, Vol. 46, No. 7, 2007