Triorganyloxo- and Diorganyloxozirconium Hydridoborates
tion, the following 11B NMR signals were observed at δ = 28.9
[HB(OBu)2], 19 [B(OBu)3], –18.2 [(BuO)2Zr(BH4)2 (5)] and
–23.9 ppm [(BuO)3ZrBH4 (4)] with relative intensities of 1:13:3:8.
1J(11B1H) = 97.5 Hz, H3B·NEt3]. After heating the solution for
96 h, the following NMR spectroscopic data were recorded: δ11B =
1
–20.4 [quint., J(11B1H) = 92.8 Hz, (tBu3CO)3Zr(BH4) (14)], –17.5
[quint., 1J(11B1H) = 86.4 Hz, (tBu3CO)2Zr(BH4)2, 10], –11.5 ppm
Attempts to Synthesize [(BuO)3ZrBH4] (4): In analogy to the pre-
vious experiment, (BuO)4Zr·BuOH (1.87 mL, 5.2 mmol) was
treated with H3B·THF (2.5 m, 8.32 mL, 20.8 mmol) while stirring.
The following 11B NMR spectra were recorded and assigned: δ11B
= 29.0, HB(OBu)2, 19.7, B(OBu)3, –12.6 [(BuO)3ZrBH4 (4)],
–16 ppm [(BuO)2Zr(BH4)2 (5)]. The last two peaks had a ratio of
8:3. After evaporating the solvents in vacuo, only HB(OBu)2 and
B(OBu)3 could be removed as liquids. Attempts to obtain single
crystals of 4 or 5 were not successful.
1
[quart., J(11B1H) = 97.5 Hz, H3B·NEt3]. On storing the solution
for 10 d at room temperature single crystals of (tBu3CO)3Zr(BH4)
(14) separated. Only a few of these crystals had the quality for X-
ray crystallography. IR: ν = 2527 (BH ), 2226 (BH ) cm–1. NMR
˜
t
b
spectroscopic data of the solution (C6D6): δ1H = 1.40, 1.42 ppm [s,
(Me3C)3CO]; δ11B = –21.8 [quint., 1J(11B1H) = 93 Hz, (tBu3O)3-
Zr(BH4) (14)], –12.9 ppm [quart., 1J(11B1H) = 96.9 Hz, H3B·NEt3].
Reaction of 10 with Trimethylphosphane: To a C6D6 solution of 10
was added an 18-fold excess of PMe3. 11B NMR spectra were re-
corded at room temperature, at –60 °C, and at –30 °C. NMR spec-
Zr(OEt)4 (7): To stirred ethanol (60 mL) was added ZrCl4 (15 g,
64.4 mmol) in portions within 1.5 h. Then Et3N (35.7 mL,
0.257 mol) was added, and the suspension was kept at reflux for
1 h followed by the addition of benzene (100 mL) at ambient tem-
perature. The suspension was heated to reflux for 5 h followed by
filtration to remove insoluble material at 20 °C. To the filtrate was
added some pentane to complete the precipitation. After filtration,
the solvent was removed from the filtrate in vacuo, leaving behind
Zr(OEt)4 (8 g, 46%) as a slightly yellow powder. M.p. not defined.
NMR (CDCl3): δ1H = 1.23 (OCH2CH3), 4.14 ppm (OCH2CH3);
δ13C = 19.5 (CH2CH3), 75.0 ppm (OCH2).
2
troscopic data at –60 °C: δ1H = 8.68 ppm [d, J(31P1H) = 43.5 Hz,
(tBu3CO)2ZrH(BH4)PMe3]; δ31P = –60.7 (PMe3), –31.1 ppm [d,
2J(31P1H) = 44.6 Hz, H3PMe3]. NMR spectroscopic data at –30 °C:
δ1H = 8.68 ppm [d, 2J(31P1H) = 40.3 Hz, (tBu3CO)2ZrH(BH4)-
PMe3]; δ31P = –60.7 (PMe3), –31.1 [d, 2J(31P1H) = 44.5 Hz,
(tBu3CO)2ZrH(BH4)PMe3 (13)], –1.8 ppm (quart., H3B·PMe3, not
well resolved). At room temperature: δ1H = 1.22 (s), 1.46 (s, Me3C),
8.95 ppm [quint. 2J(1H1H) = 2.93 Hz, (tBu3CO)2ZrH(BH4)]. δ13C
= 32.55, 34.36 (br. Me3C), 44.99, 45.78 (Me3C), 102.99 ppm (CO).
δ11B = –20.4 [quint., badly resolved, 1J(11B1H) = 93 Hz, (tBu3-
CO)3 Zr(BH4) (14)], –35.9 ppm [dq, 1J(31P11B)
H3B·PMe3].
= 95.7 Hz,
Attempts to Synthesize [(EtO)2Zr(BH4)2] (8): Zr(OEt)4 (100 mg)
was dissolved in toluene (30 mL). To this solution was added an
excess of H3B·THF (7 mmol in 5 mL of THF). The following 11B
NMR spectroscopic data were recorded: After 1 h at 20 °C: δ =
28.5 (EtO)2BH, 19.2 (EtO)3B, 0.9 (H3B·THF), –18 ppm [broad,
(EtO)xZr(BH4)3–x]. 11B NMR signals after 7 h at 60 °C: δ = 28.5,
19.3, 1.1, –12.5 ppm [1J(11B1H) = 86 Hz, (EtO)Zr(BH4)3]. Signals
after 15 h at 60 °C: 28.4, 19.1, 1.0, –12.4 [1J(11B1H) = 86 Hz, (EtO)-
Zr(BH4)3], –16 ppm [broad, (EtO)xZr(BH4)3–x]. No single crystals
could be isolated.
Bis(2,6-diisopropylphenolato)zirconium Dichloride Bis(tetrahydro-
furan) (19): To ZrCl4 (2.46 g, 10.6 mmol) was added tetrahydro-
furan (2 mL). After stirring for 1 h, the solvent was evaporated in
vacuo and Et2O (60 mL) was added to the residue. Then the lilac-
colored suspension was added dropwise at –78 °C to a solution of
2,6-iPr2C6H3OLi in Et2O (80 mL). After stirring the mixture for
20 h, the suspension was filtered. About 50% of the filtrate was
evaporated in vacuo. From the greenish brown solution, colorless
crystals (suitable for an X-ray structure analysis) of 19 separated
within two weeks at –30 °C. Yield: 800 mg of 19 (11%), m.p.
165 °C. NMR (C6D6): δ1H: = 1.26 (CH2-CH2O), 1.36 [3J(1H1H)
= 6.84 Hz, CH(CH3)2], 4.00 (CH2–CH2), 4.16 [sept., 1J(1H1H) =
Bis(tri-tert-butylmethanolato)zirconium
Bis(tetrahydridoborate)
(10): Into a nitrogen-filled 100 mL bulb were added ZrCl4 (2.71 g,
11.6 mmol) and LiOCtBu3 (4.88 g, 23.2 mmol) followed by cold
diethyl ether (100 mL) at –78 °C while stirring. After the addition,
the suspension was allowed to attain room temperature. Stirring
was continued for 7 h. Then the ether was removed by distillation,
and the residue was treated with hexane (50 mL). After filtration,
the residue was treated with Et2O (50 mL). To the resulting solu-
tion was added LiBH4 (500 mg, 23 mmol). After 30 min of stirring,
the solvent was evaporated. The residue was treated with hexane
(80 mL), and the suspension was cleared by filtration. The filtrate
was then reduced to ca. 40 mL in volume and then cooled to –78 °C
for crystallization. After 24 h 1.7 g of crystals were isolated (25%);
m.p. 143–145 °C (gas evolution). δ1H = 1.95 ppm [quint., 1J(11B1H)
= 86 Hz]. δ13C = 33.54 (CH3), 46.05 (CMe3), 103.17 ppm (OC).
δ11B = –17.13 ppm [quint., 1J(11B1H) = 86.7 Hz]. C26H62B2O2Zr
(581.56): calcd. C 60.1, H 12.03, found C 59.6, H 11.57.
3
6.84 Hz, CHCMe3], 6.95 [t, J(1H1H) = 7.84 Hz, p-CH], 7.12 ppm
[d, 3J(1H1H) = 7.84 Hz, m-CH]; δ13C = 24.56 (CHCH3), 25.32,
26.50 (CHMe, CH2CH2), 73.51 (CH2O), 122.05, 123.54 138.88,
157.17 ppm (C6). C32H50O4Cl2Zr (660.87): calcd. C 58.16, H 7.63;
found C 58.14, H 7.63.
Bis(tri-tert-butylmethanolato)zirconium Bis(9,9-dihydrocyclononyl-
9-borate) (18): To [(tBu3CO)2Zr(BH4)2] (10) (720 mg, 1.19 mmol)
and LiH2BC8H14·THF (1220 mg, 4.45 mmol) was added Et2O
(40 mL). After stirring for 1 h, the following 11B NMR signals were
recorded: δ11B = –39.2 [quint. 1J(11B1H) = 81 Hz, 20%], –17.4 [co-
upl. not observed, C8H14BH2ZrBH4, 9%], –13.4 [t, 1J(11B1H) =
71 Hz, BH2Li, 42%], 8.4 [coupl. not obs., BH2ZrBH4, 9%],
9.9 ppm [coupl. not obs., (C8H14BH2)2Zr, 10%]. After 16 h the fol-
Reaction of 10 with Pyridine: To a solution of 10 (0.5 mmol) in
C6D6 was added an excess of pyridine (2 mmol). The resulting solu-
tion was checked by NMR spectroscopy. δ1H = 1.40, 1.50, 1.58
(br., s, Me3C), 3.7 [quart., 1J(11B1H) = 98 Hz, H3B·Py], 6.83,
1
lowing signals were found: δ11B = –39.2 [quint. J(11B1H) = 81 Hz,
LiBH4, 24%], –21.8 [coupl. not obs., O3Zr(BH4), 4%], –17.4 4 [co-
upl. not observed, Zr(BH4)2, 5%], –16.6 [coupl. not observed,
C8H14BH2Zr, 9%], –13.4 [t, C8H14BH2Li, 1J(11B1H) = 71 Hz,
19%], 3.5 [coupl. not observed, O3ZrH2B, 4%], 8.4 [coupl. not ob-
served, (BH2)Zr, 5%], 9.9 [coupl. not observed, (R2BH2)Zr, 24%],
29.2 [coupl. not observed, (C8H14BH)2,5%], 57.0 ppm [s,
C8H14BOCMe3, 5%]. After removing the solvent in vacuo, hexane
(70 mL) was added to the residue, and the colorless solution was
concentrated to 5 mL. After storing the solution at –30 °C for two
weeks, colorless crystals of (tBu3CO)2Zr(H2BC8H14)2 (18) sepa-
1
8.67 ppm [o, m, (CH)]. δ11B = –17.52 [quint, J(11B1H) = 86.5 Hz,
(tBu3CO)2ZrH(BH4)], –9.8 ppm [quart., 1J(11B1H) = 98.4 Hz,
H3B·Py].
Reaction of 10 with Triethylamine: A fourfold excess of Et3N was
added to a C6D6 solution of 10 (0.5 mmol). NMR spectroscopic
data were recorded 72 h after mixing the components: δ11B =
–17.61 [quint., 1J(11B1H) = 87.2 Hz, 10], –1.55 ppm [quart.,
Eur. J. Inorg. Chem. 2011, 5548–5557
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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