Di-n-butylhafnocene
Organometallics, Vol. 28, No. 9, 2009 2869
Table 1. Crystallographic Data for 4-Hf, 5-SiMe3, 5-t-Bu-Hf, and
6-Hf
Preparation of the Hafnacyclocumulene 4-Hf. Di-tert-butyl-
butadiyne (0.374 g, 2.30 mmol) was dissolved in 15 mL of toluene,
and this solution was added to solid Cp2Hf(n-Bu)2 (0.974 g, 2.30
mmol). The obtained solution was filtered, and the filtrate was
heated to 100 °C. After 5 h all volatiles were removed under
vacuum and the residue was extracted with 8-10 mL of n-hexane
at 55 °C. The yellow solution was filtered and stored at -78 °C.
After 1 day yellow crystals had formed, which were isolated by
decanting of the mother liquor, washed with cold n-hexane, and
dried under vacuum to give complex 4-Hf: yield 0.808 g (1.72
mmol, 75%). Mp: 192-193 °C under Ar. Anal. Calcd for C22H28Hf
(470.95 g mol-1): C, 56.11; H, 5.99; Hf, 37,90. Found: C, 56.26;
4-Hf
5-SiMe3-Hf 5-t-Bu-Hf
6-Hf
cryst syst
space group
a (Å)
orthorhombic orthorhombic monoclinic monoclinic
P212121
Pbca
C2/c
P21/n
9.0260(3)
11.12668(15) 22.069(2) 7.8491(2)
b (Å)
c (Å)
13.9022(5) 19.9661(4) 15.6389(15) 26.7157(5)
15.2615(6) 30.5895(4) 20.097(2) 11.3534(3)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
90.00
90.00
90.00
90.00
90.00
90.00
90.00
119.753(2) 102.212(2)
90.00 90.00
6021.8(10) 2326.88(10)
90.00
1915.03(12) 6795.7(2)
Z
4
8
8
2
density (g cm-3
)
1.633
1.364
3.227
200(2)
90 282
6674
5230
308
0.925
0.0195
0.0446
1.397
3.483
100(2)
36 087
8013
7080
345
1.061
0.0221
0.0509
1.681
4.501
200(2)
27 477
4912
4270
286
0.969
0.0173
0.0388
1
H, 6.21; Hf, 37.60. NMR (297 K, benzene-d6): H, δ 1.53 (s, 18
µ(Mo KR) (mm-1) 5.445
H, t-Bu), 5.18 (s, 10 H, Cp); 13C, δ 33.3 (C(CH3)), 37.6 (C(CH3)3),
103.1 (Cp), 105.9 (ꢀ-C), 188.1 (R-C). MS (EI, 70 eV): m/z 472
[M]+.
T (K)
100(2)
no. of measd rflns 15 608
no. of indep rflns 5092
no. of obsd rflns 4853
Preparation of the Hafnacyclopentadiene 5-SiMe3-Hf. Cp2Hf(n-
Bu)2 (0.750 g, 1.77 mmol) was dissolved in 10 mL of toluene, and
the yellow solution was added to bis(trimethylsilyl)butadiyne (0.690
g, 3.55 mmol). The solution was filtered and warmed to 100 °C.
After 5 h all volatiles were removed from the dark yellow-brown
solution under vacuum. The residue was dissolved in 10-15 mL
of n-hexane at 55 °C, followed by filtration of the yellow-orange
solution. The filtrate was stored at -78 °C; after 1 day yellow
crystals had formed, which were isolated by decanting of the mother
liquor, washed with cold n-hexane, and dried under vacuum to give
complex 5-SiMe3-Hf: yield 1.040 g (1.49 mmol, 84%). Mp:
170-172 °C under Ar. Anal. Calcd for C30H46HfSi4 (697.52 g
mol-1): C, 51.66; H, 6.65. Found: C, 51.83; H 6.75. NMR (296 K,
benzene-d6; numbering according to the atom labeling in the
molecular structure, see Figure S2 in the Supporting Information):
1H, δ 0.22 (s, 9 H, C4-SiMe3), 0.26 (s, 9 H, C6-SiMe3), 0.28 (s, 9
H, C14-SiMe3), 0.69 (s, 9 H, C2-SiMe3), 5.97 (s, 10 H, Cp); 13C,
δ -0.2 (C15/16/17), 0.5 (C7/8/9), 0.8 (C18/19/20), 2.8 (C10/11/
12), 93.3 (C14), 107.7 (C5), 111.1 (Cp), 111.5 (C13), 123.4 (C6),
135.3 (C3), 161.4 (C2), 196.4 (C1), 225.1 (C4); 29Si, δ -20.6 (Si1),
-19.8 (Si3), -13.3 (Si4), -5.5 (Si2). IR (Nujol mull, cm-1): 2075,
2121 (CtC). MS (EI, 70 eV): m/z 698 [M]+, 504 [M -
Me3SiC4SiMe3]+, 310 [Cp2Hf]+.
no. of params
180
GOF on F2
1.039
0.0226
0.0502
R1 (I > 2σ(I))
wR2 (all data)
Preparation of Cp2Hf(n-Bu)2 (1-Hf). To a suspension of
Cp2HfCl2 (2.016 g, 5.31 mmol) in 20 mL of n-hexane was added
6.7 mL (10.72 mmol) of a 1.6 M solution of n-BuLi in n-hexane.
The mixture was stirred for 30 min at room temperature, resulting
in a yellow solution which was filtered and concentrated under
vacuum to half its volume and stored at -78 °C. After 1 day a
pale yellow precipitate had formed, which was isolated by decanting
of the mother liquor, washed with cold n-hexane, and dried under
vacuum to give complex 1-Hf: yield 1.579 g (3.73 mmol, 70%).
Mp: 32-33 °C under Ar. Anal. Calcd for C18H28Hf (422.90 g
mol-1): C, 51.12; H, 6.67. Found: C, 50.86; H, 6.43. NMR (297
1
K, benzene-d6): H, δ 0.12 (m, 4 H, R-CH2), 1.02 (t, 3 H, CH3),
1.34 (m, 4 H, γ-CH2), 1.46 (m, 4 H, ꢀ-CH2), 5.67 (s, 10 H, Cp);
13C, δ 14.2 (CH3), 31.0 (γ-CH2), 34.8 (ꢀ-CH2), 58.6 (R-CH2), 109.9
(Cp). The signal for the Cp protons in the 1H NMR at 5.67 ppm is
the same as found before and reported by Negishi et al. in ref 5b.
MS (EI, 70 eV): m/z 365 [M - Bu - 2 H]+, 311 [Cp2HfH]+, 310
[Cp2Hf]+.
Preparation of Complex 6-Hf. A solution of Cp2Hf(n-Bu)2
(1.582 g, 3.74 mmol) in 10 mL of toluene was added to a solution
of 1,4-diphenylbutadiyne (0.690 g, 3.55 mmol) in 10 mL of toluene.
The mixture was filtered and warmed to 100 °C. After 6 h the
resulting red-brown solution was cooled to room temperature. Dark
red crystals were isolated by decanting of the mother liquor, washed
four times with toluene, and dried under vacuum to give complex
6-Hf: yield 0.436 g (23%). Mp: 396-397 °C under Ar. Anal. Calcd
for C52H40Hf2 (1021.85 g mol-1): C, 61.12; H, 3.95. Found: C,
Preparation of the Alkyne Complex 2-Hf. To a solution of
1-Hf (1.351 g, 3.19 mmol) in 10 mL of toluene was added
bis(trimethylsilyl)acetylene (0.72 mL, 3.19 mmol) and pyridine
(0.60 mL, 4.33 mmol). The reaction mixture was filtered and stirred
at 100 °C. After 3.5 h all volatiles were evaporated from the dark
purple solution and the residue was extracted with 20-25 mL of
n-hexane at 55 °C. The solution was filtered, concentrated under
vacuum to 7-8 mL, and stored at -78 °C. After 1 h dark purple
crystals had formed which were isolated by decanting of the mother
liquor, washed with cold n-hexane, and dried under vacuum to give
complex 2-Hf: yield 0.786 g (1.41 mmol, 44%). Mp: 121-123 °C
under Ar. Anal. Calcd for C23H33HfNSi2 (558.18 g mol-1): C, 49.49;
H, 5.96; N, 2.51. Found: C, 49.29; H, 6.00; N, 2.71. NMR at 217
1
61.12; H, 4.02. NMR (296 K, THF-d8): H, δ 6.01 (s, 20 H, Cp),
6.68 (m, 8 H, Ph), 6.74 (m, 12 H, Ph); 13C, δ 109.2 (Cp). Due to
the low solubility in common NMR solvents, no 13C signals for
the Ph substituents and for the central C8 unit were observed. MS
(EI, 70 eV): m/z 1022 [M]+, 820 [M - PhC4Ph - H2]+, 511
[1/2M]+, 411 [Cp2Hf-C2Ph]+, 310 [Cp2Hf]+.
1
K (toluene-d8): H, δ 0.18 (s, 9 H, SiMe3), 0.52 (s, 9 H, SiMe3),
5.29 (s, 10 H, Cp), 6.17 (m, 2 H, m-Py), 6.63 (m, 1 H, p-Py), 8.84
(m, 2 H, o-Py); 13C, δ 2.6 (SiMe3), 2.7 (SiMe3), 105.3 (Cp), 123.0
(m-Py), 136.3 (p-Py), 154.3 (o-Py), 207.0 (CtC), 233.0 (CtC);
29Si, δ -7.7 (SiMe3), -5.1 (SiMe3). NMR at 297 K (toluene-d8):
1H, δ 0.24 (s, 18 H, SiMe3), 5.28 (s, 10 H, Cp), 6.40 (m, 2 H,
m-Py), 6.82 (m, 1 H, p-Py), 8.94 (m, 2 H, o-Py); 13C, δ 2.8 (SiMe3),
105.6 (Cp), 123.2 (m-Py), 136.5 (p-Py), 154.6 (o-Py). Signals for
the coordinated triple bond were not observed due to exchange
broadening. IR (Nujol mull, cm-1): 1548 (CtC). MS (CI, isobu-
tane): m/z 481 [M - Py]+, 171 [Me3SiC2SiMe3]+.
Protolysis of Complex 6-Hf to Compound 7. Complex 6-Hf
(0.448 g, 0.438 mmol) was dissolved in 10 mL of THF, and HCl
(3 mL of a 2 M solution in diethyl ether, 1.752 mmol) was added.
The resulting mixture was stirred, and after 30 min the dark red
precipitate of 6-Hf dissolved. After 45 min all volatiles were
removed under vacuum and the residue was analyzed by NMR,
indicating a mixture of compound 7/Cp2HfCl2 in a ratio of 1:2.
Compound 7 is unstable in solution and decomposes within several
days. Attempts to isolate the free [4]radialene from Cp2HfCl2 by
recrystallization were not successful, and column chromatography
on sililca gel led to decomposition. Hence, no analytically pure
samples of compound 7 were obtained. NMR (296 K, benzene-
(20) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.
(21) Brandenburg, K. DIAMOND, Version 3.1e; Crystal Impact GbR,
Bonn, Germany, 2007.
1
d6): H, δ 6.77 (m, 8 H, m-Ph), 6.89 (m, 4 H, p-Ph), 6.93 (s, 4 H,