Tungstenocene Boryl Complexes
Organometallics, Vol. 15, No. 25, 1996 5357
For intense reflections an attenuator was automatically in-
serted in front of the detector.
material. This material was recrystallized before submitting
for microanalysis: 1H NMR (C6D6) δ -10.09 (s, d; J W-H ) 72.5
Hz, 2H, W-H), 3.88 (m, 2H, C5H4BPh2), 4.08 (s, 5H, Cp), 4.75
(m, 2H, C5H4BPh2), 7.20 (t, 7.0 Hz, 2H, BPh2), 7.25 (t, 7.3 Hz,
4H, BPh2), 7.81 (d, J ) 7.2 Hz, BPh2); 11B NMR (C6D6) δ 41;
13C{1H} NMR (C6D6) δ 77.34, 78.63, 85.22, 127.37, 127.43,
134.83; the quaternary carbons bound to boron could not be
observed. Anal. Calcd for C22H21BW: C, 55.04; H, 4.41.
Found: C, 54.77; 4.33.
Cp (C5H4Bca t)WH2 (3b). F r om Li[Cp 2WH]. A procedure
identical to preparation of 1 in toluene solvent was followed
except that 1.2 equiv of chlorocatecholborane was used and
the solution was left to react overnight. Recrystallization from
toluene/pentane solutions gave 3a in 21% yield as a pale yellow
solid: 1H NMR (C6D6) δ -11.31 (s, d; J W-H ) 72 Hz; 2H, W-H),
4.14 (s, 5H, Cp), 4.23 (t, J ) 2.1 Hz, 2H, C5H4Bcat), 4.59 (t, J
) 2.1 Hz, 2H, C5H4Bcat), 6.73 (m, 2H, Bcat), 6.98 (m, 2H, Bcat);
11B NMR (C6D6) δ 33; 13C{1H} NMR (C6D6) δ 73.82, 74.23,
80.23, 111.97, 122.16, 148.81. Anal. Calcd for C16H15BO2W:
C, 44.29; H, 3.48. Found: C, 43.77; H, 3.71.
Da ta Red u ction , Str u ctu r e Solu tion , a n d Refin em en t.
Of the 2770 reflections which were collected for 1, 2641 were
unique (Rint ) 0.033). Of the 7198 reflections which were
collected for 2a , 6929 were unique (Rint ) 0.078). The
intensities of the two representative reflections which were
measured after every 60 min of X-ray exposure time declined
by -50.00% for 1 but were constant for 2a . A linear correction
factor was applied to the data to account for this phenomena
with 1, but no correction was applied for 2a . The linear
absorption coefficient for Mo KR was 84.0 cm-1 for 1 and 37.3
cm-1 for 2a . For 1 an empirical absorption correction using
the program DIFABS was applied, which resulted in transmis-
sion factors ranging from 0.60 to 1.57. The data were corrected
for Lorentz and polarization effects. For 2a , an empirical
absorption correction based on azimuthal scans of several
reflections was applied, which resulted in transmission factors
ranging from 0.77 to 1.00. The data were corrected for Lorentz
and polarization effects.
The structures were solved by the Patterson method.61 This
procedure revealed the position of the W atoms, and subse-
quent difference maps revealed the remaining atoms. The
non-hydrogen atoms were refined anisotropically. The thermal
parameters of the carbon atoms on each cyclopentadienyl ring
of 1 were somewhat larger than normal. The hydrogen atoms
were included in calculated positions. In the case of the methyl
group hydrogens of 2a , one hydrogen atom was located in the
difference map and included in an idealized position to set the
orientation of the other two hydrogen atoms. For 1, the final
cycle of full-matrix least-squares refinement was based on 1456
observed reflections (I > 3.00σ(I)), with 181 variable param-
eters, and converged (the largest parameter shift was 0.00
times its esd) with unwieghted and weighted agreement factors
of R ) Σ||Fo| - |Fc||/Σ|Fo| ) 0.039 and Rw ) [(Σw(|Fo| - |Fc|)2/
Σ|Fo|)]1/2 ) 0.039. For 2a , the final cycle of full-matrix least-
squares refinement was based on 4244 observed reflections (I
> 3.00σ(I)), with 388 variable parameters, and converged (the
largest parameter shift was 0.001 times its esd) with un-
wieghted and weighted agreement factors of R ) ∑||Fo| - |Fc||/
∑|Fo| ) 0.041 and Rw ) [(∑w(|Fo| - |Fc|)2/∑|Fo|)]1/2 ) 0.050.
The standard deviation of an observation of unit weight was
1.42 for 1 and 1.69 for 2a . The weighting scheme was based
on counting statistics and included a factor (p ) 0.03) to
downweight the intense reflections. Plots of Σw(|Fo| - |Fc|)2
versus |Fo| reflection order in data collection, (sin θ)/λ, and
various classes of indices showed no unusual trends. The
maximum and minimum peaks on the final difference Fourier
map corresponded to 1.38 (located 1.77 Å away from the W
atom) and -1.30 e/Å3 for 1 and 1.29 (located 1.04 Å from the
W atom) and -2.71 e/Å3. Neutral atom scattering factors were
taken from Cromer and Waber.62 Anomalous dispersion effects
were included in Fc; the values for ∆f ′ and ∆f ′′ were also those
of Cromer and Waber.63 All calculations were performed using
the TEXSAN crystallographic software package of the Molec-
ular Structure Corp.
F r om R ea ct ion of 1 w it h a Ca t a lyt ic Am ou n t of
Ch lor oca tech olbor a n e. Compound 1 (6.0 mg, 0.014 mmol)
was dissolved in 0.6 mL of C6D6. C6H5(t-Bu) (1-2 mg) was
added as an internal standard, and the sample was transferred
to an NMR tube equipped with a Teflon-lined screw cap. An
initial 1H NMR spectrum was obtained to determine the ratio
of 1 to internal standard. Chlorocatecholborane (ca. 0.2 mg,
10 mol %) was weighed into a vial, and the sample of 1 in
C6D6 was added to the vial. The resulting sample was
returned to the NMR tube and was warmed to 45 °C for 2 h.
A second
1H NMR spectrum showed complete consumption of
1 and formation of 3a in 82% yield as determined by integra-
tion of the cyclopentadienyl resonance versus the internal
standard.
Cp 2W(Cl)(Bca t) (4). P r ep a r a tive Sca le. To a solution
of 1 (65 mg, 0.15 mmol) in 5 mL of toluene was added 1.0 equiv
of CCl4 by syringe. The solution turned immediately dark
brown. Addition of pentane to the reaction solution precipi-
tated 4 as a brown powder (55 mg, 78%) that was roughly 90%
1
compound 4 as determined by H NMR spectroscopy. Alter-
natively 4 was prepared as dark brown analytically pure
crystals by concentrating the toluene reaction solution and
cooling to -35 °C. Once isolated, this compound was not
soluble enough in hydrocarbon solvents to obtain satisfactory
signal to noise ratios for 13C NMR spectra and decomposed
slowly in methylene chloride solvent: 1H NMR (C6D6) δ 4.49
(s, 10H), 6.88 (m, 2H), 7.24 (m, 2H); 11B NMR (C6D6): δ 49.
Anal. Calcd for C16H14BClO2W: C, 41.30; H, 3.01. Found: C,
41.29; H, 3.03.
Sm a ll-Sca le Rea ction for NMR Yield Deter m in a tion .
Compound 1 (4.0 mg) was dissolved in C6D6 solvent (0.6 mL),
C6H5(t-Bu) (1-2 mg) was added as an internal standard, and
the sample was transferred to an NMR tube equipped with a
Teflon-lined screw cap. An initial 1H NMR spectrum was
obtained to determine the ratio of 1 to internal standard. A 1
equiv amount of CCl4 was added, and a second 1H NMR
spectrum was obtained that showed complete reaction of 1 and
formation of 4 in 88% yield as determined by integration of
its cyclopentadienyl resonance versus the internal standard.
P h otolysis of 1. A 5.2 mg (0.012 mmol) amount of 1 was
dissolved in 0.6 mL of C6D6. C6H5(t-Bu) (1-2 mg) was added
as an internal standard, and the sample was transferred to
an NMR tube equipped with a Teflon-lined screw cap. An
initial 1H NMR spectrum was obtained to determine the ratio
of 1 to internal standard. The sample was then placed
approximately 2 cm from a 150 W medium-pressure Hanovia
mercury arc lamp located in a water-cooled Pyrex immersion
well. The sample was irradiated for 20 min at room temper-
Cp (C5H4BP h 2)WH2 (3a ). Li[Cp2WH] (80 mg) that was
30
prepared by deprotonation of Cp2WH2 was suspended in
5-10 mL of toluene. To this stirred solution was added
dropwise at room temperature 0.9 equiv of BrBPh2 as a
solution in 0.5 mL of toluene. The resulting solution was
allowed to react at room temperature for 30 min, after which
time the resulting yellow/orange suspension was filtered. The
filtrate was concentrated to 1-2 mL and transferred to a small
vial. The sample was layered with pentane, and 3b was
obtained in 60% yield (65 mg) as spectroscopically pure
(61) Calabrese, J . C. Ph.D. Thesis, WisconsinsMadison, 1972.
(62) Cromer, D. T.; Waber, J . T. In International Tables for X-ray
Crystallography; The Kynoch Press: Birmingham, U.K., 1974; Vol. IV,
Table 2.2A.
(63) Cromer, D. T.; Waber, J . T. In International Tables for X-ray
Crystallography; The Kynoch Press: Birmingham, U.K., 1974; Vol. IV.
1
ature, and a second H NMR spectrum was obtained. All of 1
had been consumed. Catecholborane and Cp2W(D)(C5D5) was
formed in 88% and 90% yields, as determined by comparison
of the ratio of integrals for the two products versus the internal