13412 J. Am. Chem. Soc., Vol. 120, No. 51, 1998
Polse et al.
Table 4. Crystal Parameters for Complexes 3 and 6
and 7. Cycloadducts were not observed as intermediates in these
reactions. Isolated azametallacyclobutene 3 rearranges thermally
to the novel fulvene complex 5.
Cp*2Ti(NPhCHd
CH) (3)
Cp*2Ti(NHPh)Ct
CPh (6)
empirical formula
fw (amu)
size (mm)
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
TiNC18H37
315.4
TiNC34H41
511.6
Experimental Section
0.30 × 0.30 × 0.35
P212121 (No. 19)
18.2307(4)
10.8656(2)
12.1204(3)
90.0
90.0
90.0
2400.9(2)
4
0.872
0.16 × 0.28 × 0.40
General Methods. Unless otherwise noted, all reactions and
manipulations were carried out in dry glassware under a nitrogen or
argon atmosphere at 20 °C in a Vacuum Atmospheres 553-2 drybox
equipped with a MO-40-2 inert gas purifier, or using standard Schlenk
techniques. The amount of O2 in the drybox atmosphere was monitored
with a Teledyne model #316 trace oxygen analyzer. For a description
of other instrumentation and general procedures used, see ref 22.
Unless otherwise specified, all reagents were purchased from
commercial suppliers and used without further purification. Phenyl-
and trimethylsilylacetylene were distilled from MgSO4 and stored over
4 Å molecular sieves. Acetylene gas was purified by passage through
two -78 °C traps separated by a concentrated H2SO4 trap. Pentane
and hexanes (UV grade, alkene free) were distilled from sodium
benzophenone ketyl/tetraglyme under nitrogen. Benzene, toluene,
diethyl ether, and THF were distilled from sodium benzophenone ketyl
under nitrogen. Cyclohexane was distilled from calcium hydride under
nitrogen. Deuterated solvents for NMR experiments were dried in the
same way as their protiated analogues but were vacuum transferred
from the drying agent. Tolyl azide73 and Cp*2TidNPh32 were prepared
by literature methods. Cp*2Ti(C2H4) was prepared by the literature
method,39 except that Cp*2TiCl74 was used instead of Cp*2TiCl2.
NMR Spectroscopy. NMR experiments were performed on a
P21/c
10.0432(16)
16.167(4)
17.541(4)
90.0
97.294(16)
90.0
2825.0(18)
4
1.20
Z
d
µ
calcd (g cm-3
calcd (cm-1
)
)
3.52
3.2
Cp*2Ti(N(Ph)CHdCH) (3). A Schlenk flask equipped with a
magnetic stir bar was charged with 1 (122 mg, 0.297 mmol) in 40 mL
of benzene. Acetylene gas was passed through the solution for 5 m.
The solution was allowed to stir for an additional 15 m, and then the
volatile materials were removed under reduced pressure. The red powder
was extracted with hexanes (20 mL) and filtered. The volume of the
filtrate was reduced to 8 mL in vacuo. Slow cooling to -50 °C
overnight yielded 79.8 mg of blocky red crystals of 3 (61.7%) suitable
for X-ray diffraction studies. IR (Nujol): 2771(w), 1587(s), 1459(s)
1326(s), 1236(m), 1168(m), 1114(m), 1020(m), 991(m), 776(s), 694(m)
1
1
cm-1. H NMR (toluene-d8, -40 °C): δ 7.27 (1H, m), 7.20 (1H, m),
Brucker AMX spectrometer resonating at 300.13 MHz for H, 75.42
MHz for 13C, and 30.42 MHz for 15N that was equipped with an inverse
probe. The temperature in the probe was monitored using a thermo-
couple and was calibrated with an ethylene glycol standard.75 Except
where noted, all one- and two-dimensional experiments were acquired
between 295 and 300 K. EXSY spectra were acquired at 273 K in
phase-sensitive mode using the Brucker pulse program noesytp. A
shifted sine bell window function was applied to the raw data set in
both dimensions.76 Integrations were performed on 1D slices through
the cross-peaks of interest. The rate constants were determined from
plots of cross-peak intensity vs mixing time as described elsewhere.47
Generation and Spectroscopic Characterization of 2. A solution
of 1 (5.2 mg, 0.0127 mmol) in 0.5 mL toluene-d8 was transferred to a
J-Young NMR tube. Ferrocene (2.8 mg, 0.0150 mmol) was added as
an internal standard. The sample was degassed at -195 °C under
vacuum and backfilled to 1 atm with ethylene. The sample was
transferred to a precooled NMR probe (-50.8 °C). Inspection of the
1H NMR spectrum revealed that only ethylene and 2 were present in
7.08 (1 H, d, 3J ) 9 Hz), 7.02 (1 H, d, 3J ) 9 Hz), 6.93 (1 H, m), 6.72
(1 H, m), 5.93 (1 H, m), 1.67 (30 H, s) ppm. 13C{1H} NMR (toluene-
d8, -40 °C): δ 186.2 (CH), 129.6 (CH), 128.3 (CH), 126 (C), 120.8
(CH), 152 (C), 114.9 (CH), 111.8 (CH), 96.8 (CH), 12.2 (CH3) ppm.
MS (EI): m/z 435 (M+). Anal. Calcd for C28H37NTi: C, 77.21; H,
8.58; N, 3.21. Found: C, 77.06; H, 8.58; N, 3.06.
Cp*2Ti(NPhCDdCD) (3-d2). Crystals of 1 (110.5 mg, 0.270 mmol)
were dissolved in 8 mL of benzene and transferred to a glass bomb.
The solution was degassed under vacuum, and C2D2 (0.681 mmol, 2.5
equiv) was condensed onto the frozen solution from a 138 mL bulb.
The solution was stirred for 1 h at room temperature, and the volatile
materials were removed under reduced pressure. The red powder was
extracted into hexanes and filtered. The volume of the filtrate was
reduced to 2 mL and cooled to -50 °C overnight to afford red crystals
of 3-d2 (60.3 mg, 51.1%). Examination by 1H NMR spectroscopy
showed that the doublets at 7.02 and 7.08 ppm, which correspond to
the ring methine protons of 3, were >99% deuterated.
X-ray structure of 3. A fragment of a red prismatic crystal of 3
having approximate dimensions of 0.30 × 0.30 × 0.35 mm was
mounted on a glass fiber using Paratone N hydrocarbon oil. All
measurements were made on a Siemens SMART diffractometer with
a CCD area detector using graphite-monchromated Mo KR radiation.
All calculations were performed using the TEXSAN crystallographic
software package of Molecular Structure Corporation.
Cell constants and an orientation matrix for data integration, obtained
from a least-squares refinement using the measured positions of 8192
reflections in the range 3.00 < 2θ < 45.00°, corresponded to a primitive
orthorhombic cell. The final cell parameters and specific data collection
parameters for this data set are given in Tables 4 and 5. Inspection of
the systematic absences of h00: h * 2n, 0k0: k * 2n, and 00l: l * 2n
uniquely determine the space group to be P212121 (No. 19).
Data were integrated to a maximum 2θ value of 46.5° using the
program SAINT with box parameters of 1.6 × 1.6 × 0.6°. The data
were corrected for Lorentz and polarization effects. No decay correction
was applied. The linear absorption coefficient, µ, for Mo KR radiation
is 3.5 cm-1. The program XPREP was used to make an empirical
absorption correction based on comparison of equivalent reflections
and an ellipsoidal model of the absorption surface (Tmax ) 0.94, Tmin
) 0.88). The 10520 integrated reflections were averaged in space group
Pmmm to give 1995 unique reflections (Rint ) 3.7%). These were used
for solution of the structure. The structure was solved by direct methods
and expanded using Fourier techniques. The correct enantiomer was
1
solution. H NMR (toluene-d8, -50 °C): δ 7.35 (m, 1H), 7.24 (m,
1H), 6.79 (m, 1H), 6.50 (m, 1H), 6.19 (m, 1H), 2.35 (m, 2H), 1.82 (m,
2H), 1.67 (s, 30H) ppm. 13C{1H} NMR (toluene-d8, -50 °C): δ 129.7
(CH), 129.0 (CH), 123.1 (C), 120.7 (C), 120.2 (CH), 114.3 (CH), 109.4
(CH), 64.4 (CH2), 25.5 (CH2), 12.0 (CH3) ppm.
Measurement of Keq for the Equilibration of 1 and Ethylene with
2. A 1 mL volumetric flask was charged with 1 (11.1 mg, 0.0271 mmol)
and Cp2Fe (1.3 mg, 0.00699 mmol). The solution was brought to
volume with toluene-d8. A J-Young NMR tube was charged with 0.5
mL of this solution. The sample was frozen in liquid nitrogen and
evacuated. Ethylene (0.0404 mmol) was condensed onto the frozen
solution from a 23.58 mL bulb. 1H NMR spectra were recorded at 10°
increments from 253.3 to 283.2 K. A series of three one-pulse
experiments separated by 5 min increments were acquired at each
temperature, and the concentrations of 1, 2, and ethylene were
determined by integration against the Cp2Fe standard. The concentra-
tions used to determine Keq at each temperature were calculated by
averaging the values for the three one-pulse experiments.
(73) Ugi, I.; Perlinger, H.; Behringer, L. Chem. Ber. 1958, 91, 2330.
(74) Pattiasina, J. W.; Heeres, H. J.; van Bolhuis, F.; Meetsma, A.;
Teuben, J. H.; Spek, A. L. Organometallics 1987, 6, 1004.
(75) Amman, C.; Meier, P.; Merbach, A. E. J. Magn. Reson. 1982, 46,
319.
(76) In each case, the integration was checked before and after application
of the window function. In no case were the integrals noticeably affected.