Organometallics
ARTICLE
Method 2. In a N
2
-atmosphere glovebox, a 1.5 mL vial equipped with
’ ACKNOWLEDGMENT
a stirbar was charged with 0.500 mL of CD Cl and 0.200 mL of a 10:1
2
2
This research was funded by BP through the Methane Con-
version Cooperative (MC ) program. We thank M. Findlater and
M. Brookhart for providing the PONOP complexes and Dr.
David Vander Velde for help with NMR experiments.
mixture of TFA-d and TFA and capped with a septum. In a separate vial,
the metal complex (5 mg for solids, 0.5 μL for ZnMe ) was dissolved in
.200 mL of CD Cl and capped with a septum. An NMR tube was also
2
2
0
2
2
capped with a septum under the inert atmosphere. Outside of the
glovebox, the vial containing the acid mixture and stirbar was placed into
the appropriate temperature bath and allowed to equilibrate for 5 min.
The metal solution was then injected via syringe dropwise to the stirring
mixture over a period ranging from ∼30 s to 2 min; no systematic effect
of addition rate on KIE could be seen. After complete addition, the
reaction mixture was transferred to the septum-capped NMR tube using
a gastight syringe.
Method 3. The experimental setup for this method was identical with
that of method 1 prior to removal from the glovebox. The vial and NMR
tube were taken from the glovebox and, along with a syringe, allowed to
equilibrate in the cold room at 0 °C for 1 h. The metal complex solution
was then added to the NMR tube dropwise via syringe, with continuous
inversion of the tube as in method 1.
’
REFERENCES
(
(
(
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1
and CH
3
D signals was averaged over the five spectra and multiplied by
(
10 (because of the 10:1 ratio of TFA-d and TFA used in the experi-
ments) to give the KIE value. Each experiment (at different tempera-
tures and using different methods) was carried out at least in triplicate
(
3
1
(except for the Rh and Ir samples, for which there was insufficient
(
material to do so).
1
H NMR Spectral Data for Organometallic Products. In all
(
1
cases (except ZnMe ) the H NMR spectrum of the reaction mixture
2
showed a single organometallic product, consistent with clean proto-
(
19
nolysis of one or two methyl groups, while the F NMR spectrum
showed a single peak, consistent with fast exchange between complex
1
(
and excess acid. The reaction of (cod)PtMe with excess TFA gave
2
1
(
5
cod)PtMe(TFA): H NMR (CD
2
Cl
2
) δ 5.50À5.46 (m, 2H),
118, 5961–5976.
2
.80À5.60 (m, 2H), 2.7À2.2 (m, 8H), 0.78 (s, 3H, JPtH = 30 Hz).
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The reaction of (dppe)PdMe with excess TFE gave (dppe)PdMe(TFE):
2
1
H NMR (CD Cl ) δ 7.8À7.4 (m, 20H), 2.50À2.10 (m, 4H), 0.54
2
2
(
(
2
2
br, 3H). The reaction of (dppe)PdMe with excess TFA gave
1
cod)Pt(TFA)
2
: H NMR (CD
2
Cl
2
) δ 7.88À7.56 (m, 20H), 2.8À
(
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.55 (m, 4H). The reaction of ZnMe with excess TFA (presumably)
2
1
gave Zn(TFA)
2
; no H NMR signal other than those for the acid,
(
solvent, and methane isotopologues were observed. The reaction of
tBu2
tBu2
1
Cp
2
ZrMe
2
with excess TFA gave
2
Cp ZrMe(TFA): H NMR
(
(
CD Cl ) δ6.7À6.3 (m, 6H), 1.30 (s, 3H), 1.28, (s, 9H), 1.25 (s, 9H). The
2
2
reaction of (PONOP)IrMe with excess TFA gave (PONOP)Ir(TFA):
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1
3
3
H NMR (CD
2 2
Cl ) δ 8.00 (t, 1H, JHH = 12 Hz), 7.11 (d, 2H, JHH =
(23) Bercaw, J. E.; Chen, G. S.; Labinger, J. A.; Lin, B. L. J. Am. Chem.
6
Hz), 1.6À1.3 (m, 36H). The reaction of (PONOP)RhMe with excess
Soc. 2008, 130, 17654–17655.
1
TFA gave (PONOP)Rh(TFA): H NMR (CD Cl ) δ 7.56 (t, 1H,
2
2
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Ithaca, NY, 1973.
3
3
3
J
HH = 6 Hz), 7.37 (d, 2H, JHH = 6 Hz), 1.34 (d, 18H, JHH = 6 Hz),
3
1
.26 (d, 18H, JHH = 6 Hz).
(26) Bell, R. P. The Tunnel Effect in Chemistry; Chapman and Hall:
London, 1980.
’
ASSOCIATED CONTENT
(27) Slaughter, L. M.; Wolczanski, P. T.; Klinckman, T. R.; Cundari,
T. R. J. Am. Chem. Soc. 2000, 122, 7953–7975.
S
Supporting Information. Tables of measured kinetic
b
(
(
(
28) Caldin, E. F. Chem. Rev. 1969, 69, 135–156.
29) Kwart, H. Acc. Chem. Res. 1982, 15, 401–408.
30) Limbach, H. H.; Lopez, J. M.; Kohen, A. Philos. Trans. R. Soc. B
isotope effects for the protonolyses of metal methyl complexes
at different temperatures using different methods, figures giving
Arrhenius plots, and equations. This material is available free of
charge via the Internet at http://pubs.acs.org.
2
006, 361, 1399–1415.
(31) Melander, L.; Saunders, W. H. Reaction Rates of Isotopic Molecules;
Krieger: Malabar, FL, 1987.
’
AUTHOR INFORMATION
(32) Crumpton-Bregel, D. M.; Goldberg, K. I. J. Am. Chem. Soc.
003, 125, 9442–9456.
(33) Bercaw, J. E.; Chen, G. S.; Labinger, J. A.; Lin, B. L. Organo-
2
Corresponding Author
*E-mail: bercaw@caltech.edu (J.E.B.); jal@caltech.edu (J.A.L.).
metallics 2010, 29, 4354–4359.
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dx.doi.org/10.1021/om200432b |Organometallics 2011, 30, 4374–4378