Mechanism of the reaction of vinyl chloride with (α-diimine)PdMe + species

Article abstract of DOI:10.1021/om1000925

The reaction of vinyl chloride (VC) with (α-diimine)PdMe⁺ species yields (α-diimine)PdCl(propene)⁺. Isotope labeling experiments using the deuterium-labeled vinyl chlorides 1-VC-d₁ and Z-VC-d₁ combined with DFT

Full text of DOI:10.1021/om1000925

1750 Organometallics 2010, 29, 1750–1760
DOI: 10.1021/om1000925
Mechanism of the Reaction of Vinyl Chloride with
(r-diimine)PdMeþ Species
Stefan M. Kilyanek, Edward J. Stoebenau, III, Nawaporn Vinayavekhin, and
Richard F. Jordan*
Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637
Received February 5, 2010
The reaction of vinyl chloride (VC) with (R-diimine)PdMeþ species yields (R-diimine)PdCl-
(propene)þ. Isotope labeling experiments using the deuterium-labeled vinyl chlorides 1-VC-d1 and
Z-VC-d1 combined with DFT computations establish that this reaction proceeds by 2,1-insertion of
VC to produce β-H agostic (R-diimine)Pd(CHClCH2Me)þ, chain-walking isomerization to generate
β-Cl dative (R-diimine)Pd(CHMeCH2Cl)þ, and syn β-Cl elimination. The labeling experiments rule
out mechanisms involving initial 1,2-insertion or C-Cl oxidative addition. The computational
results and the observation of small amounts of propene-d2 argue against mechanisms involving
2,1-insertion followed by R-Cl elimination and a 1,2 H-shift.
Scheme 1
Introduction
Polyvinyl chloride (PVC) and vinyl chloride copolymers
are industrially important materials with many uses.1 PVC is
produced by free radical polymerization, usually under
suspension polymerization conditions in batch processes.2
However it is difficult to produce polymers with controlled
microstructures by radical polymerization, and batch po-
lymerization processes are expensive to operate. Chlorinated
polyethylene (CPE), effectively a copolymer of ethylene
and VC, is made by postpolymerization chlorination of
polyethylene (PE) via reaction with Cl2 at high pressure. It
is difficult to control the chlorine incorporation by this
method.3 Olefin metathesis routes to CPE materials have
been reported and provide excellent microstructure control.
Wagener used acyclic diene metathesis polymerization
(ADMET) followed by hydrogenation to synthesize “preci-
sion” CPEs with halogens incorporated at predetermined
and regular intervals.4 However, ADMET requires expen-
sive specialty monomers, has poor atom economy, since one
equivalent of ethylene is produced in each chain elongation
step, and produces high molecular weight polymers only at
very high conversions, since it is a step polymerization. CPE
materials can also be produced by ring-opening metathesis
polymerization (ROMP) of chlorocyclooctenes, followed by
hydrogenation.5 However, as in the ADMET approach, the
ROMP strategy requires specialty monomers. Finally, par-
tial reduction of poly(vinyl halide)s can be used to produce
halogenated PE materials. In this case, expensive hydride
reagents are required, halide salt coproducts are produced,
and the polymer microstructure is difficult to control.6
Another possible approach to PVC and CPE materials
would be metal-catalyzed insertion polymerization, analo-
gous to olefin polymerization (Scheme 1). In this strategy,
chain growth is envisioned to occur by coordination of VC to
an active metal alkyl species (LnMR) followed by migratory
insertion. Insertion polymerizations have excellent atom
economy and enable control of the composition, molecular
*Corresponding author. E-mail: rfjordan@uchicago.edu.
(1) (a) Odian, G. Principles of Polymerization; Wiley & Sons: New
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Wiley & Sons: New York, 1983; Vol. 23, pp 865-936. (c) Alger, M. Polymer
Science Dictionary, 2nd ed.; Chapman
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r
pubs.acs.org/Organometallics
Published on Web 03/03/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 7, 2010 1751
Scheme 2
Scheme 4a
Scheme 3
weight, and microstructure of the polymer by tailoring of the
catalyst structure. However, extensive studies have shown
that VC is a potent poison for olefin polymerization cata-
lysts, and, to date, there is no well-documented case of
homopolymerization of VC or copolymerization of VC with
olefins via an insertion mechanism.
a Ar = 2,6-iPr2-Ph.
Detailed studies have shown that VC reacts with LnMR
active species of olefin polymerization catalysts by two
general pathways. In some cases, the catalyst initiates a
normal radical polymerization of VC via in situ-generated
radicals.7 This process precludes catalyst-based control over
the polymerization. For example, this pathway is observed in
the reaction of zirconocene catalysts with VC in the presence
of trace O2 (Scheme 2). Here, autoxidation reactions of metal
alkyl species derived from the catalyst and/or aluminum
alkyl activator generate radicals.
Scheme 5
In other cases, the LnMR active species reacts with VC to pro-
duce LnMCl complexes and R-olefin products (Scheme 3).7,8
Because LnMCl species are inactive for polymerization, this
reaction results in catalyst deactivation. Under anaerobic
conditions, zirconocene catalysts react with VC by this route,
producing chloride complexes derived from Cp2ZrClþ along
with olefins.7 This reaction has been proposed to occur by
“net 1,2-insertion of VC followed by a β-Cl elimination”.
Similarly, (R-diimine)PdMeþ species react with VC to pro-
duce (R-diimine)PdClþ species and propene.8 Low-temperature
NMR studies established that this reaction proceeds by initial
formation of an (R-diimine)PdMe(VC)þ π-complex, rearrange-
ment of this species to (R-diimine)PdCl(propene)þ, and loss of
propene and formation of [(R-diimine)Pd(μ-Cl)]22þ. The key
rearrangement step was again proposed to involve a “net
1,2-insertion of VC followed by β-Cl elimination” (Scheme 4).
No intermediates were observed between the initial (R-diimine)-
PdMe(VC)þ adduct and the (R-diimine)PdCl(propene)þ spe-
cies. A similar reaction was observed for vinyl bromide.9
Insertion reactions have been observed for other vinyl
halides. Neutral (diarylphosphino-arenesulfonate)PdR cat-
alysts copolymerize vinyl fluoride (VF) with ethylene to form
linear PE that contains up to 0.45 mol % vinyl fluoride units
(Scheme 5).10 Radical polymerization was conclusively ruled
out in this case, and an insertion mechanism was implicated.
However, while VF is incorporated by this system, it is also a
potent catalyst inhibitor so that polymer yields and molec-
ular weights are reduced from what is observed in ethylene
homopolymerization under the same conditions.
Scheme 6
Scheme 7
In contrast, Caulton found that Cp2ZrHCl reacts with VF
to form Cp2ZrClF, Cp2ZrCl(CH2CH3), and ethylene. DFT
computations favor a mechanism involving 1,2-insertion of
VF into the Zr-H bond followed by β-F elimination
(Scheme 6). The ethylene that is formed reacts with a second
equivalent of Cp2ZrHCl to form Cp2ZrCl(CH2CH3).11
Similarly Wolczanski found that (tBu3SiO)3TaH2 reacts
with vinyl halides by 1,2-insertion and β-X elimination to
form (tBu3SiO)3TaHX, and secondary trapping of the
evolved ethylene by (tBu3SiO)3TaH2 to form (tBu3SiO)3-
TaH(Et).12 This mechanism was established by deuterium
labeling studies (Scheme 7).
These studies highlight the key challenges that must be
overcome to achieve incorporation of vinyl halides in insertion
polymerizations. In principle, the problem of competing radi-
cal polymerization (Scheme 2) can be avoided by excluding
O2 from the reaction to preclude generation of radicals by
autoxidation chemistry, using radical inhibitors, and using
(7) (a) Stockland, R. A., Jr.; Foley, S. R.; Jordan, R. F. J. Am. Chem.
Soc. 2003, 125, 796. (b) Stockland, R. A., Jr.; Jordan, R. F. J. Am. Chem.
Soc. 2000, 122, 6315. (c) Gaynor, S. G. Macromolecules 2003, 36, 4692.
(8) Foley, S. R.; Stockland, R. A., Jr.; Shen, H.; Jordan, R. F. J. Am.
Chem. Soc. 2003, 125, 4350.
(9) Kang, M.; Sen, A.; Zakharov, L.; Rheingold, A. L. J. Am. Chem.
Soc. 2002, 124, 12080.
(11) Watson, L. A.; Yandulov, D. V.; Caulton, K. G. J. Am. Chem.
Soc. 2001, 123, 603.
(10) Weng, W.; Shen., Z.; Jordan, R. F. J. Am. Chem. Soc. 2007, 129,
15450.
(12) Strazisar, S. A.; Wolczanski, P. T. J. Am. Chem. Soc. 2001, 123,
4728.

1752 Organometallics, Vol. 29, No. 7, 2010
Kilyanek et al.
Scheme 8
second- or third-row metal catalysts that may be less likely to
generate radicals by M-R bond homolysis than first-row metal
catalysts. However, the formation of inactive metal halide species
via reaction of metal alkyls with vinyl halides (Scheme 3) is a
more serious obstacle and represents the major roadblock to
insertion polymerization and copolymerization of VC.
β carbon. Syn or anti β-Cl elimination of this species would
produce the products (mechanisms e and f, respectively).
Chain walking is rapid for (R-diimine)PdRþ species and many
other late metal catalysts.18 In this context, it is important to
note that LnMCHXCH2R species are expected to have high
barriers to olefin or vinyl halide insertion, due to the electron-
withdrawing effect of the halogen and correspondingly poor
nucleophilicity of the -CHXCH2R group. A variety of model
LnMCHXRþ and LnMCHX2Rþ (X = F, Cl) complexes
showed a low aptitude for insertion of olefins and CO.19
Therefore chain walking may be expected to compete with
subsequent insertions following 2,1 VC insertion.
Additionally, following a 2,1-insertion, R-Cl elimination
could occur to produce a metal carbeneoid intermediate.
Such species can undergo 1,2-H shifts, leading to the LnMCl
and olefin products (mechanism d). For example, Ru(H)-
(H2)Cl(PCy3)2 reacts with substituted vinyl chlorides by
2,1-insertion into the Ru-H bond followed by R-Cl elimina-
tion to form Cl2(PCy3)2RudCHR carbene species.20
Several possible mechanisms for the reaction in Scheme 3
are summarized in Scheme 8, starting with a LnMR(VC)
π-complex. VC could undergo 1,2-insertion followed by syn or
anti β-Cl elimination (mechanisms a and b, respectively). β-X
elimination is likely to be thermodynamically favored in most
cases.13,14 Nevertheless, several late metal complexes that contain
β-halogens have been reported, including PtCl5(CH2CH2Cl)2- 15
,
(2,9-Me2phen)PtCl3(CH2CH2Cl),16 and Ir(CO)Br2(PMe2Ph)2-
(CH2CH2Br).17 The stability of these compounds is likely due
to their high oxidation states and the lack of an open coordination
site, which is likely required for syn β-X elimination.
Alternatively, VC could undergo 2,1-insertion followed by
chain walking (i.e., β-H elimination, olefin rotation, and
reinsertion) to generate a metal alkyl species with the Cl on the
Finally, oxidative addition of the VC C-Cl bond followed
by C-C reductive elimination (mechanism c) might occur.
Oxidative addition of vinyl halides to low-valent metal
species, e.g., Pd0 species, are known and typically proceed
(13) Wu, F.; Dash, A. K.; Jordan, R. F. J. Am. Chem. Soc. 2004, 126,
15360.
(14) For other studies of β-X elimination see: (a) Eisenstein, O.;
Crabtree, R. H. New J. Chem. 2001, 25, 665. (b) Zaitsev, V. G.; Daugulis,
O. J. Am. Chem. Soc. 2005, 127, 4156. (c) Clot, E.; Megret, C.; Kraft, B. M.;
Eisenstein, O.; Jones, W. D. J. Am. Chem. Soc. 2004, 126, 5647. (d) Lei, A.;
Lui, G.; Lu, X. J. Org. Chem. 2002, 67, 974. (e) Zhang, Z.; Lu, X.; Xu, Z.;
Zhang, Q.; Han, X. Organometallics 2001, 21, 3724. (f) Liu, G.; Lu, X.
(18) Mecking, S.; Johnson, L.; Wang, L.; Brookhart, M. J. Am.
Chem. Soc. 1998, 120, 888.
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metallics 2004, 23, 600. (b) Axe, F. U.; Marynick, D. S. J. Am. Chem. Soc.
1988, 110, 3728. (c) Cotton, J. D.; Markwell, R. D. J. Organomet. Chem.
1990, 388, 123. (d) Cotton, J. D.; Crisp, G. T.; Daly, V. A. Inorg. Chim. Acta
1981, 47, 165. (e) Cross, R.J.;Gemmill, J. J. Chem. Soc., DaltonTrans. 1981,
2317. (f) Cawse, J. N.; Fiato, R. A.; Pruett, R. L. J. Organomet. Chem. 1979,
172, 405. (g) Anderson, G. K.; Cross, R. J. Acc. Chem. Res. 1984, 17, 67.
(h) Kuhlmann, E. J.; Alexander, J. J. Coord. Chem. Rev. 1980, 33, 195.
(i) Calderazzo, F.; Noack, K. Coord. Chem. Rev. 1966, 1, 118.
(20) (a) Belderrain, T. R.; Grubbs, R. H. Organometallics 1997, 16,
4001. (b) Wilhelm, T. E.; Belderrain, T. R.; Brown, S. N.; Grubbs, R. H.
Organometallics 1997, 16, 3867. (c) Olivan, M.; Caulton, K. G. Inorg.
Chem. 1999, 38, 566. (d) Feher, F. J.; Gergens, D. D.; Ziller, J. W.
Organometallics 1993, 12, 2810. (e) Goldman, A. S.; Tyler, D. R. Organo-
metallics 1984, 3, 449.
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Tetrahedron Lett. 2002, 6791. (g) Leon, E. I.; Paz, N. R.; Riesco-Fagundo,
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C.; Suarez, E. Tetrahedron 2008, 10706. (h) Zhu, G.; Zhang, Z. J. Org.
Chem. 2005, 70, 3339. (i) Zhao, H.; Ariafard, A.; Liu, Z. Organometallics
2006, 26, 812. (j) Cundari, T. R.; Taylor, C. D. Organometallics 2003, 23,
4047. (k) Liu, G.; Lu, X. Tetrahedron Lett. 2003, 467. (l) The reaction of
Cp*2ScMe (Cp* = C5Me5) with vinyl fluoride yields Cp*2ScF and propylene
via insertion and subsequent β-F elimination. Burger, B. Ph.D. Thesis,
California Institute of Technology, 1987.
(15) Halpern, J.; Jewsbury, R. A. J. Organomet. Chem. 1979, 181, 223.
(16) Fanizzi, F. P.; Maresca, L.; Pacifico, C.; Natile, G.; Lanfranchi,
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Article
Organometallics, Vol. 29, No. 7, 2010 1753
Scheme 9. Expected Deuterium Enrichment in the Propene Produced in the Reaction of a LnMMe Species with 1-VC-d1 and Z-VC-d1 via
Mechanisms a-f in Scheme 8
with retention of olefin configuration.21 However, oxidative
addition to high-valent LnMR active catalyst species (e.g.,
PdII species) is much less likely.22
VC can be probed using deuterium-labeled VCs. Scheme 9
provides a summary of the deuterium distributions in the
propene expected from the reaction of a LnMMe species with
1-vinyl chloride-d1 (1-VC-d1) and Z-vinyl chloride-d1 (Z-VC-
d1) for the possible mechanisms in Scheme 8. The predictions
of major and minor products for mechanisms e and f are
based on the expected kH/kD values for β-H/D elimination25
and the expected ratios of E and Z chloropropene produced
by the β-H elimination in each reaction.26
Both 1-VC-d1 and Z-VC-d1 are needed to determine the
reaction mechanism. 1-VC-d1 can unambiguously deter-
mine the regiochemistry of insertion. If 1-VC-d1 reacts by
1,2-insertion (mechanisms a and b) or oxidative addition
(mechanism c), 2-propene-d1 will be the major product. If
1-VC-d1 reacts by 2,1-insertion (mechanisms d-f), a mixture
of E- and Z-propene-d1 will be formed. 1-VC-d1 does not
provide information about the steps that occur after inser-
tion or oxidative addition of VC. However, Z-VC-d1 can
distinguish between mechanisms a and b, or between me-
chanisms e and f, once the regiochemistry of insertion is
known. In the case of 1,2-insertion of Z-VC-d1 (mechanisms
a and b), a syn β-Cl elimination will produce only E-propene-
d1, while an anti β-Cl elimination will produce only
Z-propene-d1. In the cases of 2,1-insertion, chain walk. and
β-Cl elimination (mechanisms e and f), a syn β-Cl elimination
will produce a mixture of 2-propene-d1 and Z-propene-d1,
while an anti β-Cl elimination will produce a mixture of
2-propene-d1 and E-propene-d1. However, no labeling
experiment could be devised to distinguish mechanisms
e and d.
Goddard studied the reactions of (HNdCHCHdNH)-
PdEtþ and {(2,6-iPr2Ph)NdCMeCMedN(2,6-iPr2Ph)}PdEtþ
with VC by DFT. He found that the favored path is mechan-
ism e, i.e., 2,1-insertion followed by chain-walking reaction
and syn β-Cl elimination.23 Replacing the N-H and C-H
groups with N-Ar and C-R groups and including solvent
corrections did not significantly change the energy profile. Other
computational studies have shown that VC has a preference for
2,1-insertion.24 These studies also show that insertions of polar
monomers or olefins into (R-diimine)Pd(CHXCH2R)þ species
generated by 2,1 VX insertion have high barriers.
The objective of this paper is to establish the mechanism of
the reaction of (R-diimine)PdMeþ species with VC. This
problem is addressed through a combination of isotope
labeling experiments using deuterium-labeled VCs and
DFT calculations of key reactions.
Results and Discussion
Isotopic Labeling Studies. Experimental Design. The me-
chanism of the reaction of a LnMR metal alkyl species with
(21) (a) Heck, H. R. Acc. Chem. Res. 1979, 12, 146. (b) Stille, J. K.; Lau,
K. S. Y. Acc. Chem. Res. 1977, 10, 434. (c) Fahey, D. R.; Mahan, J. E. J. Am.
Chem. Soc. 1977, 99, 2501. (d) Labinger, J. A.; Osborn, J. A.; Coville, N. J.
Inorg. Chem. 1980, 19, 3236. (e) Brown, J. M.; Cooley, N. A. J. Chem. Soc.,
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Chem. Commun. 1988, 1345. (f) Jutand, A.; Negri, S. Organometallics
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2003, 22, 4229. (g) Alvarez, R.; Faza, O. N.; Lopez, C. S.; de Lera, A. R. Org.
Lett. 2006, 8, 35. (h) Zeni, G.; Larock, R. C. Chem. Rev. 2006, 106, 4644.
(22) (a) Arnold, P. L.; Sanford, M. S.; Pearson, S. M. J. Am. Chem.
Soc. 2009, 131, 13912. (b) Welbes, L. L.; Lynos, T. W.; Cychosz, K. A.;
Sanford, M. S. J. Am. Chem. Soc. 2007, 129, 5836, and refrences therein.
(23) Philipp, D. M.; Muller, R. P.; Goddard, W. A.; Storer, J.;
McAdon, M.; Mullins, M. J. Am. Chem. Soc. 2002, 124, 10198.
(24) (a) Szabo, M. J.; Jordan, R. F.; Michalak, A.; Piers, W. E.; Weiss,
T.; Yang, S.; Ziegler, T. Organometallics 2004, 23, 5565. (b) Mitoraj, M.;
Michalak, A. J. Mol. Model. 2005, 11, 341. (c) von Schenck, H.; Stromberg,
S.; Zetterberg, K.; Ludwig, M.; Akermark, B.; Svensson, M. Organometal-
lics 2001, 20, 2813.
(25) (a) kH/kD values for β-H eliminations are in the range 2.0-5.6.
(b) Mak, K. W.; Chan, K. S. J. Am. Chem. Soc. 1998, 120, 9686.
(c) Burger, B. J.; Thompson, M. E.; Cotter, W. D.; Bercaw, J. E. J. Am.
Chem. Soc. 1990, 112, 1566. (d) Ikariya, T.; Yamamoto, A. J. Organomet.
Chem. 1976, 120, 257. (e) Evans, J.; Schwartz, J.; Urquhart, P. W.
J. Organomet. Chem. 1974, 81, C37.
(26) (a) E-Chloropropene should be preferred for steric rþeasons.
(b) For comparison, the dimerization of ethylene by (phen)PdMe yields
a ca. 2:1 mixture of trans- and cis-2-butene, along with 1-butene: Rix, F. C.;
Brookhart, M.; White, P. S. J. Am. Chem. Soc. 1996, 118, 4746.

1754 Organometallics, Vol. 29, No. 7, 2010
Kilyanek et al.
Table 1. Distribution of Isotopomers of Propene-d1 Formed in the Reaction of (N∧N)PdMeþ Species with 1-Vinyl
Chloride-d1 and Z-Vinyl Chloride-d1
a N∧N = (2,6-iPr2Ph)NdCMeCMedN(2,6-iPr2Ph). b The solvent for all reactions is CD2Cl2. c Uncertainties are the standard deviations of several
runs. d VC is in ca.100-fold excess. e Volatiles (CD2Cl2, Z-VC-d1, and trace impurities from the synthesis of Z-VC-d1) were removed at low temperature,
fresh solvent was added, and the reaction was warmed to 0 °C to liberate the bound propene, which was transferred to a new NMR tube and analyzed.
f VC is in ca. 5-10-fold excess. g In situ measurement of bound propene-d1. h VC is in ca. 4-fold excess.
Scheme 10
Scheme 12
quantitative formation of [(N∧N)PdCl(propene-d1)][MeB-
(C6F5)4] was observed, as previously reported for nondeut-
erated VC (Scheme 12).8 The bound propene-d1 comprised
74% 2-propene-d1 and 26% Z-propene-d1; E-propene-d1
was not observed (entry 7).
Scheme 11
Mechanistic Implications of the Labeling Results. The
observation that the 1-VC-d1 reactions produce no or only
trace amounts of 2-propene-d1 rules out mechanisms a-c.
The trace 2-propene-d1 observed in some experiments is
likely formed by a secondary reaction (vida infra). The
observation that the reactions of Z-VC-d1 produce no or
only trace amounts of E-propene-d1 rules out mechanisms b
and f. Only mechanisms d (2,1-insertion, R-Cl elimination,
1,2-hydrogen shift) and e (2,1-insertion, chain walk, syn β-Cl
elimination) can lead to the observed distribution of deuter-
ium in the propene products.28 This result is in agreement
with Goddard’s computational findings that 1þ reacts with
VC by 2,1-insertion.
Computational Study of a Truncated System. DFT was
used to probe the energetics of the two remaining mechanisms,
d and e. The R-diimine ligand was modeled as HNdCHCHd
NH. The computations were performed using Gaussian 03 at
the B3LYP/6-31G*, LANL2DZ level of theory.29-32 These
studies provided a qualitative overview of the reaction profiles.
We then used the full ligand system and higher levels of theory
to determine which mechanism is the lowest energy path.
Mechanism e. The reaction profile for mechanism e is
shown in Figure 1. The starting (R-diimine)PdMe(VC)þ
Reaction of {(2,6-iPr2Ph)NdCMeCMedN(2,6-iPr2Ph)}-
PdMeþ Species with Deuterium-Labeled Vinyl Chlorides. Sev-
eral salts of (N∧N)Pd(Me)(Et2O)þ (1þ, N∧N=(2,6-iPr2Ph)-
NdCMeCMedN(2,6-iPr2Ph)) were treated with 1-VC-d1 and
Z-VC-d1 under several conditions, yielding propene-d1 (>90%,
various isomers). The propene-d1 was analyzed by 1HNMR, 2H
NMR, and GC-MS. The results of these experiments are
summarized in Table 1.
[1][SbF6] was treated with a ca. 100-fold excess of 1-VC-d1
at -45 °C in CD2Cl2. NMR analysis established that the
propene-d1 product comprises 47(4)% E-propene-d1, 50(2)%
Z-propene-d1, and a trace amount of 2-propene-d1 (Scheme 10
and entry 1, Table 1). A trace of propene-d2 was detected by
GC-MS.27 Similar results were observed when the reaction was
conducted at -18 °C (entry 2). Similarly, the reaction of
[1][B(C6F5)4] with ca. 100-fold excess of 1-VC-d1 at 0 °C gives
a mixture of E- and Z-propene-d1; in this case no 2-propene-d1
was detected (entry 3).
The reaction of [1][SbF6] with a 5-10-fold excess of Z-VC-
d1 at -45 °C in CD2Cl2 yields propene-d1 comprising 22(1)%
Z-propene-d1, 71(2)% 2-propene-d1, and a small amount
(<7(3)%) of E-propene-d1 (Scheme 11 and entry 4). A trace
of propene-d2 was detected by GC-MS. Similar results were
observed when the reaction was conducted at higher tem-
peratures (entries 5 and 6).
In order to determine if the counterion or the Et2O ligand
of 1þ influences the reaction, [(N∧N)PdMe][MeB(C6F5)3]
was generated in situ from (N∧N)PdMe2 and B(C6F5)3
at -78 °C in the presence of ca. 4 equiv of Z-VC-d1 in an
NMR tube. The tube was warmed to -35 °C, and the
(28) No polyvinyl chloride is formed in these reactions, even when a
large excess of vinyl chloride is used, which argues against mechanisms
involving free radicals.
(29) Frisch; et al. et al. Gaussian 03, Revision C.02; Gaussian, Inc.:
Wallingford, CT, 2004. See the Supporting Information for the complete
citation.
(30) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Lee, C.; Yang,
W.; Parr, R. G. Phys. Rev. B 1988, 37, 785. (c) Miehlich, B.; Savin, A.; Stoll,
H.; Preuss, H. Chem. Phys. Lett. 1989, 157, 200.
(31) (a) Rassolov, V. A.; Ratner, M. A.; Pople, J. A.; Redfern, P. C.;
Curtiss, L. A. J. Comput. Chem. 2001, 22, 976. (b) Rassolov, V. A.; Pople,
J. A.; Ratner, M. A.; Windus, T. L. J. Chem. Phys. 1998, 109, 1223.
(c) Ditchfield, R.; Hehre, W. J.; Pople, J. A. J. Chem. Phys. 1971, 54, 724.
(32) (a) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 270. (b) Wadt,
W. R.; Hay, P. J. J. Chem. Phys. 1985, 82, 284. (c) Hay, P. J.; Wadt, W. R.
J. Chem. Phys. 1985, 82, 299.
(27) Trace amounts of propene-d0 may also be present in the reaction
mixture. However due to overlapping peaks from propene-d1 in the mass
spectrum, this could not be determined.

Article
Organometallics, Vol. 29, No. 7, 2010 1755
Figure 1. Reaction profile of mechanism e for the (HNdCHCHdNH)PdMeþ model system, starting with the VC π-complex.
The solid line shows the profile of the chain walking involving Z-2-chloropropene, and the dotted line shows that involving
E-2-chloropropene. The structures of key intermediates and transition states are shown above and below the reaction profile,
respectively. Barriers for key steps are shown. The barriers for C-C bond rotations have been estimated at 2-3 kcal/mol, which is
consistent with calculated barriers for C-C bond rotations in several cases. Atom colors: H, white; C, gray; Cl, green; N, blue; Pd, cyan.
π-complex undergoes 2,1-insertion to form a γ-C-H ago-
stic (R-diimine)Pd(CHClCH2Me)þ species. The γ-C-H ago-
stic species isomerizes to β-H agostic (R-diimine)Pd(CH-
ClCH2Me)þ, which chain-walks to generate β-Cl dative
(R-diimine)Pd(CHMeCH2Cl)þ, which in turn undergoes syn
β-Cl elimination. The highest point on the potential energy
surface after 2,1-insertion is the transition state of reinsertion
of 1-chloropropene into the Pd hydride formed during chain
walking (TSreinsert).
symmetrically bound between CR and Cβ (C-H distances
1.35 and 1.29 A, respectively). The angle between the
˚
Htransfer-CR-Cβ plane and the CR-Cβ-Cγ plane is 90°.
Htransfer is on the same side of the CR-Cβ-Cγ plane as
the Pd-Cl bond. Interestingly, Htransfer has a close contact
33
˚
to Cl (2.46 A), which could be considered a hydrogen bond.
The rearrangement of the R-Cl dative species to the
PdCl(propene) product can be described as a concerted
asynchronous R-Cl elimination and suprafacial transfer of
Htransfer.
34,35
Mechanism d. The reaction profile of mechanism d is sum-
marized in Figure 2. This reaction path has several surprising
features. As above, VC undergoes 2,1-insertion into the
Pd-Me bond to form the γ-C-H agostic species. In this
case, however, the γ-C-H agostic species undergoes a Pd-C
bond rotation to form a Pd-R-Cl dative interaction.
The R-Cl dative species is 7 kcal/mol more stable than the
β-C-H agostic species in mechanism e. The R-Cldative species
rearranges to form a PdCl(propene)þ complex, via a net R-Cl
elimination and 1,2-H shift without any intermediates.
The transition state for rearrangement of the R-Cl dative
species to the PdCl(propene)þ complex (TSH-shift) is shown in
Figure 3. In TSH-shift, the CR-Cl bond is fully broken and the
Pd-Cl bond is fully formed. CR and Cβ both have trigonal-
planar geometries and bond angles consistent with sp2
The 1,2-hydrogen shift that is involved in the rearrange-
ment of the R-Cl dative species to the PdCl(propene)þ species
could occur with the Cγ methyl group either trans, as shown
in Figures 2 and 3, or cis to the Pd atom with respect to the
incipient CRdCβ bond. The trans TSH-shift is lower in energy
than the cis TSH-shift by ca. 0.5 kcal/mol. A transition state
could not be found where Htransfer was on the opposite side of
the CR-Cβ-Cγ plane from the Pd-Cl bond.
˚
(33) The Htransfer-Cl distance (2.46 A) and the C(R)-Htransfer-Cl
(99°) and C(β)-Htransfer-Cl (125°) angles are within the range observed
for C-H---Cl-M hydrogen bonds. (a) Aullon, G.; Bellamy, D.; Orpen,
A. G.; Brammer, L.; Bruton, E. A. Chem. Commun. 1998, 653.
(b) Brammer, L.; Bruton, E. A.; Sherwood, P. Cryst. Growth Des. 2001, 1,
277.
˚
hybridization. The CR-Cβ bond length is 1.395 A, only
(34) (a) Nouri, D. H.; Tantillo, D. J. J. Org. Chem. 2006, 71, 3686.
(b) Domingo, L. R. J. Org. Chem. 2001, 66, 3211. (c) Kalaiselvan, A.;
Ammal, S. C.; Venuvanalingam, P.; Yamataka, H. J. Phys. Chem. A. 2005,
109, 4829. (d) Ding, L.; Chen, X.; Fang, W. H. Org. Lett. 2009, 11, 1495.
(35) The structure of the carbyl ligand in TSH-shift is similar to that of
the trans-sec-butyl cation. Vrcek, V.; Kronja, O.; Saunders, M. J. Chem.
Theory Comput. 2007, 3, 1223.
slightly longer than a typical CdC bond length. The angle
between the CR-Cβ-Pd and N-N-Pd-Cl planes is 58°.
One of the hydrogen atoms originally bonded to Cβ in
the R-Cl dative species bridges CR and Cβ in the TSH-shift
structure. The bridging H atom (Htransfer) is nearly

1756 Organometallics, Vol. 29, No. 7, 2010
Kilyanek et al.
Figure 3. Schematic drawing of key species in the rearrange-
ment of the R-Cl dative species to (HNdCHCHdNH)PdCl-
(propene)þ in mechanism e.
1.5 kcal/mol. Thus mechanism e is predicted to be favored
for the truncated system.
Figure 2. Reaction profile of mechanism d for the (HNd
CHCHdNH)PdMeþ model system, starting with the VC
π-complex. The solid line shows the profile of rearrangement
through the trans TSH-shift, and the dotted line shows the profile
of rearrangement through the cis TSH-shift. The structures of key
intermediates and transition states are shown above and below
the reaction profile, respectively. Barriers for key steps are
shown. The barriers for Pd-C bond rotations have been
estimated at 2-3 kcal/mol, which is consistent with calculated
barriers for bond rotations in several cases. Atom colors: H,
white; C, gray; Cl, green; N, blue; Pd, cyan.
Computational Study Using the Full (N∧N)Pd(Me)þ Sys-
tem. Analysis of the truncated system suggests that mechan-
ism e is slightly favored over mechanism d. We modeled the
full (N∧N)PdMeþ system using high-level DFT methods to
better differentiate these two mechanisms. The PBE0 func-
tional has been shown to be among the best functionals for
modeling the reactions of late metal complexes.36,37 The
reaction profile for the key steps in mechanisms d and e
calculated for the full (N∧N)PdMeþ sytem using the PBE0
functional is shown in Figure 5 and is very similar to that
obtained for the truncated system using the B3LYP/6-31G*,
LANL2DZ method described above.38 Mechanism e is
favored by 1.9 kcal/mol.
Comparison of Mechanisms d and e for the Truncated
System. Figure 4 compares the reaction profiles of mechan-
isms d and e for the truncated system starting from the
γ-C-H agostic species formed by 2,1-insertion. The γ-C-H
agostic species can convert to the R-Cl dative species or the
β-C-H agostic species by Pd-C bond rotation or C-C
bond rotation, respectively. The R-Cl dative and β-H agostic
species can interconvert directly by Pd-C bond rotation.
The barrier for the conversion of the R-Cl dative species to
the β-C-H agostic species is 9.6 kcal/mol. These species can
also interconvert via the γ-C-H agostic species with a
slightly higher barrier. Importantly, the barrier to intercon-
version of the R-Cl dative and β-C-H agostic species is lower
than the highest barriers leading to products from either
species, which means that this system should be under
Curtin-Hammett conditions. In this case, the competition
between mechanisms d and e will be controlled by the energy
difference between the highest barriers in the product-form-
ing reactions. That is, the competition between mechanisms e
and d will be controlled by the difference in energy between
the transition state of insertion of 1-chloropropene into the
Pd-H bond in mechanism e (TSreinsert) and TSH-shift of
mechanism d. TSreinsert is lower in energy than TSH-shift by
B2GP-PLYP is a “fifth rung” double hybrid func-
tional that was designed and shown to be an excellent ge-
neral purpose functional for H and heavy atom transfer
reactions.39 The B2GP-PLYP results for the full (N∧N)Pd-
Meþ are very similar to the PBE0 results, except that the
mechanism e is favored over mechanism d by 1.6-4.1 kcal/mol
depending on the basis set used. Table 2 lists the difference
between TSH-shift of mechanism d and TSreinsert of mechanism e
at several levels of theory with several basis sets. It is notable
that the higher levels of theory consistently predict that
mechanism e is the lower energy path. We conclude that
mechanism e is favored.
(36) Quintal, M. A.; Karton, A.; Iron, M. A.; Boese, A. D.; Martin,
J. M. L. J. Phys. Chem. A 2006, 110, 709.
(37) (a) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1996,
77, 3865. (b) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 1997,
78, 1396.
(38) The barrier for 2,1-insertion calculated for the full system at the
PBE0 level of theory is 13.4 kcal/mol.
(39) (a) Karton, A.; Tarnopolsky, A.; Lamere, J.; Schatz, G. C.;
ꢁ
Martin, J. M. L. J. Phys. Chem. A 2008, 112, 12868. (b) Korth, M.;
Grimme, S. J. Chem. Theory Comput. 2009, 5, 993.

Article
Organometallics, Vol. 29, No. 7, 2010 1757
Figure 4. Comparison of energy profiles for mechanism e (blue) and mechanism d (red) for the (HNdCHCHdNH)PdMeþ model
system, starting from the γ-C-H agostic species. The energy profile for direct interconversion of the R-Cl dative and β-H agostic species
is shown in green. The solid red line shows the profile of rearrangement through the trans TSH-shift, and the dotted red line shows
the profile of rearrangement through the cis TSH-shift. The solid blue line shows the profile of the chain walking involving
Z-2-chloropropene, and the dotted blue line shows that involving E-2-chloropropene.
Figure 5. Comparison of energy profiles for mechanism e (blue, abbreviated as described in the text) and mechanism d (red) for the full
(N(N)PdMeþ system starting with the γ-C-H agostic species at the B3LYP//PBE0/6-31G*,LANL2DZ level. The energy profile for
direct interconversion of the R-Cl dative and β-H agostic structures is shown in green. The dotted line shows an estimate of the
remaining energy profile since only the highest barriers after insertion were calculated.
Secondary Scrambling Processes. The trace amounts of
2-propene-d1 that are observed in some 1-VC-d1 reactions
and E-propene-d1 observed in some Z-VC-d1 reactions likely
result from secondary deuterium scrambling reactions, which
are expected for mechanism e. For example, small amounts of
E-propene-d1 are produced in the reaction of [1][SbF6] and
Z-VC-d1 (Table 1, entries 4-6) but not in the correspond-
ing reaction of [(N∧N)PdMe][MeB(C6F5)3] and Z-VC-d1

1758 Organometallics, Vol. 29, No. 7, 2010
Kilyanek et al.
Table 2. Difference in Energy Barriers of Mechanisms e and d for
the Full Ligand System
Scheme 14
a
functional
ΔΔEpath
B3LYP/6-31G*,LANL2DZ
PBE0/6-31G*,LANL2DZ
B2GP-PLYP/6-311þþG**,SDDþ[2f1g]
B2GP-PLYP/cc-pVTZ,cc-pVTZ-PP
B2GP-PLYP/cc-pVTZ,SDD[2f1g]
-0.8
1.9
1.6
4.1
3.9
a ΔΔEpath is defined as (energy TSH-shift, mechanism d) - (energy of
TSreinsert, mechanism e), in kcal/mol.
Scheme 13
the VC C-Cl bond, or 2,1 VC insertion followed by chain
walking and anti β-Cl elimination. DFT calculations at
several levels of theory show that mechanism e is favored
over mechanism d. The formation of propylene-d2 as a minor
product supports this conclusion since only chain-walking
mechanisms could produce a doubly deuterated product.
Analogous reactions of (R-diimine)PdRþ active species
(R = growing polyolefin chain) with VC to produce inactive
(R-diimine)PdClþ species preclude the incorporation of VC
in olefin polymerization by this catalyst. The results reported
here suggest that VC incorporation in olefin polymeriza-
tion might be possible using late metal catalysts that do not
chain walk, since 2,1-insertion is heavily favored and chain
walking would be required to generate a β-Cl-alkyl species
that could β-Cl eliminate. However the low insertion reac-
tivity of LnMCHClR species will still be a problem in this
approach.
(entry 7). A likely explanation is that the initially formed
propene-d1 reacts with the transient Pd-H or Pd-D species
involved in the chain-walking steps of mechanism e, leading to
deuterium scrambling, as illustrated in Scheme 13.40 The key
step in this process, substitution of E-chloropropene-d1 or
Z-chloropropene-d1 by propene-d1, may be influenced by the
presence of Et2O, the counterion, and other factors. An
analogous mechanism would explain the formation of small
amounts of 2-propene-d1 in several of the reactions of [1][SbF6]
and [1][B(C6F5)4] with 1-VC-d1. Similar processes could
produce propene-d2, which is observed in trace amounts in
some experiments (Scheme 14). Propene-d2 cannot form by
mechanism d.
Experimental Section
General Comments. All manipulations were performed using
drybox or Schlenk techniques under a N2 atmosphere or on a
high-vacuum line unless otherwise noted. Nitrogen was purified
by passage through activated molecular sieves and a Q-5 oxygen
scavenger. Deuterated solvents were obtained from Cambridge
Isotopes. CD2Cl2 was dried over dried over P2O5. C6D6 was
dried over Na/benzophenone ketyl. DBr was obtained from
Cambridge Isotopes and used as is. Vinylidene dichloride was
purchased from Aldrich and distilled and degassed before each
use. 1-VC-d1 (94% deuterium labeled) was prepared by UV
irradiation of vinylidene dichloride in the presence of DBr
followed by reaction with zinc.41 Z-VC-d1 (97% deuterium
labeled) was prepared by reaction of acetylene with Cp2ZrDCl
followed by treatment with excess N-chlorosuccinamide.42
Cp2ZrDCl was prepared using LiAlD4 in place of LiAlH4 in
the literature procedure for Cp2ZrHCl.43 [((2,6-iPr2Ph)Nd
CMeCMedN(2,6-iPr2Ph))Pd(Me)(OEt2)][SbF6] ([1][SbF6]) and
Conclusion
(R-diimine)PdMeþ species react with vinyl chloride to
produce the π-complex (R-diimine)Pd(Me)(VC)þ, which re-
arranges to (R-diimine)Pd(Cl)(propene)þ at -45 °C. The
results of deuterium labeling experiments using 1-vinyl
chloride-d1 and Z-vinyl chloride-d1 are consistent with two
mechanisms for this rearrangement: mechanism d, which
comprises 2,1 VC insertion followed by R-Cl elimination and
a 1,2 H shift; and mechanism e, which comprises 2,1 VC
insertion followed by chain walking and syn β-Cl elimina-
tion. The labeling experiments rule out mechanisms invol-
ving initial 1,2-insertion of VC, initial oxidative addition of
(41) Francis, J. E.; Leitch, L. C. J. Can. Chem. 1957, 35, 500.
(42) (a) Hart, D. W.; Blackburn, T. F.; Schwartz, J. J. Am. Chem. Soc.
€
€
1975, 97, 679. (b) Schottek, J.; Rottger, D.; Erker, G.; Frohlich, R. J. Am.
Chem. Soc. 1998, 120, 5264. (c) Erker, G.; Kropp, K.; Atwood, J. L.; Hunter,
W. E. Organometallics 1983, 2, 1555.
(40) An analogous mechanism involving 2,1-insertion into the Pd-H
bond is also possible. However, this mechanism predicts dueterium
enrichment in the propene methyl group, which could not be conclu-
sively detected.
(43) Buchwald, S. L.; LaMaire, S. J.; Nielson, R. B.; Watson, B. T.;
King, S. M. Org. Synth. 1993, 71, 77.

Article
Organometallics, Vol. 29, No. 7, 2010 1759
[((2,6-iPr2Ph)NdCMeCMedN(2,6-iPr2Ph))PdMe2 ((N∧N)PdMe2)
were prepared using literature procedures.44,45 [((2,6-iPr2Ph)Nd
CMeCMedN(2,6-iPr2Ph))Pd(Me)(OEt2)][B(C6F5)4] ([1][B(C6F5)4])
was prepared by the reaction of ((2,6-iPr2Ph)NdCMeCMed
N(2,6-iPr2Ph))PdMeCl and in situ-generated Ag[B(C6F5)4]46
using the procedure for [1][SbF6].43b B(C6F5)3 was purchased
from Boulder Scientific and sublimed before use.
NMR spectra were obtained using a Bruker DRX 500 NMR
spectrometer. 1H NMR spectra of propene mixtures were
obtained using 90° pulses with a pulse delay of 60 s; detailed
results of 1H NMR integrations for several experiments are
provided in Table S2 in the Supporting Information. GC-MS
analyses were performed using an Agilent 6890 GC coupled to
an Agilent 5973 quadrupole MS. Samples (ca. 1 μL) were
injected into a 250 °C injector oven, feeding to a 30 °C capillary
column.
Reaction of [1][SbF6] with 1-VC-d1. A Teflon-valved NMR
tube was charged with [1][SbF6] (10-15 mg, 0.012-0.018
mmol), and CD2Cl2 (0.6 mL) was added by vacuum transfer
at -196 °C. 1-VC-d1 (ca. 100 equiv) was added by vacuum
transfer. The tube was thawed in a cold bath at -78 °C. After
1 h, the tube was warmed to -45 °C. After 2.5 h the volatiles
were removed by vacuum transfer at -45 °C. NMR analysis
showed that the volatiles contained a mixture of Z-propene-d1
and E-propene-d1. 1H NMR (CD2Cl2): δ 5.83 (m, 1H, Hint), 5.02
(m, 0.5H, Hcis), 4.92 (m, 0.5H, Htrans), 1.71 (dd, J = 6.5, J = 1.4,
3H, CH3). GC-MS analysis showed that propylene-d1 (m/z = 43)
and a trace amount of propylene-d2 (m/z = 44) were present
in the sample. This reaction was carried out at temperatures in the
range -45 °C to room temperature for various lengths of time. In
all cases, the ratio of the integral of the methyl resonance to the
internal hydrogen resonance was 3:1, confirming the absence of
deuterium at the internal hydrogen position. There was some
variation ((10%) in the ratio of deuterium enrichment in the cis
and trans positions at different temperatures.
amount of E-propene-d1. 1H NMR (CD2Cl2): δ 5.83 (m, 0.25H,
H
int), 5.02 (m, 0.7H, Hcis), 4.92 (m, 1H, Htrans), 1.71 (d, J = 1.4,
3H, CH3). GC-MS analysis showed that propylene-d1 and a
small amount (<7%) of propylene-d2 were present.
Reaction of [1][B(C6F5)4]1-VC-d1 with 1-VC-d1. These reac-
tions were carried out using the procedures given above for the
reaction of [1][SbF6] and 1-VC-d1.
Reaction of [(N∧N)PdMe][MeB(C6F5)3] with Z-VC-d1. An
NMR tube was charged with (N∧N)PdMe2 (4.9 mg, 0.0087
mmol) and B(C6F5)3 (4.9 mg, 0.0095 mmol). A mixture of
CD2Cl2 (ca. 0.6 mL) and Z-VC-d1 (0.035 mmol) was added by
vacuum transfer at -196 °C. The tube was thawed in a -78 °C
cold bath. After 30 min, the tube was placed in an NMR probe
that had been precooled to -78 °C. The probe was warmed
to -68 °C for 45 min, then to -43 °C for 30 min, and finally to
-33 °C for 15 min. Data for [(N∧N)PdCl(propylene-d1)][MeB-
1
(C6F5)3]: H NMR (CD2Cl2): δ 7.54 m, 1H, Ar), 7.45 (m, 1H,
Ar) 7.41 (m, 2H, Ar) 7.29 (m, 2H, Ar), 5.40 (m, 0.25H, Hint of
bound propylene), 5.31 (m, 0.70H, Hcis of bound propylene),
i
4.31 (m, 1H, Htrans of bound propylene), 3.00 (m, 2H, Pr),
i
2.90-2.75 (m, 2H, Pr), 2.35 (s, 3H, CMe), 2.31 (s, 3H, CMe),
1.90 (m, 3H, Me of bound propylene), 1.47 (d, J = 7, 3H, iPr),
1.45 (d, J = 7, 3H, iPr), 1.47 (d, J = 7.0, 3H, iPr) 1.45 (d, J = 7.0,
3H, iPr), 1.21-1.09 (m, 6H, iPr), 0.40 (br s, 3H, BMe).
Computational Methods. DFT computations were performed
using either Gaussian 03 or a modified version of NWChem.29,47
All stationary points and transition states were characterized
using vibrational frequency analysis ensuring that they con-
tained zero or one negative frequency, respectively. Transition
states were found using the QST3 algorithm.48 The geometries
of the stationary points and transition states of the truncated
{HNdCHCHdNH}Pd model system were found using the
B3LYP functional.30 All main group atoms were modeled using
the 6-31G* basis set.31 Pd was modeled using the LANL2DZ
basis set including the relativistic pseudopotentials of Hey and
Wadt.32 The geometries of the stationary points and transition
states of the full {(2,6-iPr2Ph)NdCMeCMedN(2,6-iPr2Ph)}Pd
system were found using the same methodology used for the
truncated system. Once the geometries were located, the PBE0
functional was used to determine the energies using the 6-31G*
basis set for the main group atoms and the LANL2DZ basis set
for Pd.37 Energies using the B2GP-PLYP functional were
computed using various basis sets.39 Main group atoms
were modeled by either the 6-311þþG** or the cc-pVTZ basis
sets.49,50 Pd was modeled using either the cc-pVTZ-PP basis set
and pseudopotential or the SDD basis set and pseudopotential
augmented with additional 2f1g polarization functions.48,51
2H NMR Analysis of the Reaction of [1][SbF6] with 1-VC-d1. A
Teflon-valved NMR tube was charged with [1][SbF6] (13.6 mg,
0.016 mmol), and CH2Cl2 (0.6 mL) was added by vacuum
transfer at -196 °C. A solution of 1-VC-d1 (ca. 100 equiv) in
CH2Cl2 was added by vacuum transfer. The tube was thawed in
a -78 °C bath. After 30 min, the tube was warmed to room
temperature. After 1 h at room temperature the solution was
pale orange and an orange-red precipitate ([{R-diimine)PdCl}2]-
[SbF6]2) had formed. 2H NMR showed that Z-propene-d1 and
E-propene-d1 were present. 2H NMR (CH2Cl2): δ 5.06 (d, J = 3,
0.9D, Z-propene-d1) 4.95 (d, J = 1, 1D, E-propene-d1).
Reaction of [1][SbF6]with Z-VC-d1. A Teflon-valved NMR
tube was charged with [1][SbF6] (10-15 mg, 0.012-0.018
mmol). A mixture of CD2Cl2 (ca. 0.6 mL) and Z-VC-d1 (ca. 6
equiv) was added by vacuum transfer at -196 °C. The tube was
thawed in a -78 °C bath. After 1 h, the tube was placed in an
NMR probe that had been precooled to -78 °C. The sample was
warmed to -45 °C and monitored periodically for 2 h. The
volatiles were removed by vacuum transfer at this temperature;
this procedure removed CD2Cl2, unreacted Z-VC-d1, and trace
volatile impurities from the synthesis of the VC. Fresh CD2Cl2
(ca. 0.6 mL) was added by vacuum transfer. The tube was
warmed to 0 °C. After 30 min, the volatiles were transferred
by vacuum transfer at 0 °C to a new NMR tube. This fraction
contained a mixture of Z-propene-d1, 2-propene-d1, and a small
(47) Bylaska, E. J.; et al. et al. NWChem, A Computational Chemistry
Package for Parallel Computers, Version 5.1.1; Pacific Northwest National
Laboratory: Richland, WA, 2009. A modified version. See the Supporting
Information for the complete citation.
(48) (a) Peng, C.; Ayala, P. Y.; Schlegel, H. B.; Frisch, M. J.
J. Comput. Chem. 1996, 17, 49. (b) Peng, C.; Schlegel, H. B. Isr. J. Chem.
1993, 33, 449.
(49) For the 6-311þþG** basis set see: (a) Krishnan, R.; Binkley, J.
S.; Seeger, R.; Pople, J. A. J. Chem. Phys. 1980, 72, 650. (b) Clark, T.;
Chandrasekhar, J.; Spitznagel, G. W; Schleyer, P. V. R. J. Comput. Chem.
1983, 4, 294.
(50) For the cc-pVTZ and cc-pVTZ-PP basis sets see: (a) Dunning,
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1760 Organometallics, Vol. 29, No. 7, 2010
Kilyanek et al.
In some cases additional s, p, d, f, and g diffuse functions were
added to the SDD basis set.49e All structures were drawn using
the MOLEKEL 4.3 software package.52
full system, and Changle Chen for the synthesis of
[1][B(C6F5)4]. Parts of the computational research were
performed using EMSL, a national scientific user facility
sponsored by the Department of Energy’s Office of
Biological and Environmental Research and located at
Pacific Northwest National Laboratory.
Acknowledgment. This work was supported by the
Department of Energy (DE-FG-02-00ER15036). We
thank Dr. Jeff Hammond for implementing DHDF in
NWChem and running some of the calculations on the
Supporting Information Available: Additional experimental
and computational details, schemes showing the origin of pre-
dicted dueterium distribution for mechanisms a-f, and com-
plete citations for refs 29 and 45. This material is available free of
charge via the Internet at http://pubs.acs.org.
€
€
(52) Flukiger, P.; Luthi, H. P.; Portmann, S.; Weber, J. MOLEKEL
4.3; Swiss Center for Scientific Computing: Manno, Switzerland,
2000-2002. Portmann, S.; L€uthi, H. P. MOLEKEL: An Interactive Molec-
ular Graphics Tool. CHIMIA 2000, 54, 766.