An easy conversion from platinum(II) reagents to platinum(IV) products: κ3 to κ2 coordination mode interconversion, phenyl migration, and ortho C-H activation cascade in a hemilabile "click"-triazole scorpionate platinum system

Article abstract of DOI:10.1021/om2010595

A series of platinum phenyl olefin complexes has been prepared that bear hemilabile "Click"-triazole based scorpionate ligands (Tt ^R). Mild heating of the olefin adducts initiates a reaction sequence to form stable, cationic Pt(IV) hydride meta

Full text of DOI:10.1021/om2010595

Article
pubs.acs.org/Organometallics
An Easy Conversion from Platinum(II) Reagents to Platinum(IV)
Products: κ3 to κ2 Coordination Mode Interconversion, Phenyl
Migration, and Ortho C−H Activation Cascade in a Hemilabile
“Click”-Triazole Scorpionate Platinum System
Bryan E. Frauhiger and Joseph L. Templeton*
W. R. Kenan Laboratory, Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
27599-3290, United States
S
* Supporting Information
ABSTRACT: A series of platinum phenyl olefin complexes has
been prepared that bear hemilabile “Click”-triazole based
scorpionate ligands (TtR). Mild heating of the olefin adducts
initiates a reaction sequence to form stable, cationic Pt(IV) hydride
metallacycles. An attractive mechanism involves κ3/κ2 conversion,
phenyl migration, and ortho C−H activation. Activation parameters
for the overall C−C bond-forming and C−H bond-breaking pro-
cess were obtained. Insertion products from mono- and
disubstituted olefins reveal a kinetic preference for phenyl migration
to the less sterically hindered olefin position but a thermodynamic
preference for the β-substituted metallacycle isomer, in which steric
bulk is further away from the metal center and the TtR ligand.
Thermolysis converts the kinetically favored products to their
thermodynamically stable isomers via a reversible C−C bond cleavage and formation reaction. EXSY NMR and deuterium-
labeling studies reveal facile scrambling processes in the metallacycles due to the hemilabile ligand.
́
Jimenez and co-workers have developed Ir NHC complexes
INTRODUCTION
■
with pendant hemilabile ethers and amines, which are critical
to the complexes’ functionality as transfer hydrogenation
catalysts.19
The incorporation of hemilable motifs into organometallic
system design has become a growing area of interest, due to the
ease of forming unsaturated compounds and thus initiating
reactivity.1−3 A plethora of multidentate ligand scaffolds have
been reported containing weakly coordinating and easily
tunable heteroatom donors that can reversibly bind to a
metal center.1−11 Although strongly donating chelates often
result in stable, well-defined complexes, they can impede
desirable chemical reactions.12
The introduction of a hemilabile functionality adds versatility
by providing a flexible coordination mode geometry that can
promote a variety of fundamental organometallic processes,
including reductive couplings, oxidative addition, organic
substrate binding, and insertion reactions.2,11,13 For example,
Lindner et al. demonstrated that the utilization of hemilabile
P,O chelates assists in the Co- or Rh-catalyzed carbonylation of
methyl iodide by promoting substrate binding and CO
insertion reactions through flexible ligand denticity.5,11,14−17
Shaw and co-workers have shown that a metal center’s aptitude
toward oxidative addition can be significantly increased by the
introduction of a pendant ether that can reversibly donate and
amplify the nucleophilicity of Ir in IrCl(CO)[PMe2(o-
MeOC6H4)]2.13 More recently, Lassaletta et al. have reported
on κ1/κ2 interconversions in a bidentate N,N ligand Ir system
that promote the catalyzed borylation of arenes.18 Furthermore,
Some transformations involving hemilabile ligands require an
external reagent to sever the metal−ligand bond and initiate
reactivity. Braunstein has reported on P,O chelated Pd
complexes that do not exhibit hemilabile behavior until the
addition of carbon dioxide or isocyanate, which can reversibly
trap the substrate to form a C−C bond and a new dynamic
system.2,20,21 Our group has reported on both Lewis acid and
thermolysis promoted κ3/κ2 conversions to initiate reactivity in
the Tp′Pt system (Tp′ = hydridotris(3,5-dimethylpyrazolyl)-
borate) (Figure 1a).22−26 One particularly interesting example
is phenyl migration to a bound olefin and subsequent intra-
molecular C−H activation in Tp′Pt(Ph)(η2-C2H4) to form
stable metallacyclic Pt(IV) products (eq 1).24 Such trans-
formations occur at 60 °C in the presence of a strong Lewis
acid, such as B(C6F5)3, or at 80 °C in the absence of borane.
Mechanistically, the Lewis acidic borane is postulated to
promote dechelation of one of the pyrazolyl rings to form an
Special Issue: F. Gordon A. Stone Commemorative Issue
Received: November 1, 2011
Published: January 9, 2012
© 2012 American Chemical Society
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Figure 1. The Tp′ (a) and TtR (b) tridentate ligands.
[TtRPtMe]+ fragment with an olefin generates a five-coordinate κ3
coordinated cation (eq 2). With this reactivity in mind, we sought
to further exploit the TtR ligand’s facile coordination mode inter-
conversions by exploring the TtRPt fragment’s reactivity toward
C−C bond-forming and aryl C−H activation reactions. Will
replacing Tp′ with TtR result in lower energy barriers for the
transformation of Pt(II) olefin adducts to Pt(IV) C−H activated
metallacyclic products? Herein, we report the synthesis of TtRPt
phenyl η2-olefin complexes and their reactivity with respect to
phenyl migration and subsequent C−H activation.
unsaturated 16-electron intermediate from which aryl migration
to the olefin occurs. The resulting three-coordinate Pt(II)
species undergoes ortho C−H activation of the tethered phenyl
ring to form a coordinatively saturated, 18-electron Pt(IV)
product. Given the well-established trend for preliminary
ligand dissociation from Pt(IV) to produce reactive inter-
mediates,27−36 we postulate that a κ3/κ2 interconversion step
initiates migration in the η2-olefin Pt(II) starting material.24
The utilization of hemilabile ligands can be an important
factor in Pt(II)/Pt(IV) interconversion chemistry. Vedernikov
and co-workers have extensively employed the hemilabile di-2-
pyridylmethanesulfonate (dpms) ligand to achieve platinum−
carbon functionalization in aqueous media.7,37−43 The flexible
denticity provided by the reversible sulfonate group binding in
dpms assists in stabilizing oxidized Pt(IV) species en route to
functionalized products. Furthermore, the dipyridyl ketone
ligand used by both Puddephatt and Vedernikov readily adds
nucleophiles to create an anionic ligand that can be either
bidentate or tridentate.44,45
Recently, we have found that utilizing Lammertsma’s Click-
derived46−49 1,2,3-triazolyl-based scorpionate ligand TtR
(Figure 1b, R = Ph (L1), Cy (L2)) lowers the barrier for
κ3/κ2 interconversion relative to the analogous Tp′Pt system
due to significantly weaker donation from the triazolyl moiety.50
Gentle heating of the [TtRPtMe2H]+ cation at 35 °C induces
methane elimination, and our hypothesis is that conversion to the
κ2 five-coordinate isomer is the first step. Trapping the resulting
RESULTS AND DISCUSSION
■
Protonation and Trapping Reactions. In a fashion
similar to the previously reported synthesis of cationic Pt(II)
methyl η2-olefin complexes [TtRPtMeL][BF4], we sought to
generate the analogous phenyl complexes [TtRPtPhL][BF4].
The synthetic route for the methyl derivatives involves
protonation of κ2-TtRPtMe2 to form a dimethyl hydride species
followed by gentle heating in the presence of an olefin to lose
methane and form the trapped product. Likewise, we targeted
the corresponding [κ3-TtRPtPh2H]+ complexes 2 via proton-
ation of their Pt(II) precursors κ2-TtRPtPh2 (1). However,
addition of HBF4·Et2O to a methylene chloride solution of 1 at
−78 °C and subsequent warming to room temperature did not
produce the desired diphenyl hydride. Rather, consumption of
the starting material occurred and production of benzene was
1
observed in the H NMR spectrum. Was it possible that room
temperature was sufficient to promote benzene loss from the
target hydride 2? Indeed, protonation of the neutral platinum(II)
reagent at low temperature and recording the 1H NMR
spectrum at −78 °C revealed clean conversion to hydride
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Scheme 1. Proposed Mechanism of the Protonation and Subsequent Trapping Sequence for the Conversion of 1 to 3−9
complex 2. The diphenyl hydride complexes 2-L1 and 2-L2
display a Pt−H signal with large platinum coupling (1JPt,H
metal−ethylene triangle that averages the up and down olefin
signals (Hu and Hd, Figure 2). Variable-temperature proton
=
1581 Hz (2-L1) and 1554 Hz (2-L2)), which is in accord with
weak donation from the trans triazolyl nitrogen.50 For
comparison, strongly donating pyrazolyl-based systems, such
as [Tp′PtMe2H]+ and TpmPtMeH2 (Tpm = trispyrazolyl-
methane), result in a substantial decrease in the one-bond
platinum−hydride coupling and are less than 1400 Hz.51,52
A
slight increase in this one-bond coupling value relative to the
analogous dimethyl complexes (1JPt,H = 1541 Hz (L1) and 1519
Hz (L2)) is expected as a result of less electron donation from
the phenyl ligand, thereby inducing a more electrophilic metal
center and a stronger Pt−H bond.
Warming 2 to room temperature in the presence of a
trapping π-acid ligand yielded the expected trapped product
[TtRPt(Ph)(L)][BF4] (L = CO (3), ethylene (4), propylene
(5), 1-hexene (6), cis-2-butene (7), trans-2-butene (8), and
1
isobutylene (9)) in good to quantitative conversion by H
NMR (85−100%). Attempts at isolating adducts 5−9 were
unsuccessful. The mechanism for this transformation is
believed to mimic the Tp′PtPh2H system, notably without
the need of a Lewis acid promoter.24 Dechelation of the apical
triazole ring generates a κ2 five-coordinate unsaturated
intermediate upon warming to room temperature from
which benzene elimination occurs. Subsequent trapping of
the resulting three-coordinate Pt(II) fragment accounts for
3−9 (Scheme 1).
The carbon monoxide complexes 3-L1 and 3-L2 display a
Figure 2. Variable-temperature 1H NMR study of ethylene rotation in
4-L1.
1
2:1 ratio in the TtR triazolyl proton signals in the H NMR
spectrum, suggesting a κ3 trigonal-bipyramidal complex, which
is consistent with the previously reported [TtRPt(CH3)(CO)]-
[BF4]. A strong CO stretching absorption at high frequency
(νCO 2128 and 2126 cm−1, respectively) was observed,
reflecting an electron-deficient metal center and limited back-
donation. These high-frequency CO stretches are compatible
with other Pt(II) CO cationic complexes.50,53
The ethylene adducts 4-L1 and 4-L2 exhibit a 2:1 ratio in
each set of the TtR 1H NMR signals, indicating Cs symmetry.
The four olefinic protons in both of these complexes appear as
a singlet with platinum satellites (2JPt,H = 81 and 86 Hz,
respectively), reflecting rapid rotation about the bisector of the
NMR studies revealed that the ethylene ligand is static at 200 K
in 4-L1, with two separate resonances (3.1 and 3.6 ppm) as a
result of inequivalent sites for the bound olefin (Figure 2). The
coalescence temperature for this process was found to be 229
K, which translates to a rotation barrier of 10.5 kcal/mol. The
TtCy analogue, 4-L2, had a coalescence temperature of 238 K
and a rotation barrier of 10.9 kcal/mol. The decreased energy
barrier for rotation in these platinum phenyl complexes relative
to the previously reported methyl analogues (11.1 kcal/mol (L1)
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and 11.5 kcal/mol (L2)) continues the expected trend that
a more electron deficient metal center results in less back-
bonding in the ground state.50 The spectroscopic data collected
for the mono- and disubstituted olefin complexes 5−9 were
consistent with that of ethylene adduct 4 and the related
[TtRPt(Me)(L)]+ complexes. The activation barrier for rotation
in the trans-2-butene adducts 7-L1 and 7-L2 was found to be
13.6 and 13.7 kcal/mol, respectively. This increase of ca. 3 kcal/mol
relative to 4 is consistent with the increased steric bulk of the
substituted olefin inhibiting rotation, thus suggesting that the
transition state for rotation is more hindered than the ground
state.
formation of the five-membered metallacyclic hydride species
(Scheme 2). Metallacycle formation under milder conditions from
Scheme 2. Proposed Mechanism for Phenyl Migration and
Subsequent Ortho C−H Activation of 4 To Form the
Metallacycle Hydride Complex 10
Kinetic studies on the conversion of the diphenyl hydride
cation complex 2-L2 to olefin adduct 6-L2 were performed by
monitoring the decay of the Pt−H signal with 1H NMR
spectroscopy. The reaction displayed first-order kinetics
between 245 and 270 K in the presence of 1.2 equiv of
1-hexene. The conversion was also monitored using a large
excess of 1-hexene (4 equiv), and the reaction rate remained
constant to within experimental error, indicating a zero-order
dependence on the olefin substrate. The reaction rate at 270 K
was found to be [1.38( 0.05)] × 10−3 s−1, giving rise to a
ΔG⧧270 value of 19.3( 0.1) kcal/mol. An Eyring plot (Figure 3)
4 compared to those for the electron-rich Tp′ analogue is credited
to the weakly donating hemilabile TtR ligand for allowing easier
access to the κ2 intermediate.24
Kinetic studies on the conversion of ethylene adduct 4-L2 to
metallacycle complex 10-L2 were performed by monitoring the
disappearance of the ortho proton of the phenyl ligand in the
Pt(II) reagent. The reaction was observed between 293 and
328 K and displayed first-order kinetics. The rate at 303 K was
found to be [5.7( 0.9)] × 10−5 s−1, giving rise to a ΔG⧧
303
value of 23.7( 0.2) kcal/mol. An Eyring plot (Figure 4) was
Figure 3. Eyring plot for the conversion of 2-L2 to 6-L2.
was constructed using rate constants from a temperature range
of 245−270 K: ΔH⧧ and ΔS⧧ are 25.5( 0.7) kcal/mol and
+23( 3) eu, respectively. The large positive value for ΔS⧧
suggests that the rate-determining step is the reductive
elimination of benzene to form two species.54 Note that the
putative η2-benzene intermediate was never observed.
Phenyl Migration and Ortho C−H Activation. With the
η2 olefin reagents in hand, we wished to compare the migratory
aptitude of the phenyl ligand in these TtR complexes to that of
their corresponding Tp′ analogues.24 Allowing the ethylene-
bound complex 4-L1 to stand at room temperature overnight
resulted in partial conversion to a new C1-symmetric species
that displayed a 1:1:1 ratio in the TtR proton signals.
Concurrently, growth of a Pt−H signal was observed at ca.
−19.0 ppm (1JPt,H = 1579 Hz). Heating the starting material at
50 °C for 30 min successfully drove the conversion
Figure 4. Eyring plot for the conversion of the ethylene adduct 4-L2
to metallacyclic hydride 10-L2.
constructed using rate constants from this temperature range;
ΔH⧧ and ΔS⧧ are 24.8 ( 1.1) kcal/mol and +3.4( 3) eu,
respectively. The near-zero value for ΔS⧧ is compatible with an
intramolecular rearrangement.
Metallacycle Dynamics and D-Labeling Studies. With
the dynamic nature of similar TtR dimethyl Pt−H complexes in
mind,50 we wished to examine the dynamics of the cationic
metallacycle complexes. The NOESY NMR spectrum of metal-
lacycle 10-L1 is shown in Figure 5. A cross peak that is out of
phase with the diagonal signals is observed that correlates the
hydride, Ha, and two of the alkyl bridge protons, Hb and Hd. This
cross peak is due to a through-space NOE interaction. An intense
cross peak that is in phase with the diagonal is observed between
Ha and the ortho proton Hf of the aryl ring, and this cross peak
1
quantitatively to the new product. The H NMR spectrum is
consistent with the formation of a Pt(IV) metallacyclic hydride
complex, [TtRPt(CH2CH2-o-C6H4)(H)][BF4] (10), which is
analogous to the insertion product formed in the Tp′Pt system.
We propose a mechanism that is initiated by a facile κ3/κ2 con-
version, resulting in an unsaturated metal species. Phenyl migration
to the metal-bound ethylene would then result in a three-
coordinate Pt(II) fragment. In the absence of trapping ligand, C−H
activation of the ortho proton dominates and accounts for the
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product is compatible with aryl elimination being considerably
faster than alkyl elimination.
Activation parameters for the exchange process between the
Pt−H position and the ortho arene position adjacent to the
alkyl substituent were obtained by variable-temperature 1H
NMR studies of 10. Upon heating to temperatures in excess of
338 K, line broadening of the hydride signal occurs and a rate
constant was estimated using the slow-exchange approximation.
At 345 K the rate constant was found to be 12.6 s−1, giving rise to
a ΔG⧧345 value of 18.6 kcal/mol for this reductive coupling C−H
activation process. An Eyring plot was constructed using the rate
constants collected between 338 and 358 K; ΔH⧧ and ΔS⧧ are
estimated to be 23.1 kcal/mol and +12.8 eu, respectively.
Phenyl Migration in Substituted Adducts. Heating the
various substituted alkene adducts 5−9 at 50 °C for 30 min
induced phenyl migration and subsequent C−H activation to
afford the corresponding metallacycle products (eqs 4−7).
Figure 5. NOESY NMR spectrum of complex 10-L1.
results from site exchange between these two proton positions on
the NMR time scale.55
To confirm this exchange process, excess D2O was added to
a solution of 10-L1 and the 1H NMR was recorded. Deuterium
was rapidly incorporated into the acidic Pt−H position, as is the
case for other TtR platinum hydride species.50 In the aromatic
region (Figure 6a), the signal for Hf significantly diminished
while the signal for the adjacent proton, Hg, collapsed from a
triplet to a doublet, confirming D incorporation into the adjacent
Hf position. In the alkyl region near 3 ppm (Figure 6b), D
incorporation was also observed for the α-carbon protons, Hb and
Hc. As a result, the 1H NMR spectrum converts from a complex
pattern in the alkyl region with four inequivalent protons each
with unique coupling to the other protons and also with platinum
coupling to a simple spectrum of two signals.
The proposed mechanism for proton exchange in 10 is
shown in Scheme 3. In analogy to elimination mechanisms
from previously described dialkyl and diaryl TtR complexes, an
initiating low-barrier κ3/κ2 conversion produces an unsaturated
five-coordinate intermediate. In 10, aryl elimination or alkyl
elimination can occur and, in either case, free rotation of the
resulting phenyl or alkyl group scrambles the ortho aryl or
methyl protons, respectively. Subsequent C−H reactivation and
κ2/κ3 conversion regenerates 10 and accounts for exchange
between Ha and Hb or between Ha and Hf. The absence of an
exchange cross peak between the hydride and either Hb or Hc
3
in the NOESY NMR spectrum of 10 indicates that the Csp −H
2
reductive elimination is slower than Csp −H elimination and
does not occur on the NMR time scale. The relative energy
barriers of these two processes are consistent with rate com-
parisons for methane elimination vs benzene elimination from
the dimethyl and diphenyl hydride reagents, respectively.
To probe the proposed mechanism in Scheme 3, we sought
to trap the putative unsaturated intermediates [κ2-TtRPtR]+.
Carbon monoxide was added to the headspace of an NMR
sample of 10 at room temperature and continuously mixed
overnight. The 1H NMR displayed clean conversion to a single
product, [TtRPt(CH2CH2Ph)(CO)][BF4] (11), which is the
product expected from aryl elimination (eq 3). The IR spectrum
of 11 shows a single strong CO stretch (νCO 2117 cm−1 (11-L1)
and 2114 cm−1 (11-L2)) at a frequency that is consistent with
the related cationic complex [TtRPt(CH3)(CO)][BF4]. This
Phenyl migration of the propylene adduct 5 resulted in four
unique Pt−H signals (Figure 7), reflecting the four possible
insertion isomers 12a−d. The methyl group on the alkyl bridge
of each isomer resonates as a doublet in the 1.0−1.5 ppm
1
region of the H NMR spectrum and was confirmed to couple
1
with the bridge methine proton by H,1H-COSY NMR. The
aryl ligand can migrate to either the α or β carbon to give rise
to two structural isomers in which the methyl is located on
either carbon of the alkyl bridge. A stereocenter is produced,
resulting in up and down options for the methyl substituent.
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1
Figure 6. Aryl (a) and alkyl (b) regions of the H NMR spectrum of 10-L1 before and after excess D2O addition.
from the propylene adduct 5-L1. To our surprise, the insertion
reaction of the 1-hexene adduct 6 to afford metallacycles
13a−d did not significantly change this isomeric distribution of
products.
Metallacycle formation resulting from the cis-2-butene and
trans-2-butene adducts 7 and 8 also resulted in four prominent
Pt−H signals, and these isomer distributions were identical in
chemical shift, platinum coupling, and ratio (2:5:4:1) to one
another, indicating that both starting materials converge to the
same set of isomeric products. This outcome is consistent with
the fluxional nature of the parent compound 10, in which the
aryl and alkyl fragments undergo facile C−H reductive
elimination and oxidative addition. Reductive elimination of
the hydride and alkyl bridge followed by free rotation and
reactivation erases the cis or trans relationship of the two
methyl substituents in the bridge, allowing each adduct to form
The metal center is also chiral, thereby generating a total of
eight isomers, half of which are enantiomeric pairs that are not
differentiated by routine NMR. The Pt−H signal intensity
ratios display a 4:6:2:1 distribution of metallacycle products
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1H,13C-HMQC NMR (Figure 8) spectrum reveals that, in the
major isomer, a cross peak exists that correlates protons Hb and
Hc with the α carbon, consistent with 15a.
Scheme 3. Proposed Mechanism for Proton Exchange in
Complex 10
Migration of phenyl to the sterically hindered β carbon of
isobutylene gave rise to the major isomer, a result we found
1
counterintuitive. Monitoring the insertion by H NMR while
heating 9 at 35 °C demonstrated the appearance of both
isomers in a 3:1 ratio (15a:15b). After several hours, only one
Pt−H signal (that of 15a) and a single TtR species remained,
suggesting that 15b undergoes rearrangement to 15a (Figure 9).
We believe that 15b, generated from phenyl migration to the
less sterically hindered α carbon, is the kinetic product of
insertion. The resulting metallacycle contains geminal methyl
substituents proximal to the metal center and bulky TtR ligand.
The lower steric energy penalty associated with moving the
methyl groups further away from the metal center provides a
driving force to the thermodynamically favored isomer 15a.
Conversion from 15b to 15a presumably proceeds through the
original isobutylene adduct 9 as an intermediate and implies
reversible C−C bond formation. This rearrangement is con-
sistent with similar reactivity observed in metallacycle
formation from Tp′Pt(Ph)(CH2CHCH3).24
The isobutylene adduct reveals the thermodynamic prefer-
ence for forming isomers in which substituents are located on
the β carbon, but these isomers did not assist in differentiating
preferences for the up or down options at a stereocenter, such
as in 12−14. We therefore sought an adduct that would retain
its cis or trans geometry regardless of rapid and reversible alkyl
reductive elimination and oxidative addition. Cyclopentene
served as an attractive olefin that met this criteria. When the
protonation and warming sequence was performed with
cyclopentene as the trapping alkene, the expected η2-bound
adduct was not produced; rather, rapid phenyl migration
occurred upon alkene binding, resulting in metallacycle
formation (eq 7, 16a/16b). Recalling that the similar cis-2-
butene complexes formed an isolable olefin adduct which
required mild heating to induce metallacycle formation, the
rapid insertion of cyclopentene demonstrates that alkene strain
has a profound influence on the rate of migration of the phenyl
1
ligand. In the H NMR spectrum, two Pt−H signals in a 3:1
ratio were observed, reflecting the up and down orientations
accessible to the original cyclopentyl ring. The NOESY NMR
of this mixture (Figure 10) indicated that, in the major isomer
16a, there is an NOE through-space interaction between the
hydride Ha and four protons of the cyclopentyl ring. Likewise,
in the minor isomer 16b, a through-space interaction is present
between Ha and Hb, revealing a preference for olefin
substituents in the “down” position relative to the apical TtR
nitrogen and extending in the same direction as the hydride
from the plane of the metallacycle.
With these results in mind, we reexamined the more
complicated propylene insertion scenario. Heating the
propylene adduct 5 at 50 °C overnight and monitoring the
1H NMR produced isomer ratio shifts with time reminiscent of
isobutylene complex 9. The two initial minor Pt−H signals
decrease in intensity, leaving only the two major products 12a,b
after several hours. Ultimately, the two major isomers
decompose upon prolonged heating. We believe this system
displays isomer preferences similar to those described for the
conversion of 9 to 15a. The two minor isomers, 12c,d, contain
a methyl group on the α carbon and, upon heating, rearrange to
the less sterically hindered pair of diastereomers 12a,b. Given
the preference for substituents to extend in the same direction
1
Figure 7. Pt−H region of the H NMR spectrum of 12a−d.
four isomers. It is conceivable that after alkyl elimination
another mechanistic possibility would be C−H activation of the
terminal methyl of the now three-carbon parent alkyl chain,
resulting in a six-membered ring with a stereocenter at the γ
carbon. Indeed, two additional Pt−H signals of minute
intensity at −19.0 and −19.2 ppm with identical platinum
coupling (1JPt−H = 1544 Hz) are observed in the H NMR
1
spectrum, which may reflect this rearrangement to form a six-
membered metallacycle product.
In order to elucidate the identity of each metallacycle isomer
from the corresponding Pt−H signals, we examined a simpler
systemthe insertion product formed from the isobutylene
adduct 9. As expected, only two Pt−H signals resulted from
phenyl migration (50 °C, 30 min), reflecting geminal methyls
on either the α or β carbons, 15b and 15a, respectively. The
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1
Figure 8. H,13C-HMQC NMR spectrum of 15a-L1. The cross peak correlating Hb and Hc with the α carbon confirms the identity of the major
isomer having geminal methyl groups on the β carbon.
Figure 9. Pt−H region of the 1H NMR spectrum of 15a/15b during thermolysis at 35 °C. The initial ratio of 15a: to 15b is 3:1. After several hours,
15a is the dominant product.
as the hydride from the metallacyclic plane, we postulate that
the more populated diastereomer 12a has the methyl pointed
“down” relative to the apical nitrogen (Figure 11).
Reaction Sequence Energy Barriers. The thermody-
namic parameters obtained and the intermediates isolated for
the reaction sequence reveal that the pathway from diphenyl
hydride 2 to metallacycle products 10−16 traverses two
significant energy barriers. After a κ3/κ2 conversion, the first
barrier is reductive coupling and arene loss from the putative
η2-benzene adduct, which is trapped with an olefin to form a
π-bound alkene complex. The second energy barrier, which is
phenyl migration, varies depending on the identity of the olefin.
For ethylene and simple mono- and disubstituted olefins this
barrier is greater than that of the initial reductive coupling and
allows the isolation of the η2-alkene adduct. However, for cyclic
alkenes, we postulate that the added strain provides a less
hindered route for the phenyl ligand to migrate, resulting in
a barrier that is less than the reductive coupling step.
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Figure 10. NOESY NMR spectrum of 16a/16b.
chloride solution of metallacycle 17 with methyl triflate at room
temperature generated 18, the methyl analogue of the hydride
10 (eq 8). Metallacycle 18 exhibits a resonance in the 1H NMR
spectrum at 1.5 ppm with two-bond platinum coupling of 74
Hz, which is compatible with other reported Pt(IV) methyl
complexes.26,56−58 Allowing 18 to stand at room temperature
overnight did not result in the appearance of a platinum
Figure 11. The four metallacycle products from propylene insertion
in 5.
After elimination of benzene from 2 and displacement by
cyclopentene, the η2-alkene adduct is not observed and the
cascade continues to the final metallacyclic product.
Formation of Alkyl Metallacycle Complexes. In our
studies of the dimethyl and diphenyl hydride reagents
[TtRPtMe2H]+ and [TtRPtPh2H]+ 2, we found the hydride to
be acidic: addition of base regenerated the respective κ2 Pt(II)
precursors.50 In view of the acidity of these Pt(IV) hydride
complexes, triethylamine was added to a methylene chloride
solution of 10-L2 in hopes of obtaining the neutral product, κ2-
hydride NMR signal. Note that C−C reductive elimination of
the methyl group and C−H activation of the aryl would be
expected to produce a Pt−H product. Similar to the synthesis
of 18, addition of allyl iodide to 17 produced the Pt allyl
metallacycle 19. The allyl complex 19 also did not result in
C−C elimination and rearrangement, even upon gentle heating
at 35 °C, in contrast to previously reported C−C coupling and
formation of biphenyl from [TtRPtPh2(σ-allyl)]+.50 These
results indicate that both 18 and 19 are static complexes at
moderate temperatures and do not undergo facile reductive
C−C bond formation, presumably due to a significantly higher
barrier for C−C coupling than for the comparable C−H
formation and cleavage reactions evident in the hydride
analogues 10−16.
TtCyPt(CH2CH2-o-C6H4) (17-L2). Indeed, the addition of base
generated the neutral metallacycle 17-L2 in 90% yield, as
monitored by 1H NMR. The TtR triazolyl proton signals
exhibited a 1:1:1 ratio with a characteristically large chemical
shift difference (ca. 0.6 ppm) between the two bound arms and
the one free arm, clearly indicating κ2 coordination of the TtCy
ligand.
Similar to the case for other κ2-TtRPtR2 compounds, the
metal center in this Pt(II) metallacycle was susceptible to
oxidation to form cationic Pt(IV) complexes by the addition of
electrophilic alkyl or allyl reagents. Treating a methylene
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Article
added through the septum, and the reaction mixture was stirred for 30
min at room temperature. After evaporation of the solvent, the resulting
oil was purified by flash chromatography on alumina. The column was
flushed with ethyl acetate and then by methanol. The methanol eluent
was collected, and the solvent was removed by rotary evaporation to
produce (κ2-TtPh)Pt(Ph)2 (0.033 g, 0.039 mmol) as a white solid in 56%
Summary. Pt(II) phenyl olefin complexes 4−9 have been
prepared via benzene loss from [TtRPtPh2H][BF4] and
subsequent trapping with added olefin. Mild heating of the
olefin adducts promotes migratory insertion of the olefin into
the phenyl−platinum bond, and this is followed by ortho C−H
activation and metallacycle formation. The mechanism for this
transformation is believed to be initiated by a facile κ3/κ2
interconversion, leading to a reactive unsaturated Pt(II) fragment.
The reversible coordination of the apical triazolyl nitrogen results
in a dynamic metallacycle complex from which aryl and aliphatic
elimination and reactivation readily occur. Thermolysis of the
isobutylene insertion products reveals conversion of the kineti-
cally favored α-substituted metallacycle to the thermodynamically
favored β-substituted isomer, and this isomerization proceeds via
a reversible C−C bond-forming step.
1
yield. H NMR (CD2Cl2, 300 K, δ): 9.27, 8.87 (s, 1H, 2H, TtPhCH),
7.80−7.51 (m, 15H, TtPhC6H5), 7.07 (d, 4H, 3JPt−H = 52 Hz, Pt−Ar Ho),
6.70−6.77 (m, 6H, Pt−Ar Hm and Hp). 31P{1H} NMR (CD2Cl2, 294 K,
δ): −8.7 (s, 1P, TtPhPO). 13C{1H} NMR (CD2Cl2, 293 K, δ): 141.0
(s, 2C, Pt−Ar ipso-Ph), 140.5 (d, 1C, OPC, 1JP−C = 170 Hz), 139.0 (d,
2C, OPC, 1JP−C = 149 Hz), 138.8 (s, 4C, Pt−Ar m-Ph), 136.5, 136.2
(s, 1C, 2C, TtPh ipso-Ph), 130.9 (s, 2C, TtPh p-Ph), 130.6 (s, 4C, TtPh o-
1
Ph), 130.5 (d, 1C, JP−C = 33 Hz, OPC), 130.3 (s, 2C, TtPh o-Ph),
2
130.1 (s, 1C, TtPh p-Ph), 130.1 (d, 2C, JP−C = 25 Hz, OPCCH),
126.3 (s, 4C, Pt−Ar o-Ph), 122.2 (s, 2C, Pt−Ar p-Ph), 121.4 (s, 2C, 4C,
TtPh m-Ph). Anal. Calcd for C36H28N9OPPt: C, 52.18; H, 3.41; N, 15.21.
Found: C, 52.35; H, 3.24; N, 15.07.
(κ2-TtCy)Pt(Ph)2 (1-L2). [Pt(Ph)2(SEt2)]2 (0.061 g, 0.070 mmol) and
TtCy (0.035 g, 0.070 mmol) were placed in a Schlenk flask under
nitrogen. CH2Cl2 (10 mL) was added through the septum, and the
reaction mixture was stirred for 30 min at room temperature. After
removal of the solvent, the resulting oil was purified by flash
chromatography on alumina. The column was first flushed with ethyl
acetate and then by methanol. The methanol eluent was collected, and
the solvent was removed by rotary evaporation to produce (κ2-
TtCy)Pt(Ph)2 (0.043 g, 0.051 mmol) as a white solid in 74% yield (by
EXPERIMENTAL SECTION
■
Materials and Methods. All reactions were performed under an
atmosphere of dry nitrogen using standard Schlenk and drybox
techniques. Nitrogen was purified by passage through columns of
BASF R3-11 catalyst and 4 Å molecular sieves. Methylene chloride,
hexanes, and pentane were purified under an argon atmosphere and
passed through a column packed with activated alumina. All other
chemicals were used as received without further purification.
1H, 31P, and 13C NMR spectra were recorded on Bruker DRX400,
1
TtCy ligand) . H NMR (CD2Cl2, 291 K, δ): 8.96, 8.36 (s, 1H, 2H,
AVANCE400, and AMX300 spectrometers. H NMR and 13C NMR
1
3
3
TtCyCH), 7.04 (d, 4H, JPt−H = 63 Hz, JH−H = 7 Hz, Ho), 6.72−6.80
(m, 6H, Hm and Hp), 4.50 (m, 3H, NCHCy), 1.21−2.22 (m, 30H,
cyclohexyl). 31P{1H} NMR (CD2Cl2, 293 K, δ): −7.09 (s, 1P, TtCyP
O). 13C{1H} NMR (CD2Cl2, 292 K, δ): 141.7 (s, 2C, ipso-Ph), 139.1
chemical shifts were referenced to residual H and 13C signals of the
1
deuterated solvents. Elemental analyses were performed by Robertson
Microlit Laboratories of Madison, NJ. High-resolution mass spectra
were recorded on a Bruker BioTOF II ESI-TOF mass spectrometer.
Mass spectral data are reported for the most abundant platinum
isotope. Tris(1-phenyl-1H-1,2,3-triazol-4-yl)phosphine oxide (TtPh),49
tris(1-cyclohexyl-1H-1,2,3-triazol-4-yl)phosphine oxide (TtCy),50 and
1
(s, 4C, m-Ph), 139.1 (d, 1C, OPC, JP−C = 169 Hz), 138.1 (d, 2C,
1
2
OPC, JP−C = 149 Hz), 129.7 (d, 1C, OPCCH, JP−C = 33 Hz),
2
129.1 (d, 2C, OPCCH, JP−C = 24 Hz), 126.1 (s, 4C, o-Ph), 121.9
(s, 2C, p-Ph), 62.4, 61.2 (s, 2C, 1C, CA), 33.8−33.1 (s, 1:1:1, 6C, CB),
25.4−25.1 (s, 1:1:1 and 2:1, 9C, CC and CD). HRMS (ESI): m/z calcd
59
[Pt(C6H5)2(SEt2)]2 were synthesized using published procedures.
For simplicity in presenting NMR data, the carbon atoms of the
cyclohexyl group of the TtCy ligand are designated by the labeling
scheme in Figure 12. Likewise, in metallacycle complexes, the carbon
atoms are designated by the labeling scheme in Figure 13.
979.2265 (M
+
Cs+), found 979.2296. Anal. Calcd for
C36H28N9OPPt·1/2CH2Cl2: C, 49.30; H, 5.29; N, 14.18. Found: C,
48.54; H, 5.24; N, 14.22.
Synthesis of [(κ3-TtR)Pt(Ph)2H][X] Complexes. [(κ3-TtPh)Pt-
(Ph)2H][BF4] (2-L1). TtPhPtPh2 (1-L1; 0.030 g, 0.035 mmol) was
weighed into an NMR tube in a drybox. CD2Cl2 (0.6 mL) was added
through the septum, and the solution was cooled to −78 °C outside of
the drybox. The methylene chloride solution was treated with 1 equiv
of HBF4·Et2O (4.5 μL, 0.035 mmol) and placed inside the cold probe
of the NMR spectrometer. The 1H NMR spectrum showed
1
quantitative conversion to 2-L1. H NMR (CD2Cl2, 195 K, δ): 9.41,
9.30 (s, 1H, 2H, TtPhCH), 7.79−6.96 (m, 25H, TtPhC6H5 and Pt−
1
C6H5), −19.18 (s, 1H, JPt−H = 1581 Hz, Pt−H). 31P{1H} NMR
(CD2Cl2, 195 K, δ): −6.5 (s, 1P, TtPhPO). 13C {1H} NMR
(CD2Cl2, 195 K, δ): 137.2 (s, 3C, TtPh ipso-Ph), 134.9 (d, 2C, OPC,
Figure 12. Carbon labels in the cyclohexyl group of the TtCy ligand.
1
1JP−C = 155 Hz), 134.5 (s, Pt−Ar m-Ph), 134.4 (d, 1C, OPC, JP−C
= 155 Hz), 130.7 (s, 3C, TtPt p-Ph), 130.5 (d, 3C, OPCCH, 2JP−C
=
30 Hz), 129.8 (s, 6C, TtPh o-Ph), 128.2 (s, 2C, Pt−Ar ipso-Ph), 127.3
(s, 4C, 2JPt−C = 62 Hz, Pt−Ar o-Ph), 124.9 (s, 2C, Pt−Ar p-Ph), 120.9
(s, 6C, TtPh m-Ph).
[(κ3-TtCy)Pt(Ph)2H][BF4] (2-L2). The same procedure was performed
using the analgous TtCyPt(Ph)2 (1-L2) starting material. Quantitative
conversion to 2-L2 was observed. 1H NMR (CD2Cl2, 200 K, δ): 8.81,
3
8.75 (s, 1H, 2H, TtCyCH), 7.16 (s, 4H, JPt−H = 53 Hz, Pt−Ar Ho),
6.99, 6.90 (m, 6H, Pt−Ar Hm and Hp), 4.67, 4.58 (m, 1H, 2H, CA-H),
2.10−1.09 (m, 30H, cyclohexyl), −19.40 (s, 1H, 1JPt−H = 1554 Hz, Pt−
H). 31P{1H} NMR (CD2Cl2, 200 K, δ): −5.7 (s, 1P, TtCyPO).
13C{1H} NMR (CD2Cl2, 200 K, δ): 137.3 (s, 4C, Pt−Ar m-Ph), 134.3,
133.7 (d, 2C, 1C, OPC, 1JP−C = 150 Hz), 129.2 (d, 3C, OPCCH,
2JP−C = 23 Hz), 127.9 (s, 2C, Pt−Ar ipso-Ph), 127.2 (s, 4C, 2JPt−C = 60
Hz, Pt−Ar o-Ph), 124.6 (s, 2C, Pt−Ar p-Ph), 62.5, 62.4 (s, 1C, 2C,
CA), 32.7−32.2 (s, 6C, CB), 24.4−23.9 (s, 9C, CC and CD).
Figure 13. Carbon labels in the metallacycle complexes.
Synthesis of κ2 TtRPtPh2 Complexes. (κ2-TtPh)Pt(Ph)2 (1-L1).
[Pt(Ph)2(SEt2)]2 (0.061 g, 0.070 mmol) and TtPh (0.033 g, 0.070 mmol)
were placed in a Schlenk flask under nitrogen. CH2Cl2 (10 mL) was
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Elimination and Trapping Reactions. In a typical experiment, 1
(0.035 mmol) was placed in a Schlenk flask under nitrogen. Methylene
chloride (10 mL) was added through the septum, and the solution was
cooled to −78 °C in a dry ice/isopropyl alcohol bath. The solution
was treated with 1 equiv of HBF4·Et2O (0.035 mmol). The mixture
was warmed to room temperature while being sparged with the
appropriate trapping gas. The solvent was removed by rotary
evaporation and the resulting oil triturated with pentane to afford
the desired trapped product 3−9 as a white powder in high yield by 1H
NMR.
137.1 (d, 1C, OPC, 1JP−C = 156 Hz), 136.5 (d, 1C, OPC, 1JP−C
=
151 Hz), 135.5, 135.4, 135.3 (s, 1C, 1C, 1C, TtPh ipso-Ph), 134.9 (s,
2C, Pt−Ar m-Ph), 132.1 (d, 2C, OPCCH, 2JP−C = 24 Hz), 131.7 (d,
2
1C, OPCCH, JP−C = 24 Hz), 131.0 (s, 2C, Pt−Ar o-Ph), 130.7,
130.3, 130.2 (s, 1C, 1C, 1C, TtPh p-Ph), 130.2 (s, 6C, TtPh o-Ph), 127.9
(s, 1C, Pt−Ar p-Ph), 124.7 (s, 1C, Pt−Ar ipso-Ph), 121.5, 121.0, 120.9
(s, 2C, 2C, 2C, TtPh m-Ph), 93.8 (s, 1C, H2CCHCH3), 70.7 (s, 1C,
H2CCHCH3), 20.6 (s, 1C, H2CCHCH3). HRMS (ESI): m/z
calcd 793.1881 (M+), found 793.1816.
[(κ3-TtCy)Pt(η2-propylene)(Ph)][BF4] (5-L2). 1H NMR exhibited 86%
1
1
[(κ3-TtPh)Pt(CO)(Ph)][BF4] (3-L1). H NMR exhibited quantitative
conversion to 5-L2. H NMR (CD2Cl2, 298 K, δ): 8.72, 8.67 (s, 2H,
1
conversion to 3-L1. H NMR (CD2H2, 291 K, δ): 9.45, 9.34 (s, 1H,
1H, TtCyCH), 7.20 (d, 2H, Pt−Ar Ho), 6.98−6.90 (m, 3H, Pt−Ar Hm
and Hp), 5.01 (m, 1H, H2CCHCH3), 4.63, 4.55 (m, 1H, 2H, CA-H),
4.47 (d, 1H, Hcis to HHCCHCH3), 4.45 (d, 1H, Htrans to HHC
CHCH3), 2.27−1.26 (m, 30H, cyclohexyl). 31P{1H} NMR (CD2Cl2,
255 K, δ): −6.1 (s, 1P, TtCyPO). 13C{1H} NMR (CD2Cl2, 270 K,
2H, TtPhCH), 7.90−715 (m, 25H, TtPhC6H5 and Pt−C6H5). 31P{1H}
NMR (CD2Cl2, 291 K, δ): −5.7 (s, 1P, TtPhPO). 13C {1H} NMR
(CD2Cl2, 284 K, δ): 159.1 (s, 1C, Pt−CO), 138.2 (d, 3C, OPC,
1JP−C = 160 Hz), 137.1 (s, 2C, Pt−Ar m-Ph), 135.8, 135.6 (s, 2C, 1C,
1
2
TtPh ipso-Ph), 132.3 131.9 (d, 1C, 2C, OPCCH, JP−C = 23 Hz),
δ): 137.1 (d, 1C, OPC, JP−C = 159 Hz), 137.0 (d, 1C, OPC,
1JP−C = 159 Hz), 136.4 (d, 1C, OPC, 1JP−C = 152 Hz), 135.5 (s, 2C,
Pt−Ar m-Ph), 131.0 (d, 1C, OPCCH, 2JP−C = 24 Hz), 130.5 (d, 1C,
OPCCH, 2JP−C = 26 Hz), 130.2 (d, 1C, OPCCH, 2JP−C = 27 Hz),
127.0 (s, 2C, Pt−Ar o-Ph), 124.4 (s, 1C, Pt−Ar p-Ph), 121.6 (s, 1C,
Pt−Ar ipso-Ph), 62.9, 62.3, 62.0 (s, 1C, 1C, 1C, CA), 60.7 (s, 1C,
H2CCHCH3), 33.5−32.5 (s, 6C, CB), 25.6−24.7 (s, 9C, CC and
CD), 14.1 (s, 1C, H2CCHCH3). HRMS (ESI): m/z calcd 811.3289
(M+), found 811.3308.
131.6, 130.9 (s, 1C, 2C, TtPt p-Ph), 130.6, 130.4 (s, 2C, 4C, TtPh
o-Ph), 128.9 (s, 2C, Pt−Ar o-Ph), 126.8 (s, 1C, Pt−Ar p-Ph), 122.9 (s,
1C, Pt−Ar ipso-Ph), 121.9, 121.4 (s, 2C, 4C TtPh m-Ph). IR (CH2Cl2
solution) νCO = 2128 cm−1. HRMS (ESI): m/z calcd 779.1360 (M+),
found 779.1376. Anal. Calcd for C32H27BF4N9OPPt: C, 42.97; H,
2.68; N, 14.55. Found: C, 43.45; H, 2.91; N, 14.15.
1
[(κ3-TtCy)Pt(CO)(Ph)][BF4] (3-L2). H NMR exhibited quantitative
1
conversion to 3-L2. H NMR (CD2Cl2, 292 K, δ): 8.82, 8.72 (s, 1H,
2H, TtCyCH), 7.31−7.11 (m, 5H, Pt−C6H5), 4.55, 4.52 (m, 1H, 2H,
CA-H), 2.31−1.30 (m, 30H, cyclohexyl). 31P{1H} NMR (CD2Cl2, 292
K, δ): −6.8 (s, 1P, TtCyPO). 13C{1H} NMR (CD2Cl2, 292 K, δ):
[(κ3-TtPh)Pt(η2-1-hexene)(Ph)][BF4] (6-L1). H NMR exhibited 96%
1
conversion to 6-L1. 1H NMR (CD2Cl2, 275 K, δ): 9.39, 9.35, 9.30 (s,
1H, 1H, 1H, TtPhCH), 7.88−7.51 (m, 15H, TtPhC6H5), 7.35−6.96 (m,
5H, Pt−C6H5), 4.98 (m, 1H, H2CCH(Bu)), 4.60, 4.50 (s, 2H,
H2CCH(Bu)), 1.73−0.64 (m, 9H, H2CCH(Bu)). 31P{1H} NMR
(CD2Cl2, 255 K, δ): −4.9 (s, 1P, TtPhPO). 13C {1H} NMR
(CD2Cl2, 275 K, δ): 138.0 (d, 1C, 1JP−C = 161 Hz, OPC), 137.7 (d,
2C, 1JP−C = 160 Hz, OPC), 135.7 (s, 3C, TtPh ipso-Ph), 135.2 (s, 2C,
Pt−Ar m-Ph), 132.3 (d, 2C, 2JP−C = 28 Hz, OPCCH,), 131.3 (d, 2C,
OPCCH), 130.8, 130.7, 130.4 (s, 1C, 1C, 1C, TtPh p-Ph), 130.3 (s,
6C, TtPh o-Ph), 127.2 (s, 2C, Pt−Ar o-Ph), 124.9 (s, 1C, Pt−Ar p-Ph),
121.7 (s, 1C, Pt−Ar ipso-Ph), 121.7, 121.2 (s, 2C, 4C, TtPh m-Ph), 96.8
(s, 1C, H2CCH(Bu)), 68.7 (s, 1C, H2CCH(Bu)), 34.5 (s, 1C,
H2CCH(CH2CH2CH2CH3)), 31.7 (s, 1C, H2CCH-
(CH2CH2CH2CH3)), 22.3 (s, 1C, H2CCH(CH2CH2CH2CH3)),
13.9 (s, 1C, H2CCH(CH2CH2CH2CH3)). HRMS (ESI): m/z calcd
835.2350 (M+), found 835.2335.
1
159.5 (s, 1C, Pt−CO), 137.2 (d, 3C, OPC, JP−C = 155 Hz), 137.2
(s, 2C, Pt−Ar m-Ph), 131.4 (d, 3C, OPCCH, 2JP−C = 28 Hz), 128.7
(s, 2C, Pt−Ar o-Ph), 126.6 (s, 1C, Pt−Ar p-Ph), 123.4 (s, 1C, Pt−Ar
ipso-Ph), 63.9, 62.8 (s, 1C, 2C, CA), 33.2, 33.1 (s, 6C, CB), 25.2−25.0
(s, 9C, CC and CD). IR (CH2Cl2 solution): νCO 2126 cm−1. HRMS
(ESI): m/z calcd 797.2769 (M+), found 797.2777. Anal. Calcd for
C31H41N9O2PPt·1/2CH2Cl2: C, 40.84; H, 4.54; N, 13.61. Found: C,
41.25; H, 4.36; N, 13.29.
1
[(κ3-TtPh)Pt(η2-C2H4)(Ph)][BF4] (4-L1). H NMR exhibited quantita-
1
tive conversion to 4-L1. H NMR (CD2Cl2, 260 K, δ): 9.28, 9.27 (s,
1H, 2H, TtPhCH), 8.03−7.49 (m, 15H, TtPhC6H5), 7.10−7.01 (m, 5H,
2
Pt−C6H5), 3.50 (s, 4H, JPt−H = 81 Hz, Pt−C2H4). 31P{1H} NMR
(CD2Cl2, 260 K, δ): −7.6 (s, 1P, TtPhPO). 13C{1H} NMR (CD2Cl2,
260 K, δ): 136.9 (d, 2C, OPC, 1JP−C = 152 Hz), 136.7 (s, 2C, Pt−Ar
1
1
m-Ph), 136.5 (d, 1C, OPC, JP−C = 150 Hz), 135.6, 135.5 (s, 2C,
[(κ3-TtCy)Pt(η2-1-hexene)(Ph)][BF4] (6-L2). H NMR exhibited 94%
1C, TtPh ipso-Ph), 131.2, 130.8 (s, 1C, 2C, TtPt p-Ph), 130.4 (s, 6C,
TtPh o-Ph), 127.8 (s, 2C, Pt−Ar o-Ph), 124.9 (s, 1C, Pt−Ar p-Ph),
122.2 (s, 1C, Pt−Ar ipso-Ph), 121.8, 121.5 (s, 2C, 4C, TtPh m-Ph), 41.8
(s, 2C, 1JPt−C = 316 Hz, Pt−C2H4). HRMS (ESI): m/z calcd 779.1724
(M+), found 779.1693. Anal. Calcd for C32H27BF4N9OPPt: C, 44.36;
H, 3.14; N, 14.55. Found: C, 44.62; H, 2.96; N, 14.30.
conversion to 6-L2. 1H NMR (CD2Cl2, 298 K, δ): 8.66, 8.65, 8.61 (s,
1H, 1H, 1H, TtCyCH), 7.33 (d, 2H, Pt−Ar Ho), 7.00−6.93 (m, 3H,
Pt−Ar Hm and Hp), 4.77 (m, 1H, H2CCH(Bu)), 4.62, 4.56 (m, 1H,
2H, CA−H), 4.29 (d, 1H, 3JH−H = 18 Hz, Htrans to HCCH(Bu)), 4.26
(d, 1H, 3JH−H = 9 Hz, Hcis to HCCH(Bu)), 2.23−0.77 (m, cyclohexyl
and H2CCH(Bu)). 31P{1H} NMR (CD2Cl2, 275 K, δ): −7.3 (s, 1P,
TtCyPO). 13C{1H} NMR (CD2Cl2, 275 K, δ): 137.2 (d, 1C, O
PC, 1JP−C = 154 Hz), 136.7 (d, 2C, OPC, 1JP−C = 146 Hz), 135.6 (s,
2C, Pt−Ar m-Ph), 130.8 (d, 1C, OPCCH, 2JP−C = 24 Hz), 130.5 (d,
1C, OPCCH, 2JP−C = 27 Hz), 130.2 (d, 1C, OPCCH, 2JP−C = 26
Hz), 127.7 (s, 2C, Pt−Ar o-Ph), 124.6 (s, 1C, Pt−Ar p-Ph), 121.8 (s,
1C, Pt−Ar ipso-Ph), 87.2 (s, 1C, H2CCH(Bu)), 77.6 (s, 1C, H2C
CH(Bu)), 63.9, 62.5, 62.4 (s, 1C, 1C, 1C, CA), 33.2−33.1 (s, 7C, CB and
H2CCH(CH2CH2CH2CH3)), 31.8 (s, 1C, H2CCH-
(CH2CH2CH2CH3)), 25.0−24.9 (s, 9C, CC and CD), 22.4 (s, 1C,
H2CCH(CH2CH2CH2CH3)), 13.9 (s, 1C, H2CCH-
(CH2CH2CH2CH3)). HRMS (ESI): m/z calcd 853.3758 (M+), found
853.3746.
1
[(κ3-TtCy)Pt(η2-C2H4)(Ph)][BF4] (4-L2). H NMR exhibited quantita-
1
tive conversion to 4-L2. H NMR (CD2Cl2, 270 K, δ): 8.70 (s, 3H,
TtCyCH), 7.89 (d, 2H, Pt−Ar Ho), 7.04−6.97 (m, 3H, Pt−Ar Hm and
2
Hp), 4.63 (m, 3H, CA-H), 3.25 (s, 4H, JPt−H = 86 Hz, Pt−C2H4),
2.20−1.31 (m, 30H, cyclohexyl). 31P{1H} NMR (CD2Cl2, 270 K, δ):
−8.2 (s, 1P, TtCyPO). 13C{1H} NMR (CD2Cl2, 270 K, δ): 137.1 (s,
1
2C, Pt−Ar m-Ph), 135.6 (d, 2C, OPC, JP−C = 151 Hz), 135.3 (d,
1
2
1C, OPC, JP−C = 150 Hz), 130.2 (d, 1C, OPCCH, JP−C = 24
Hz), 129.8 (d, 1C, OPCCH, 2JP−C = 24 Hz), 127.6 (s, 2C, Pt−Ar o-
Ph), 124.6 (s, 1C, Pt−Ar p-Ph), 122.1 (s, 1C, Pt−Ar ipso-Ph), 63.1,
1
62.7 (s, 1C, 2C, CA), 38.0 (s, 2C, JPt−C = 363 Hz, Pt−C2H4), 33.2−
32.9 (s, 6C, CB), 25.0−24.7 (s, 9C, CC and CD). HRMS (ESI): m/z
calcd 797.3133 (M+), found 797.3108.
[(κ3-TtPh)Pt(η2-cis-2-butylene)(Ph)][BF4] (7-L1). H NMR exhibited
1
[(κ3-TtPh)Pt(η2-propylene)(Ph)][BF4] (5-L1). 1H NMR exhibited 85%
conversion to 5-L1. 1H NMR (CD2Cl2, 298 K, δ): 9.33, 9.31, 9.25 (s,
1H, 1H, 1H, TtPhCH), 7.86−7.44 (m, 15H, TtPhC6H5), 7.32−6.96 (m,
85% conversion to 7-L1. H NMR (CD2Cl2, 275 K, δ): 9.36, 9.32 (s,
1
1H, 2H, TtCyCH),), 7.86−7.49 (m, 15H, TtPhC6H5), 7.09−6.90 (m,
5H, Pt−Ar), 5.50 (s, 2H, CH3CHCHCH3), 1.49 (s, 6H, CH3CH
CHCH3). 31P{1H} NMR (CD2Cl2, 295 K, δ): −8.9 (s, 1P, TtCyPO).
13C{1H} NMR (CD2Cl2, 275 K, δ): 140.6 (d, 1C, OPC, 1JP−C = 159
Hz), 138.8 (d, 2C, OPC, 1JP−C = 159 Hz), 136.3 (s, 1C, TtPh ipso-Ph),
135.7 (s, 2C, Pt−Ar m-Ph), 134.9 (s, 2C, TtPh ipso-Ph), 131.3 (d, 1C,
OPCCH, 2JP−C = 28 Hz), 130.5 (d, 2C, OPCCH, 2JP−C = 23 Hz),
5H, Pt−C6H5), 5.26 (m, 1H, H2CCHCH3), 4.71 (d, 1H, 3JH−H = 8
3
Hz, Pt−Hcis
HHCCHCH3), 4.67 (d, 1H, JH−H = 14 Hz,
to
Htrans to HHCCHCH3), 1.39 (d, 3H, 3JH−H = 6 Hz, H2CCHCH3).
31P{1H} NMR (CD2Cl2, 255 K, δ): −4.6 (s, 1P, TtPhPO). 13C {1H}
1
NMR (CD2Cl2, 255 K, δ): 137.8 (d, 1C, OPC, JP−C = 162 Hz),
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1
130.4−129.76 (4C, 2C, 2C, 1C, TtPh o-Ph and p-Ph), 127.3 (s, 2C, Pt−
Ar o-Ph), 124.4 (s, 1C, Pt−Ar p-Ph), 121.1, 121.0 (s, 2C, 4C, TtPh
m-Ph), 90.9 (s, 2C, CH3CHCHCH3), 15.6 (s, 2C, CH3CHCHCH3).
HRMS (ESI): m/z calcd 807.2037 (M+), found 807.2019.
NMR (CD2Cl2, 260 K, δ): 137.2 (d, 2C, OPC, JP−C = 158 Hz),
1
136.7 (d, 1C, OPC, JP−C = 147 Hz), 134.6 (s, 2C, Pt−Ar m-Ph),
2
134.2 (s, 1C, Pt−Ar ipso-Ph), 131.5 (d, 1C, OPCCH, JP−C = 25
Hz), 130.8 (d, 2C, OPCCH, 2JP−C = 28 Hz), 127.4 (s, 2C, Pt−Ar o-
1
[(κ3-TtCy)Pt(η2-cis-2-butylene)(Ph)][BF4] (7-L2). H NMR exhibited
1
Ph), 124.2 (s, 1C, Pt−Ar p-Ph), 73.2 (s, 1C, JPt−C = 190 Hz, H2C
1
95% conversion to 7-L2. H NMR (CD2Cl2, 275 K, δ): 8.62 (s, 3H,
CH(CH3)2), 63.1, 62.1 (s, 1C, 2C, CA), 28.9 (s, 2C, H2C
CH(CH3)2), 33.0, 32.9 (s, 2C, 4C, CB), 25.2−24.7 (s, 9C, CC and CD).
HRMS (ESI): m/z calcd 825.3446 (M+), found 825.3413.
Phenyl Migration Reactions. In a typical experiment, TtRPt-
(Ph)(L) (4−9; 0.035 mmol) was weighed into an NMR tube in the
glovebox. CDCl3 (0.6 mL) was added through the septum. The
sample was heated in a 50 °C oil bath for 30 min. The solution was
transferred to a round-bottom flask, and the solvent was removed by
rotary evaporation. The resulting oil was triturated with pentane to
afford the metallacycle product as a pale yellow power in high yield by
1H NMR.
TtCyCH), 7.07−6.87 (m, 5H, Pt−Ar), 5.32 (s, 2H (CH3)CH
CH(CH3)), 4.62, 4.53 (m, 1H, 2H, CA−H), 2.23−1.22 (m, 30H,
cyclohexyl), 1.41 (d, (CH3)CHCH(CH3)). 31P{1H} NMR
(CD2Cl2, 275 K, δ): −8.7 (s, 1P, TtCyPO). 13C{1H} NMR
(CD2Cl2, 275 K, δ): 137.5 (d, 3C, OPC, 1JP−C = 156 Hz), 135.0 (s,
2C, Pt−Ar m-Ph), 131.3, 130.6 (d, 1C, 2C OPCCH, 2JP−C = 24 Hz,
28 Hz), 127.1 (s, 2C, Pt−Ar o-Ph), 124.7 (s, 1C, Pt−Ar ipso-Ph),
124.2 (s, 1C, Pt−Ar p-Ph), 88.8 (s, 2C, (CH3)CHCH(CH3)), 63.1,
62.3 (s, 1C, 2C, CA), 33.6−33.0 (s, 6C, CB), 25.3−24.9 (s, 9C, CC and
CD), 15.5 (s, 2C, (CH3)HCCH(CH3)). HRMS (ESI): m/z calcd
825.3446 (M+), found 825.3477.
[κ3-TtPhPt(CH2CH2-o-C6H4)(H)][BF4] (10-L1) by Ethylene Insertion.
[(κ3-TtPh)Pt(η2-trans-2-butene)(Ph)][BF4] (8-L1). 1H NMR ex-
hibited 91% conversion to 8-L1. 1H NMR (CD2Cl2, 300 K, δ):
9.37, 9.34, 9.17 (s, 1H, 1H, 1H, TtPhCH), 7.86−7.35 (m, 15H,
TtPhC6H5), 7.28 (d, 2C, Pt−Ar Ho), 7.00−6.94 (m, 3H, Pt−Ar Hm and
Hp), 5.68, 4.79 (s, 1H, 1H, (CH3)HCCH(CH3)). 1.63, 1.33 (s, 3H,
3H, (CH3)CHCH(CH3)). 31P{1H} NMR (CD2Cl2, 260 K, δ): −8.5
(s, 1P, TtPhPO). 13C {1H} NMR (CD2Cl2, 260 K, δ): 139.1 (d, 1C,
1
1
Quantitative conversion from 4-L1 was observed by H NMR. H
NMR (CD2Cl2, 293 K, δ): 9.420, 9.35.,9.29 (s, 1H, 1H, 1H, TtPhCH),
7.91−7.51 (m, 15H, TtPh C6H5), 7.21 (d, 1H, Hf), 7.05 (t, 1H, Hg),
7.01 (d, 1H, Hi), 6.81 (t, 1H, Hh), 3.47 (m, 1H, Ha), 3.31, (m, 2H, Hb
and Hc), 2.97 (m, 1H, Hd, 3JPt,H = 117 Hz), −19.0 (s, 1H, Pt−H, 1JPt,H
= 1579 Hz). 31P{1H} NMR (CD2Cl2, 293 K, δ): −6.3 (s, 1P, TtCyP
O). 13C{1H} NMR (CD2Cl2, 293 K, δ): 156.6 (s, 1C, CK, 2JPt,C = 125
1
1
OPC, JP−C = 163 Hz), 137.5 (d, 1C, OPC, JP−C = 148 Hz),
137.2 (d, 1C, OPC, 1JP−C = 151 Hz), 135.7, 135.6, 135.3 (s, 1C, 1C,
1C, TtPh ipso-Ph), 135.3 (s, 2C, Pt−Ar m-Ph), 132.5 (d, 1C, O
1
Hz), 137.0, 136.0 (d, 2C, 1C, OPC, JP−C = 151, 152 Hz), 135.9,
135.8, 135.8 (s, 1C, 1C, 1C, TtPh ipso-Ph), 132.0 (s, 1C, CI), 131.4,
131.3, 131.3 (s, 1C, 1C, 1C, TtPh p-Ph), 131.1−130.8 (d, 3 O
PCCH), 130.8 (s, 1C, CJ), 130.6, 130.5 (s, 4C, 2C, TtPh o-Ph), 125.7
2
2
PCCH, JP−C = 24 Hz), 131.6 (d, 1C, OPCCH, JP−C = 25 Hz),
2
131.0 (d, 1C, OPCCH, JP−C = 25 Hz), 131.0, 130.8, 130.0 (s, 1C,
1C, 1C, TtPh p-Ph), 130.2 (s, 6C, TtPh o-Ph), 128.4 (s, 1C, Pt−Ar ipso-
Ph), 126.4 (s, 2C, Pt−Ar o-Ph), 124.5 (s, 1C, Pt−Ar p-Ph), 121.7,
120.9 (s, 2C, 4C, TtPh m-Ph), 96.0, 93.2 (s, 1C, 1C, (CH3)HC
CH(CH3)), 20.7, 19.5 (s, 1C, 1C, (CH3)HCCH(CH3)). HRMS
(ESI): m/z calcd 807.2037 (M+), found 807.2071.
(s, 1C, CG), 125.2 (s, 1C, CH, 3JPt,C = 43 Hz), 123.5 (s, 1C, CF, 3JPt,C
=
47 Hz), 122.0, 121.8, 121.8 (s, 2C, 2C, 2C, TtPh m-Ph), 42.3 (s, 1C, C ,
β
2JPt,C = 53 Hz), 19.2 (s, 1C, C , JPt,C = 599 Hz). HRMS (ESI): m/z
1
α
calcd 779.1724 (M+), found 779.1699. Anal. Calcd for
C32H27BF4N9OPPt: C, 44.36; H, 3.14; N, 14.55. Found: C, 44.61;
H, 3.18; N, 14.27.
[(κ3-TtCy)Pt(η2-trans-2-butene)(Ph)][BF4] (8-L2). 1H NMR exhibited
90% conversion to 8-L2. 1H NMR (CD2Cl2, 260 K, δ): 8.73, 8.71, 8.56
(s, 1H, 1H, 1H, TtCyCH), 7.24 (d, 2H, Pt−Ar Ho), 6.96−6.88 (m, 3H,
Pt−Ar Hm and Hp), 5.55, 4.75 (s, 1H, 1H, (CH3)CHCH(CH3)),
4.62, 4.49 (m, 2H, 1H, CA−H), 2.24−1.23 (m, 36H, cyclohexyl and
(CH3)CHCH(CH3)). 31P{1H} NMR (CD2Cl2, 260 K, δ): −6.2 (s,
1P, TtCyPO). 13C{1H} NMR (CD2Cl2, 260 K, δ): 137.8 (d, 1C,
[κ3-TtCyPt(CH2CH2-o-C6H4)(H)][BF4] (10-L2) by Ethylene Insertion.
1
1
Quantitative conversion from 4-L2 was observed by H NMR. H
NMR (CD2Cl2, 293 K, δ): 8.79, 8.75, 8.69 (s, 1H, 1H, 1H, TtCyCH),
7.17 (d, 1H, Hf), 7.00 (t, 1H, Hg), 6.83 (d, 1H, Hh), 6.79 (t, 1H, Hi),
4.69, 4.67, 4.57 (m, 1H, 1H, 1H, CA−H), 3.25−2.87 (m, 4H, Ha−Hd),
1
1
1
2.24−1.15 (m, 30H, cyclohexyl), −19.4 (s, 1H, Pt−H, JPt,H = 1559
OPC, JP−C = 162 Hz), 136.8 (d, 1C, OPC, JP−C = 148 Hz),
Hz). 31P{1H} NMR (CD2Cl2, 293 K, δ): −3.7 (s, 1P, TtCyPO).
13C{1H} NMR (CD2Cl2, 293 K, δ): 156.7 (s, 1C, CK, 2JPt,C = 125 Hz),
135.6, 135.6, 134.9 (d, 1C, 1C, 1C, OPC, 1JP−C = 152, 151, 153 Hz),
132.0 (s, 1C, CI), 130.9 (s, 1C, CJ, 1JPt,C = 900 Hz), 130.6, 130.5, 130.0
(d, 1C, 1C, 1C OPCCH, 2JP−C = 24, 25, 23 Hz), 125.5 (s, 1C, CG),
1
136.1 (d, 1C, OPC, JP−C = 153 Hz), 135.5 (s, 2C, Pt−Ar m-Ph),
2
131.6 (d, 1C, OPCCH, JP−C = 20 Hz), 131.4 (d, 1C, OPCCH,
2JP−C = 24 Hz), 130.4 (d, 1C, OPCCH, JP−C = 30 Hz), 128.4 (s,
2
1C, Pt−Ar ipso-Ph), 127.3 (s, 2C, Pt−Ar o-Ph), 124.1 (s, 1C, Pt−Ar
p-Ph), 94.5, 91.8 (s, 1C, 1C, (CH3)CHCH(CH3)), 63.1, 62.6, 61.7
(s, 1C, 1C, 1C, CA), 34.2−32.7 (s, 6C, CB), 25.0−24.8 (s, 9C, CC and
CD), 20.6, 19.5 (s, 1C, 1C, (CH3)HCCH(CH3)). HRMS (ESI):
m/z calcd 825.3446 (M+), found 825.3420.
3
3
125.0 (s, 1C, CH, JPt,C = 42 Hz), 123.4 (s, 1C, CF, JPt,C = 47 Hz),
2
63.7, 63.6, 63.3 (s, 1C, 1C, 1C, CA), 42.4 (s, 1C, C , JPt,C = 54 Hz),
β
33.6−33.0 (s, 6C, CB), 25.2−24.9 (s, 9C, CC and CD), 18.3 (s, 1C, Cα,
1JPt,C = 597 Hz). HRMS (ESI): m/z calcd 797.3133 (M+), found
797.3132.
[κ3-TtPhPt(CH2CH(CH3)-o-C6H4)(H)][BF4] (12a-L1/12b-L1) and [κ3-
TtPhPt(CH(CH3)CH2-o-C6H4)(H)][BF4] (12c-L1/12d-L1) Mixture by
Propylene Insertion. 1H NMR (CDCl3, 298 K, δ): −18.9 (s, 1H,
1JPt−H = 1576 Hz, Pt−H, 12b), −19.0 (s, 1H, 1JPt−H = 1572 Hz, Pt−H,
[(κ3-TtPh)Pt(η2-isobutylene)(Ph)][BF4] (9-L1). 1H NMR exhibited
1
87% conversion to 9-L1. H NMR (CD2Cl2, 260 K, δ): 9.38, 9.34 (s,
1H, 2H, TtPhCH), 7.87−7.46 (m, 15H, TtPhC6H5), 7.23−6.98 (m, 5H,
Pt−C6H5), 4.78 (s, 2H, H2CC(CH3)2), 1.16 (s, 6H, H2C
C(CH3)2). 31P{1H} NMR (CD2Cl2, 260 K, δ): −8.4 (s, 1P, TtPhP
O). 13C{1H} NMR (CD2Cl2, 260 K, δ): 138.1 (d, 2C, OPC, 1JP−C
=
158 Hz), 137.3 (1, 1C, OPC, 1JP−C = 149 Hz), 135.6, 135.5 (s, 1C,
1
1
2C, TtPh ipso-Ph), 134.6 (s, 2C, Pt−Ar m-Ph), 132.4 (d, 2C, O
12a), −19.6 (s, 1H, JPt−H = 1620 Hz, 12c), −19.99 (s, 1H, JPt−H
1627 Hz, 12d). Ratio: 12b:12a:12c:12d = 4.1:6.3:1.7:1.
=
2
2
PCCH, JP−C = 24 Hz), 131.4 (d, 1C, OPCCH, JP−C = 28 Hz),
130.5−130.0 (s, 1C, 1C, 1C, TtPh p-Ph), 130.2, 130.0 (s, 4C, 2C, TtPh
o-Ph), 127.6 (s, 2C, Pt−Ar o-Ph), 124.4 (s, 1C, Pt−Ar p-Ph), 121.6,
121.0 (s, 2C, 4C, TtPh m-Ph), 73.3 (s, 1C, H2CC(CH3)2), 29.1 (s,
2C, H2CC(CH3)2). HRMS (ESI): m/z calcd 807.2037 (M+), found
807.1966.
[κ3-TtCyPt(CH2CH(CH3)-o-C6H4)(H)][BF4] (12a-L2/12b-L2) and [κ3-
TtCyPt(CH(CH3)CH2-o-C6H4)(H)][BF4] (12c-L2/12d-L2) Mixture by
1
Propylene Insertion. H NMR (CDCl3, 298 K, δ): −19.04 (s, 1H,
1JPt−H = 1545 Hz, Pt−H, 12b), −19.21 (s, 1H, 1JPt−H = 1542 Hz, Pt−
H, 12a), −19.70 (s, 1H, 1JPt−H = 1585 Hz, 12c), −20.10 (s, 1H, 1JPt−H
1590 Hz, 12d). Ratio: 12b:12a:12c:12d = 3.1:4.9:1.6:1.
=
[(κ3-TtCy)Pt(η2-isobutylene)(Ph)][BF4] (9-L2). 1H NMR exhibited
1
92% conversion to 9-L2. H NMR (CD2Cl2, 292 K, δ): 8.72 (s, 3H,
[κ3-TtPhPt(CH2CH(nBu)-o-C6H4)(H)][BF4] (13a-L1/13b-L1) and [κ3-
TtCyCH), 7.09 (d, 2H, Pt−Ar Ho), 6.93, 6.92 (m, 3H, Pt−Ar Hm and
Hp), 4.70 (s, 2H, H2CC(CH3)2), 4.62, 4.51 (m, 1H, 2H, CA−H),
2.25−1.17 (m, 36H, cyclohexyl), 1.10 (s, 6H, H2CCH(CH3)2).
31P{1H} NMR (CD2Cl2, 260 K, δ): −5.2 (s, 1P, TtCyPO). 13C{1H}
TtPhPt(CH(nBu)CH2-o-C6H4)(H)][BF4] (13c-L1/13d-L1) Mixture by 1-
Hexene Insertion. 1H NMR (CDCl3, 298 K, δ): −18.8 (s, 1H,
1JPt−H = 1576 Hz, Pt−H, 13b), −19.0 (s, 1H, JPt−H = 1577 Hz,
1
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1
1
1
Pt−H, 13a), −19.5 (s, 1H, JPt−H = 1624 Hz, 13c), −19.9 (s, 1H,
conversion by H NMR. H NMR (CD2Cl2, 292 K, δ): 8.72 (s, 3H,
TtCyCH), 7.28−7.26 (m, 5H, Pt−CH2CH2C6H5), 4.63 (m, 3H, CA−
H), 2.80, 2.56 (t, 2H, 2H, Pt−CH2CH2C6H5), 1.93−0.88 (m, 30H,
cyclohexyl). 31P{1H} NMR (CD2Cl2, 292 K, δ): −8.7 (s, 1P, TtCyP
O). 13C{1H} NMR (CD2Cl2, 292 K, δ): 161.2 (s, 1C, Pt−CO), 144.6
(s, 1C, Pt−CH2CH2Ph ipso-Ph), 137.6−136.5 (d, 3C, OPC),
131.9−131.1 (d, 3C, OPCCH), 128.9 (s, 1C, Pt−CH2CH2Ph o-Ph),
128.8 (s, 1C, Pt−CH2CH2Ph m-Ph), 126.3 (s, 1C, Pt−CH2CH2Ph
p-Ph), 63.6, 63.0 (s, 1C, 2C, CA), 38.5 (s, 1C, Pt−CH2CH2Ph), 33.3
(s, 6C, CB), 25.2−25.0 (s, 9C, CC and CD), 11.5 (s, 1C, Pt−
CH2CH2Ph). IR (CH2Cl2 solution): νCO 2114 cm−1. HRMS (ESI):
m/z calcd 825.3082 (M+), found 825.3055.
1JPt−H = 1627 Hz, 13d). Ratio: 13b:13a:13c:13d = 6.2:5.9:2.3:1.
[κ3-TtCyPt(CH2CH(nBu)-o-C6H4)(H)][BF4] (13a/13b-L2) and [κ3-
TtCyPt(CH(nBu)CH2-o-C6H4)(H)][BF4] (13c/13d-L2) Mixture by 1-
Hexene Insertion. 1H NMR (CDCl3, 298 K, δ): −19.04 (s, 1H,
1JPt−H = 1548 Hz, Pt−H, 13b), −19.23 (s, 1H, 1JPt−H = 1548 Hz, Pt−
H, 13a), −19.65 (s, 1H, 1JPt−H = 1594 Hz, 13c), −20.07 (s, 1H, 1JPt−H
1600 Hz, 13d). Ratio: 13b:13a:13c:13d = 4.4:4.0:1.6:1.
=
[κ3-TtPhPt(CH(CH3)CH(CH3)-o-C6H4)(H)][BF4] (14a-L1−14d-L1)
1
Mixture by 2-Butene Insertion. H NMR (CDCl3, 298 K, δ): −19.3
(s, 1H, 1JPt−H = 1613 Hz, Pt−H, 14c), −19.3 (s, 1H, 1JPt−H = 1614 Hz,
1
Pt−H, 14a), −19.8 (s, 1H, JPt−H = 1633 Hz, 14b), −20.2 (s, 1H,
Deprotonation and Alkylation Reactions. κ2-TtCyPt(CH2CH2-
1JPt−H = 1649 Hz, 14d). Ratio: 14c:14a:14b:14d = 1.6:4.7:4.4:1.
[κ3-TtCyPt(CH(CH3)CH(CH3)-o-C6H4)(H)][BF4] (14a-L1−14d-L2)
o-C6H4) (17-L2). [TtCyPt(CH2CH2-o-C6H4)(H)][BF4] (10-L2; 0.030
g, 0.034 mmol) was placed in a Schlenk flask under nitrogen.
Methylene chloride (10 mL) was added through the septum. The
solution was treated with triethylamine (14 μ, 0.102 mmol) and stirred
for 20 min. The solvent was removed by rotary evaporation and the
resulting oil triturated with pentane to afford 17-L1 in 90% conversion
1
Mixture by 2-Butene Insertion. H NMR (CDCl3, 298 K, δ): −19.4
(s, 1H, 1JPt−H = 1572 Hz, Pt−H, 14c), −19.5 (s, 1H, 1JPt−H = 1574 Hz,
1
Pt−H, 14a), −20.0 (s, 1H, JPt−H = 1586 Hz, 14b), −20.3 (s, 1H,
1JPt−H = 1600 Hz, 14d). Ratio: 14c:14a:14b:14d = 1.3:5.0:5.3:1.
1
1
[κ3-TtPhPt(CH2C(CH3)2-o-C6H4)(H)][BF4] (15a-L1) and [κ3-TtPh-
from 10-L2 by H NMR. H NMR (CD2Cl2, 293 K, δ): 8.97, 8.37,
8.33 (s, 1H, 1H, 1H, TtCyCH), 7.12−6.71 (m, 4H, Pt−C6H4), 4.63,
4.53, 4.25 (m, 1H, 1H, 1H, CA−H), 2.58−1.29 (m, 4H, 30H, Pt−
CH2CH2, cyclohexyl). 31P{1H} NMR (CD2Cl2, 293 K, δ): −7.1 (s, 1P,
TtCyPO). 13C{1H} NMR (CD2Cl2, 293 K, δ): 162.8 (s, 1C, CK),
Pt(C(CH3)21CH2-o-C6H4)(H)][BF4] (15b-L1) Mixture by Isobutylene
1
Insertion. H NMR (CDCl3, 298 K, δ): −18.8 (s, 1H, JPt−H = 1569
1
Hz, Pt−H, 15a), −20.7 (s, 1H, JPt−H = 1648 Hz, Pt−H, 15b). Ratio:
15a:15b = 31:1. Complete spectroscopic characterization of 15a can
1
138.6, 137.5, 137.6 (d, 1C, 1C, 1C, OPC, JP−C = 151 Hz, 151 Hz,
be found in the Supporting Information.
[κ3-TtCyPt(CH2C(CH3)2-o-C6H4)(H)][BF4] (15a-L2) and [κ3-TtCy-
170 Hz), 134.5 (s, 1C, CI), 131.2, 129.3, 128.9 (d, 1C, 1C, 1C, O
2
PCCH, JP−C = 33, 25, 26 Hz), 129.0 (s, 1C, CJ), 122.8 (s, 1C, CG),
Pt(C(CH3)21CH2-o-C6H4)(H)][BF4] (15b-L2) Mixture by Isobutylene
122.7 (s, 1C, CH), 121.4 (s, 1C, CF), 62.6, 62.4, 60.6 (s, 1C, 1C, 1C,
1
Insertion. H NMR (CDCl3, 298 K, δ): −19.1 (s, 1H, JPt−H = 1540
CA), 41.7 (s, 1C, C ), 33.8−32.3 (s, 6C, CB), 25.3−24.9 (s, 9C, CC and
β
1
Hz, Pt−H, 15a), −20.6 (s, 1H, JPt−H = 1620 Hz, Pt−H, 15b). Ratio:
1
CD), 8.1 (s, 1C, Cα, JPt,C = 834 Hz). HRMS (ESI): m/z calcd
797.3133 (M + H+), found 797.3168.
15a:15b = 4.7:1.
[κ3-TtPhPt(CHC(CH2)3-o-C6H4)(H)][BF4] (16a-L1/b-L1) Mixture by
Cyclopentene Insertion. TtPhPtPh2 (1; 0.030 g, 0.036 mmol) was
placed in a Schlenk flask under nitrogen. Methylene chloride (10 mL)
was added through the septum, and the solution was cooled to −78 °C
in a dry ice/isopropyl alcohol bath. The solution was treated with
HBF4·Et2O (4.5 μL, 0.035 mmol) and cyclopentene (16.4 μL, 0.18
mmol). The mixture was warmed to room temperature. The solvent
was removed by rotary evaporation and the resulting oil triturated with
pentane to afford a mixture of 16a and 16b as a white powder in high
[κ3-TtCyPt(CH2CH2-o-C6H4)(CH3)][OTf] (18-L2). 17-L2 (0.010 g,
0.013 mmol) was placed in a Schlenk flask under nitrogen. Methylene
chloride (10 mL) was added through the septum. The solution was
treated with 1.2 equiv of methyl triflate and stirred for 20 min. The
solvent was removed by rotary evaporation and the resulting oil
triturated with pentane to afford the alkylated product as a pale yellow
powder. H NMR showed quantitative conversion from 17-L2. H
NMR (CD2Cl2, 293 K, δ): 8.68, 8.65, 8.57 (s, 1H, 1H, 1H, TtCyCH),
7.15−6.78 (m, 4H, Pt−C6H4), 4.73, 4.66, 4.52 (m, 1H, 1H, 1H, CA−
1
1
yield by 1H NMR. 1H NMR (CDCl3, 298 K, δ): −19.3 (s, 1H, 1JPt−H
=
H), 2.58−1.29 (m, Pt−CH2CH2, cyclohexyl), 1.47 (s, Pt−CH3, 2JPt,H
=
1
1626 Hz, Pt−H, 16a), −19.9 (s, 1H, JPt−H = 1621 Hz, Pt−H, 16b).
Ratio: 16a:16b = 2.8:1. Complete spectroscopic characterization of
16a can be found in the Supporting Information.
74 Hz). 31P{1H} NMR (CD2Cl2, 293 K, δ): −7.9 (s, 1P, TtCyPO).
13C{1H} NMR (CD2Cl2, 293 K, δ): 155.9 (s, 1C, CK, 2JPt,C = 118 Hz),
1
135.9, 135.6, 135.3 (d, 1C, 1C, 1C, OPC, JP−C = 151 Hz each),
[κ3-TtCyPt(CHC(CH2)3-o-C6H4)(H)][BF4] (16a-L2/b-L2) Mixture by
131.2 (s, 1C, CI), 129.9, 129.8, 129.3 (d, 1C, 1C, 1C, OPCCH,
2JP−C = 24, 23, 23 Hz), 129.0 (s, 1C, CJ, 1JPt,C = 956 Hz), 125.3 (s, 1C,
1
Cyclopentene Insertion. H NMR (CDCl3, 298 K, δ): −19.4 (s, 1H,
1JPt−H = 1594 Hz, Pt−H, 16a), −20.0 (s, 1H, 1JPt−H = 1586 Hz, Pt−H,
3
3
CG), 124.9 (s, 1C, CH, JPt,C = 44 Hz), 123.9 (s, 1C, CF, JPt,C = 48
16b). Ratio: 16a:16b = 2.7:1.
Hz), 63.5, 63.0 (s, 2C, 1C, CA), 37.8 (s, 1C, C , 2JPt,C = 27 Hz), 33.7−
β
CO Trapping Reactions. [(κ3-TtPh)Pt(CO)(CH2CH2Ph)][BF4] (11-
L1). [TtPhPt(CH2CH2-o-C6H4)(H)][BF4] (10-L1; 0.015 g, 0.017
mmol) was weighed in an NMR tube. The tube was purged with CO,
and CD2Cl2 (0.6 mL) was added through the septum. The sample was
placed in an NMR tube spinner overnight at room temperature. 11-L1
was generated in 95% conversion by 1H NMR. 1H NMR (CD2H2, 295
K, δ): 9.35 (s, 3H, TtPhCH), 7.85−7.22 (m, 25H, TtPhC6H5 and Pt−
CH2CH2C6H5), 2.89, 2.72 (t, 2H, Pt−CH2CH2Ph). 31P{1H} NMR
(CD2Cl2, 291 K, δ): −4.9 (s, 1P, TtPhPO). 13C{1H} NMR (CD2Cl2,
284 K, δ): 161.3 (s, 1C, Pt−CO), 144.4 (s, 1C, Pt−CH2CH2Ph ipso-
Ph), 130.7 (s, 3C, TtPt p-Ph), 130.7, 130.4 (s, 6C, TtPh o-Ph), 128.9
(s, 2C, Pt−CH2CH2Ph o-Ph), 128.8 (s, 2C, Pt−CH2CH2Ph m-Ph),
126.4 (s, 2C, Pt−CH2CH2Ph p-Ph), 121.8, 121.6 (s, 2C, 4C TtPh
m-Ph), 38.5 (s, 1C, Pt−CH2CH2Ph), 12.5 (s, 1C, Pt−CH2CH2Ph). IR
(CH2Cl2 solution): νCO 2171 cm−1. HRMS (ESI): m/z calcd 807.1673
(M+), found 807.1658.
32.9 (s, 6C, CB), 25.2−24.8 (s, 9C, CC and CD), 21.7 (s, 1C, C , 1JPt,C
=
α
667 Hz), −6.0 (s, 1C, Pt−CH3, 1JPt,C = 690 Hz). HRMS (ESI): m/z calcd
811.3289 (M+), found 811.3301.
[κ3-TtCyPt(CH2CH2-o-C6H4)(CH2CHCH2)][I] (19-L2). 17-L2 (0.010
g, 0.013 mmol) was placed in a Schlenk flask under nitrogen.
Methylene chloride (10 mL) was added through the septum. The
solution was treated with 1.2 equiv of allyl iodide and stirred for 20
min. The solvent was removed by rotary evaporation and the resulting
oil triturated with pentane to afford the alkylated product as a pale
yellow powder. 1H NMR showed quantitative conversion from 17-L2.
1H NMR (CD2Cl2, 293 K, δ): 8.71, 8.70, 8.56 (s, 1H, 1H, 1H,
TtCyCH), 7.14−6.78 (m, 4H, Pt−C6H4), 5.76 (m, 1H, Pt−CH2CH
CH2), 4.85 (d, 1H, Pt−CH2CHCHtrans to H, 3JH,H = 17 Hz, 4JPt,H = 23
Hz), 4.75, 4.70, 4.51 (m, 1H, 1H, 1H, CA-H), 4.61 (dd, 1H, Pt−
CH2CHCHcis to H, 3JH,H = 10 Hz), 3.26−2.84 (m, 4H, Pt−CH2CH2),
2.29−1.25 (m, 30 H, cyclohexyl). 31P{1H} NMR (CD2Cl2, 293 K, δ):
−8.3 (s, 1P, TtCyPO). 13C{1H} NMR (CD2Cl2, 293 K, δ): 155.7 (s,
1C, CK, 2JPt,C = 109 Hz), 141.9 (s, 1C, Pt−CH2CHCH2, 2JPt,C = 60 Hz),
[(κ3-TtCy)Pt(CO)(CH2CH2Ph)][BF4] (11-L2). [TtCyPt(CH2CH2-o-
C6H4)(H)][BF4] (10-L2; 0.015 g, 0.017 mmol) was weighed in an
NMR tube. The tube was purged with CO, and CD2Cl2 (0.6 mL) was
added through the septum. The sample was placed in an NMR tube
spinner overnight at room temperature. 11-L1 was generated in 93%
1
136.0, 135.8, 135.6 (d, 1C, 1C, 1C, OPC, JP−C = 149 Hz each), 131.0
2
(s, 1C, CI), 130.1, 129.9, 129.3 (d, 1C, 1C, 1C, OPCCH, JP−C = 24,
2782
dx.doi.org/10.1021/om2010595 | Organometallics 2012, 31, 2770−2784

Organometallics
Article
26, 24 Hz), 129.1 (s, 1C, CJ), 125.4 (s, 1C, CG), 124.8 (s, 1C, CH,
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ASSOCIATED CONTENT
■
S
* Supporting Information
Text and figures giving representative 1H and 13C NMR
spectra, complete characterization data for complexes 15a-L1
and 16a-L1, and kinetic data. This material is available free of
charge via the Internet at http://pubs.acs.org.
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ACKNOWLEDGMENTS
■
We thank the National Science Foundation (Grant CHE-
1058675) for support of this research. Infrared spectroscopy
was performed by B. E. Frauhiger in the UNC EFRC
Instrumentation Facility funded by the UNC EFRC: Solar
Fuels and Next Generation Photovoltaics, an Energy Frontier
Research Center funded by the U.S. Department of Energy,
Office of Science, Office of Basic Energy Sciences under Award
Number DE-SC0001011, and by UNC SERC: “Solar Energy
Research Center Instrumentation Facility” funded by the U.S.
Department of Energy, Office of Energy Efficiency and
Renewable Energy under Award Number DE-EE0003188.
DEDICATION
■
2004, 126, 11160.
Dedicated to the memory of Prof. F. Gordon A. Stone.
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