Mechanistic comparison of β-H elimination, β-OH elimination, and nucleophilic displacement reactions of β-hydroxy alkyl rhodium porphyrin complexes

Article abstract of DOI:10.1039/c0dt01146k

This article reports on kinetic studies for three alternate pathways, including β-hydrogen elimination, β-hydroxy elimination, and intramolecular nucleophilic displacement reactions, for rhodium porphyrin β-hydroxy alkyl reactions in water and DMSO to form ketone, alkene, and epoxide, respectively. Comparisons of activation parameters for these processes indicate that the β-hydroxy elimination process has the lowest activation enthalpy in water, but the intramolecular nucleophilic displacement pathway predominates in DMSO.

Full text of DOI:10.1039/c0dt01146k

View Article Online / Journal Homepage / Table of Contents for this issue
This article is published as part of the Dalton Transactions themed issue entitled:
New Talent Asia
Highlighting the excellent work being carried out by younger members
of the inorganic academic community in Asia
Guest Editor Masahiro Yamashita
Tohoku University, Japan
Published in issue 10, 2011 of Dalton Transactions
Image reproduced with permission of Kenneth Kam-Wing Lo
Articles in the issue include:
PERSPECTIVES:
Pyrazolin-4-ylidenes: a new class of intriguing ligands
Yuan Han and Han Vinh Huynh, Dalton Trans., 2011, DOI: 10.1039/C0DT01037E
Solvent induced molecular magnetic changes observed in single-crystal-to-single-crystal
transformation
Zheng-Ming Hao and Xian-Ming Zhang, Dalton Trans., 2011, DOI: 10.1039/C0DT00979B,
ARTICLES:
Negative thermal expansion emerging upon structural phase transition in ZrV2O7 and HfV2O7
Yasuhisa Yamamura, Aruto Horikoshi, Syuma Yasuzuka, Hideki Saitoh and Kazuya Saito
Dalton Trans., 2011, DOI: 10.1039/C0DT01087A
Preparation of surface molecularly imprinted Ru-complex catalysts for asymmetric transfer
hydrogenation in water media
Zhihuan Weng, Satoshi Muratsugu, Nozomu Ishiguro, Shin-ichi Ohkoshi and Mizuki Tada
Dalton Trans., 2011, DOI: 10.1039/C0DT00950D
Visit the Dalton Transactions website for more cutting-edge inorganic and organometallic research
www.rsc.org/dalton

Dynamic Article Links
Dalton
Transactions
Cite this: Dalton Trans., 2011, 40, 2213
www.rsc.org/dalton
PAPER
Mechanistic comparison of b-H elimination, b-OH elimination, and
nucleophilic displacement reactions of b-hydroxy alkyl rhodium porphyrin
complexes
Bing Wu, Jiadi Zhang, Lin Yun and Xuefeng Fu*
Received 1st September 2010, Accepted 1st November 2010
DOI: 10.1039/c0dt01146k
This article reports on kinetic studies for three alternate pathways, including b-hydrogen elimination,
b-hydroxy elimination, and intramolecular nucleophilic displacement reactions, for rhodium porphyrin
b-hydroxy alkyl reactions in water and DMSO to form ketone, alkene, and epoxide, respectively.
Comparisons of activation parameters for these processes indicate that the b-hydroxy elimination
process has the lowest activation enthalpy in water, but the intramolecular nucleophilic displacement
pathway predominates in DMSO.
alkene product to reach a four-centered transition state. The BOE
Introduction
processes can be viewed as the microscopic reverse of nucleophilic
Metal catalyzed oxidation of alkenes leads to the formation
attack by hydroxide on an alkene coordinated to a transition
metal complex.15,16 There are relatively few reports of direct C–O
bond formation through nucleophilic displacement reaction,7,17,18
and IND processes to form sp3-carbon–oxygen bonds are also
not common.17 Although each of these processes including BHE,
BOE, and IND has been extensively studied, direct observation
and comparison of all three processes occurring for a single b-
hydroxy metal alkyl complex in water has not been previously
reported. Comparison of these three processes provided insights
into obtaining selectivity in catalytic oxidation of alkenes and
may lead to the development of water soluble catalysts useful
for a wide range of “green” oxidation chemistry. This article
reports on kinetic studies for these three alternate pathways for
rhodium porphyrin b-hydroxy alkyl reactions in water and DMSO.
Comparisons of activation parameters for these processes indicate
that the BOE process has the lowest activation enthalpy in water,
but the IND pathway predominates in DMSO.
of a variety of value-added organic products including ke-
tones/aldehydes, carboxylic acids, epoxides, and diols where b-
hydroxy alkyl metal complexes (M-CH2CH(OH)R) have been
reported to be the intermediates in the catalytic oxidation
processes.1–8 Generally, the M-CH2CH(OH)R may undergo (1)
b-hydrogen elimination (BHE) reactions to form enols and metal
hydride, (2) b-oxygen elimination (BOE) reactions to form alkenes
and metal cation, or (3) intramolecular nucleophilic displacement
(IND) reactions to form epoxides and metal anion (Scheme 1).
Results
Scheme 1 Three possible pathways for conversion of b-hydroxy metal
alkyl complexes.
Tetra (p-sulfonatophenyl) porphyrin rhodium b-hydroxy alkyl
complex (TSPP)Rh-CH2CH(OH)CH2CH2CH2OH (1) was pre-
pared and purified following our previously reported method.16
The kinetic studies for reactions of 1 were run in J. Young Valve
NMR tubes. The organic products were extracted into CDCl3,
Beta hydrogen elimination (BHE) reactions are among the most
important fundamental organometallic transformations which are
ubiquitously observed in a variety of transition metal alkyl and
alkoxide complexes.9–14 Extensive mechanistic studies of metal
alkyl complexes have revealed that BHE is a facile process when
the complexes have a vacant cis coordination site for binding of the
1
and the H NMR and GC-MS are compared with commercially
available samples of alkenes and ketones.
BHE of (TSPP)Rh-CH2CH(OD)CH2CH2CH2OD in D2O to
form (TSPP)RhI/(TSPP)Rh-D and 5-hydroxypentan-2-one
Beijing National Laboratory for Molecular Sciences, State Key Lab of Rare
Earth Materials Chemistry and Applications, Peking University, Beijing,
100871, China. E-mail: fuxf@pku.edu.cn; Fax: +86 10 6275 1708; Tel: +86
10 6275 6035
The kinetics of thermal dissociation of 1 resulting in the formation
of (TSPP)RhI/(TSPP)Rh-D and 5-hydroxypentan-2-one (eqn (1))
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 2213–2217 | 2213
©

at different pH values (pH = 8–12) at 338 K were studied by
following the progress of the reaction by 1H NMR.
(TSPP)Rh-CH2CH(OD)CH2CH2CH2OD ꢀ
(1)
(TSPP)RhI/(TSPP)Rh-D + CH3C(O)CH2CH2CH2OD
The rate plots showed that the reaction rates were first order in
complex 1 and the rate constant kobs decreased with increasing pH
value (Fig. 1).
Scheme 2 Thermal reaction of 18O-labeled complexes 1 in water.
Fig. 1 The thermal dissociation rates of 1 at 338 K in buffers of pH 8–12,
respectively. The kobs was measured from first-order decay of the intensity
of pyrrole hydrogen resonances of 1 by 1H NMR. [1]0 = 2.9 ¥ 10-3 M. The
yields were calculated based on the ratio of intensity integration of the
resulting products with internal standard.
Fig. 2 BHE kinetics of 1 in pH = 8.0 buffers at 318 ~ 338 K. [1]0 = 4.4
¥ 10-3 M. Activation enthalpy (DH‡) and entropy (DS‡) for BHE of 1 are
estimated as 24.2 0.9 kcal mol-1 and -1.8 3.0 cal mol-1K-1.
BOE of (TSPP)Rh-CH2CH(OD)CH2CH2CH2OD in D2O to
form (TSPP)RhIII and 4-penten-1-ol
The thermal dissociation of 18O-labeled complexes
1
(TSPP)Rh-CH2CH(18OH)CH2CH2CH2OH exclusively resulted in
the formation of CH3C(18O)CH2CH2CH2OH in H218O while
CH3C(16O)CH2CH2CH2OH formed in H216O from GC-MS anal-
ysis (Scheme 2). The loss of 18O in the product when the reaction
was performed in H216O suggested that both the forward (k1)
and reverse (k-1) reaction occurred before BHE (k2) occurred,
i.e. k1> k-1>k2. So the kobs is dominated by the BHE rate, k2
(Scheme 2).
Addition of strong donor ligands such as pyridine, pyrrolidine,
and butylamine to an aqueous solution of 1 resulted in an
immediate color change from red to pink and the high field H
NMR resonances for the Rh-alkyl group of 1 shifted significantly
indicative of adduct formation. The 1H NMR changes upon
pyridine complex formation with 1 (1(py)) are shown in Fig. 3
(eqn (2)).
1
The activation parameters of BHE of 1 were obtained by
measuring the rate constant in pH = 8.0 buffers through the
temperature range of 318–338 K. The first order rate kinetics at
[(TSPP)Rh-CH2CH(OD)CH2CH2CH2OD(D2O)]-4 + py ꢀ
(2)
[(TSPP)Rh-CH2CH(OD)CH2CH2CH2OD(py)]-4 + D2O
1
different temperatures from H NMR spectroscopy (Fig. 2) gave
Heating the solution of 1 with 10 equiv. of pyridine at 353 K for
the activation enthalpy (DH‡) and entropy (DS‡) for BHE of 1
which are estimated as 24.2 0.9 kcal mol-1 and -1.8 3.0 cal
mol-1K-1, respectively, according to the Eyring plot (Fig. 2).
35 min, both RhIII(py)2 and 4-penten-1-ol were formed with 95%
1
yields as observed by H NMR spectroscopy and GC-MS (eqn
(3), Table 1).
2214 | Dalton Trans., 2011, 40, 2213–2217
This journal is
The Royal Society of Chemistry 2011
©

Table 1 Thermal dissociation of 1 at 353 K with different ligands
Product
Entry
Ligand
Time
BHE
BOE
1
2
3
4
5
6
D2O/OD-(pH = 9)
Triethylamine
CD3OD
Pyrrolidine
Pyridine
3 h
2 h
2 h
45 min
35 min
25 min
90%
90%
82%
9%
<5%
0%
10%
10%
NA
91%
>95%
100%
n-butylamine
Fig. 3 High field 1H NMR (400 MHz) for 1 in D2O. (A) before addition
of pyridine, (B) after addition of pyridine.
[(TSPP)Rh-CH2CH(OD)CH2CH2CH2OD(py)]-4 + py ꢀ
(3)
[(TSPP)RhIII(py)2]-3 + CH2 CHCH2CH2CH2OD + OD-
Fig. 4 BOE kinetics of 1 in pH = 9.0 buffers at 288–308 K. [1]0 = 2.9 ¥
10-3 M. Activation enthalpy (DH‡) and entropy (DS‡) for BOE of 1 are
estimated as 16.4 0.6 kcal mol-1 and -19.9 2.0 cal mol-1K-1.
The rate constants for BOE of 1 (eqn (3)) at 288–308 K in
pH = 9.0 buffers with addition of 30 equiv. of pyrrolidine gave the
activation enthalpy (DH‡) and entropy (DS‡) 16.4 0.6 kcal mol-1
and -19.9 2.0 cal mol-1 K-1, respectively (Fig. 4).
in an immediate color change from orange–yellow to orange–
red and the high field resonances of Rh-alkyl group in 1H NMR
changed significantly indicating pyrrolidine coordinated trans to
the (TPP)Rh-alkyl group. However, complex 2 was stable and no
further reaction occurred after heating at 353 K for 24 h.
Thermal dissociation of (TSPP)Rh-CH2CH(OH)(CH2)3OH in
DMSO
Groves previously reported a facile C–O reductive elimina-
tion from b-hydroxy alkyl complexes of rhodium tetraphenyl
porphyrin in KOtBu/C6D6 by a proposed SN2 pathway.17 The
KOH/DMSO solution of complex 1 underwent immediate (<5
min) IND at room temperature to form (TSPP)RhI and 1,2-
epoxyalkanes in quantitative yield which was observed by both 1H
NMR and GC-MS (eqn (4)). The six-membered-ring product 3-
hydroxytetrahydropyran that would result from IND of the distal
hydroxyl group was not observed. The IND process is sufficiently
more favorable kinetically over the BHE and BOE processes that
neither the ketone product from BHE nor the alkene product from
BOE was observed in KOH/DMSO medium.
Discussion
The mechanistic details of BHE of porphyrin rhodium alkyl
complexes where porphyrin ligand blocks the cis coordination
site are not yet known. Metal complexes that lack a cis co-
ordination site such as coenzyme B12, generally undergo BHE
by a radical pathway through homolysis of the Co–C bond.
Many tetraazamacrocyclic transition metal complexes were used
as model molecules of coenzyme B12 to elucidate mechanistic
features of this rare BHE process by trapping the intermediates.19–22
The reported BHE of porphyrin rhodium alkyl complexes in
hydrocarbon media most probably occurs by bond homolysis
to form metal-centered and alkyl radicals.22,23 Observation of
BHE for (TSPP)Rh-CH2CH(OH)R in water compared with the
absence of BHE for (TPP)Rh-CH2CH(OH)R in benzene along
with TEMPO not affecting the BHE rate supports a non-radical
pathway in water.
(4)
Reactions of (TPP)Rh-CH2CH(OH)CH2CH2CH2CH3 in
hydrocarbon media
When the analogous complex tetraphenyl porphyrin rhodium b-
hydroxy hexyl (TPP)Rh-CH2CH(OH)CH2CH2CH2CH3 (2), was
heated in benzene at 353 K for 24 h, no products from BHE,
BOE, or IND were observed by H NMR or GC-MS. Addition
of pyrrolidine or other amines to a C6D6 solution of 2 resulted
Effect of adduct formation on the reactivity of 1
Dramatic decrease of the reaction rate of BHE with increasing pH
values of the solution (Fig. 1) may result from hydroxide occupying
the sixth coordination site as a more strongly bound ligand than
1
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 2213–2217 | 2215
©

D2O. Strong bonding of ligands to the metal b-hydroxy alkyl
complex is expected to slow down or entirely shut off the BHE
reaction. The loss of O18 in the product when BHE of (TSPP)Rh-
CH2CH(18OH)CH2CH2CH2OH occurs in H2O16 indicates that k-1
is much larger than k2 (Scheme 2) and BOE is highly favored
over BHE in water. The BOE is an unproductive process due
to the relatively fast reversible b-hydroxyalkyl complex formation
in basic aqueous solution. Nitrogen donor ligands like pyridine
tenaciously bind to (TSPP)RhIII to form (TSPP)RhIII(py)2 (eqn (3))
(Scheme 3) which blocks the coordination site for alkene binding
and direct the reaction exclusively toward product formation by
BOE.
Scheme 4 BHE, BOE and IND of b-hydroxy alkyl rhodium porphyrin
complexes.
Experimental
General considerations
D2O, DMSO-d6 and CDCl3 were purchased from Cambridge
Isotope Laboratory Inc., tetra (p-sulfonatophenyl) porphyrin from
Tokyo Chemical Industry (TCI), (Rh(CO)2Cl)2 from Stream, and
all other chemicals were purchased from Aldrich or Alfa Aesar
unless otherwise noted and used as received. Room temperature
1H NMR spectra were recorded on a Bruker AV-400 spectrometer
and variant temperature 1H NMR spectra on a Bruker AV-
600 spectroscopy. The chemical shifts were referenced to 3-
trimethylsilyl-1-propanesulfonic acid sodium salt. The products of
dissociation of complex 1 were extracted by CDCl3 for 1H NMR
and GC-MS analysis.
Scheme 3 The proposed mechanism for BOE of b-hydroxyalkyl rhodium
porphyrin complexes.
Solvent effects on reaction pathways
Both BHE and BOE were observed when the reactions were
run in water. However, the analogous complex of 1, (TPP)Rh-
CH2CH(OH)CH2CH2CH2CH3 (2) showed no reactivity with and
without nitrogen ligand in benzene.24 The facile BOE and BHE
in water which were not observed in benzene most probably
resulted from the efficacy of ionic pathways for these processes
in water.16,25 The origin of rapid and selective formation of
epoxide in KOH/DMSO solution may be due to the enhanced
nucleophilicity of the alkoxy group which is dramatically reduced
in water due to the solvation. And the favored formation of
three-membered oxygen heterocycles through IND is driven by
the strong nucleophilicity of the alkoxy group formed from
deprotonation in strong basic conditions of the KOH/DMSO
medium.
Preparation of (TSPP)Rh-CH2CH(OD)CH2CH2CH2OD (1) in
water
Tetra (p-sulfonatophenyl) porphyrin rhodium complexes
(TSPP)RhIII (1.1 mg, 0.001 mmol) and 4-penten-1-ol (0.01 mmol)
were dissolved in 0.4 mL borate buffer D2O solution (pH = 9.0)
in J. Young Valve NMR tubes at room temperature, respectively.
The reaction reached completion within 5 min.
Typical procedure for b-hydrogen elimination of (1) in water
Comparisons of activation parameters
The (1) was dissolved in fresh D2O in the J. Young Valve
NMR tube and subjected to three freeze–pump–thaw cycles.
The sample was heated in a water bath and the progress of
the reaction was monitored by 1H NMR spectroscopy. When
the reactions reached completion where all the (TSPP)Rh-
CH2CH(OD)CH2CH2CH2OD complex was converted to ketones
and (TSPP)RhI.
The activation enthalpy of BHE was 8.3 kcal mol-1 higher than that
of the BOE process which accounted for the favorable formation
of RhIII(py)2 and 4-penten-1-ol through the lower energy pathway
of the BOE reaction. The small DS‡ value for the b-H process
is consistent with an intramolecular elimination although further
details for this reaction mechanism are not yet known. The large
negative value of DS‡ of BOE may result from a second amine
binding with the pyridine adduct of 1.
Thermal reactions of 18O-labeled
(TSPP)Rh-CH2CH(18OH)CH2CH2CH2OH
Conclusions
The 18O-labeled complex 1 was obtained by adding 4-penten-1-
ol (0.01 mmol) to the 0.4 mL borate buffer H218O solution of
(TSPP)RhIII (1.1 mg, 0.001 mmol) in a J. Young Valve NMR tube
and the extra alkene was extracted by Et2O. After solvent H218O
was pumped out, fresh H218O was added to 18O-labeled complexes
1. The solution was heated at 353 K for 4 h after degassing.
The product, mono 18O-substituted-5-hydroxypentan-2-one
(CH3C(18O)CH2CH2CH2OH), was extracted into Et2O and
Rhodium porphyrin b-hydroxyalkyl complexes ((TSPP)Rh-
CH2CH(OH)CH2CH2CH2OH) in water undergo BHE to form
(TSPP)Rh–H and ketones, nitrogen donor ligands direct the
reaction toward irreversible BOE to form alkenes by produc-
ing coordinately saturated complexes of (TSPP)RhIII, but in
KOH/DMSO exclusive formation of epoxides occurs by an IND
process (Scheme 4). Reactivity studies and activation parameters
indicate that the BOE reaction is highly favored over BHE and
IND in water.
examined by GC-MS.
A parallel sample of (TSPP)Rh-
CH2CH(18OH)CH2CH2CH2OH in H216O was also heated under
2216 | Dalton Trans., 2011, 40, 2213–2217
This journal is
The Royal Society of Chemistry 2011
©

the same reaction conditions resulting in 5-hydroxypentan-2-one
(CH3C(16O)CH2CH2CH2OH) which was extracted by Et2O for
GC-MS analysis.
9 (a) O. Blum and D. Milstein, J. Am. Chem. Soc., 1995, 117, 4582; (b) A.
Vigalok, H. B. Kraatz, L. Konstantinovsky and D. Milstein, Chem.–
Eur. J., 1997, 3, 253; (c) M. E. Van Der Boom, C. L. Higgitt and D.
Milstein, Organometallics, 1999, 18, 2413; (d) O. Blum and D. Milstein,
J. Organomet. Chem., 2000, 593–594, 479.
10 (a) E. J. Alexanian and J. F. Hartwig, J. Am. Chem. Soc., 2008, 130,
15627; (b) J. Zhao, H. Hesslink and J. F. Hartwig, J. Am. Chem. Soc.,
2001, 123, 7220; (c) C. Krug and J. F. Hartwig, J. Am. Chem. Soc., 2002,
124, 1674.
11 (a) J. X. McDermott, J. F. White and G. M. Whitesides, J. Am. Chem.
Soc., 1976, 98, 6521; (b) J. A. Keith, J. Oxgaard and W. A. Goddard
III, J. Am. Chem. Soc., 2006, 128, 3132; (c) K. A. Bernard, W. M. Rees
and J. D. Atwood, Organometallics, 1986, 5, 390; (d) J. C. M. Ritter
and R. G. Bergman, J. Am. Chem. Soc., 1998, 120, 6826; (e) J. Vela, S.
Vaddadi, T. R. Cundari, J. M. Smith, E. A. Gregory, R. J. Lachicotte,
J. Flaschenriem and P. L. Holland, Organometallics, 2004, 23, 5226;
(f) D. M. Hoffman, D. Lappas and D. A. Wierda, J. Am. Chem. Soc.,
1989, 111, 1531.
12 (a) H. E. Bryndza, J. C. Calabrese, M. Marsi, D. C. Roe, W. Tam and J.
E. Bercaw, J. Am. Chem. Soc., 1986, 108, 4805; (b) P. J. Chirik and J. E.
Bercaw, Organometallics, 2005, 24, 5407; (c) P. J. Chirik, M. W. Day, J.
A. Labinger and J. E. Bercaw, J. Am. Chem. Soc., 1999, 121, 10308.
13 (a) J. P. Collman, A. S. Chien, T. A. Eberspacher and J. I. Brauman,
J. Am. Chem. Soc., 1998, 120, 425; (b) J. P. Collman and R. Boulatov,
Inorg. Chem., 2001, 40, 560.
Kinetics of BHE of (1) in pH = 8.0 buffers at 318–338 K
The degassed samples containing complex 1 and 10 equiv. of 4-
penten-1-ol in pH = 8.0 buffers were heated in a water bath at
318–338 K, and the progress of the reaction was monitored by
1H NMR spectroscopy. The BHE kinetics data were obtained
1
from the integration ratio of pyrrole hydrogen resonances in H
NMR of 1 and (TSPP)RhI. First order rate kinetics were observed
1
at different temperatures from H NMR spectroscopy and the
activation enthalpy (DH‡) and entropy (DS‡) of the BHE of 1 are
derived according to the Eyring plot.
BHE of (1) in pH = 9.0 buffers at 353 K with TEMPO
The degassed sample containing complex 1 and TEMPO in pH =
9.0 buffer D2O solution in a J. Young Valve NMR tube was heated
in a water bath at 353 K for 4 h. After the reactions reached
completion, ketones and (TSPP)RhI were confirmed by 1H NMR
spectroscopy.
14 (a) N. A. Smythe, K. A. Grice, B. S. Williams and K. I. Goldberg,
Organometallics, 2009, 28, 277; (b) T. R. Cundari and C. D. Taylor,
Organometallics, 2003, 22, 4047; (c) I. Matas, J. Ca´mpora, P. Palma and
´
E. Alvarez, Organometallics, 2009, 28, 6515; (d) J. Muzart, Tetrahedron,
2007, 63, 7505.
Kinetics of BOE of (1) in pH = 9.0 buffers at 288–308 K
15 (a) R. Pryadun, D. Sukumaran, R. Bogadi and J. D. Atwood, J. Am.
Chem. Soc., 2004, 126, 12414; (b) R. S. Pryadun and J. D. Atwood,
Organometallics, 2007, 26, 4830.
The complex 1 and 30 equiv. of pyrrolidine in pH = 9.0 buffers
were transferred to J. Young Valve NMR tubes and degassed. The
progress of the reaction was monitored by 1H NMR spectroscopy
in the range of 288–308 K. First order rate kinetics were observed
16 X. Fu, S. Li and B. B. Wayland, J. Am. Chem. Soc., 2006, 128, 8947.
17 (a) Y. Han, M. S. Sanford, M. D. England and J. T. Groves, Chem.
Commun., 2006, 549; (b) M. S. Sanford and J. T. Groves, Angew. Chem.,
Int. Ed., 2004, 43, 588.
18 (a) B. S. Williams and K. I. Goldberg, J. Am. Chem. Soc., 2001, 123,
2576; (b) B. S. Williams, A. W. Holland and K. I. Goldberg, J. Am.
Chem. Soc., 1999, 121, 252; (c) A. J. Canty, M. C. Denney, G. Koten,
B. W. Skelton and A. H. White, Organometallics, 2004, 23, 5432; (d) U.
Fekl and K. I. Goldberg, Adv. Inorg. Chem., 2003, 54, 259; (e) A.
N. Vedernikov, S. A. Binfield, P. Y. Zavalij and J. R. Khusnutdinova,
J. Am. Chem. Soc., 2006, 128, 82; (f) J. R. Khusnutdinova, P. Y.
Zavalij and A. N. Vedernikov, Organometallics, 2007, 26, 3466; (g) J.
R. Khusnutdinova, L. L. Newman, P. Y. Zavalij, Y.-F. Lam and A. N.
Vedernikov, J. Am. Chem. Soc., 2008, 130, 2174.
19 (a) G. N. Schrauzer and J. H. Grate, J. Am. Chem. Soc., 1981, 103,
541; (b) J. H. Grate and G. N. Schrauzer, J. Am. Chem. Soc., 1979, 101,
4601.
20 (a) B. P. Hay and R. G. Finke, J. Am. Chem. Soc., 1987, 109, 8012;
(b) G. N. Schrauzer, J. H. Weber and T. M. Beckham, J. Am. Chem.
Soc., 1970, 92, 7079.
21 (a) T. Tsou, M. Loots and J. Halpern, J. Am. Chem. Soc., 1982, 104,
623–624; (b) J. Halpern, Acc. Chem. Res., 1982, 15, 238–244; (c) M.
P. Jensen and J. Halpern, J. Am. Chem. Soc., 1999, 121, 2181; (d) M.
Okazaki, H. Tobita and H. Ogino, Dalton Trans., 2003, 493.
22 (a) K. J. Del Rossi and B. B. Wayland, J. Am. Chem. Soc., 1985, 107,
7941; (b) B. B. Wayland, S. L. V. Voorhees and K. J. Del Rossi, J. Am.
Chem. Soc., 1987, 109, 6513.
23 (a) K. W. Mak and K. S. Chan, J. Am. Chem. Soc., 1998, 120, 9686;
(b) S. K. Yeung and K. S. Chan, Organometallics, 2005, 24, 2561; (c) K.
W. Mak, F. Xue, T. C. W. Mak and K. S. Chan, Dalton. Trans., 1999,
3333.
24 (TPP)Rh-CH2CH(OH)CH2CH2CH2CH3 was synthesized following
reference 17a. To a solution of 10 mg (TPP)Rh–I in 10 mL of degassed
ethanol, 0.5 mL of 0.5 N aqueous NaOH solution containing 5 mg
NaBH4was added. The mixture was degassed and stirred at 60 ◦C for
2 h and then cooled down to room temperature. 1,2-expoxyhexane
(2 mL) was added and the product was isolated by chromatographic
column.
25 (a) J. Zhang, B. B. Wayland, L. Yun, S. Li and X. Fu, Dalton Trans.,
2010, 39, 477; (b) J. Zhang, B. B. Wayland, L. Yun, S. Li and X. Fu,
Dalton Trans., 2010, 39, 477; (c) L. Liu, M. Yu, B. B. Wayland and X.
Fu, Chem. Commun., 2010, 46, 6353.
1
at different temperatures from H NMR spectroscopy. The first
order rate kinetics of BOE at different temperatures gave activation
enthalpy (DH‡) and entropy (DS‡) of the BOE of 1 according to
the Eyring plot.
The IND of (TSPP)Rh-CH2CH(OH)CH2CH2CH2OH in DMSO
The (TSPP)Rh-CH2CH(OH)CH2CH2CH2OH was dissolved in
KOH/DMSO-d6 (cKOH = 3.3 mg mL-1) under an argon atmosphere
in vacuum adapted NMR tubes and the solution underwent a
color change to a brownish solution within minutes at room tem-
perature. 1H NMR spectra confirmed the formation of (TSPP)RhI.
The resulting 4,5-epoxypentan-1-ol was extracted into Et2O and
examined by GC-MS.
Notes and references
1 B. de Bruin, P. H. M. Budzelaar and A. W. Gal, Angew. Chem., Int.
Ed., 2004, 43, 4142.
2 C. Hahn, Chem.–Eur. J., 2004, 10, 5888–5899.
3 A. R. Chianese, S. J. Lee and M. R. Gagne´, Angew. Chem., Int. Ed.,
2007, 46, 4042.
4 K. M. Gligorich and M. S. Sigman, Chem. Commun., 2009, 3854.
5 S. S. Stahl, Angew. Chem., Int. Ed., 2004, 43, 3400–3420.
6 T. Punniyamurthy, S. Velusamy and J. Iqbal, Chem. Rev., 2005, 105,
2329–2363.
7 C. Liu, C. F. Bender, X. Han and R. A. Widenhoefer, Chem. Commun.,
2007, 3607.
8 (a) D. Dolphin, A. Matsumoto and C. Shortman, J. Am. Chem.
Soc., 1989, 111, 411; (b) Y. S. Lin, S. Takeda and K. Matsumoto,
Organometallics, 1999, 18, 4897; (c) N. Saeki, N. Nakamura, T.
Ishibashi, M. Arime, H. Sekiva, K. Ishihara and K. Matsumoto, J. Am.
Chem. Soc., 2003, 125, 3605; (d) D. J. Nelson, R. Li and C. Brammer,
J. Am. Chem. Soc., 2001, 123, 1564.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 2213–2217 | 2217
©