Reactions of an arylrhodium complex with aldehydes, imines, ketones, and alkynones. New classes of insertion reactions

Article abstract of DOI:10.1021/om0496582

Organorhodium complexes of the general formula (DPPE)Rh(pyridine)(R) (R = p-tol (2a) and CH₂SiMe₃ (2b), DPPE = 1,2- bis(diphenylphosphino)ethane) were prepared from [(DPPE)-Rh(μ-Cl)] ₂, pyridine, and p-tolyllithium or Me₃SiCH ₂MgCl. Complex 2a inserted the electron-poor aldimines (p-tol)CH=N(C₆H₄-p-CO₂Me) (3a-Tol) and (Ph)CH-N(C₆H₄-p-CO₂Me) (3a-Ph) to give amide complexes that were isolated directly or trapped with PEt₃. In contrast, the reaction of aryl complex 2a with the electron-neutral and electron-rich imines PhCH = NPh (3b) and (p-tol)CH=N(C₆H ₄-p-OMe) (3c) did not form stable amide products. Instead, the amide from insertion of imines 3b or 3c underwent β-hydrogen elimination, followed by metalation of the resulting ketimine. The reaction of 2a with 3a-Ph was first order in arylrhodium complex and inverse first order in the concentration of pyridine. Aldehydes that cannot enolize, such as PhCHO and Me₃CCHO, inserted into the Rh-aryl bond of 2a to form ketones and esters. The esters were formed from insertion of a second aldehyde into the Rh-O bond of an intermediate alkoxide, followed by β-hydride elimination. Complex 2a underwent proton transfer with acetophenone to give π-oxaallyl complex 24 and with water to generate toluene and the dimeric hydroxide [(DPPE)Rh(μ-OH)]₂ (36). It also reacted with the tert-butyl-substituted ynone 25 to form a product that contained a metalated isobutyl group. Quenching the reaction between aryl complexes 2a and 3a-Ph with H₂O instead of PEt₃ also formed hydroxide 36 and the diarylmethylamine (Ph)(p-tol)CH-NH(C₆H₄-p-CO ₂-Me) (35).

Full text of DOI:10.1021/om0496582

4594
Organometallics 2004, 23, 4594-4607
Rea ction s of a n Ar ylr h od iu m Com p lex w ith Ald eh yd es,
Im in es, Keton es, a n d Alk yn on es. New Cla sses of
In ser tion Rea ction s
Christopher Krug and J ohn F. Hartwig*
Department of Chemistry, Yale University, P.O. Box 208107,
New Haven, Connecticut 06520-8107
Received May 13, 2004
Organorhodium complexes of the general formula (DPPE)Rh(pyridine)(R) (R ) p-tol (2a )
and CH2SiMe3 (2b), DPPE ) 1,2-bis(diphenylphosphino)ethane) were prepared from [(DPPE)-
Rh(µ-Cl)]2, pyridine, and p-tolyllithium or Me3SiCH2MgCl. Complex 2a inserted the electron-
poor aldimines (p-tol)CHdN(C6H4-p-CO2Me) (3a -Tol) and (Ph)CHdN(C6H4-p-CO2Me) (3a -
P h ) to give amide complexes that were isolated directly or trapped with PEt3. In contrast,
the reaction of aryl complex 2a with the electron-neutral and electron-rich imines PhCHd
NPh (3b) and (p-tol)CHdN(C6H4-p-OMe) (3c) did not form stable amide products. Instead,
the amide from insertion of imines 3b or 3c underwent â-hydrogen elimination, followed by
metalation of the resulting ketimine. The reaction of 2a with 3a -P h was first order in
arylrhodium complex and inverse first order in the concentration of pyridine. Aldehydes
that cannot enolize, such as PhCHO and Me3CCHO, inserted into the Rh-aryl bond of 2a
to form ketones and esters. The esters were formed from insertion of a second aldehyde into
the Rh-O bond of an intermediate alkoxide, followed by â-hydride elimination. Complex 2a
underwent proton transfer with acetophenone to give π-oxaallyl complex 24 and with water
to generate toluene and the dimeric hydroxide [(DPPE)Rh(µ-OH)]2 (36). It also reacted with
the tert-butyl-substituted ynone 25 to form a product that contained a metalated isobutyl
group. Quenching the reaction between aryl complexes 2a and 3a -P h with H2O instead of
PEt3 also formed hydroxide 36 and the diarylmethylamine (Ph)(p-tol)CH-NH(C6H4-p-CO2-
Me) (35).
In tr od u ction
this elementary reaction is part of many catalytic
processes.24 Insertions of imines, aldehydes, and ketones
into the metal-carbon or -hydrogen linkages of analo-
gous complexes to form metal amides or alkoxides are
less common, and direct observation of this elementary
reaction is particularly rare.25-29
Nevertheless, late transition metal-catalyzed reac-
tions of aldehydes and imines that are likely to occur
by insertion of aldehydes or imines have emerged
recently. For example, additions of aryl and vinyl groups
to R,â-unsaturated carbonyl compounds, aldehydes, and
imines catalyzed byrhodium30,31 and other late metals32-76
have become a versatile method for the construction of
Insertions of alkenes into the metal-carbon bonds of
late transition metal complexes are common,1-23 and
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10.1021/om0496582 CCC: $27.50 © 2004 American Chemical Society
Publication on Web 08/24/2004

New Classes of Insertion Reactions
Organometallics, Vol. 23, No. 20, 2004 4595
Sch em e 1
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These insertions would be analogous to classic insertions
of alkenes into metal-carbon bonds.
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insertion of aldehydes into acyclic late metal-carbon
bonds was unknown.25
1,2-Insertions of imines into late metal-carbon bonds
have not been reported. Arndtsen and Sen have de-
scribed insertions of imines into Ni- and Pd-acyl
linkages, but these reactions occur with 2,1-insertion
regiochemistry and generate a metal-carbon bond.77-80
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imine into a late metal-hydrogen bond to form a
transition metal amide complex as product.29
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tions of alkenes into discrete late metal hydride and
alkyl complexes and the small number of insertions of
aldehydes and imines with analogous complexes may
result from unfavorable thermodynamic and kinetic
factors. The insertion of an aldehyde or imine cleaves a
stronger C-X π-bond than does the insertion of an
olefin81 and forms a product with an alkoxo or amido
group that is matched less favorably with a soft metal
center than is an alkyl group from olefin insertion. In
addition, stable aldimines bear substituents at N and
C and are, therefore, more hindered than R-olefins.
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nitrogen lone pair, and complexes with such σ-bound
imines are less likely to undergo insertion than those
with π-bound imines. Recent theoretical work by Cavallo
support these claims, and an activation barrier for 2,1-
insertion of an imine into a Pd-methyl bond was found
to be greater than 40 kcal/mol.82 The computed barrier
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4596 Organometallics, Vol. 23, No. 20, 2004
Krug and Hartwig
Sch em e 2
p-tol, o-tol, Me) inserted aromatic aldehydes to form
alkoxide intermediates. However, these complexes were
unreactive toward imines. To promote insertions of
imines, we sought to study complexes that contained
an aryl group located cis to a ligand that is more labile
than PPh3 or CO. To prepare complexes with such a
coordination sphere, we targeted arylrhodium complexes
with one chelating phosphine and one pyridine ligand.
Herein we describe the preparation of arylrhodium(I)
complex (DPPE)Rh(py)(p-tol) (2a , DPPE ) 1,2-bis-
(diphenylphosphino)ethane, py ) pyridine) and its
unusual reactivity with imines, aldehydes, ketones, and
alkynones. Portions of this work have been reported in
communication form.26
F igu r e 1. ORTEP diagram of (DPPE)Rh(py)(p-tol) 2a .
Ta ble 1. Selected In tr a m olecu la r Bon d Dista n ces
a n d An gles for (DP P E)Rh (p yr id in e)(p-tolyl) (2a )
Bond Distances (Å)
Resu lts a n d Discu ssion
Rh(1)-C(27)
Rh(1)-N(1)
2.097(3)
2.132(3)
Rh(1)-P(1)
Rh(1)-P(2)
2.1797(8)
2.2481(8)
P r ep a r a tion of Or ga n or h od iu m (I) Com p lexes.
To enhance the reactivity of arylrhodium complexes83-94
toward insertion of aldehydes and imines, we sought
complexes with dative ligands bound less tightly than
those in the rhodium Vaska-type complexes we studied
previously.25 More specifically, we pursued rhodium
complexes that contained a diphosphine backbone and
a labile monodentate ligand. We envisioned the latter
would be displaced by the aldehyde or imine to generate
an intermediate that would undergo insertion.
Isolation of a stable arylrhodium complex with a
pyridine ligand was accomplished with the diphosphine
ligand DPPE (DPPE ) 1,2-bis(diphenylphosphino)-
ethane). Reaction of the isolated chloride dimer [(DP-
PE)Rh(µ-Cl)]2 with pyridine (15 equiv) gave a yellow
solution containing the monomeric (DPPE)Rh(Cl)(py)
(1), as determined by 1H and 31P NMR spectroscopy.
Addition of solid p-tolyllithium to the bright yellow
solution gave the desired arylrhodium complex (DPPE)-
Rh(py)(p-tol) (2a ) in 65% isolated yield (Scheme 2). An
analogous sequence was also conducted with DPPB
(DPPB ) 1,4-bis(diphenylphosphino)butane) as sup-
Bond Angles (deg)
87.50(10) C(27)-Rh(1)-P(2) 174.94(8)
C(27)-Rh(1)-N(1)
C(27)-Rh(1)-P(1)
N(1)-Rh(1)-P(1)
90.96(8)
177.77(7)
N(1)-Rh(1)-P(2)
P(1)-Rh(1)-P(2)
96.16(7)
85.47(3)
porting ligand because this ligand generated active
catalysts for the rhodium-catalyzed addition of arylbo-
ron and aryltin reagents to imines.95 However, the final
arylrhodium complex was unstable at room tempera-
ture. Reaction of (CH3)3SiCH2MgCl with the pyridine
adduct 1 formed the alkylrhodium(I) complex (DPPE)-
Rh(py)(CH2SiMe3) (2b) in 76% isolated yield (Scheme
2).
DPPE-ligated aryl and trimethylsilylmethyl com-
plexes 2a and 2b were characterized by H, 13C, and
1
31P NMR spectroscopy and elemental analysis. Complex
2a was also characterized by single-crystal X-ray dif-
fraction. An ORTEP diagram of complex 2a is provided
in Figure 1, and selected bond distances and bond angles
are given in Table 1. In the solid state, the ligands of
2a are arranged in a typical square planar geometry.
The Rh-N bond length is similar to other distances
between rhodium(I) and a pyridine ligand.96-99 The
Rh-C bond length of 2a (2.097 Å) is slightly longer than
that in other rhodium aryl complexes that do not contain
a CO ligand.85,89,94
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New Classes of Insertion Reactions
Organometallics, Vol. 23, No. 20, 2004 4597
In contrast to NMR data obtained at room tempera-
ture, 1H NMR spectra of 4 obtained at -20 °C were
sharp and confirmed the identity of this complex in
solution. Two signals for the p-tolyl methyl groups, four
doublets corresponding to the aromatic protons of the
p-tolyl groups, and a single methine resonance were
observed. The p-tolyl groups are most likely diaste-
reotopic because of slow rotation about the Rh-amide
bond on the NMR time scale at -20 °C. 31P NMR
spectra acquired at -20 °C consisted of a single doublet,
which was attributed to a small difference in chemical
shifts of the phosphines and small PA-PB coupling.
NMR simulations showed that the pair of doublets of
doublets for an ABX pattern collapses to one doublet if
the PA-PB coupling is small and the difference in
chemical shift is small. Thus, to demonstrate the
inequivalence of the phosphorus nuclei, a 31P-decoupled
1H NMR spectrum was acquired at -20 °C. Four
inequivalent protons were observed for the methylene
backbone of the DPPE ligand. Coalescence of the dia-
F igu r e 2. ORTEP diagram of (DPPE)Rh(pyridine)(NAr-
CH(p-tolyl)2) (4) (Ar ) C6H4-p-CO2Me).
Ta ble 2. Selected In tr a m olecu la r Bon d Dista n ces
a n d Bon d An gles for (DP P E)Rh (p yr id in e)-
[NAr CH(p-tol)2] (Ar ) p-C6H4-CO2Me) (4)
Bond Distances (Å)
Rh(1)-N(2)
Rh(1)-N(1)
N(1)-C(35)
2.145(3)
2.153(2)
1.465(3)
Rh(1)-P(2)
Rh(1)-P(1)
2.2055(9)
2.2055(9)
Bond Angles (deg)
1
N(2)-Rh(1)-N(1)
N(2)-Rh(1)-P(2)
N(1)-Rh(1)-P(2)
88.44(9) N(2)-Rh(1)-P(1)
91.09(7) N(1)-Rh(1)-P(1)
179.14(7) P(2)-Rh(1)-P(1)
170.71(7)
96.09(7)
84.27(3)
stereotopic p-tolyl groups in the H NMR spectrum of
amide 4 at ambient temperature most likely results
from an increased rate of rotation about the rhodium-
nitrogen bond.
C(27)-N(1)-C(35) 115.7(2)
C(36)-C(35)-C(43) 109.6(2)
center in aryl complex 2a was observed by 13C NMR
spectroscopy as a doublet of doublets of doublets reso-
Bound pyridine in amide 4 exchanges with added
pyridine at -20 °C, as determined by spin saturation
experiments on samples of 4 containing 1 equiv of added
pyridine. Selective irradiation of the ortho protons of
bound pyridine resulted in complete saturation of the
signals of both free and bound pyridine, suggesting that
exchange between bound and free ligand is fast. This
exchange with added pyridine is likely to be an associa-
tive process, considering the square planar, 16-electron
configuration of 2a .
nance at 175.0 (J CRh ) 94.1 Hz, J CP ) 31.5 Hz, J CP
)
15.0 Hz), and a similar signal was observed for the
methylene carbon of the (trimethylsilyl)methyl fragment
of 2b (9.23 ppm, ddd, J CRh ) 69.1 Hz, J CP ) 22.4 Hz,
1
J CP ) 10.7 Hz). The H NMR spectrum of 2b contained
a doublet of doublets centered at 0.34 ppm for the
methylene protons.
Rea ction s of Or ga n or h od iu m (I) Com p lexes w ith
Im in es. Addition of 1 equiv of the N-aryl aldimine (p-
tol)CHdN(C6H4-p-CO2Me) (3a -Tol) to an arene solution
of tolyl complex 2a resulted in an immediate change of
color from orange to red and formation of insertion
Arylrhodium 2a also underwent insertion of the
aldimine (Ph)CHdN(C6H4-p-CO2Me) (3a -P h ). In this
case, the amide resulting from insertion (5) was treated
with PEt3 to replace the pyridine ligand and to form
two diastereomers of PEt3-ligated 6 (Scheme 3) that
were isolated in 71% yield. Amides 6 were characterized
1
product 4 (eq 1). The H NMR spectrum of the reaction
mixture obtained at room temperature contained broad
signals, and the 31P NMR spectra contained one broad
doublet at 68.0 ppm (J ) 178 Hz). Concentration of the
reaction solution, followed by cooling to -35 °C, gave
an orange crystalline material in 88% yield.
1
by H and 31P NMR spectroscopy, elemental analysis,
1
and single-crystal X-ray diffraction. H and 31P NMR
spectra of 6 obtained at room temperature contained
sharp signals. The NMR spectral features, which in-
cluded two p-tolyl resonances, two methyl ester reso-
nances, and two methine resonances, were consistent
with insertion to generate an amide with a stereocenter
R to nitrogen and slow rotation about the Rh-N bond
that creates a second stereochemical element. An ORTEP
diagram of 6 is provided in Figure 3, and selected bond
distances and bond angles are given in Table 3. The
overall geometry of PEt3-ligated 6 is similar to that of
amido complex 4, but the rhodium-nitrogen bond has
been further lengthened by roughly 0.02 Å.
Single-crystal X-ray diffraction showed that the prod-
uct was the pyridine-ligated amide complex 4, resulting
from insertion of the imine. An ORTEP diagram is
provided in Figure 2, and selected bond distances and
bond angles are given in Table 2. In the solid state, 4
adopts a square planar geometry with the bulky diaryl-
methyl and aryl substituents of the amide ligand
positioned on either side of the plane of the molecule.
The rhodium-nitrogen bond to the amido group is
slightly longer than the rhodium-nitrogen bond to the
pyridine ligand. This longer distance to the formally
anionic amido group than to the dative pyridine is
presumably due to the sterically demanding substitu-
ents on the amido nitrogen.
Complex 2a also appeared to react with electron-
neutral and electron-rich aldimines (Ph)CHdNPh (3b)
and (p-tol)CHdN(C6H4-p-OMe) (3c) by insertion of the
imine into the aryl-rhodium bond. However, the amido

4598 Organometallics, Vol. 23, No. 20, 2004
Krug and Hartwig
The results of several experiments support our pro-
posal that an amide is formed by insertion and that it
undergoes â-hydrogen elimination and cyclometalation.
Most definitive, the major product from reaction of 2a
with the electron-rich aldimine (p-tol)CHdN(C6H4-p-
OMe) (3c) was isolated, and this product 9 was shown
to possess a cyclometalated ketimine, as shown in eq 3.
This material was formed in a 3.5:1 ratio with a second
material we have not yet identified. The 31P NMR
spectrum of 9 consisted of a pair of doublets of doublets
at 55.0 (J PRh ) 123 Hz, J PP ) 19.5 Hz) and 76.3 (J PRh
)
203 Hz, J PP ) 19.5 Hz) ppm for the two inequivalent
phosphorus atoms. The 1H NMR spectrum contained
two signals in the tolyl region and one signal for a
methoxy group. Single-crystal X-ray diffraction con-
firmed its identity. An ORTEP diagram of 9 is provided
in Figure 4, and selected bond distances and bond angles
are given in Table 4. Complex 9 was formed by ortho-
metalation of one of the C-aryl groups of the ketimine
to form a five-membered metallacycle.
F igu r e 3. ORTEP diagram of (DPPE)Rh(PEt3)[NArCH-
(Ph)(p-tolyl)] (Ar ) C6H4-p-CO2Me) (6).
Sch em e 3
To obtain information on the connectivity of the minor
product, DCl was added to a crude mixture generated
from arylrhodium 2a and aldimine 3c, and the released
ketimine was hydrolyzed with aqueous HCl. This hy-
drolysis generated monodeuterio 4,4′-dimethylbenzophe-
none and unlabeled p-anisidine, as determined by GC/
MS (eq 4). These results indicated that the second
product also results from metalation of a C-aryl group,
but we have not been able to make a definitive assign-
ment of the structure of this minor rhodium product.
Ta ble 3. Selected Bon d Dista n ces a n d Bon d
An gles for (DP P E)Rh (P Et3)[NAr CH(p-tol)(P h )] (Ar
) p-C6H4-CO2Me) (6)
Bond Distances (Å)
Rh(1)-N(1)
Rh(1)-P(2)
N(1)-C(41)
2.170(3)
2.2266(11)
1.467(4)
Rh(1)-P(1)
Rh(1)-P(3)
2.2866(11)
2.3416(11)
Bond Angles (deg)
N(1)-Rh(1)-P(2)
N(1)-Rh(1)-P(1)
P(2)-Rh(1)-P(1)
172.06(8)
95.43(8)
82.88(4)
N(1)-Rh(1)-P(3)
P(2)-Rh(1)-P(3)
P(1)-Rh(1)-P(3)
90.91
92.33(4)
166.97
complexes formed from these insertions were less stable
than those formed by insertion of the electron-poor
imines 3a -Tol and 3a -P h . This instability led to differ-
ent final products.
Addition of 3b (5 equiv) to a C6D6 solution of aryl-
rhodium complex 2a generated free diarylmethylamine
(Ph)(p-tol)CH-NHPh (7) in 25% yield and toluene in
15% yield. Subsequent addition of Et3NHCl (2-4 equiv)
to the reaction solution generated the E and Z isomers
of the ketimine (Ph)(p-tol)CdNPh (8) in 50% combined
1
yield, as determined by H NMR spectroscopy (eq 2). A
1H NMR spectrum of the reaction mixture obtained
prior to addition of Et3NHCl showed that 2a was fully
consumed and that diarylmethylamine 7 and toluene
were formed, along with complexes corresponding to two
signals in the tolyl region (1:1 ratio) that comprised
roughly 50% of the amount of 2a . After addition of acid,
these signals were absent, and two new signals corre-
sponding to E and Z ketimine 8 were observed. We
speculated that insertion of the imines with electron-
neutral and electron-rich N-aryl groups occurred, but
that these amides underwent â-hydrogen elimination
and cyclometalation to form stable azametallacycles.
Thus, we added ammonium salts to protonate the Rh-
carbon bond and release the free imine.
Scheme 4 shows the individual steps in the reaction
between 2a and 3c that would generate metallacycle 9.
Insertion of imine into the Rh-aryl bond of 2a would
give an amide intermediate 10. â-Hydrogen elimination
would generate the hydridorhodium complex 11, which
contains bound ketimine (p-tol)2CdN(C6H4-p-OMe). Met-
alation of a C-aryl group of the ketimine would generate
a Rh(III) metallacycle (12) containing two hydride
ligands. Reductive elimination of H2 would form 9.
Similar ortho-metalations involving imines and azoben-
zenes have been previously described by Bruce et al.100
(100) Bruce, M. I.; Goodall, B. L.; Stone, F. G. A. J . Chem. Soc.,
Dalton Trans. 1978, 687, and references therein.

New Classes of Insertion Reactions
Organometallics, Vol. 23, No. 20, 2004 4599
complex 4, rather than by hydrogenation of the CdN
bond in free or metalated ketimine.
The intermediacy of an amido complex from insertion
of imines 3b and 3c into the Rh-aryl bond of 2a was
further supported by the reactivity of isolated amide 4.
As depicted in eq 5, heating of a C6D6 solution of 4 at
75 °C generated amine 14 and ketimine 15 in 50% and
45% yield. The products from this thermal chemistry
are similar to those formed from the overall reaction of
2a with aldimines 3b and 3c. We attribute the higher
reactivity of the amide intermediates formed from
reaction of aryl complex 2a with imine 3b or 3c, in
comparison to the reactivity of the amide generated from
2a containing an electron-poor N-aryl group, to the
electronic effect of the aryl group on the rate of
â-hydrogen elimination of amides. â-Hydrogen elimina-
tions from isolated complexes of the general formula
[(PPh3)2Ir(CO)(OCH(Me)(Ar)] have been shown to be
slower when the aryl group contains a strong electron-
withdrawing substituent in the para-position.101
F igu r e 4. ORTEP diagram of (DPPE)Rh{C6H3-5-Me-2-
C[(dN(Ar)(p-tol)]} (Ar ) C6H4-p-OMe) (9).
Ta ble 4. Selected In tr a m olecu la r Bon d Dista n ces
a n d Bon d An gles for Meta lla cycle 9
Bond Distances (Å)
Rh(1)-C(29)
Rh(1)-N(1)
2.068(4)
2.108(3)
Rh(1)-P(2)
2.1939(10)
2.2766(11)
An alternative mechanism for the formation of
ketimine products could involve the oxidative addition
of the iminoacyl C-H bonds of 3b or 3c to 2a ,102-106
followed by reductive elimination of the iminoacyl and
aryl ligands. However, two factors argue against forma-
tion of ketimines by this pathway. First, if formation of
ketimine occurred by a C-H activation mechanism,
then the mechanisms for the reaction of 2a with two
imines, one with an electron-neutral and one with an
electron-poor N-aryl group, would be completely differ-
ent. Amide complex 4 is clearly generated by insertion.
Second, the products formed from thermolysis of amide
4 are similar to those formed from the overall reaction
of aryl complex 2a with imine 3b.
Rh(1)-P(1)
Bond Angles (deg)
79.57(12) C(29)-Rh(1)-P(1) 170.98(10)
94.36(10) N(1)-Rh(1)-P(1)
173.84(8) P(2)-Rh(1)-P(1)
C(29)-Rh(1)-N(1)
C(29)-Rh(1)-P(2)
N(1)-Rh(1)-P(2)
101.13(8)
84.70(4)
N(1)-C(27)-C(28) 116.3(3)
N(1)-C(27)-C(35) 123.3(3)
Sch em e 4
Mech a n ist ic Con sid er a t ion s. E ffect of Ad d ed
P yr id in e. As noted above, free pyridine undergoes
rapid exchange with the coordinated pyridine of 2a . To
determine if a similar exchange of imine for coordinated
pyridine contributes to the higher reactivity of aryl-
rhodium 2a for insertion of imines, in comparison to the
reactivity of (PPh3)2(CO)Rh(p-tol), kinetic experiments
on the insertion reaction were conducted. Reactions of
0.026 M 2a with 0.13 M imine (Ph)CHdN(C6H4-p-CO2-
Me) (3a -P h ) were conducted at 2.0 °C with concentra-
tions of added pyridine ranging from 0.089 to 0.46 M.
The consumption of 2a was monitored by 31P NMR
spectroscopy, and rate constants were obtained by
fitting the curves to an exponential decay. The kinetic
data showed a clear first-order decay in rhodium
complex 2a , first-order dependence on imine, and a
clean inverse-first-order dependence on the concentra-
The formation of H2 by cyclometalation of the ketimine
may explain the formation of diarylmethylamine 7 and
toluene in the reaction between aryl complex 2a and
N-phenyl imine 3b. This hydrogen may react with
amide intermediate 10 and starting aryl complex 2a to
generate the amine and arene product. Alternatively,
amine 7 could form from a combination of hydrogenoly-
sis of the Rh-N bond in a metallacycle similar to 9 and
hydrogenation of the CdN bond of the metalated unit.
To distinguish between these two paths, aryl complex
2a was allowed to react with aldimine 3b in the
presence of 1 equiv of ketimine (p-tol)(Ph)CdN(C6H4-
p-CO2Me) (13). Amine 7 was generated from reaction
of 2a with aldimine 3b, but no amine from hydrogena-
tion of added ketimine 13 was observed. Thus amine 7
is likely formed from hydrogenolysis of an amide
intermediate that is analogous to the directly observed
(101) Zhao, J .; Hesslink, H.; Hartwig, J . F. J . Am. Chem. Soc. 2001,
123, 7220.
(102) Milstein, D. Chem. Commun. 1982, 1357.
(103) Suggs, J . W. J . Am. Chem. Soc. 1979, 101, 489.
(104) Fairlie, D. P.; Bosnich, B. Organometallics 1988, 7, 946.
(105) Barnhart, R. W.; Bosnich, B. Organometallics 1995, 14, 4343.
(106) Miller, R. G. J . Am. Chem. Soc. 1976, 98, 1281.

4600 Organometallics, Vol. 23, No. 20, 2004
Krug and Hartwig
Sch em e 7
F igu r e 5. Plot of the inverse dependence of the observed
rate constant on the concentration of pyridine.
complex and formed ester 19a in 85% yield, as measured
by 1H NMR spectroscopy with an internal standard. The
ketone 4-methylbenzophenone (18a ), which would result
from insertion of benzaldehyde followed by â-hydride
elimination, was formed in only 5% yield. In addition,
the ester 21a , which contains two benzaldehyde units
and no aryl group from rhodium, was formed. These
three products were identified by comparison of NMR
and GC/MS of crude reactions with those of material
prepared independently or purchased commercially.
Several rhodium products were formed after the com-
plete consumption of rhodium complex 2a .
Sch em e 5
Sch em e 6
The ester 19a would form by insertion of PhCHO into
the Rh-aryl bond and insertion of a second aldehyde
into the resulting rhodium alkoxide 22 to form alkoxide
23 (Scheme 7, bottom path). â-Hydrogen elimination
would then generate the final ester 19a . The second
ester 21a would form by a rhodium-catalyzed Tischenko
reaction, presumably initiated by the rhodium hydride
generated from â-hydrogen elimination of alkoxides 22
and 23. Insertion of 2 equiv of PhCHO into the rhodium
hydride, followed by â-hydride elimination, would form
ester 21a and regenerate the starting hydride.
As shown in Scheme 6, reaction of the aliphatic
aldehyde Me3CCHO with aryl complex 2a formed
ketone and ester products that were analogous to those
formed from reaction of benzaldehyde. In addition, the
alcohol 20b and some toluene were formed. The organic
products were identified by independent synthesis of
ketone 18b, alcohol 20b, and esters 19b and 21b. The
toluene and alcohol 20b may form from reaction of
intermediate 22 with a rhodium hydride or H2 (Scheme
7, middle path), as was proposed to account for forma-
tion of the small amount of amine from the reaction of
aryl complex 2a with imine 3b.
In contrast to arylrhodium complex 2a , alkylrhodium
complex 2b did not insert imines or aldehydes to form
products that we were able to characterize. Complex 2b
was consumed upon reaction with imine 3a -Tol, but
several rhodium products were formed, as determined
by 31P NMR spectroscopy. Similarly, the reaction of
benzaldehyde with 2b did not form ketone or ester
products similar to 18a , and 19a formed from 2a ,
although the ester 21a from a Tischenko process was
observed by GC/MS. The distinct reactivity of aryl
complex 2a and alkyl complex 2b is not currently
understood.
tion of added pyridine (Figure 5). Although these data
do not reveal the coordination mode of the imine prior
to insertion, they do imply that coordination of imine
to the site occupied by pyridine in 2a precedes the
insertion process.
Scheme 5 shows two pathways for formation of amide
intermediate 5. The top path is initiated by reversible
dissociation of pyridine to form a three-coordinate
intermediate (16) followed by coordination of imine to
form imine-bound aryl complex 17 and insertion to form
amide 5. The bottom path involves an associative
displacement of pyridine to form 17 prior to insertion.
Both paths would predict a first-order dependence on
the concentration of aryl complex 2a and imine 3a -P h
and an inverse dependence on the concentration of
pyridine. Although our data are consistent with both
mechanisms, we favor generation of the imine complex
17 by the associative path because 2a is a square planar,
d8 species.
Rea ction of Or ga n or h od iu m (I) Com p lexes w ith
Ald eh yd es. Reactions of arylrhodium complex 2a with
aryl and tert-butyl aldehydes are summarized in Scheme
6. Addition of 1.1-2 equiv of benzaldehyde to 2a in C6D6
resulted in a dark colored solution after a few minutes,
but 31P NMR spectroscopy showed that most of 2a
remained. In contrast, reaction of 2a with 10 equiv of
benzaldehyde fully consumed the starting rhodium
Rea ction of Ar ylr h od iu m (I) Com p lex 2a w ith
Acet op h en on e a n d Ald eh yd es w it h E n oliza b le
Hyd r ogen s. The facile insertion of aldehydes and
imines into the Rh-aryl bond of 2a led us to investigate

New Classes of Insertion Reactions
Organometallics, Vol. 23, No. 20, 2004 4601
F igu r e 6. ORTEP diagram of (DPPE)Rh[CH2CHMeCH2C(p-tol)dCHC(O)Ph] (26).
Ta ble 5. Selected Bon d Dista n ces a n d Bon d
the reactions of 2a with ketones. Heating of a solution
of 2a and PhC(O)Me (1.1 equiv) at 70 °C consumed 2a
and formed in 43% isolated yield the π-oxaallyl complex
24 (eq 6). Similar complexes containing PPh3 ligands
were prepared by Slough from [(PPh3)2Rh(µ-Cl)]2 and a
potassium enolate.107 The 1H NMR spectrum of 24
contained broad signals at 3.54 and 4.37 ppm for the
syn- and anti-protons of the methylene group, and the
13C NMR spectrum contained signals at 51.6 and 157.6
ppm for the methylene and carbonyl carbons of the
π-oxaallyl ligand. Such fast proton transfer of a low-
valent, late metal hydrocarbyl complex is unusual.108,109
An gles for 26
Bond Distances (Å)
Rh(1)-C(45)
Rh(1)-C(34)
Rh(1)-C(35)
Rh(1)-C(33)
C(33)-C(34)
2.079(3)
Rh(1)-O(1)
Rh(1)-P(1)
Rh(1)-P(2)
O(1)-C(33)
C(34)-C(35)
2.276(2)
2.2880(10)
2.3035(9)
1.300(3)
1.453(4)
2.167(3)
2.181(3)
2.232(3)
1.411(4)
Bond Angles (deg)
C(45)-Rh(1)-C(34) 92.88(12) C(35)-Rh(1)-C(33) 69.59(11)
C(45)-Rh(1)-C(35) 82.98(12) C(45)-Rh(1)-O(1) 156.50(10)
C(34)-Rh(1)-C(35) 39.06(11) C(34)-Rh(1)-O(1)
C(45)-Rh(1)-C(33) 124.55(12) C(35)-Rh(1)-O(1)
C(34)-Rh(1)-C(33) 37.40(11) C(33)-Rh(1)-O(1)
63.70(10)
79.55(10)
33.49(9)
C(45)-Rh(1)-P(1)
C(34)-Rh(1)-P(1) 148.69(8) C(33)-Rh(1)-P(1) 143.03(8)
P(1)-Rh(1)-P(2) 85.16(3)
91.28(9) C(35)-Rh(1)-P(1) 111.10(8)
contained a broad singlet at 47.1 ppm and a multiplet
of equal intensity centered at 48.3 ppm.
The identity of the isolated product was established
by single-crystal X-ray diffraction. An ORTEP diagram
of 26 is provided in Figure 6, and selected bond
distances and angles are given in Table 5. Apparently,
reaction of 2a with 25 resulted in exclusive addition of
the p-tolyl group of 2a to the â-position of the ynone,
but subsequent rearrangement of the tert-butyl group
to form the stable polyhapto ligand of 26 generates the
final product.
In contrast to the reactions of aryl complex 2a with
benzaldehyde and pivalaldehyde, reactions of aliphatic
aldehydes containing enolizable hydrogens did not
cleanly form products from insertion. The reaction of
aryl complex 2a with 1-hexanal formed several products,
as judged by NMR spectroscopy.
C-C Bon d Clea va ge fr om Rea ction of Ar yl-
r h od iu m Com p lex 2a w it h a n Yn on e. The proton
transfer between 2a and acetophenone suggested that
insertion of a ketone CdO bond into the rhodium-aryl
bond of 2a would require a more electrophilic ketone.
Thus, we conducted the reaction of 2a with ynone 25.
Reaction of 25 with 2a in C6D6 immediately consumed
the arylrhodium complex and formed the unexpected
complex 26 shown in eq 7. The 1H NMR spectrum of
the product did not contain a singlet corresponding to
a tert-butyl group. Instead, it contained a doublet at 0.60
ppm (J ) 9.6 Hz). The 31P NMR spectrum of the product
Three potential mechanisms that account for the
formation of 26 are shown in Scheme 8. Each path is
initiated by addition of the p-tolyl group of 2a to the
â-position of 25 to generate the rhodium allenoate 27.
C-H activation of a methyl group would give metalla-
cyclic intermediate 28, and reductive elimination to form
an O-H bond and tautomerization of the resulting
allenol would give 29. Path A consists of an intramo-
lecular Michael addition of rhodium alkyl 29 to the
enone to give the cyclopropylmethyl enolate complex 30.
(107) Slough, G. A.; Hayashi, R.; Ashbaugh, J . R.; Shamblin, S. L.;
Aukamp, A. M. Organometallics 1994, 13, 890.
(108) Holland, A. W.; Bergman, R. G. J . Am. Chem. Soc. 2002, 124,
14684.
(109) Fulton, J . R.; Sklenak, S.; Boukamp, M.; Bergman, R. G. J .
Am. Chem. Soc. 2002, 124, 4722.

4602 Organometallics, Vol. 23, No. 20, 2004
Krug and Hartwig
Sch em e 8
Sch em e 9
alcohol product. Thus, we conducted reactions of aryl-
rhodium complex 2a with imine 3a -P h , and instead of
trapping the amide with PEt3, the product was quenched
with water. This reaction sequence generated amine 35
and the dimeric Rh-hydroxide complex 36 in essentially
quantitative yields (eq 8). The identity of the hydroxide
complex was confirmed by independent synthesis
(Scheme 9).
We previously reported25 that the arylrhodium com-
plexes (PPh3)2Rh(CO)(Ar), which contain a carbonyl
ligand, did not react with water, and reactions of these
complexes with aldehydes in mixtures of THF and water
gave diarylcarbinol products instead of the diaryl ke-
tones formed in dry arene solvents. In contrast, aryl-
rhodium complex 2a reacted rapidly with H2O (1.5
equiv) to form toluene and the hydroxide complex 36 in
quantitative yields (Scheme 9) at room temperature.
Thus, the stability of the Rh-carbon bond to hydrolysis
is highly dependent on the set of ligands and is appar-
ently much faster with a full set of σ-donors as ancillary
ligands and a phosphine trans to the aryl group.
Hydrolyses of late metal-carbon bonds to form arenes
or alkanes and metal hydroxides are uncommon,27,114-116
and the rate of hydrolysis is likely to be an important
factor in determining which Rh complexes catalyze the
additions of main group aryl reagents discussed in the
Introduction. Rapid hydrolysis of the rhodium aryl
intermediate would prevent catalytic reactions that
occur by insertion of aldehyde or imine into the rhodium-
aryl bond, followed by hydrolysis of the amide or
alkoxide.
Com p a r ison of th e Rea ctivity of 2a w ith Im in es
a n d Ald eh yd es to Oth er La te Meta l Or ga n om eta l-
lic Com p lexes. The directly observed insertion of 3a -
Tol into the Rh-aryl bond of 2a is the first example of
a 1,2-insertion of an imine into a late metal-carbon
bond to form a stable amide. Piers and Fryzuk have
observed directly the insertion of imines into the Rh-H
bond of a dimeric rhodium hydride complex to give
amido hydride products. The reactions were proposed
to occur through an imine that was bound through two
metals, one at the CdN π-bond and the second at the
nitrogen lone pair.29 Arendtsen and Sen both have
reported 2,1-insertions of imines into Pd- or Ni-acyl
complexes.77-80 These insertions may occur by direct
nucleophilic attack of the imine nitrogen at the electro-
philic acyl carbon. Indeed, Yamamoto has studied the
Cleavage of the cyclopropane at the Ca-Cb bond would
give the tertiary alkyl complex 31.110 â-Hydrogen elimi-
nation and reinsertion would produce 26. Alternatively,
path B consists of â-vinyl elimination of 29 to generate
coordinated isobutylene and vinylrhodium 33. Olefin
rotation and reinsertion would give 31. Path C involves
C-H activation of a methyl group of the coordinated
isobutylene of 33 to give π-allyl 34. C-C reductive
elimination would generate the alkene hydride 32, and
26 would form from insertion of the alkene into the
rhodium hydride.
Although we do not have mechanistic data on the
formation of 26, bond-breaking steps similar to those
shown in paths A-C have been reported previously with
other late metal complexes. â-Carbon elimination of
strained cycloalkyl ligands, analogous to the ring-
opening of cyclopropylmethyl intermediate 30 in path
A of Scheme 8, has been reported by Murakami and
Bergman.111-113 1,2-Insertion of propylene into a Pd-
Me bond followed by â-hydride elimination, rotation of
the resulting olefin, and reinsertion to generate an
agostic, tertiary alkyl has been demonstrated.17 Also,
the activation of sp3 C-H bonds of R-olefins has been
observed directly114 and is likely an important step in
the Ni-catalyzed isomerization of olefins. By any mech-
anism, the mild conditions for this structural rearrange-
ment are remarkable.
Hyd r olysis of Rh od iu m Am id e a n d Ar yl Com -
p ou n d s. Hydrolysis of amide and alkoxide complexes
has been proposed to be the step of the Rh-catalyzed
additions of organoboron or organotin reagents to alde-
hydes and imines that releases the final amine or
(110) We thank a reviewer for suggesting this pathway.
(111) Murakami, M.; Takahashi, K.; Amii, H.; Ito, Y. J . Am. Chem.
Soc. 1997, 119, 9307.
(112) Murakami, M.; Ito, Y. Top. Organomet. Chem. 1999, 3, 97.
(113) McNeill, K.; Andersen, R. A.; Bergman, R. G. J . Am. Chem.
Soc. 1995, 117, 3625.
(115) Burn, M. J .; Fickes, M. G.; Hartwig, J . F.; Hollander, F. J .;
Bergman, R. G. J . Am. Chem. Soc. 1993, 115, 5875.
(116) Klein, H.-F.; Karsch, H. H. Chem. Ber. 1973, 106, 1433.
(114) Cole-Hamilton, D. J .; Wilkinson, G. New J . Chem. 1977, 1,
141.

New Classes of Insertion Reactions
Organometallics, Vol. 23, No. 20, 2004 4603
mechanism of Pd-catalyzed aminocarbonylation of aryl
halides and concluded that direct attack of amine on a
Pd-acyl intermediate may account for the observed
products.117 Further, Arndtsen prepared a cationic Pd-
Me complex containing a σ-bound imine ligand and
showed that it did not insert imine.78 Thus, the inser-
tions of imines and aldehydes into the rhodium-aryl
bond of 2a reported here are likely to occur by a
mechanism that is distinct from that of the previously
reported 2,1-insertions. The pathway for 1,2-insertion
is most likely akin to the migratory insertion pathway
that is common for the insertion of olefins into late metal
carbon bonds.
Few examples of 1,2-insertions of aldehydes into late
metal-carbon bonds to form stable alkoxides have been
reported. These examples were limited to insertions of
aldehydes into strained metal-carbon bonds of metal-
lacycles. Insertions of aldehydes into metal-carbon
bonds of discrete complexes to form alkoxides that
undergo â-hydrogen elimination have been reported in
a few cases. Consistent with the instability of late metal
alkoxides with â-hydrogens, the reactions of (PPh3)2Rh-
(CO)R with aldehydes we reported previously generated
an alkoxide intermediate that eliminated ketone and
formed a rhodium hydride product.
3a -P h , 3a -Tol, 3b, and 3c into the Rh-aryl bond of 2a
formed isolable amide products, or metallacycles result-
ing from a sequence of imine insertion, â-hydride
elimination from the amide intermediate, and ortho-
metalation of the resulting ketimine. Aryl aldehydes and
aliphatic aldehydes that did not contain acidic protons
reacted with 2a to form organic products that are
consistent with insertion of aldehyde. In contrast, aryl
complex 2a reacted with acetophenone or H2O to form
toluene and an enolate or hydroxide complex.
We propose that two factors lead to the unusually
high reactivity of 2a with aldehydes and imines. First,
the presence of a weakly bound pyridine ligand allows
coordination of aldehydes and imines in the square
plane of the rhodium and reaction by migratory inser-
tion. Second, proton transfer between weak acids and
2a suggests that the rhodium-carbon bond of 2a or the
intermediate generated from exchange of water for
pyridine is more polar than the metal-carbon bond in
a typical late metal organometallic complex. This po-
larization may make the aryl group of 2a or the species
resulting from dissociation of pyridine more nucleophilic
toward insertion of aldehydes and imines. At the same
time, this basicity limits the chemistry between 2a and
aldehydes such as n-hexanal and ketones such as
acetophenone, which possess enolizable hydrogens.
Further studies to delineate the factors that control the
reactivity of late metal-aryl bonds with aldehydes and
imines and that promote reactions with late metal alkyl
complexes should lead to new transformations of these
common organic reagents.
The alkoxides resulting from insertion of aldehyde are
not just reactive toward â-hydrogen elimination. The
formation of ester products 19a and 19b from reaction
of aryl complex 2a with aromatic aldehydes suggests
that the alkoxide intermediates formed from insertion
of aldehyde into the Rh-aryl bond are also highly
reactive toward insertion of a second aldehyde.
Such insertion of aldehydes into late metal-oxygen
bonds has also been reported only a few times previ-
ously.25,118 We showed that an ester analogous to 19a
and 19b formed if an excess of aldehyde was added to
(PPh3)2Rh(CO)Ar or if aldehyde was added to the
isolated alkoxide (PPh3)2Rh(CO)OR resulting from in-
sertion of aldehyde.25 Further, a rhodium-catalyzed
Tischenko reaction that presumably occurs by a mech-
anism similar to that shown in Scheme 7 has been
reported by Slough,119 and Tischenko reactions cata-
lyzed by isolated metal hydrides of other metals have
been reported.120-122 In addition, Kaplan and Bergman
reported the reaction of a ruthenium hydroxide with
aldehydes to form carboxylate complexes by a mecha-
nism involving attack of a dissociated hydroxide on a
Ru-bound aldehyde.123
Exp er im en ta l Section
Gen er a l P r oced u r es. Unless noted otherwise, all manipu-
lations were carried out under an inert atmosphere using a
nitrogen-filled glovebox or standard Schlenk techniques. All
glassware was oven-dried for approximately 1 h prior to use.
THF, toluene, diethyl ether, and pentane were distilled from
sodium benzophenone ketyl under nitrogen or were collected
after passing through Q-5 and alumina in a solvent purifica-
tion system. C6D6 and THF-d8 were dried over sodium ben-
zophenone ketyl and vacuum transferred prior to use. CDCl3
1
was used as received. H NMR spectra were obtained on 300,
400, or 500 MHz spectrometers. 1H NMR spectra were
recorded relative to residual protiated solvent. 13C NMR
spectra were obtained at 100.6 or 125.0 MHz, and chemical
shifts were recorded relative to the solvent resonance. Both
1H NMR and 13C NMR chemical shifts are reported in parts
per million downfield from tetramethylsilane. 31P NMR spectra
were obtained at 121.6, 162.0, or 202.4 MHz, and chemical
shifts are reported relative to 85% H3PO4. The temperature
of the NMR probe was calibrated for kinetic experiments using
a digital thermometer. The aldimines (p-tol)CHdN(C6H4-p-
CO2Me) (3a -Tol), (Ph)CHdN(C6H4-p-CO2Me) (3a -P h ), (Ph)-
CHdNPh (3b), and (p-tol)CHdN(C6H4-p-OMe) (3c) were pre-
pared using procedures reported for the preparation of similar
compounds.124 [(DPPE)Rh(µ-Cl)]2,125 4-methylbenzophenone
imine,126 4,4′-dimethylbenzophenone imine,126 solid p-tolyl-
lithium,127 20b,128 21b,121 and 25129 were prepared according
to literature procedures. Compound 18b130 was synthesized
Con clu sion s
The reactions of 2a with imines, aldehydes, ketones,
and water provide insight into the factors that promote
insertion of C-N and C-O multiple bonds into late
metal-carbon bonds. Insertion of N-aryl benzaldimines
(117) Lin, Y.-S.; Yamamoto, A. Organometallics 1998, 17, 3466.
(118) Han, R.; Hillhouse, G. L. J . Am. Chem. Soc. 1997, 119, 8135.
(119) Slough, G. A.; Ashbaugh, J . R.; Zannoni, L. A. Organometallics
1994, 13, 3587.
(120) Ito, T.; Horino, H.; Koshiro, Y.; Yamamoto, A. Bull. Chem. Soc.
J pn. 1982, 55, 504.
(121) Morita, K.-I.; Nishiyama, Y.; Ishii, Y. Organometallics 1993,
12, 3748.
(122) Hayashi, Y.; Yamamoto, T.; Yamamoto, A.; Komiya, S.; Kushi,
Y. J . Am. Chem. Soc. 1986, 108, 385.
(124) Castellano, J . A.; Goldmacher, J . E.; Barton, L. A.; Kane, J .
S. J . Org. Chem. 1968, 33, 3501.
(125) Fairlie, D. P.; Bosnich, B. Organometallics 1988, 7, 936.
(126) Cristau, H.-J .; Lambert, J .-M.; Pirat, J .-L. Synthesis 1998,
1167.
(123) Kaplan, A. W.; Bergman, R. G. Organometallics 1998, 17,
5072.
(127) Chetcuti, M. J .; Chisholm, M. H.; Folting, C. K.; Haitko, D.
A.; Huffman, J . C.; J anos, J . J . Am. Chem. Soc. 1983, 105, 1163.

4604 Organometallics, Vol. 23, No. 20, 2004
Krug and Hartwig
by PCC oxidation of 20b in CH2Cl2. PhBr, NaO-t-Bu, Cs2CO3,
C6H4Br-p-CO2Me, dodecahydrotriphenylene, 1,3,5-trimethoxy-
benzene, Et3NHCl, DCl (1.0 M solution in Et2O), Me3SiCH2-
MgCl (1.0 M solution in Et2O), 18a , 20a , 21a , acetophenone,
anhydrous EtOH and MeOH, Me3CCHO, PhC(O)Cl, Na metal,
Me3CC(O)Cl, NaBH4, triethylamine, and PEt3 were used as
received. PhCHO was distilled and stored in a glovebox.
Pd2(dba)3, Pd(OAc)2, and (()-BINAP were used as received.
Pyridine and distilled H2O were degassed by sparging with
nitrogen prior to use. KOH pellets were crushed into a powder
using a mortar and pestle.
mL) was added, and the solution stirred for 10-15 min at room
temperature. The solution was concentrated under reduced
pressure to 1 mL and cooled at -35 °C for 12 h. An orange
solid precipitated, which was isolated from the supernatant,
washed with cold toluene, and dried to give 150 mg of 4 (88%).
Complex 4 was stored at -35 °C. 1H NMR (400 MHz, THF-d8,
-20 °C): δ 1.54-2.25 (m, 4H), 2.10 (s, 3H), 2.31 (s, 3H), 2.37
(s, 3H), 3.57 (s, 3H), 4.84 (s, 1H), 5.49 (dd, J ) 9.4 Hz, J ) 2.2
Hz, 1H), 6.32 (d, J ) 7.6 Hz, 2H), 6.46 (d, J ) 7.6 Hz, 2H),
6.59 (d, J ) 4 Hz, 2H), 6.78 (d, J ) 8.0 Hz, 2H), 7.10-7.50 (m,
26 H), 7.69 (m, 4H), 8.45 (d, J ) 5.2 Hz, 2H), 8.51 (dd, J ) 9.0
Hz, J ) 2.2 Hz, 1H). 31P NMR (162 MHz, THF-d8, -20 °C): δ
67.5 (d, J ) 177 Hz). Anal. Calcd for C61H59N2O2P2Rh: C,
72.04; H, 5.85; N, 2.75. Found: C, 72.04; H, 5.90; N, 2.52.
P r ep a r a tion of (DP P E)Rh (P Et3)[NAr CH(P h )(p-tol)]
(Ar ) C6H4-p-CO2Me) (6). Into a 20 mL scintillation vial
equipped with magnetic stir bar were placed 2a (142 mg, 0.211
mmol) and 3a -P h (56.1 mg, 0.222 mmol, 1.05 equiv). Toluene
(8 mL) was added, and the solution was stirred for 5 min at
room temperature. PEt3 (32.4 µL, 0.222 mmol, 1.05 equiv) was
added by microliter syringe. The solution was concentrated
in vacuo to about 2 mL and diluted with Et2O (approximately
4 mL total volume). The solution was layered with pentane
and allowed to stand overnight at room temperature, giving a
yellow precipitate. The supernatant was removed using a
pipet, and the solid was washed with pentane and dried under
reduced pressure to give 142 mg (71%) of a 1:1.25 mixture of
diastereomers. Complex 6 was stored at -35 °C. 1H{31P} NMR
(400 MHz, C6D6, integrations are approximated to a 1:1 ratio
of diastereomers): δ 0.71-0.76 (m, 18 H), 0.97-1.04 (m, 6H),
1.30-1.37 (m, 8H), 1.41-1.53 (m, 2H), 1.63-1.68 (m, 2H),
1.76-1.84 (m, 2H), 2.07 (s, 3H), 2.17 (s, 3H), 3.62 (s, 3H), 3.64
(s, 3H), 5.42 (s, 1H), 5.44 (s, 1H), 6.81 (d, J ) 8.0 Hz, 2H),
6.88 (d, J ) 8.0 Hz, 2H), 6.96-7.14 (m, 32H), 7.17-7.46 (m,
24H), 8.02-8.10 (m, 6H). 31P NMR (202.4 MHz, C6D6): δ 6.80
(ddd, J PRh ) 346 Hz, J PP ) 142 Hz, J PP ) 43.9 Hz), 48.3-51.1
(m), 64.2-65.6 (m). All signals for both diastereomers were
P r ep a r a tion of (DP P E)Rh (p yr id in e)(p-tolyl) (DP P E )
1,2-bis(d ip h en ylp h osp h in o)eth a n e) (2a ). Into a 50 mL
round-bottom flask equipped with a magnetic stir bar was
placed [(DPPE)Rh(µ-Cl)2] (185 mg, 0.172 mmol). THF (10 mL)
and pyridine (209 µL, 2.58 mmol) were added to generate a
cloudy yellow solution after ca. 10 min. p-Tolyllithium (34.6
mg, 0.353 mmol) was added as a solid, and an orange solution
was generated. After 5 min of stirring at room temperature,
all volatile materials were removed under reduced pressure.
The product was extracted into Et2O, and the resulting
solution filtered through Celite. The clear orange solution was
slowly concentrated and cooled to -35 °C to give 150.0 mg of
1
orange crystalline 2a (65% yield). H NMR (400 MHz, C6D6):
δ 1.87-2.05 (m, 4H), 2.20 (s, 3H), 6.08 (t, J ) 6.8 Hz, 2H),
6.46 (t, J ) 8.0 Hz, 1H), 6.91 (d, J ) 6.8 Hz, 2H), 7.05-7.16
(m, 12H), 7.64-7.73 (m, 6H), 7.83-7.88 (m, 4H), 8.53-8.55
(m, 2H). 13C NMR (125.8 MHz, THF-d8): δ 21.3, 28.5-28.8
(m), 31.0-31.5 (m), 124.2, 126.6 (d, J ) 5.7 Hz), 127.9 (d, J )
9.3 Hz), 128.5, 128.6 (d, J ) 8.4 Hz), 129.0, 129.7, 133.8 (d, J
) 12.3 Hz), 134.4 (d, J ) 11.6 Hz), 135.7, 138.7 (d, J ) 38.2
Hz), 139.3 (d, J ) 21.1 Hz), 139.4, 153.2, 175.0 (ddd, J RhC
)
2
2
94.1 Hz, J CP ) 31.5 Hz, J CP ) 15.0 Hz). 31P NMR (202 MHz,
C6D6): δ 57.6 (dd, J RhP ) 122 Hz, J PP ) 19.6 Hz), 74.3 (dd,
J RhP ) 200 Hz, J PP ) 19.6 Hz). Anal. Calcd for C38H36NP2Rh:
C, 67.96; H, 5.40; N, 2.09. Found: C, 67.69; H, 5.30; N, 1.94.
P r ep a r a tion of (DP P E)Rh (p yr id in e)(CH2SiMe3) (2b).
Into a 50 mL round-bottom flask equipped with a magnetic
stir bar was placed [(DPPE)Rh(µ-Cl)2] (170 mg, 0.158 mmol).
THF (10 mL) and pyridine (192 µL, 2.38 mmol) were added,
and a cloudy yellow solution was generated after ca. 10 min.
Me3SiCH2MgCl (325 µL, 0.325 mol) was added by syringe, and
an orange solution was generated. After 5 min of stirring at
room temperature, all volatile materials were removed under
reduced pressure. The product was extracted into Et2O, and
the resulting solution filtered through Celite. The clear orange
solution was slowly concentrated and cooled at -35 °C to give
161 mg of bright orange 2b (76% yield). 2b was stored at -35
not observed due to overlap of signals. Anal. Calcd for C54H59
-
NO2P3Rh: C, 68.28; H, 6.26; N, 1.47. Found: C, 67.94; H, 6.53;
N, 1.33.
Rea ction of 2a w ith P h CHdNP h (3b). To a small vial
were placed 2a (10.0 mg, 0.0149 mmol) and dodecahydro-
triphenylene (1 mg) as internal standard. These compounds
were dissolved in C6D6 (0.7 mL), and an 1H NMR spectrum
was acquired. The solution was then added to a separate vial
containing 3b (13.6 mg, 0.0744 mmol, 5 equiv), and the
resulting solution stirred at room temperature for 1 h.
Et3NHCl (6.20 mg, 0.0447 mmol, 3 equiv) was added, and the
solution stirred for 2 h or until the solution had changed from
a dark color to an orange color. An 1H NMR spectrum was
acquired, and yields of ketimine 8 and diarylmethylamine 7
were calculated to be 50% and 25%.
In d ep en d en t P r ep a r a t ion of N-[(4-Met h ylp h en yl)-
(p h en yl)m eth yl]-N-p h en yla m in e (7).131 The following reac-
tion was not conducted in an inert atmosphere. Into a 250 mL
round-bottom flask equipped with a magnetic stir bar was
placed ketimine 8 (200 mg, 0.738 mmol). The ketimine was
dissolved in EtOH (30 mL), and NaBH4 (2.21 g, 59.0 mmol,
80 equiv) was added in four portions. The yellow color
eventually dissipated to give a colorless solution after 2-3 h.
When the reaction was complete, as determined by TLC, the
volatile materials were removed by rotary evaporation. The
remaining solid was quenched with water, and the product
was extracted into Et2O. The organic layer was separated and
dried over MgSO4 and filtered. The Et2O was removed by
rotary evaporation, and the residue was purified by silica gel
chromatography eluting with 30% ethyl acetate in hexane to
give 173 mg (86%) of the diarylmethylamine. 1H NMR (300
MHz, C6D6): δ 2.08 (s, 3H), 3.91 (d, J ) 3.6 Hz, 1H), 5.41 (d,
1
°C. H NMR (400 MHz, C6D6): δ -0.03 (s, 9H), 0.34 (dd, J )
5.6 Hz, J ) 5.6 Hz, 2H), 1.76-2.02 (m, 4H), 6.23 (t, J ) 6.8
Hz, 2H), 6.60 (t, J ) 7.6 Hz, 1H), 7.02-7.07 (m, 6H), 7.12-
7.14 (m, 2H), 7.20-7.25 (m, 4H), 7.60-7.64 (m, 4H), 7.98-
8.03 (m, 4H), 8.68 (d, J ) 4.8 Hz, 2H). 13C NMR (125.8 MHz,
THF-d8): δ 4.24, 9.23 (ddd, J CRh ) 69.1 Hz, J CP ) 22.4 Hz,
J CP ) 10.7 Hz), 29.7-30.1 (m), 31.3-31.8 (m), 124.4, 128.2 (d,
J CP ) 7.8 Hz), 128.4 (d, J CP ) 8.6 Hz), 129.0, 129.2, 133.6 (d,
J ) 12.7 Hz), 134.5 (d, J ) 10.8 Hz), 135.7, 139.4 (d, J CP
)
38.5 Hz), 139.5 (d, J CP ) 21.3 Hz), 153.5. 31P NMR (202 MHz,
C6D6): δ 55.9 (dd, J PRh ) 137 Hz, J PP ) 23.6 Hz), 80.0 (dd,
J PRh ) 195 Hz, J PP ) 23.2 Hz). Anal. Calcd for C35H40NP2-
RhSi: C, 62.96; H, 6.04; N, 2.10. Found: C, 62.76; H, 5.87; N,
2.02.
P r ep a r a tion of Am id e 4. Into a 20 mL scintillation vial
equipped with a stir bar were placed 2a (112 mg, 0.167 mmol)
and 3a -Tol (46.4 mg, 0.184 mmol, 1.1 equiv). Toluene (6-8
(128) Pini, D.; Rosini, C.; Bertucci, C.; Altemura, P.; Salvadori, P.
Gazz. Chim. Ital. 1986, 116, 603.
(129) Brown, H. C.; Racherla, U. S.; Singh, S. M. Tetrahedron Lett.
1984, 25, 2411.
(130) Seyferth, D.; Wang, W.-L.; Hui, R. C. Tetrahedron Lett. 1984,
25, 1651.
(131) Zhu, Z.; Espenson, J . H. J . Org. Chem. 1996, 61, 324.

New Classes of Insertion Reactions
Organometallics, Vol. 23, No. 20, 2004 4605
J ) 4.2 Hz, 1H), 6.44 (d, J ) 7.8 Hz, 2H), 6.70 (m, 1H), 6.93
(d, J ) 7.8 Hz, 2H), 7.01-7.25 (m, 9H).
placed 2a (10.0 mg, 0.0149 mmol) and 3c (3.70 mg, 0.0164
mmol, 1.10 equiv). These compounds were dissolved in C6D6
(0.7 mL), and the resulting solution was stirred for 3 h. DCl
(48.0 µL of a 1.0 M Et2O solution, 0.045 mmol, 3.0 equiv) was
added by syringe. After 15 min, 10 drops of a 1 N aqueous
HCl solution were added, and the contents were stirred
overnight at room temperature. A 6 M aqueous solution of
NaOH was added dropwise until the solution was basic. GC/
MS analysis of the C6D6 layer showed the products of ketimine
hydrolysis (4,4′-dimethylbenzophenone and p-anisidine). (M +
1)/(M+) ratios (authentic material in parentheses): p-anisi-
dine, 0.083 (0.073); 4,4′-dimethylbenzophenone, 2.39 (0.14).
Th er m olysis of 4. Into a small vial were placed 2a (10.0
mg, 0.0149 mmol) and 1,3,5-trimethoxybenzene (1 mg) as
internal standard. These compounds were dissolved in C6D6
In d ep en d en t P r ep a r a tion of N-[(E,Z)-(4-Meth ylp h en -
yl)(p h en yl)m eth ylen e]-N-p h en yla m in e (8).132 Into a 20 mL
scintillation vial were placed 4-methylbenzophenone imine
(500 mg, 2.56 mmol), bromobenzene (402 mg, 2.56 mmol),
Pd2(dba)3 (6.60 mg, 0.00641 mmol, 0.25 mol %), (()-BINAP
(12.0 mg, 0.0192 mmol, 0.75 mol %), and NaOt-Bu (345 mg,
3.59 mmol, 1.4 equiv). Toluene (10 mL) was added, and the
vial capped. The mixture was heated at 80 °C for 12 h. The
yellow solution was allowed to cool to room temperature and
was filtered through Celite. The volatile materials were
removed under reduced pressure, and the imine was purified
by silica gel chromatography, eluting with 10% ethyl acetate
in hexane. Compound 8 (636 mg, 92%) was obtained as a 1:1
mixture of E and Z isomers. 1H NMR (300 MHz, C6D6): δ 1.91
(s, 3H), 2.05 (s, 3H), 6.72 (d, J ) 7.8 Hz, 2H), 6.74-7.06 (m,
22H), 7.94 (d, J ) 8.1 Hz, 2H), 7.98-8.01 (m, 2H).
P r ep a r a tion of Cyclom eta la ted Com p lex 9. To a 20 mL
scintillation vial equipped with a magnetic stir bar were added
2a (114 mg, 0.170 mmol) and imine 3c (57.3 mg, 0.255 mmol,
1.50 equiv). Toluene (4-6 mL) was added, and the resulting
solution was stirred at room temperature for 3 h. The dark
solution was concentrated in vacuo, was layered with pentane,
and cooled overnight at -35 °C. An olive green solid precipi-
tated. The dark supernatant was removed with a pipet, and
the solid was washed with pentane and dried in vacuo to give
62.0 mg of 9 (44%). Crystals suitable for X-ray diffraction were
grown by vapor diffusion of pentane into a concentrated
toluene solution of 9. 1H NMR (400 MHz, C6D6): δ 1.77 (s,
3H), 1.85 (m, 4H), 1.95 (s, 3H), 2.94 (s, 3H), 5.93 (d, J ) 7.6
Hz, 2H), 6.60-6.62 (m, 4H), 6.68 (d, J ) 7.6 Hz, 1H), 6.84 (d,
J ) 8.0 Hz, 2H), 6.98-7.16 (m, 13H), 7.51 (br s, 1H), 7.73-
7.77 (m, 4H), 8.32-8.36 (m, 4H). 31P NMR (121.6 MHz, C6D6):
δ 55.0 (dd, J PRh)123 Hz, J PP ) 19.5 Hz), 76.3 (dd, J PRh ) 203
Hz, J PP ) 19.5 Hz).
1
(0.7 mL), and a H NMR spectrum was acquired. The solution
was then added to a separate vial containing 3a -Tol (3.56 mg,
0.0156 mmol, 1.05 equiv), and the resulting solution was
stirred at room temperature for 10 min. The red-orange
solution was transferred to an NMR tube and heated at 75 °C
for about 0.5 h. Et3NHCl (6.20 mg, 0.0447 mmol, 3 equiv) was
added, and the solution was stirred for 2 h or until it had
1
changed from a dark color to a red-orange color. A H NMR
spectrum was acquired, and the yields of diarylmethylamine
14 and ketimine 15 were calculated to be 50% and 45%.
In d ep en d en t P r ep a r a tion of Meth yl 4-{[Bis(4-m eth yl-
p h en yl)m eth yl]a m in o}ben zoa te (14). This reaction was not
conducted under an inert atmosphere. Into a 250 mL round-
bottom flask equipped with a magnetic stir bar was placed
ketimine 15 (95.0 mg, 0.277 mmol). The ketimine was sus-
pended in MeOH (30 mL), and NaBH4 (0.842 g, 22.2 mmol,
80 equiv) was added in four portions. The yellow color of the
ketimine faded after 2-3 h of heating at reflux. However, the
ketimine was not completely consumed, as determined by TLC,
after additional heating at reflux or upon addition of excess
NaBH4. The volatile materials were removed by rotary evapo-
ration, and the remaining solid was quenched with water. The
product was extracted into Et2O. The organic layer was
separated and dried over MgSO4 and filtered. The Et2O was
removed by rotary evaporation, and the residue was purified
by silica gel chromatography eluting with 10% ethyl acetate
in hexane to give 51.1 mg (54%) of 14. 1H NMR (500 MHz,
C6D6): δ 2.08 (s, 6H), 3.52 (s, 3H), 4.28 (d, J ) 5.0 Hz, 1H),
5.37 (d, J ) 5.0 Hz, 1H), 6.28 (d, J ) 7.3 Hz, 2 H), 6.94 (d, J
) 8.0 Hz, 4H), 7.06 (d, J ) 8.5 Hz, 4H), 8.07 (d, J ) 7.0 Hz,
2H). 13C NMR (125.8 MHz, C6D6): δ 21.0, 51.1, 61.9, 112.9,
119.7, 127.9, 129.6, 131.7, 137.2, 139.7, 151.2, 166.9. Anal.
Calcd for C23C23NO2: C, 79.97; H, 6.71; N, 4.05. Found: C,
79.75; H, 6.95; N, 3.91.
In d ep en d en t P r ep a r a tion of Meth yl 4-{[Bis(4-
m eth ylp h en yl)m eth ylen e]a m in o}ben zoa te (15). To a 20
mL scintillation vial equipped with a magnetic stir bar were
added 4,4′-dimethylbenzophenone imine (0.500 g, 2.39 mmol),
C6H4Br-p-CO2Me (540 mg, 2.63 mmol, 1.10 equiv), Pd(OAc)2
(10.7 mg, 0.0478 mmol, 2 mol %), (()-BINAP (44.7 mg, 0.0718
mmol, 3 mol %), and Cs2CO3 (1.09 g, 3.35 mmol, 1.4 equiv).
Toluene (∼8 mL) was added, and the mixture was heated at
100 °C for 5 h. The yellow solution was allowed to cool to room
temperature and filtered. The volatile materials were removed
under reduced pressure, and the ketimine was purified by
silica gel chromatography using 10% ethyl acetate in hexane
as eluent. Recrystallization from EtOH gave 410 mg (50%) of
15. 1H NMR (400 MHz, C6D6): δ 1.91 (s, 3H), 2.07 (s, 3H),
3.42 (s, 3H), 6.74 (m, 4H), 6.88 (d, J ) 7.6 Hz, 2H), 7.00 (d, J
) 8.0 Hz, 2H), 7.92 (d, J ) 8.4 Hz, 2H), 7.99 (d, J ) 8.4 Hz,
2H). 13C NMR (100 MHz, C6D6): δ 21.1, 21.3, 51.2, 120.9, 125.2,
128.9, 129.2, 129.6, 130.0, 130.8, 133.4, 137.2, 138.7, 141.4,
156.7, 166.4, 168.3. Anal. Calcd for C23C21NO2: C, 80.44; H,
6.16; N, 4.08. Found: C, 80.46; H, 5.71; N, 3.67.
Rea ction of 2a w ith P h CHdNP h (3b) in th e P r esen ce
of Ad d ed Ketim in e 13. To a small vial were added 2a (10.0
mg, 0.0149 mmol), 3b (3.00 mg, 0.0164 mmol, 1.1 equiv), and
13 (4.90 mg, 0.0149 mmol). These compounds were dissolved
in C6D6 (0.7 mL), and the resulting solution was stirred for 2
h. GC/MS analysis of the solution showed the formation of
amine 7 and ketimine 8 and no formation of the diarylmethyl-
amine from 13.
P r ep a r a t ion of Met h yl 4-{[(E,Z)-(4-Met h ylp h en yl)-
(p h en yl)m eth ylen e]a m in o}ben zoa te (13). To a 20 mL
scintillation vial equipped with a magnetic stir bar were added
4-methylbenzophenone imine (0.500 g, 2.56 mmol), C6H4Br-
p-CO2Me (543 mg, 2.56 mmol), Pd(OAc)2 (11.5 mg, 0.0513
mmol, 2 mol %), (()-BINAP (47.9 mg, 0.0769 mmol, 3 mol %),
and Cs2CO3 (1.17 g, 3.59 mmol, 1.4 equiv). Toluene (∼8 mL)
was added, and the mixture heated at 100 °C for 5 h. The
yellow solution was allowed to cool to room temperature and
filtered. The volatile materials were removed under reduced
pressure, and the ketimine was purified by silica gel chroma-
tography using 10% ethyl acetate in hexane as eluent. The
ketimine (689 mg, 82%) was obtained as a 1:1 mixture of E
and Z isomers. 1H NMR (400 MHz, C6D6): δ 1.90 (s, 3H), 2.05
(s, 3H), 3.42 (s, 3H), 3.43 (s, 3H), 6.70-6.74 (m, 6H), 6.83 (d,
J ) 7.6 Hz, 2H), 6.86-6.91 (m, 6H), 6.98 (d, J ) 8.0 Hz, 2H),
7.88 (d, J ) 8.0 Hz, 2H), 7.93-7.95 (m, 2H), 7.99-8.01 (m,
6H). 13C NMR (100 MHz, CDCl3): δ 21.3, 21.4, 51.8, 120.5,
120.6, 124.5, 127.9, 128.2, 128.7, 128.8, 129.0, 129.3, 129.4,
129.5, 130.2, 130.3, 131.0, 132.5, 135.7, 136.2, 139.2, 141.6,
155.7, 155.8, 166.9, 168.7, 169.0. Anal. Calcd for C22H19NO2:
C, 80.22; H, 5.81; N, 4.25. Found: C, 79.98; H, 5.90; N, 4.02.
Deu ter iu m La belin g Stu d y of th e Rea ction of 2a w ith
(p-tol)CHdN(C6H4-p-OMe) (3c). Into a small vial were
Rep r esen ta tive P r oced u r e for th e Kin etic Exp er i-
m en ts of th e Rea ction betw een 2a a n d 3a -P h . Into a small
(132) Arndtsen, B. A.; Sleiman, H. F.; Chang, A. K.; McElwee-White,
L. J . Am. Chem. Soc. 1991, 113, 4871.

4606 Organometallics, Vol. 23, No. 20, 2004
Krug and Hartwig
vial was placed 2a (12.0 mg, 0.0179 mmol), toluene (0.40 mL),
and pyridine (5.1 µL, 0.0625 mmol, 3.5 equiv). This solution
was transferred to an NMR tube equipped with a screw-capped
top containing a Teflon septum. The solution was cooled with
dry ice. In a separate vial was placed imine 3a -P h (21.5 mg,
0.0893 mmol, 5 equiv), which was then dissolved in toluene
(0.30 mL). This solution was drawn into a 1 mL syringe and
added to the cold solution contained in the NMR tube. The
contents of the NMR tube were mixed briefly, and the tube
was placed into the NMR probe cooled to 2.0 °C. The consump-
tion of 2a was monitored by 31P NMR spectroscopy, and the
rate constants were determined by fitting the data to an
exponential decay using KaleidaGraph software. This proce-
dure was repeated using 5, 8, and 18 equiv of pyridine.
Rep r esen ta tive P r oced u r e for th e Rea ction of 2a w ith
P h CHO or Me3CCHO. Into a small vial were placed 2a (10.0
mg, 0.0149 mmol) and 1 mg of 1,3,5-trimethoxybenzene. The
contents were dissolved in C6D6 (0.7 mL), and an 1H NMR
spectrum was acquired. The sample was returned to a small
vial equipped with a magnetic stir bar, and aldehyde (10 equiv)
was added by microliter syringe. The solution was stirred at
natant was removed by pipet, and the solid recrystallized a
second time from toluene to give 43.0 mg of 24 (43%). 1H NMR
(400 MHz, C6D6): δ 1.80 (m, 4H), 3.54 (br s, 1H), 4.37 (br s,
1H), 6.87-7.17 (m, 15H), 7.36 (br m, 2H), 7.73 (br m, 2H),
8.00-8.17 (m, 6H). 31P NMR (202.4 MHz, C6D6): δ 79.0 (dd,
J PRh ) 215 Hz, J PP ) 34.2 Hz), 65.4 (dd, J PRh ) 198 Hz, J PP
)
34.2 Hz). Anal. Calcd for C34H31OP2Rh: C, 65.82; H, 5.04.
Found: C, 65.67; H, 5.00.
P r ep a r a tion of 26. Into a 20 mL scintillation vial equipped
with a magnetic stir bar was placed 2a (196 mg, 0.292 mmol).
The solid was dissolved in 8 mL of toluene. Addition of a
toluene solution of ynone 25 (57.0 mg, 0.306 mmol, 1.05 equiv)
by pipet generated a dark colored solution. The solution was
filtered through Celite and concentrated under reduced pres-
sure to about 1 mL. Cooling the solution to -35 °C gave a
yellow-orange solid. The dark supernatant was removed by
pipet, and the solid was washed with a minimal amount of
cold Et2O and pentane. The solid was then dissolved in THF
and concentrated to about 2 mL. The solution was layered with
pentane and cooled to -35 °C overnight. The mother liquor
was decanted from the yellow-orange crystals, which were
dried in vacuo to give 102 mg (41%) of 26. 1H NMR (400 MHz,
C6D6): δ 0.60 (d, J ) 9.6 Hz, 3H), 0.65-0.74 (m, 2H), 1.71-
1.78 (m, 2H), 1.95-2.05 (m, 3H), 2.27 (s, 3H), 2.40-2.51 (m,
1H), 2.62 (m, 1H), 5.20 (s, 1H), 6.78-7.13 (m, 21H), 7.26-7.38
(m, 2H), 7.51 (d, J ) 7.6 Hz, 2H), 7.61-7.64 (m, 2H), 7.80 (d,
J ) 8.0 Hz, 2H). 31P NMR (121.6 MHz, C6D6): δ 47.1 (br s),
48.1-48.7 (m). Anal. Calcd for C46H45OP2Rh‚C4H8O: C, 70.58;
H, 6.28. Found: C, 70.88; H, 6.25.
1
room temperature for 1 h. An H NMR spectrum was acquired,
and the yields of products shown in Scheme 6 were calculated.
In d ep en d en t P r ep a r a tion of (4-Meth ylp h en yl)(p h en -
yl)m eth yl Ben zoa te (19a ). Into a 50 mL two-neck round-
bottom flask equipped with magnetic stir bar was placed
4-methyl benzhydrol (150 mg, 0.758 mmol). The flask was
flushed with nitrogen, and CH2Cl2 (8 mL) was added by
syringe. Fresh PhC(O)Cl (260 µL, 2.27 mmol, 3 equiv) and
Et3N (15 equiv) were added by syringe. The resulting solution
was stirred for 3 h at room temperature. The solution was
diluted with CH2Cl2, and 10% aqueous HCl was added to
quench the excess benzoyl chloride. The mixture was washed
with aqueous NaHCO3, and the organic layer was separated
and dried over MgSO4. The solution was decanted from MgSO4,
and the volatile materials were removed under rotary evapo-
ration. The crude material was purified by silica gel chroma-
tography using 10% ethyl acetate in hexane to give the title
In depen den t P r epar ation of Meth yl 4-{[(4-Meth ylph en -
yl)(p h en yl)m eth yl] a m in o}ben zoa te (35). The reaction was
not conducted under an inert atmosphere. Into a 250 mL
round-bottom flask equipped with a magnetic stir bar was
placed 13 (170 mg, 0.517 mmol). The ketimine was suspended
in EtOH (30 mL), and NaBH4 (1.56 g, 41.3 mmol, 80 equiv)
was added in four portions. The yellow color of the ketimine
faded after 2-3 h of heating at reflux. Upon complete
consumption of the starting material, as determined by TLC,
the volatile materials were removed by rotary evaporation, and
the remaining solid was quenched with water and the product
was extracted into Et2O. The organic layer was separated and
dried over MgSO4 and filtered. The Et2O was removed by
rotary evaporation, and the residue was purified by silica gel
chromatography eluting with 10% ethyl acetate in hexane to
give 118 mg (70%) of 35. 1H NMR (500 MHz, C6D6): δ 2.08 (s,
3H), 3.53 (s, 3H), 4.15 (d, J ) 4.5 Hz, 1H), 5.35 (d, J ) 4.5 Hz,
1H), 6.24 (d, J ) 9.0 Hz, 2H), 6.92 (d, J ) 8.0 Hz, 2H), 7.00-
7.05 (m, 3H), 7.07-7.12 (m, 4H), 8.06 (d, J ) 8.5 Hz, 2H). 13C
NMR (100 MHz, C6D6): δ 21.0, 51.1, 62.1, 112.8, 119.5, 127.6,
127.7, 127.8, 129.0, 129.6, 131.7, 137.2, 139.5, 142.6, 151.2,
167.0. Anal. Calcd for C22H21NO2: C, 79.73; H, 6.39; N, 4.25.
Found: C, 79.73; H, 6.55; N, 4.10.
1
compound in 63% yield (145 mg). H NMR (400 MHz, C6D6):
δ 2.05 (s, 3H), 6.93 (d, J ) 8.0 Hz, 2H), 7.00-7.13 (m, 6H),
7.30-7.34 (m, 3H), 7.40 (d, J ) 8.0 Hz, 2H), 8.19-8.21 (m,
2H). 13C NMR (100 MHz, C6D6): δ 21.0, 77.5, 127.5, 127.7,
128.0, 128.6, 128.7, 129.4, 130.0, 130.9, 132.9, 137.6, 138.1,
141.1, 165.4. Anal. Calcd for C21H18O2: C, 83.42; H, 6.00.
Found: C, 83.15; H, 6.01.
In d ep en d en t P r ep a r a tion of 2,2-Dim eth yl-1-(4-m eth -
ylp h en yl)p r op yl P iva la te (19b). Into a 20 mL scintillation
vial were placed alcohol 20b (212 mg, 1.07 mmol) and Na metal
(82.0 mg, 3.57 mmol, 3 equiv). THF (6-8 mL) was added and
the mixture stirred for 6 h at room temperature. The cloudy
pale yellow solution was decanted into a separate vial contain-
ing Me3CC(O)Cl (214 mg, 1.79 mmol, 1.5 equiv). The solution
became colorless upon addition of the sodium alkoxide. After
1 h of stirring, the volatile materials were removed by rotary
evaporation, and the product was extracted into hexane. The
solution was filtered through Celite and concentrated. Silica
gel chromatography using 2.5% ethyl acetate in hexane gave
66.0 mg of 19b (21%). 1H NMR (500 MHz, C6D6): δ 0.91 (s,
9H), 1.17 (s, 9H), 2.10 (s, 3H), 5.67 (s, 1H), 6.96 (d, J ) 7.5
Hz, 2H), 7.15 (d, J ) 8.0 Hz, 2H). 13C NMR (125.8 MHz,
CDCl3): δ 21.1, 26.1, 27.2, 35.2, 38.9, 82.4, 127.5, 128.3, 135.7,
136.9, 177.1. Anal. Calcd for C17H26O2: C, 77.82; H, 9.99.
Found: C, 77.58; H, 10.17.
P r ep a r a tion of 24. Into a 20 mL scintillation vial equipped
with a magnetic stir bar was placed 2a (109 mg, 0.162 mmol).
The solid was dissolved in toluene (8 mL), and acetophenone
(21.0 µL, 0.179 mmol, 1.1 equiv) was added by syringe. The
solution was heated at 70 °C for 0.5 h. The solution was then
allowed to cool to room temperature and was concentrated
under reduced pressure to about 1 mL. Cooling of the concen-
trated solution gave an orange solid. The dark colored super-
P r ep a r a tion of [(DP P E)Rh (µ-OH)]2 (36). Into a 50 mL
Schlenk flask equipped with a magnetic stir bar were placed
[(DPPE)Rh(µ-Cl)]2 (150 mg, 0.140 mmol) and KOH (783 mg,
14.0 mmol, 100 equiv). These were suspended in toluene (10
mL), and H2O (6 mL) was added by cannula. The biphasic
mixture was heated at 75 °C for 2 h. The orange-brown organic
layer was removed by cannula to a separate flask, and MgSO4
was added to remove water. The solution was filtered through
Celite and concentrated under reduced pressure. Addition of
pentane gave a yellow-orange precipitate. The solution was
cooled briefly to complete the precipitation. The supernatant
was removed by pipet and redissolved in THF. Concentration
of the solution and layering with Et2O gave an orange solid,
which was isolated from the supernatant and dried to give 109
mg (75%) of 36. 1H NMR (400 MHz, C6D6): δ -0.55 (s, 2H),
1.72 (d, J ) 17.2 Hz, 8H), 6.98 (m, 24H), 8.03 (m, 16H). 31P
NMR (202.4 MHz, C6D6): δ 74.4 (d, J ) 190 Hz). Anal. Calcd
for C52H50O2P4Rh2: C, 60.25; H, 4.86. Found: C, 59.99; H, 5.07.

New Classes of Insertion Reactions
Organometallics, Vol. 23, No. 20, 2004 4607
Rea ction of 2a a n d P h CHdN(C6H4-p-CO2Me (3a -P h )
w ith Aqu eou s Wor k u p . Into a small vial equipped with a
magnetic stir bar were placed 2a (10 mg, 0.0149 mmol) and 1
mg of 1,3,5-trimethoxybenzene. C6D6 (0.7 mL) was added, and
an 1H NMR spectrum was acquired. The sample was added
to a separate vial containing 3a -P h (3.7 mg, 0.0156 mmol, 1.05
equiv), and the solution stirred for 5 min at room temperature.
H2O (1.0 µL, 0.0521 mmol, 3.5 equiv) was added by microliter
syringe, and the solution was stirred for 0.5 h. An 1H NMR
spectrum was acquired, and the yields of hydroxide 36 and
amine 35 were calculated to be >95%.
µL, 0.0833 mmol, 5.5 equiv) was added by microliter syringe.
The solution was stirred for 2 h at room temperature. An 1H
NMR spectrum after this time showed the quantitative forma-
tion of toluene and hydroxide 36.
Ack n ow led gm en t. Financial support for this work
was provided by the Department of Energy, Office of
Basic Energy Sciences.
Su p p or t in g In for m a t ion Ava ila b le: Full crystallo-
graphic reports for compounds 2a , 4, 6, 9, and 26 and
corresponding .cif files are available free of charge via the
Internet at http://www.pubs.acs.org.
Rea ction of 2a w ith H2O. Into a small vial equipped with
a stir bar were placed 2a (10 mg, 0.0149 mmol) and 1 mg of
1,3,5-trimethoxybenzene. Complex 2a was dissolved in C6D6
(0.7 mL), and an 1H NMR spectrum was acquired. H2O (1.5
OM0496582