Carbon-oxygen bond formation at organopalladium centers: The reactions of PdMeR(L2) (R = Me, 4-tolyl; L2 = tmeda, bpy) with diaroyl peroxides and the involvement of organopalladium(IV) species

Article abstract of DOI:10.1021/om030644q

The group 16 oxidants dibenzoyl- and bis(4-trifluoromethylbenzoyl)-peroxide react with dimethylpalladium(II) and methyl(4-tolyl)palladium(II) complexes of the bidentate nitrogen donor ligands 2,2′-bipyridine and N,N,N′,N′-tetramethylethylenediamine in discrete stepwise processes as the temperature is raised from -70°C. Carbon-oxygen bonds are formed during this reaction sequence but not from those Pd(IV) complexes detected spectroscopically. The initial reaction gives undetected "Pd^IV(O₂CAr)₂MeR(L₂)" (Ar = Ph, Ar_F; R = Me, Tol; L₂ = bpy, tmeda), which immediately undergo methyl aroate exchange with Pd^IIMeR(L₂) to give Pd^II(O₂CAr)R(L₂) and Pd^IV(O₂CAr)Me₂R(L₂), where all products except for Pd^IV(O₂CAr)Me₂-Tol(tmeda) were detected by ¹H NMR spectroscopy. On raising the temperature, the Pd^IVMe₃ complexes reductively eliminate Me-Me, and the Pd^IVMe₂Tol complexes eliminate Me-Me and Tol-Me. The resultant Pd(II) complexes Pd^II(O₂CAr)R(L₂) react with (ArCO₂)₂ at higher temperatures to form Pd^II(O₂CAr)₂(L₂) and R-O₂CAr (R = Me, Tol), except for Pd^II(O₂CAr)Tol(tmeda), which forms Pd^II(O₂CAr)₂(tmeda) and 4,4′-bitolyl. Each reaction step has been confirmed by the independent synthesis of intermediates Pd^II(O₂CAr)₂(L₂) and Pd^II(O₂CAr)R(L₂) (Ar = Ph, Ar_F; R = Me, Tol; L₂ = bpy, tmeda) and Pd^IV(O₂CR)Me₂R(L₂) (R = Ph, Ar_F; R = Me, Tol; L₂ = bpy) by metathesis reactions of halogeno complexes with Ag[O₂CAr], followed by temperature-dependent studies of both the decomposition of Pd(IV) complexes and reactions of Pd(II) complexes with (ArCO₂)₂. Attempts to prepare "Pd^IV(O₂CAr)₂ MeR(bpy)" in a similar manner (and thus in the absence of PdMeR(bpy) with which they undergo exchange reactions) were unsuccessful, but the complexes Pd^IVI₂MeR(bpy) (R = Me, Tol) that formed on reaction of diiodine with PdMeR(L₂) were detected and found to reductively eliminate iodomethane. X-ray structural studies are reported for the square-planar palladium(II) complexes Pd(O₂CPh)₂(bpy), Pd(O₂CAr)₂(tmeda) (Ar = Ph, Ar_F), and Pd(O₂CPh)(Tol) (bpy)?CH₂Cl₂.

Full text of DOI:10.1021/om030644q

1122
Organometallics 2004, 23, 1122-1131
Ca r bon -Oxygen Bon d F or m a tion a t Or ga n op a lla d iu m
Cen ter s: Th e Rea ction s of P d MeR(L2) (R ) Me, 4-tolyl;
L2 ) tm ed a , bp y) w ith Dia r oyl P er oxid es a n d th e
In volvem en t of Or ga n op a lla d iu m (IV) Sp ecies
Allan J . Canty* and Melanie C. Denney
School of Chemistry, University of Tasmania, Private Bag 75,
Hobart, Tasmania, 7001, Australia
Brian W. Skelton and Allan H. White
School of Biomedical and Chemical Sciences, University of Western Australia,
Crawley, Western Australia, 6009, Australia
Received October 28, 2003
The group 16 oxidants dibenzoyl- and bis(4-trifluoromethylbenzoyl)-peroxide react with
dimethylpalladium(II) and methyl(4-tolyl)palladium(II) complexes of the bidentate nitrogen
donor ligands 2,2′-bipyridine and N,N,N′,N′-tetramethylethylenediamine in discrete stepwise
processes as the temperature is raised from -70 °C. Carbon-oxygen bonds are formed during
this reaction sequence but not from those Pd(IV) complexes detected spectroscopically. The
initial reaction gives undetected “PdIV(O2CAr)2MeR(L2)” (Ar ) Ph, ArF; R ) Me, Tol; L2 )
bpy, tmeda), which immediately undergo methyl aroate exchange with PdIIMeR(L2) to give
PdII(O2CAr)R(L2) and PdIV(O2CAr)Me2R(L2), where all products except for PdIV(O2CAr)Me2-
1
Tol(tmeda) were detected by H NMR spectroscopy. On raising the temperature, the PdIV-
Me3 complexes reductively eliminate Me-Me, and the PdIVMe2Tol complexes eliminate Me-
Me and Tol-Me. The resultant Pd(II) complexes PdII(O2CAr)R(L2) react with (ArCO2)2 at
higher temperatures to form PdII(O2CAr)2(L2) and R-O2CAr (R ) Me, Tol), except for PdII(O2-
CAr)Tol(tmeda), which forms PdII(O2CAr)2(tmeda) and 4,4′-bitolyl. Each reaction step has
been confirmed by the independent synthesis of intermediates PdII(O2CAr)2(L2) and PdII(O2-
CAr)R(L2) (Ar ) Ph, ArF; R ) Me, Tol; L2 ) bpy, tmeda) and PdIV(O2CR)Me2R(L2) (R ) Ph,
ArF; R ) Me, Tol; L2 ) bpy) by metathesis reactions of halogeno complexes with Ag[O2CAr],
followed by temperature-dependent studies of both the decomposition of Pd(IV) complexes
and reactions of Pd(II) complexes with (ArCO2)2. Attempts to prepare “PdIV(O2CAr)2MeR-
(bpy)” in a similar manner (and thus in the absence of PdMeR(bpy) with which they undergo
exchange reactions) were unsuccessful, but the complexes PdIVI2MeR(bpy) (R ) Me, Tol)
that formed on reaction of diiodine with PdMeR(L2) were detected and found to reductively
eliminate iodomethane. X-ray structural studies are reported for the square-planar palla-
dium(II) complexes Pd(O2CPh)2(bpy), Pd(O2CAr)2(tmeda) (Ar ) Ph, ArF), and Pd(O2CPh)-
(Tol)(bpy)‚CH2Cl2.
In tr od u ction
butylhydroperoxide,4 molybdenum peroxides,5 and hyper-
valent iodine(III) reagents.3g,h,6 However, the suggested
intermediates have yet to be detected spectroscopically.
In contrast, the intermediacy of Pd(IV) has been de-
tected for closely related carbon-selenium coupling, the
first demonstrated model reaction for carbon-hetero-
atom (group 16) coupling at Pd(IV). Crystalline trans-
Carbon-oxygen bond formation at palladium centers
is an important process currently attracting consider-
able attention. Although much of this interest has
focused on coupling occurring from Pd(II) centers,1
organopalladium(IV) species have been postulated as
intermediates in a variety of processes including the
acetoxylation of arenes (eq 1)2 and the formation of
carbon-oxygen bonds in the reaction of organopalla-
dium(II) complexes with oxygen-atom-containing oxidiz-
ing agents such as 3-chloroperbenzoic acid,3 tert-
(2) (a) Henry, P. M. J . Org. Chem. 1971, 36, 1886-1890. (b) Stock,
L. M.; Tse, K.-t.; Vorvick, L. J .; Walstrum, S. A. J . Org. Chem. 1981,
46, 1757-1759. (c) Yoneyama, T.; Crabtree, R. H. J . Mol. Catal. A 1996,
108, 35-40.
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1976, 369-370. (b) Mahapatra, A. K.; Bandyopadhyay, D.; Bandyo-
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Bandyopadhyay, D.; Chakravorty, A. Inorg. Chem. 1988, 27, 1173-
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438-446.
* Corresponding author. Fax:
Allan.Canty@utas.edu.au.
(61-3) 6226-2858. E-mail:
(1) (a) Palucki, M.; Wolfe, J . P.; Buchwald, S. L. J . Am. Chem. Soc.
1996, 118, 10333-10334. (b) Mann, G.; Hartwig, J . F. J . Am. Chem.
Soc. 1996, 118, 13109-13110. (c) Hartwig, J . F. Acc. Chem. Res. 1998,
31, 852-860. (c) Muci, A. R.; Buchwald, S. L. Top. Curr. Chem. 2002,
219, 131-209. (d) Kuwabe, S.; Torraca, K. E.; Buchwald, S. L. J . Am.
Chem. Soc. 2001, 123, 12202-12206. (e) Mann, G.; Shelby, Q.; Roy,
A. H.; Hartwig, J . F. Organometallics 2003, 22, 2775.
10.1021/om030644q CCC: $27.50 © 2004 American Chemical Society
Publication on Web 01/29/2004

C-O Bond Formation at Organopalladium Centers
Organometallics, Vol. 23, No. 5, 2004 1123
Sch em e 1. Rea ction of a 2:3 Ra tio of P d IIMe2(L2)
(L2 ) bp y, tm ed a ) a n d (Ar CO2)2 (Ar ) P h , Ar F ) in
Aceton e-d 6 or CD2Cl2
Pd(SePh)2Me2(bpy) (bpy ) 2,2′-bipyridine) has been
isolated from the reaction of PdMe2(bpy) with diphenyl
diselenide and characterized by X-ray crystallography.
When redissolved in CDCl3, this complex decomposes,
resulting in the formation of carbon-carbon bonds (Me-
Me) and carbon-selenium bonds (Me-SePh) in ∼1:1
ratio, together with Pd(II) products (eq 2).7
MeCO2H/Pd(O2CMe)2
arene
8 f Ar-O2CMe
(1)
oxidant
PdIIMe2(bpy) + (PhSe)2 f PdIV(SePh)2Me2(bpy) f
∼0.5 Me-Me + ∼0.5 Me-SePh (2)
Both carbon-carbon and carbon-oxygen coupling
have been directly observed in reductive elimination
from triorganoplatinum(IV) complexes of the form fac-
Pt(OR)Me3L2 [L2 ) 1,2-bis(diphenylphosphino)ethane,
1,2-bis(diphenylphosphino)benzene; OR ) O2CMe, O2-
CCF3, OTol-4; L ) PMe3, OR ) OTol-4].8 In each case,
reductive elimination occurs by preliminary dissociation
of a ligand (OR- in the case of carbon-oxygen coupling,
and OR- or unidentate phosphine in the case of carbon-
carbon coupling) to give a five-coordinate intermediate.
This is followed by either nucleophilic attack by OR-
on a Pt(IV)-bound methyl group to give Me-OR, or
carbon-carbon coupling from the five-coordinate species
to give ethane. The selectivity of this reaction has been
demonstrated to be highly solvent dependent.
mediates in the catalysis shown in eq 1. Structural
studies of Pd(II) products and a Pd(II) intermediate
complex are presented, together with an assessment of
the potential involvement of Pd(IV) species in carbon-
oxygen coupling processes. A preliminary communica-
tion of part of this work has appeared.10
In view of the success in detecting C-Se coupling from
Pd(IV) (eq 2), where the Pd(IV) species is formed using
diphenyl diselenide as an oxidant, the reactivity of
PdMe2(bpy) toward dibenzoyl peroxide was investigated
showing that, along with Pd(II) products, ethane, Me-
O2CPh, and PhCO2H (upon workup) were formed.7 This
reaction was assumed to proceed via an intermediate
of the form “PdMe2(O2CPh)2(bpy)”,7 related to eq 2 and
to stable Pt(IV) complexes formed on oxidative addition
of (PhCO2)2 to dimethyl- and diaryl-platinum(II) com-
plexes.9 A detailed analysis of this and related reaction
systems is reported here, showing that Pd(IV) interme-
diates are involved and that methyl group exchange
reactions occur between Pd(II) and Pd(IV) centers, but
that C-O coupling does not occur from the proposed
diorganopalladium(IV) intermediate or from a detected
triorganopalladium(IV) intermediate. Arylpalladium(II)
substrates have been included in this study in an
attempt to detect C(sp2)-O coupling from species con-
taining carboxylate ligands coordinated to arylpalla-
dium(IV) and in an attempt to model proposed inter-
Resu lts a n d Discu ssion
The reactivity of PdMeR(bpy) complexes toward di-
aroyl peroxides was monitored by 1H NMR spectroscopy.
Addition of a solution of the peroxide in acetone-d6 or
CD2Cl2 to the complex at low temperature (< -50 °C),
followed by slow warming, allowed the elucidation of a
complicated series of reactions leading to the products
observed at ambient temperature. Studies were initially
confined to the reaction of PdMe2(bpy) with (PhCO2)2.
Investigations were then extended to include methyl-
(aryl)palladium systems, for which less stable Pd(IV)
species would be anticipated, and N,N,N′,N′-tetrameth-
ylethylenediamine (tmeda) as an aliphatic and more
flexible ligand than bpy. Solubility difficulties led to the
use of bis(4-trifluoromethylbenzoyl) peroxide, (ArFCO2)2,
to enhance the solubility of intermediates and end-
products.
1H NMR Stu d ies of th e Rea ction of P d Me2(L2)
(L2 ) bp y, tm ed a ) w ith (Ar CO2)2 (Ar ) P h , Ar F ).
1
Variable-temperature H NMR studies of the reaction
of PdMe2(bpy) with (PhCO2)2 revealed a complex series
of reactions, which proceed in the same manner in both
acetone-d6 and CD2Cl2. Several mole ratios of reagents
were explored, and it was found that only in the case of
a 2PdMe2(L2):3(ArCO2)2 ratio did the reaction proceed
to completion with full consumption of both reagents.
At temperatures below -30 °C PdMe2(bpy) and (Ph-
CO2)2 reacted slowly to form Pd(O2CPh)Me3(bpy) (1) and
Pd(O2CPh)Me(bpy) (5). The proposed intermediacy of
“Pd(O2CAr)2Me2(L2)” (A, eq 3 in Scheme 1) and the
subsequent exchange reactions (eq 4) are discussed
below. Warming to -30 °C led to a decrease in 1,
(4) (a) Alsters, P. L.; Teunissen, H. T.; Boersma, J .; van Koten, G.
Recl. Trav. Pays-Bas 1990, 109, 487-489. (b) Alsters, P. L.; Teunissen,
H. T.; Boersma, J .; Spek, A. L.; van Koten, G. Organometallics 1993,
12, 4691-4696. (c) Valk, J . M.; Boersma, J .; van Koten, G. Organo-
metallics 1996, 15, 4366-4372. (d) Wadhwani, P.; Mukerjee, D.;
Bandyopadhyay, D. J . Am. Chem. Soc. 2001, 123, 12430-12431.
(5) (a) Alsters, P. L.; Boersma, J .; van Koten, G. Tetrahedron Lett.
1991, 32, 675-678. (b) Alsters, P. L.; Boersma, J .; van Koten, G.
Organometallics 1993, 12, 1629-1638.
(6) Bhawmick, R.; Biswas, H.; Bandyopadhyay, P. J . Organomet.
Chem. 1995, 498, 81-83.
(7) Canty, A. J .; J in, H.; Skelton, B. W.; White, A. H. Inorg. Chem.
1998, 37, 3975-3981.
(8) (a) Williams, B. S.; Holland, A. W.; Goldberg, K. I. J . Am. Chem.
Soc. 1999, 121, 252-253. (b) Williams, B. S.; Goldberg, K. I. J . Am.
Chem. Soc. 2001, 123, 2576-2587.
(9) (a) Aye, K.-T.; Vittal, J . J .; Puddephatt, R. J . J . Chem. Soc.,
Dalton Trans. 1993, 1835. (b) Rashidi, M.; Nabavizadeh, M.; Hakimela-
hi, R.; J amali, S. J . Chem. Soc., Dalton Trans. 2001, 23, 3430-3434.
(10) Canty, A. J .; Done, M. C.; Skelton, B. W.; White, A. H. Inorg.
Chem. Commun. 2001, 4, 648-650.

1124 Organometallics, Vol. 23, No. 5, 2004
Canty et al.
Sch em e 2. Syn th esis a n d Decom p osition of
accompanied by an increase in the amount of 5 and the
formation of ethane (eq 5). At -10 °C, 5 decreased and
the formation of Me-O2CPh along with the precipitation
of a yellow crystalline solid was observed (eq 6), result-
ing in the overall reaction shown in eq 7. X-ray crystal-
lographic studies confirmed the identity of the solid as
Pd(O2CPh)2(bpy) (9). An identical reaction sequence was
observed for the reaction of PdMe2(bpy) with (ArFCO2)2,
although C-O coupling to form Me-O2CArF (eq 6)
occurred at a lower temperature (-30 °C). Unlike 9, the
inorganic product, Pd(O2CArF)2(bpy) (10), was soluble,
allowing the stoichiometry of the reaction to be deter-
mined. Complex 10 and Me-O2CArF were present in
equal amounts, but ethane could not be quantified
reliably by NMR due to its volatility.
Un sta ble Tr im eth ylp a lla d iu m (IV) Com p lexes in
Aceton e-d 6
The reaction of PdMe2(tmeda) with (ArCO2)2 (R ) Ph,
ArF) followed an identical series of reactions with
analogous intermediates identified at similar temper-
atures. The inorganic product Pd(O2CArF)2(tmeda) (12)
and Pd(O2CPh)2(tmeda) (11) were soluble, allowing the
product ratio Pd(O2CAr)2(tmeda):Me-O2CPh to be de-
termined as 1:1. As seen in the reaction of the bpy
complexes, the formation Me-O2CArF was observed at
a lower temperature than Me-O2CPh (eq 6).
as intermediates, and their reactions with (ArCO2)2
proceeded as shown by eq 6.
The proposed sequence of eqs 3-6 was studied in
detail by carrying out a series of specific reactions.
Reagents were mixed in different ratios and held at
different temperatures in order to halt the reaction
sequence at different stages. The specific reactions
proceeded at temperatures identical to those of related
reactions in Scheme 1. Thus, when the reagents PdMe2-
(L2) and (PhCO2)2 were mixed in a 2:1 ratio and the
reaction allowed to go to completion below -30 °C, Pd-
(O2CPh)Me3(L2) (1, 3) and Pd(O2CPh)Me(L2) (5, 7) were
observed in ∼1:1 ratio with no reagents remaining, in
1H NMR Stu d ies of th e Rea ction of P d MeTol-
(bp y) (Tol ) 4-tolyl) a n d (Ar CO2)2 (Ar ) P h , Ar F ).
The reaction of PdMeTol(bpy) with (PhCO2)2 displayed
close similarities to eqs 3-7 (Scheme 3). When (PhCO2)2
was added to PdMeTol(bpy) at temperatures below -30
°C in acetone-d6, a slow reaction to form Pd(O2CPh)-
Me2Tol(bpy) (13) and Pd(O2CPh)Tol(bpy) (15) was ob-
served. On warming to -30 °C, the quantity of 13
observed decreased and Pd(O2CPh)Me(bpy) (5), Pd(O2-
CPh)Tol(bpy) (15), 1,4-xylene (Tol-Me), and ethane were
detected. At -10 °C, the appearance of Me-O2CPh and
Pd(O2CPh)2(bpy) (9) was accompanied by a decrease in
5. Further warming to ambient temperature led to the
very slow appearance of Tol-O2CPh along with an
increase in 9 and the slow disappearance of 15. These
observations are consistent with the reaction sequence
shown in eqs 8-12 to give the overall reaction in eq 13,
where n ) 0.6. Using (ArFCO2)2 as the oxidant, a
different product ratio was observed for Tol-Me and
Me-Me coupling in eq 10 to give n ) 0.4. In several of
the specific reactions, 4,4′-bitolyl was observed as a
minor product. Its presence predominantly occurred in
reactions carried out entirely at room temperature and
was largely suppressed in reactions performed at low
temperature. The formation of biaryls as a product in
palladium-mediated reactions is common, and several
mechanisms for their formation have been proposed.12
When the reagents PdMeTol(bpy) and (ArCO2)2 were
mixed in a 2:1 ratio in acetone-d6 and the reaction was
allowed to go to completion at -40 °C, all reagents were
consumed and Pd(O2CAr)Me2Tol(bpy) (13, 14; isomers
illustrated in Scheme 4) and Pd(O2CAr)Tol(bpy) (15, 16)
were observed in 1:1 ratio, in accord with eqs 8 and 9.
The ratio of Pd(IV) isomers depended on the solvent
agreement with eqs 3 and 4. In the case where L2
)
bpy with the reaction carried out in acetone-d6, Pd(O2-
CPh)Me(bpy) (5) gradually precipitated at low temper-
ature, generating uncertainty in the accuracy of the
observed product ratio, but this limitation was overcome
by performing the reaction in CD2Cl2. Warming to
temperatures above -30 °C led to the decomposition of
Pd(O2CPh)Me3(L2) (1, 3) (eq 5), with Pd(O2CPh)Me(L2)
(5, 7) and ethane the only species observed at the
completion of the reaction. Undetected “PdIV(O2CPh)2Me2-
(L2)” (A) is assumed to undergo the exchange reaction
shown in eq 4. Such reactions are often observed in Pd-
(IV) chemistry on reaction of triorganopalladium(IV)
complexes with diorganoplatinum(II)11a and diorgano-
palladium(II) substrates.11b,c
Some of the intermediates were synthesized indepen-
dently and their proposed reactions investigated. The
reactions of eq 5 were investigated by the in situ
preparation of the Pd(IV) intermediates Pd(O2CAr)Me3-
(L2) (1-4) from PdIMe3(L2) and Ag[O2CAr] at -50 °C
in acetone-d6 (Scheme 2). Decomposition to Pd(O2CAr)-
Me(L2) (5-8) and ethane was observed at ca. -30 °C.
The independent syntheses of Pd(O2CAr)Me(L2) (5-8)
from PdIMe(L2) and Ag[O2CAr] confirmed their identity
(12) (a) Ozawa, F.; Fujimori, M.; Yamamoto, T.; Yamamoto, A.
Organometallics 1986, 5, 2144-2149. (b) Ozawa, F.; Hidaka, T.;
Yamamoto, T.; Yamamoto, A. J . Organomet. Chem. 1987, 330, 253-
263. (c) Yagyu, T.; Hamada, M.; Osakada, K.; Yamamoto, T. Organo-
metallics 2001, 20, 1087-1101. (d) Kraatz, H.-B.; van der Boom, M.
E.; Ben-David, Y.; Milstein, D. Isr. J . Chem. 2001, 41, 163-171.
(11) (a) Aye, K.-T.; Canty, A. J .; Crespo, M.; Puddephatt, R. J .; Scott,
J . D.; Watson, A. A. Organometallics 1989, 8, 1518-1522. (b) Markies,
B. A.; Canty, A. J .; Boersma, J .; van Koten, G. Organometallics 1994,
13, 2053-2058. (c) Kruis, D.; Markies, B. A.; Canty, A. J .; Boersma,
J .; van Koten, G. J . Organomet. Chem. 1997, 532, 235-242.

C-O Bond Formation at Organopalladium Centers
Organometallics, Vol. 23, No. 5, 2004 1125
Sch em e 3. Rea ction of P d IIMeTol(bp y) w ith (Ar CO2)2 (Ar ) P h , Ar F ) in 2:3 Ra tio in Aceton e-d 6 or CD2Cl2
1
Sch em e 4. Syn th esis a n d Decom p osition of
Dim eth yl(tolyl)(2,2′-bip yr id in e)p a lla d iu m (IV)
Com p lexes in Aceton e-d 6
(Scheme 4). H NMR spectroscopy confirmed the pres-
ence of the above as two isomers, PdIV(O2CAr)Me2Tol-
(bpy) (13, 14), which persisted to ca. -30 °C, at which
temperature they decomposed to give the products
according to eq 10. Independently synthesized Pd(O2-
CAr)Tol(bpy) (15, 16) was shown to react with (ArCO2)2
very slowly at ambient temperature to form Tol-O2CAr
and Pd(O2CAr)2(bpy) (9, 10), in agreement with eq 12.
1H NMR Stu d ies of th e Rea ction of P d MeTol-
(tm ed a ) (Tol ) 4-tolyl) w ith (Ar CO2)2 (Ar ) P h ,
Ar F). In view of the results obtained for the bpy systems,
reactions of PdMeTol(tmeda) with (ArCO2)2 were ini-
tially studied in a 2:3 ratio in acetone-d6. No reaction
was observed until > -30 °C (Ar ) Ph) or -50 °C (Ar
) ArF), when Pd(O2CAr)Me(tmeda) (7, 8), Pd(O2CAr)-
Tol(tmeda) (17, 18), 1,4-Tol-Me, and ethane began to
form (Scheme 5). No Pd(IV) intermediates were ob-
served. Warming to > -20 °C (Ar ) Ph) or -30 °C (Ar
) ArF) led to the appearance of Pd(O2CAr)2(tmeda) (11,
12) and Me-O2CAr and a decreased amount of Pd(O2-
CAr)Me(tmeda) (7, 8). At ambient temperature, the
reaction continued over several days, forming 4,4′-bitolyl
and further Pd(O2CAr)2(tmeda) (11, 12), while Pd(O2-
CAr)Tol(tmeda) (17, 18) decreased. The final products,
after several days at ambient temperature, were Pd-
(O2CAr)2(tmeda) (11, 12), 1,4-Tol-Me, Me-O2CAr, and
4,4′-Tol2, with the notable absence of Tol-O2CAr. Not
all of the peroxide was consumed in these reactions.
used but not on the choice of oxidant. In acetone-d6
1:1 ratio of isomers was seen, while in CD2Cl2 a 1:2 ratio
was observed.
a
To model eq 10 and to confirm the identity of the
observed Pd(IV) intermediates (13, 14), PdIMe2Tol(bpy)
was reacted with Ag[O2CAr] at -70 °C in an NMR tube
On the basis of results for the bpy systems, these
reactions are anticipated to proceed as shown in eqs 14-
17. Unlike Pd(O2CAr)Tol(bpy) (15, 16), which react with

1126 Organometallics, Vol. 23, No. 5, 2004
Sch em e 5. Rea ction of P d IIMeTol(tm ed a ) w ith (Ar CO2)2 (Ar ) P h , Ar F ) in Aceton e-d 6
Canty et al.
Sch em e 6. Syn th esis a n d Decom p osition of P d I2MeR(bp y) Com p lexes in Aceton e-d 6
1 equiv of (ArCO2)2, Pd(O2CAr)Tol(tmeda) (17, 18) react
with only half an equivalent of (ArCO2)2, as shown in
eq 18. Consequently, the overall stoichiometry for
complete consumption of reagents would not be a 2:3
ratio, but rather would require a reagent ratio of 2:{(1
+ n) + [(2 - n)/2]} ) 2:[2 + (n/2)] (from eqs 14-18). To
determine the stoichiometry of the reaction, n would
need to be determined from the product distribution of
eq 16, but this proved to be very difficult owing to some
competition, even at low temperature, between the
reactions of eq 16 and Pd(O2CAr)Me(tmeda) (7, 8) with
(ArCO2)2 (eq 17). In addition, PdIMe2Ph(tmeda) is too
unstable to be observed,11b and thus specific reactions
using “Pd(O2CAr)Me2Tol(tmeda)” (D) were not consid-
ered feasible. The independently prepared complexes
Pd(O2CAr)Tol(tmeda) (17, 18) reacted slowly with di-
aroyl peroxide at ambient temperature to form Pd(O2-
CAr)2(tmeda) (11, 12) and 4,4′-bitolyl (eq 18), but no Tol-
O2CAr was formed.
tathesis involving Ag[O2CAr] (Schemes 2 and 4), and
so we investigated the reaction of diiodine with PdMeR-
(bpy) (R ) Me, Tol), followed by reaction with Ag[O2-
CPh], in an attempt to generate “Pd(O2CPh)2MeR(bpy)”
in the absence of PdMeR(bpy). Reaction with diiodine
generated PdI2MeR(bpy) at low temperature (< -50 °C),
1
where the complexes exhibit H NMR spectra indicating
trans oxidative addition of diiodine and the absence of
other isomers, e.g., one pyridyl and one PdMe environ-
ment for 19, two pyridyl and one PdMe environment
for 20, the PdMe chemical shifts for 19 (2.75 ppm) and
20 (2.30 ppm) being typical for methyl groups trans to
bpy but different from methyl groups trans to iodo
groups, e.g., 1.12 ppm for PdIMe3(bpy).19 Similar com-
(13) van Asselt, R.; Rijnberg, E.; Elsevier, C. J . Organometallics
1994, 13, 706-720.
(14) Panunzi, A.; Roviello, G.; Ruffo, F. Organometallics 2002, 21,
3503-3505.
(15) Canty, A. J .; Denney, M. C.; Patel, J .; Sun, H.; Skelton, B. W.;
White, A. H. J . Organomet. Chem. 2003, 689, 672-677.
(16) (a) Neo, Y. C.; Vittal, J . J .; Andy Hor, T. S. J . Chem. Soc., Dalton
Trans. 2002, 337-342. (b) Neo, Y. C.; Yeo, J . S. L.; Low, P. M. N.;
Chien, S. W.; Mak, T. C. W.; Vittal, J . J .; Hor, T. S. A. J . Organomet.
Chem. 2002, 658, 159-168.
Syn th esis a n d Decom p osition of P d I2MeR(bp y)
(R ) Me, 4-tolyl). It is proposed above that undetected
species “Pd(O2CAr)2MeR(L2)” react with PdMeR(L2), as
shown in Schemes 1, 3, 5, and 6. It was possible to
synthesize Pd(O2CAr)Me2R(L2) (1-4, 13, 14) by me-
(17) de Graaf, W.; Boersma, J .; Smeets, W. J . J .; Spek, A. L.; van
Koten, G. Organometallics 1989, 8, 2907-2917.

C-O Bond Formation at Organopalladium Centers
Organometallics, Vol. 23, No. 5, 2004 1127
Sch em e 7. Exch a n ge Rea ction s betw een Un obser ved “P d (O2CAr )2MeR(L2)” a n d P d MeR(L2)
plexes PdI2Me2(L2) [L2 ) bis(4-tolylimino)acenaphthene,
bis(phenylimino)camphane]13 have been reported. Com-
plexes 19 and 20 cleanly reductively eliminate io-
domethane at ca. -10 °C [R ) Me (19)] and ca. -50
°C [R ) Tol (20)] (Scheme 7). However, when monitored
by NMR spectroscopy, Ag[O2CPh] did not react with 19
or 20 at temperatures below those at which 19 and 20
decompose.
alkyl group bonded to a Pd(IV) cationic species formed
by dissociation of an anionic ligand, to generate a more
stable Pd(IV) product and a less nucleophilic Pd(II)
product,11 and thus are consistent with the proposed
reactions of eqs 4, 9, and 15 in Schemes 1, 3, and 5. By
analogy with reported reactions, including a kinetic
study of the reaction of PdBrMe2(CH2Ph)(phen) with
PtMe2(phen),11a initial dissociation of one benzoate
moiety from “Pd(O2CAr)2MeR(L2)” (A-C) would result
in the formation of a five-coordinate intermediate E
(Scheme 7). As the configurations of A-C are unknown,
isomerization may be required on the pathway to F ,
followed by nucleophilic attack by the diorganopalla-
dium(II) reagent at a methyl group (F ), with Me+
transfer forming a new cationic Pd(IV) species (G) and
the Pd(II) species Pd(O2CAr)R(L2) (5-8, 15-18). Reat-
tachment of the benzoate anion with the newly formed
Pd(IV) cation would then lead to the observed, more
stable, Pd(IV) species Pd(O2CAr)Me2R(L2) (1-4, 13, 14)
and undetected “Pd(O2CAr)Me2Tol(tmeda)” (D).
Mech a n istic Con sid er a tion s. Diaroyl peroxides
react with PdMe2(L2) and PdMeTol(L2) species in a
complex series of reactions, affording a combination of
carbon-carbon and carbon-oxygen coupling products
along with bis(carboxylato)palladium(II) species. The
diorganopalladium(II) reagents are expected to undergo
an initial oxidative addition to form an undetected
“PdIV(O2CAr)2MeR(L2)” (A-C) intermediate, similar to
observations of the reaction of dibenzoyl peroxide with
PtMe2(phen) (phen ) 1,10-phenanthroline) and PtAr2-
(L2) (Ar ) Ph, 4-Tol, 3-Tol, or 4-MeOC6H4; L2 ) bpy,
phen) to form octahedral cis,cis- and trans,cis-PtIV(O2-
CPh)2Me2(phen) and cis,cis- and trans,cis-PtIV(O2CPh)2-
Ar2(L2), respectively.9 The reactions of eq 2, involving
oxidative addition of Se-Se bonds to Pd(II), together
with more recent observations of reversible oxidative
addition of diphenyl diselenide to Pt(4-MeOC6H4)R(4,4′-
But-6,6′-bpy) [R ) CH(CO2Me)2, CH(CO2Et)2, CH(CO2-
Pri)2] to give octahedral PtIV(SePh)2(4-MeOC6H4)R(4,4′-
But-6,6′-bpy)14 and of bis(4-chlorophenyl)diselenide to
PdMe(Ar′)(bpy) (Ar′ ) 4-Tol, 4-MeOC6H4) to give octa-
hedral PdIV(SeC6H4Cl-4)2Me(Ar′)(bpy),15 also provide a
model for this reactivity.
Decomposition of the triorganopalladium(IV) species
(1-4, 13, 14, D) by reductive elimination follows,
forming a second monoorganopalladium(II) species and
carbon-carbon coupling products (eqs 5, 10, 16 in
Schemes 1, 3, 5). It is of particular interest that carbon-
oxygen coupling does not occur from the observed Pd-
(IV) species, illustrating the complexity of organopal-
ladium(IV) chemistry and the extreme caution needed
in deducing mechanisms of catalytic processes on the
basis of model reactions.
Syn th esis a n d Ch a r a cter iza tion of Com p lexes.
Complexes of the form Pd(O2CAr)2(L2) (9-12), Pd(O2-
CAr)R(L2) (5-8, 15, 16), and Pd(O2CAr)Me2R(L2) (Ar
) Ph, ArF; L2 ) bpy, tmeda; R ) Me, Tol) (1-4, 13, 14)
were prepared by metathesis reactions involving PdCl2-
(L2), PdIR(L2), or PdIMe2R(L2) and the appropriate
silver(I) salt. On several occasions, significant difficulty
was encountered in obtaining pure samples suitable for
elemental analysis, although in most instances this was
overcome by obtaining the complexes in crystalline form.
The undetected Pd(IV) species are immediately in-
volved in exchange reactions with remaining Pd(II)
starting complex to form the detected triorganopalla-
dium(IV) species. Reactions of this type reported to date
occur via nucleophilic attack by a Pd(II) reagent at an
(18) Kruis, D.; Markies, B. A.; Canty, A. J .; Boersma, J .; van Koten,
G. J . Organomet. Chem. 1997, 532, 235-242.
(19) Byers, P. K.; Canty, A. J .; Skelton, B. W.; White, A. H.
Organometallics 1990, 9, 826-832.

1128 Organometallics, Vol. 23, No. 5, 2004
Canty et al.
F igu r e 1. Projections of molecules of (a) Pd(O2CPh)2(bpy) (9), (b) Pd(O2CPh)2(tmeda) (11), (c) Pd(O2CArF)2(tmeda) (12),
and (d) Pd(O2CPh)(Tol)(tmeda) (15). Ellipsoids are shown at the 50% probability level for the non-hydrogen atoms, hydrogen
atoms having arbitrary radii of 0.1 Å.
However, for Pd(O2CPh)Me(tmeda) (7) and Pd(O2CPh)-
Tol(bpy) (15) several attempts at attaining accurate
microanalyses failed. Similar difficulties were experi-
enced by Neo et al. in characterization of a number of
palladium(II) phosphine carboxylates.16
In 12, one-half of the neutral molecule comprises the
asymmetric unit of the structure, a crystallographic
2-axis passing through the metal atom and the central
bond of the ordered diamine ligand to place the unco-
ordinated oxygen atoms of carboxylate ligands above
and below the mean coordination plane. The other
tmeda complex (11) has quasi-2 symmetry with the
tmeda ligand disordered. The bpy complexes (9, 15‚CH2-
Cl2) are devoid of crystallographic symmetry, and a full
molecule comprises the asymmetric unit of the struc-
ture. In contrast to the tmeda complexes, 9 has the
uncoordinated oxygen atoms of the benzoate group to
the same side of the coordination plane. In all com-
plexes, the carboxylate CCO2 planes are quasi-coplanar
with their aromatic C6 parent and lie quasi-normal to
the coordination plane. In 12 the Pd-O-C angle is
appreciably smaller (∼6-11°) than in the other com-
plexes; the consistency of the other bonding parameters
in relation to those across the series suggests that it is
unlikely to be a consequence of any electronic effect due
to the CF3 substituent.
The unstable Pd(IV) complexes were generated and
used in situ and characterized by NMR spectroscopy.
1H NMR characterization of trimethylpalladium(IV)
complexes 1-4 was straightforward because of the
symmetry of the complexes, the presence of only one
isomer, and the consequently uncomplicated spectra.
Two isomers were present for the dimethyl(aryl)palla-
dium(IV) complexes (13, 14), the spectra being consis-
tent with the expected facial arrangement of organic
ligands. All of the observed Pd(IV) complexes displayed
lower stability than the related iodo complexes PdIMe3-
(L2) (L2 ) tmeda, bpy)17,18 and PdIMe2Tol(bpy).11c
Str u ctu r a l Stu d ies of 9, 11, a n d 12 a n d th e
Dich lor om eth a n e Solva te of 15. The complexes are
mononuclear, containing approximate square-planar
geometry for palladium on the basis of the presence of
cis-bidentate nitrogen donor ligands (bpy or tmeda) and
two unidentate carboxylate groups (9, 11, 12) or a
unidentate carboxylate group and a tolyl group (15‚CH2-
Cl2) (Figure 1).
Exp er im en ta l Section
Gen er a l P r oced u r es. The reagents PdCl2(L2),17 PdITol-
(L2),18 PdMeTol(L2),18 PdIMe3(L2)11b,19 (L2 ) bpy, tmeda),

C-O Bond Formation at Organopalladium Centers
Organometallics, Vol. 23, No. 5, 2004 1129
PdIMe(tmeda),17 PdIMe2Tol(bpy),18 and (ArFCO2)2 were pre-
18). Gen er a l Syn th esis. Silver aroate (0.34 mmol) was added
to a suspension of PdIR(L2) (0.31 mmol) in dichloromethane
(10 mL). The suspension quickly became yellow in color. It was
then stirred for 15 min in the absence of light and filtered
through a plug of glass fiber filter paper and Celite, and the
filtrate was evaporated to dryness in vacuo. The resulting
yellow solids were rinsed with n-pentane (3 × 5 mL) and dried
in vacuo.
20
pared as previously reported; Ag[O2CArF] was prepared as
described for the analogue Ag[O2CPh],21 and (PhCO2)2 was
used as received (BDH). The complex PdIMe(bpy) was pre-
pared as described for PdIMe(tmeda) but starting with PdMe2-
(bpy).17 All other reagents were used as received. NMR spectra
were measured on Varian Gemini-200 NMR, Varian INOVA-
400 NMR, or Varian Mercury-300 NMR spectrometers. Infra-
red spectra were measured as KBr disks or Nujol mulls using
P d (O2CP h )Me(bp y) (5). Yield: 0.12 g (97%). 1H NMR
(acetone-d6): δ 8.60 (d, 1H, 3J ) 5.6 Hz, H6), 8.55 (d, 1H, 3J )
a
Bruker IFS 66 FTIR spectrometer or a Perkin-Elmer
Paragon 100 FTIR in the mid-IR range (400-4000 cm-1).
Elemental analyses were performed by the Central Science
Laboratory, University of Tasmania, using a Carlo Erba EA
1108 elemental analyzer or a ThermoFinnigan Flash EA 1112
elemental analyzer. Coupled GC-MS was carried out using a
HP 5890 gas chromatograph fitted with a 25 m × 0.52 mm
and connected to a 5970B mass selective detector (70 eV ET
with He carrier gas).
3
3
8.4 Hz, H3′), 8.49 (d, 1H, J ) 8.0 Hz, H3), 8.36 (d, 1H, J )
3
4
4.8 Hz, H6′), 8.21 (td, 1H, J ) 8.0 Hz, J ) 1.2 Hz, H4), 8.2-
3
4
8.0 (m, 3H, ortho-Ph and H4′), 7.65 (ddd, 1H, J ) 5.6 Hz, J
3
4
) 1.6 Hz, H5), 7.56 (ddd, 1H, J ) 5.2 Hz, J ) 0.8 Hz, H5′),
7.5-7.3 (m, 3H, meta- and para-Ph), 0.87 (s, 3H, PdMe). IR
(Nujol mull): ν(CO2) 1613 s, 1572 m, 1353 vs cm-1. Anal.
Calcd: C, 54.22; H, 4.04; N, 7.02. Found: C, 54.01; H, 3.76;
N, 6.81.
P d (O2CAr F )Me(bp y) (6). Yield: 0.081 g (87%). 1H NMR
Syn th esis of P a lla d iu m (II) Com p lexes P d (O2CAr )2(L2)
(Ar ) P h , Ar F ; L2 ) tm ed a , bp y) (9-12). Gen er a l Syn th e-
sis. Silver aroate (1.20 mmol) was added to a suspension of
PdCl2(L2) (0.60 mmol) in dichloromethane (10 mL). The
suspension quickly became yellow in color. It was then stirred
for 15 min in the absence of light and filtered through a plug
of glass fiber filter paper and Celite, and the filtrate was
evaporated to dryness in vacuo. The resulting yellow solids
were rinsed with n-pentane (3 × 5 mL) and dried in vacuo.
P d (O2CP h )2(bp y) (9). Yield: 0.23 g (76%). Crystals suit-
able for the X-ray work were obtained from the reaction of
PdMe2(bpy) with (PhCO2)2 in acetone-d6 (vide infra). 1H NMR
(CDCl3): δ 8.40 (d, 2H, 3J ) 7.6 Hz, H3), 8.30 (dd, 2H, 3J ) 5.
(acetone-d6): δ 8.67 (d, 1H, 3J ) 5.6 Hz, H6), 8.57 (d, 1H, 3J )
3
8.0 Hz, H3 or H3′), 8.53 (d, 1H, J ) 8.0 Hz, H3 or H3′), 8.43
(d, 1H, 3J ) 4.4 Hz, H6′), 8.3-8.2 (m, 3H, ortho-ArF and H4 or
3
4
H4′), 8.18 (td, 1H, J ) 7.6 Hz, J ) 1.6 Hz, H4 or H4′), 7.72
3
(m, 3H, meta-ArF and H5 or H5′), 7.64 (dd, 1H, J ) 6.4 Hz,
4J ) 1.2 Hz, H5 or H5′), 0.86 (s, 3H, PdMe). IR (Nujol mull):
ν(CO2) 1626 s, 1563 m, 1352 s; ν(CF3) 1321 vs cm-1. Anal.
Calcd: C, 48.89; H, 3.24; N, 6.00. Found: C, 48.97; H, 3.29;
N, 5.89.
P d (O2CP h )Me(tm ed a ) (7). Yield: 0.0222 g (99%). 1H NMR
3
4
(acetone-d6): δ 7.95 (dd, 2H, J ) 8.0 Hz, J ) 1.6 Hz, ortho-
Ph), 7.4-7.2 (m, 3H, meta- and para-Ph), 2.84 (m, 2H, NCH2),
2.69 (s, 6H, NCH3), 2.62 (m, 2H, NCH2), 2.50 (s, 6H, NCH3),
0.28 (s, 3H, PdMe). IR (Nujol mull): ν(CO2) 1594 s, 1549 m,
4
3
4
6 Hz, J ) 1.0 Hz, H6 bpy), 8.12 (d, 4H, J ) 7.2 Hz, J ) 1.6
Hz, ortho-Ph), 8.08 (td, 2H, 3J ) 8.0 Hz, 4J ) 1.6 Hz, H4), 7.41
(m, 2H, para-Ph), 7.34 (m, 4H, meta-Ph), 7.26 (ddd [overlaps
with solvent peak], 2H, 3J ) 5.6 Hz, 4J ) 1.2 Hz, H5). IR (KBr
disk): ν(CO2) 1622 s, 1343 s cm-1. Anal. Calcd: C, 57.10; H,
3.59; N, 5.55. Found: C, 57.05; H, 3.53; N, 5.43.
∼1350 vs (overlaps with Nujol peak) cm-1
.
P d (O2CAr F )Me(tm ed a ) (8). Yield: 0.0453 g (99%). 1H
3
4
NMR (acetone-d6): δ 8.13 (dd, 2H, J ) 8.6 Hz, J ) 0.86 Hz,
ortho-ArF), 7.67 (dd, 2H, 3J ) 8.7 Hz, 4J ) 0.68 Hz, meta-ArF),
2.85 (m, 2H, NCH2), 2.72 (s, 6H, NCH3), 2.67 (m, 2H, NCH2),
2.52 (s, 6H, NCH3), 0.32 (s, 3H, PdMe). IR (Nujol mull): ν(CO2)
1621 s, 1574 m, 1360 s; ν(CF3) 1320 vs cm-1. Anal. Calcd: C,
42.21; H, 5.43; N, 6.56. Found: C, 42.09; H, 5.56; N, 6.45.
P d (O2CAr F )2(bp y) (10). Yield: 0.0900 g (93%). 1H NMR
3
3
(acetone-d6): δ 8.70 (d, 2H, J ) 7.6 Hz, H3), 8.39 (td, 2H, J
) 7.6 Hz, 4J ) 1.6 Hz, H4), 8.32 (dd, 2H, 3J ) 5.6 Hz, 4J ) 1.2
Hz, H6), 8.19 (d, 4H, 3J ) 8.0 Hz, ortho-ArF), 7.73 (ddd, 2H, 3J
) 5.6 Hz, 4J ) 1.2 Hz, H5), 7.69 (d, 4H, 3J ) 8.0 Hz, meta-
ArF). IR (KBr disk): ν(CO2) 1635 s, 1566 m, 1350 s cm-1; ν(CF3)
1319 vs cm-1. Anal. Calcd: C, 48.73; H, 2.52; N, 4.37. Found:
C, 48.75; H, 2.52; N, 4.19.
P d (O2CP h )Tol(bp y) (15). Yield: 0.0209 g (100%). Crystals
suitable for the X-ray work were obtained from the slow
1
diffusion of n-pentane into a CH2Cl2 solution of 15. H NMR
3
(acetone-d6): δ 8.58 (m, 2H, H3 and H3′), 8.45 (dd, 1H, J )
P d (O2CP h )2(tm ed a ) (11). Yield: 0.0342 g (96%). Crystals
suitable for the X-ray work were obtained from the reaction
4
5.2 Hz, J ) 0.8 Hz, H6′), 8.26 (m, 3H, H6, H4 and H4′), 8.02
(m, 2H, ortho-Ph), 7.70 (ddd, 1H, 3J ) 5.2 Hz, 4J ) 0.8 Hz,
H5′), 7.59 (ddd, 1H, 3J ) 6.0 Hz, 4J ) 1.2 Hz, H5), 7.41 (d, 2H,
3J ) 8.0 Hz, ortho-Tol) 7.40-7.28 (m, 3H, meta- and para-Ph
1
of PdMe2(tmeda) with (PhCO2)2 in acetone-d6 (vide infra). H
NMR (acetone-d6): δ 7.91 (d, 4H, 3J ) 7.6 Hz [complex 4J
coupling also observed], ortho-Ph), 7.34 (m, 2H, para-Ph), 7.27
(m, 2H, meta-Ph), 3.05 (s, 4H, NCH2), 2.82 (s, 12H, NCH3). IR
(KBr disk): ν(CO2) 1616 s, 1576 m, 1336 vs cm-1. Anal.
Calcd: C, 51.68; H, 5.64; N, 6.03. Found: C, 51.76; H, 5.61;
N, 5.43.
3
4
and ortho-Tol), 6.79 (dd, 2H, J ) 8.0 Hz, J ) 0.6 Hz, meta-
Tol), 2.20 (s, 3H, Me). IR (Nujol mull): ν(CO2) 1598 s, 1571 m,
1347 vs cm-1
.
P d (O2CAr F )Tol(bp y) (16). Yield: 0.0286 g (100%). 1H
NMR (acetone-d6): δ 8.58 (d, 2H, 3J ) 8.0 Hz, H3 and H3′),
P d (O2CAr F )2(tm ed a ) (12). Yield: 0.0215 g (38%). Crystals
suitable for the X-ray work were obtained from the reaction
of Pd(O2CArF)Me(tmeda) with (ArFCO2)2 in acetone-d6 (vide
infra). 1H NMR (CD2Cl2): δ 8.04 (d, 4H, 3J ) 7.9 Hz, ortho-
3
8.44 (d, 1H, J ) 4.8 Hz, H6′), 8.25 (m, 3H, H6, H4 and H4′),
8.18 (d, 2H, 3J ) 8.0 Hz, ortho-ArF), 7.7 (m, 3H, H5′ and meta-
3
3
ArF), 7.58 (t, 1H, J ) 5.2 Hz, H5), 7.39 (d, 2H, J ) 8.0 Hz,
ortho-Tol), 6.80 (d, 2H, 3J ) 7.8 Hz, meta-Tol), 2.21 (s, 3H,
Me). IR (Nujol mull): ν(CO2) 1627 s, 1573 m, ∼1360 m
(overlaps with Nujol peak) cm-1; ν(CF3) 1320 vs cm-1. Anal.
Calcd: C, 55.31; H, 3.53; N, 5.16. Found: C, 55.03; H, 3.48;
N, 5.01.
3
ArF), 7.57 (d, 4H, J ) 8.0 Hz, meta-ArF), 2.85 (s, 4H, NCH2),
2.79 (s, 12H, NCH3). 13C NMR (CD2Cl2): δ 172.1 (CdO), 139.1,
130.6, 125.4, 63.2 (NCH2), 51.9 (NCH3). IR (KBr disk): ν(CO2)
1622 s, 1564 m, 1356 s cm-1; ν(CF3) 1320 vs cm-1. Anal.
Calcd: C, 43.98; H, 4.03; N, 4.66. Found: C, 43.90; H, 3.98;
N, 4.64.
P d (O2CP h )Tol(tm ed a ) (17). Yield: 0.039 g (99%). 1H NMR
3
4
(acetone-d6): δ 7.86 (dd, 2H, J ) 8.4 Hz, J ) 1.6 Hz, ortho-
Ph), 7.34 (d, 2H, 3J ) 8.0 Hz, ortho-Tol), 7.3-7.2 (m, 3H, meta-
and para-Ph), 6.64 (dd, 2H, 3J ) 8.0 Hz, 4J ) 0.6 Hz, meta-
Tol), 2.91 (m, 2H, NCH2), 2.17 (m, 2H, NCH2), 2.55 (s, 6H,
NCH3), 2.53 (s, 6H, NCH3), 2.10 (s, 3H, Me). IR (Nujol mull):
ν(CO2) 1614 s, 1574 m, 1352 vs cm-1. Anal. Calcd: C, 55.24;
H, 6.49; N, 6.44. Found: C, 55.36; H, 6.29; N, 6.53.
Syn th esis of P a lla d iu m (II) Com p lexes P d (O2CAr )R(L2)
(Ar ) P h , Ar F ; R ) Me, Tol; L2 ) tm ed a , bp y) (5-8, 15-
(20) Rakhimov, A. I.; Androsyuk, E. R.; Shelyazhenko, S. V.;
Yagupol’skii, L. M. J . Org. Chem. USSR 1981, 17, 1470-1475.
(21) Rubottom, G. M.; Mott, R. C.; J uve, R. K., J r. J . Org. Chem.
1981, 46, 2717-2721.

1130 Organometallics, Vol. 23, No. 5, 2004
Canty et al.
3
3
P r ep a r a tion of P d (O2CAr F)Tol(tm ed a ) (18). Yield: 0.022
g (92%). 1H NMR (acetone-d6): δ 8.01 (dd, 2H, 3J ) 8.2 Hz, 4J
isomer], J ) 8.0 Hz, meta-ArF), 7.04 (d (br), 2H, J ) 7.6 Hz,
meta-Tol), 2.29 (s, 3H, Me), 2.02 (s, 3H, PdMe), 1.20 (s, 3H,
PdMe).
3
4
) 0.8 Hz, ortho-ArF), 7.57 (dd, 2H, J ) 8.2 Hz, J ) 0.8 Hz,
meta-ArF), 7.32 (d, 2H, ortho-Tol), 6.64 (d, 2H, 3J ) 7.6 Hz,
meta-Tol), 2.95 (m, 2H, NCH2), 2.74 (m, 2H, NCH2), 2.58 (s,
6H, NCH3), 2.56 (s, 6H, NCH3), 2.12 (s, 3H, Me). IR (Nujol
mull): ν(CO2) 1613 s, 1572 m, ∼1360 s (overlaps with Nujol
peak); ν(CF3) 1321 vs. Anal. Calcd: C, 50.16; H, 5.41; N, 5.57.
Found: C, 50.30; H, 5.33; N, 5.56.
1H NMR Stu d ies of th e Rea ction of P a lla d iu m (II)
Com p lexes w ith (Ar CO2)2 (Ar ) P h , Ar F ). P d MeR(L2) (R
) Me, Tol; L ) bp y, tm ed a ) w ith (Ar CO2)2. In a typical
experiment, a solution of PdMeR(L2) in acetone-d6 (0.3 mL)
in an NMR tube was cooled to eThinSpace-50 °C. To this was
added a solution of (ArCO2)2 in acetone-d6 (0.3 mL) in the ratios
outlined in the Results section. The tube was placed in a NMR
probe, precooled to eThinSpace-50 °C, and the solution was
warmed in 10 °C intervals with monitoring. Products of the
reaction were identified by GC-MS and by comparison of the
In Situ Syn th esis of P a lla d iu m (IV) Com p lexes P d -
(O2CAr )Me2R(L2) (Ar ) P h , Ar F ; R ) Me, Tol; L2 ) tm ed a ,
bp y) (1-4, 13, 14). Gen er a l Syn th esis. Iodomethane (1 mL)
was cooled to -35 °C. To this was added PdMeR(L2) (0.0294
mmol) and the solution stirred for 30 min. The volatile
components were removed in vacuo at low temperature,
leaving a pale yellow solid, [PdIMe2R(L2)]. The solid was
redissolved in acetone-d6 (0.6 mL) at -70 °C. To this was added
silver aroate (0.0297 mmol), and a reaction was observed
immediately. The suspension was stirred for 30 min at -50
°C, then quickly filtered through a plug of glass fiber filter
paper into a precooled NMR tube.
1
observed H NMR to the 1H NMR of known and independently
synthesized compounds.
P d (O2CAr )R(L2) (R ) Me, Tol; L ) bp y, tm ed a ) w ith
(Ar CO2)2. In a typical experiment, a solution of (ArCO2)2 in
acetone-d6 (0.3 mL) was added to a solution of Pd(O2CAr)R-
(L2) in acetone-d6 (0.3 mL) and allowed to go to completion at
ambient temperature (several hours for R ) Me and several
days for R ) Tol). Products of the reaction were identified by
GC-MS and by comparison of the observed 1H NMR to the
1H NMR of known and independently synthesized compounds.
1H NMR Stu d ies of th e Rea ction of Diiod in e w ith
P d MeR(bp y) (R ) Me, Tol). In a typical experiment, a
solution of I2 in acetone-d6 (0.4 mL) in an NMR tube was cooled
to ∼ThinSpace-50 °C. To this was added a solution of PdMeR-
(bpy) in acetone-d6 (0.3 mL) in 1:1 ratio. 1H NMR spectra
showed the presence of PdI2MeR(bpy) (19, 20) (see below). The
solutions were warmed in 10 °C intervals with monitoring.
Iodomethane and PdIMeR(bpy) were formed at ca. ThinSpace-
10 °C (R ) Me) and at -50 °C (R ) Tol).
fa c-P d (O2CP h )Me3(bp y) (1). 1H NMR (acetone-d6, -30
3
3
°C): δ 9.01 (d, 2H, J ) 4.0 Hz, H6), 8.59 (d, 2H, J ) 8.0 Hz,
H3), 8.22 (td, 2H, 3J ) 8.0 Hz, 4J ) 1.6 Hz, H4), 7.79 (ddd,
2H, J ) 5.2 Hz, J ) 1.2 Hz, H5), 7.65 (d, 2H, J ) 6.4 Hz,
ortho-Ph), 7.18 (t, 1H, 3J ) 6.8 Hz, para-Ph), 7.11 (t, 2H, 3J )
7.2 Hz, meta-Ph), 1.72 (s, 6H, PdMe), 0.64 (s, 3H, PdMe).
3
4
3
fa c-P d (O2CAr F )Me3(bp y) (2). 1H NMR (acetone-d6, -30
°C): δ 9.03 (dd, 2H, 3J ) 5.6 Hz, 4J ) 0.8 Hz, H6), 8.40 (d, 2H,
3
4
3J ) 8.0 Hz, H3), 8.26 (td, 2H, J ) 8.0 Hz, J ) 1.6 Hz, H4),
7.84-7.51 (m, 4H, H5 and ortho-ArF), 7.50 (d, 2H, 3J ) 8.0
Hz, meta-ArF), 1.71 (s, 6H, PdMe), 0.69 (s, 3H, PdMe).
1
P d I2Me2(bp y) (19). H NMR (acetone-d6, -40 °C): δ 9.01
fa c-P d (O2CP h )Me3(tm ed a ) (3). 1H NMR (acetone-d6, -40
(d, 2H, 3J ) 5.6 Hz, H6), 8.77 (d, 2H, 3J ) 8.4 Hz, H3), 8.32 (t,
2H, 3J ) 7.6 Hz, H4), 7.86 (t, 2H, 3J ) 6.8 Hz, H5), 2.75 (s,
6H, PdMe).
3
4
°C): δ 7.99 (dd, 2H, J ) 8.0 Hz, J ) 1.6 Hz, ortho-Ph), 7.35
(m, 3H, meta- and para-Ph), 3.0 (br, 2H, NCH2), 2.7 (br, 2H,
NCH2), 2.49 (s, 6H, NCH3), 2.36 (s, 6H, NCH3), 1.53 (s, 6H,
PdMe), 0.78 (s, 3H, PdMe).
P d I2MeTol(bp y) (20). 1H NMR (acetone-d6, -50 °C): δ 9.12
(d, 1H, J ) 4.8 Hz, H6 or H6′), 8.94 (d, 1H, J ) 4.4 Hz, H6
or H6′), 8.85 (m, 2H, H3 and H3′), 8.35 (m, 2H, H4 and H4′),
7.99 (d, 2H, 3J ) 8.4 Hz, ortho-Tol), 7.88 (m, 2H, H5 and H5′),
6.90 (d, 2H, J ) 8.4 Hz, meta-Tol), 3.19 (s, 3H, Me), 2.30 (s,
3H, PdMe).
3
3
fa c-P d (O2CAr F )Me3(tm ed a ) (4). 1H NMR (acetone-d6, -40
3
3
°C): δ 8.18 (d, 2H, J ) 8.4 Hz, ortho-ArF), 7.72 (d, 2H, J )
8.4 Hz, meta-ArF), 3.20-2.82 (br, 2H, NCH2), 2.82-2.60 (br,
2H, NCH2), 2.50 (s, 6H, NCH3), 2.37 (s, 6H, NCH3), 1.53 (s,
6H, PdMe), 0.82 (s, 3H, PdMe).
3
X-r a y Da ta Collection , Str u ctu r e Deter m in a tion , a n d
Refin em en t for 9, 11, a n d 12 a n d th e Solva ted Cr ysta l
Con ta in in g Molecu les of 15. Full spheres of CCD area-
detector diffractometer data were measured (Bruker AXS
instrument, ω-scans; monochromatic Mo KR radiation, λ )
0.71073 Å; T ca. 153 K), yielding Nt(otal) reflections, these
merging to N unique (Rint cited) after “empirical”/multiscan
absorption correction (proprietary software), No with F > 4σ-
(F) being considered “observed” and used in the full matrix
least-squares refinements. Anisotropic displacement param-
eter forms were refined, (x,y,z,Uiso)H, also. Conventional residu-
als R, Rw (weights: ((σ2(F) + 0.0004F2)-1) on |F| are quoted at
convergence. Neutral atom complex scattering factors were
employed within the context of the Xtal 3.7 program system.22
Figure 1 depicts non-hydrogen atoms with 50% probability
amplitude displacement envelopes, hydrogen atoms where
shown having arbitrary radii of 0.1 Å.
P d (O2CP h )Me2Tol(bp y) (13). 13a : 1H NMR δ 9.36 (dd, 2H,
4
3
3J ) 4.8 Hz, J ) 0.8 Hz, H6), 8.42 (d, 2H, J ) 8.4 Hz, H3),
3
4
3
8.15 (td, 2H, J ) 8.0 Hz, J ) 1.6 Hz, H4), 7.84 (ddd, 2H, J
) 5.2 Hz, 4J ) 0.8 Hz, H5), 7.68 (m [overlaps with other
isomer], ortho-Ph), 7.19 (m [overlaps with other isomer], para-
Ph), 7.14 (m [overlaps with other isomer], meta-Ph), 6.87 (d,
2H, 3J ) 8.0 Hz, ortho-Tol), 6.61 (d, 2H, 3J ) 7.6 Hz, meta-
Tol), 2.09 (s, 6H, PdMe), 2.08 (s, 3H, Me). 13b: δ 9.08 (d, 1H,
3J ) 5.6 Hz, H6), 8.60 (m, 2H, H3 and H3′), 8.52 (dd, 1H, 3J )
5.2 Hz, 4J ) 1.2 Hz, H6′), 8.20 (m, 2H, H4 and H4′), 7.79 (ddd,
1H, 3J ) 5.6 Hz, 4J ) 1.2 Hz, H5), 7.68 (m [overlaps with other
isomer], ortho-Ph, H5′), 7.19 (m [overlaps with other isomer],
para-Ph), 7.14 (m [overlaps with other isomer], meta-Ph), 7.03
3
(d (br), 2H, J ) 8.0, meta-Tol), 2.29 (s, 3H, Me), 2.00 (s, 3H,
PdMe), 1.14 (s, 3H, PdMe).
1
P d (O2CAr F )Me2Tol(bp y) (14). H NMR (acetone-d6, -30
3
3
°C): 14a : δ 9.34 (d, 2H, J ) 5.2 Hz, H6), 8.49 (d, 2H, J )
Va r ia ta . Complex 9: (x,y,z,Uiso
)
were constrained at
H
3
4
8.4 Hz, H3), 8.20 (td, 2H, J ) 8.0 Hz, J ) 1.6 Hz, H4), 7.86
(ddd, 2H, 3J ) 5.2 Hz, 4J ) 0.8 Hz, H5) 7.83 (m [overlaps with
other isomer], ortho-ArF), 7.50 (d [overlaps with other isomer],
3J ) 8.0 Hz, meta-ArF), 6.88 (d, 2H, 3J ) 8.0 Hz, ortho-Tol),
estimates in the refinement. Complex 11: Disorder was
modeled in the hydrocarbon bridge of the chelate in terms of
pairs of methylene sites, occupancies 0.770(5), and comple-
ment, not being resolvable beyond. (x,y,z,Uiso
)
were con-
H
3
strained throughout in the refinement at estimates. Complex
15: The dichloromethane solvent molecule was modeled in
terms of two components with common carbon, occupancies
6.63 (d, 2H, J ) 8.0 Hz, meta-Tol), 2.11 (s, 6H, PdMe), 2.08
(s, 3H, Me); 14b: δ 9.08 (dd, 1H, 3J ) 5.2 Hz, 4J ) 0.8 Hz,
3
3
H6), 8.64 (d, 2H, J ) 8.0 Hz, H3 and H3′), 8.52 (dd, 1H, J )
3
5.2 Hz, J ) 0.8 Hz, H6′), 8.24 (m, 2H, H4 and H4′), 7.83 (m
[overlaps with other isomer], ortho-ArF, H5), 7.71 (ddd, 1H,
3J ) 5.6 Hz, 4J ) 1.2 Hz, H5′), 7.50 (d [overlaps with other
(22) Hall, S. R.; du Boulay, D. J .; Olthof-Hazekamp, R., Eds. The
Xtal 3.7 System; University of Western Australia: Perth, 2001.

C-O Bond Formation at Organopalladium Centers
Organometallics, Vol. 23, No. 5, 2004 1131
refining to 0.778(2) and complement; (x,y,z,Uiso
were not refined.
)
(solvent only)
Su p p or tin g In for m a tion Ava ila ble: Atomic parameters,
bond distances and angles, and crystallographic details for 9,
11, 12, and 15‚CH2Cl2, and H NMR spectra of representative
H
1
Ack n ow led gm en t. We thank the Australian Re-
search Council for financial support, and Dr. Evan
Peacock of the Central Science Laboratory for technical
support with NMR spectroscopy.
reaction sequences. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM030644Q